Ribarstvo 71.3

Volume 71

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September 2013

UDK 639.2/.3 UDK 597

Croatian Journal of Fisheries

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CODEN RIBAEG ISSN 1848-0586 (Online) ISSN 1330-061X (Print)

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Izvorni znanstveni članak UTJECAJ ČOVJEKA NA MAKROZOOBENTOS I IHTIOFAUNU NA DONJIM TOKOVIMA RIJEKA MORAVE I DYJE (SLIV RIJEKE DUNAVA U ČEŠKOJ) Zdeněk Adámek, Světlana Zahrádková, Pavel Jurajda, Ilja Bernardová, Zdenka Jurajdová, Michal Janáč, Denisa Němejcová

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UPOTREBA SJEMENA FERMENTIRANOG MANGA (Mangifera indica) U HRANIDBI MLAđI TILAPIJE (Oreochromis niloticus) Samuel Olubodun Obasa, Segun Peter Alatise, Isaac Tunde Omoniyi, Wilfred Olusegun Alegbeleye, Francisca Adebukola George PROBIOTICI U PROIZVODNJI POTOMSTVA TIGRASTE KOZICE (Penaeus monodon) Sheikh Aftab Uddin, M. Abdul Kader, M. Nurul Azim Sikder, M. Abdul Hakim, M. Mahbub Alam, Ashraful Haque Azad, Chowdhury Kamrul Hasan ODNOS PLODNOSTI I BIOMETRIJSKIH INDEKSA KOD SREBRNOG SOMA Chrysichthys nigrodigitatus (Lacepede) U ESTUARIJU RIJEKE CROSS U NIGERIJI Victor Oscar Eyo, Albert Philip Ekanem, George Eni, Asikpo Patience Edet Prethodno priopćenje GOSPODARSKI RIBOLOV NA DUNAVU U REPUBLICI HRVATSKOJ KROZ FOxOV I SCHAEFEROV MODEL Dinko Jelkić, Anđelko Opačak, Tomislav Treer, Ivica Aničić, Roman Safner Kratko priopćenje PROCJENA PRODUKCIJE RIBA U JEZERU GBEDIKERE (BASSA, DRŽAVA KOGI, NIGERIJA) Samuel Olusegun Adeyemi UGROŽENE VRSTE RIBA U SVIJETU: Iberochondrostoma almacai COELHO, MESqUITA & COLLARES-PEREIRA, 2005 (Cyprinidae) Joana Isabel Robalo, Carla Sousa-Santos, Maria Manuela Coelho, Vítor Carvalho Almada Prilozi ribarstvenoj struci DR. SC. ZLATICA TESKEREDŽIĆ – MARLJIVA I POŽRTVOVNA GLAVNA UREDNICA ČASOPISA „CROATIAN JOURNAL OF FISHERIES“ („RIBARSTVO“) Tea Tomljanović

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

CODEN RIBAEG ISSN 1330-061X

ORIGINAL SCIENTIFIC PAPER

THE RESPONSE OF BENTHIC MACROINVERTEBRATE AND FISH ASSEMBLAGES TO HUMAN IMPACT ALONG THE LOWER STRETCH OF THE RIVERS MORAVA AND DYJE (DANUBE BASIN, CZECH REPUBLIC) Zdeněk Adámek1*, Světlana Zahrádková2, Pavel Jurajda1, Ilja Bernardová2, Zdenka Jurajdová1, Michal Janáč1, Denisa Němejcová2 Department of Fish Ecology, Institute of Vertebrate Biology AS CR, p.r.i., Květná 8, 603 65 Brno, Czech Republic, phone +420 543422523 2 T. G. Masaryk Water Research Institute, p.r.i., Mojmírovo nám. 16, 612 00 Brno, Czech Republic * Corresponding Author, E-mail: adamek@ivb.cz 1

ARTICLE INFO

ABSTRACT

Received: 29 January 2013 Received in revised form: 25 June 2013 Accepted: 5 July 2013 Available online: 7 July 2013

The lower Morava and Dyje rivers belong among the large lowland rivers on the southeast of the Czech Republic flowing into the Danube 69 km downstream of their confluence. Despite their high nature value and environment protection, both rivers suffered from heavy pollution from the sixties to the eighties of the last century. Significant improvement of their water quality during the last two decades resulted in the partial recovery of former assemblages of both benthic macroinvertebrates and fish. Recently, altogether 262 and 137 taxa of macrozoobenthos were recorded at the Dyje and Morava rivers, respectively. In the River Dyje, 3 and 21 non-native and threatened (according to IUCN categories) invertebrate species, respectively, were ascertained, whilst in the River Morava their numbers were 2 and 10, respectively. The fish assemblage consisted of 23 and 24 species, respectively, plus one hybrid in each of the rivers, bleak being by far the most abundant fish. In the sections under study, several rare and/or protected species were also recorded. Two of them, ide (Leuciscus idus) and burbot (Lota lota) belong among vulnerable fish species and four others, white-eye bream (Abramis sapa), striped ruffe (Gymnocephalus schraetser), streber (Zingel streber) and zingel (Zingel zingel), are considered as critically endangered species. Currently, both lower stretches of the rivers Morava and Dyje have been heavily invaded by round goby, Neogobius melanostomus.

Keywords: Macrozoobenthos Fish Diversity River pollution River regulation Joint Danube Survey

INTRODUCTION Large lowland rivers and their alluvial floodplains comprise a wide range of biotopes inhabited by many animal and plant species (Adámek and Sukop, 1992; Schiemer, 1999; Schomaker and Wolter, 2011).

Rivers represent dynamic, continuously changing,

systems, supported by an extensive ability to recover former and to create new biotopes. Natural, non-impacted lowland streams display a rich and diverse lateral and longitudinal zonation of a river and alluvial biotopes, with good hydrological and ecological interconnection of pools, riffles, side arms and oxbow lakes, riparian wetlands, flooded 93

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

meadows and wooded alluvial land.

Under the framework of the Joint Danube Survey 2 (JDS2), an evaluation of ecosystem functioning along the River Morava and its main tributary, the River Dyje, took place in August 2007. JDS2 represented a unique coordinated research activity along the most international river basin in the world, in which scientists from fourteen Danubian countries actively participated. One of the basic objectives of JDS2 was to get a better view of specific water quality parameters and in-depth characterisation of river biology through the establishment of complementary monitoring activity along the Danube and its important tributaries. This is the first time that investigation of fish and river hydromorphology has been performed to such an extent within the Danube basin. Though the key aim of JDS2 was to produce a homogenous data set of specific water quality elements for the Danube, the results obtained by national teams along tributaries are also of great importance for overall documentation. The study has also provided a forum for riparian countries to develop and test evaluation methods for river health. In addition to its scientific results, a major contribution of JDS2 has been in the dissemination of information to the public and getting inhabitants more involved in water protection issues (Liška et al., 2008). The JDS2 concept has now been formally included into the EUs Water Framework Directive (WFD) monitoring strategy as a tool for investigative monitoring.

This manuscript presents results from a detailed assessment of biota in the rivers Morava and Dyje, belonging among the richest of European rivers as far as benthic macroinvertebrate and fish communities are concerned. Data from two TransNational Monitoring Network (TNMN) sites upstream of the Morava and Dyje confluence are also included, as well as a literature review evaluating changes that have occurred over recent decades.

GENERAL CHARACTERISTICS OF THE MORAVA RIVER BASIN The catchment areas of three main European rivers occur within the Czech Republic - those of the River Elbe, which empties into the North Sea (65% of land surface); the River Odra, draining into the Baltic Sea (7%); and the River Morava, which flows into the Danube and on to the Black Sea (27%). Both the Morava and its main tributary, the Dyje, originally meandered through large floodplains; however, both these rivers have been regulated and channelised, to varying extent, over the last century.

The watershed of the River Morava on the ter94

ritory of the Czech Republic (Fig.1) has an area of 20,692 km2. However, 64.9% (13,419 km2) of this area belongs to the River Dyje. The Morava River basin may be characterised as being densely populated (137 inhabitants per km2) and highly exploited by both industry (machinery, food and chemical) and agriculture. Agricultural land represents around 60% of the basin surface, forests 32% and urbanised areas around 6%. Hydrologically, the Morava river basin is poor in water sources. Average annual precipitation is 635 mm and mean annual catchment runoff reaches 3,430 million m3. The average annual discharge of only 1.16 m3 for each of its 2.7 million inhabitants is only one third of the European average, and one sixth of the global average. The basin has 38 important storage reservoirs, with a total capacity amounting to approximately 568 million m3.

Fig 1. The Morava River basin on the territory of the Czech Republic with the indication of JDS2 sites location The qualitative state of running waters in the Morava river basin reflects a long-term development of landscape, municipalities, agriculture, industry, forestry, water management and other infrastructures. Although water quality has improved significantly over the past 20 years (e.g. all 34 towns with more than 10,000 inhabitants have been equipped with biological wastewater treatment plants), issues related to high nutrient and/or organic loading of surface waters still remain.

Historically, this river system was naturally inundated up to five times a year (Kux 1956) and the floodplains around the confluence provided extremely favorable conditions for reproduction and nursing of the majority of riverine fish (Jurajda and Peňáz, 1994, Jurajda, 1995, 1999, Jurajda et al., 2000, 2001). Between 1968 and 1982, however, the Morava was largely channelised and its meanders, disconnected from the main channel by levees, now exist as isolated oxbow lakes. Environmental protection

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

and maintenance of plant and animal diversity is implemented through a network of protected areas and sites, particularly in the upper mountainous and lower lowland parts of the river basin. The territory around the confluence has been designed as a “Protected Landscape Area” (the Soutok PLA; 139 km2) and mostly comprises floodplain forest with a rich system of canals, oxbow lakes, river side-arms and pools subject to controlled flooding over spring.

CURRENT SITUATION AS REGARDS HABITAT AND WATER QUALITY DEGRADATION ALONG THE LOWER MORAVA AND DYJE Physical habitat degradation Human activities had a significant impact on the hydromorphological status of both the Morava and Dyje river basin districts (RBDs), with natural stream processes being rare and aquatic biocenoses degraded at present. Around 80% of all water bodies have been modified, with stream channelisation, bank strengthening, channel hardening and cross barrier construction being the dominant factors. There are substantial differences between the hydrological characteristics of the two RBDs (summarised in Table 1). Despite having almost the same average annual precipitation (590 and 670 mm for the Morava and Dyje rivers, respectively), annual surface runoff for the Dyje is only half of that of the Morava (109 and 206 mm, respectively). As such, the number of reservoirs in the Morava River basin (upstream of the confluence) is one third of that in the Dyje basin (10 and 28, respectively), while total storage capacity in the Morava River basin is only Table 1. General characteristics of the Morava & Dyje river basin districts upstream of the TNMN sites

Upstream river basin area (km2) Altitude TNMN site (m a.s.l.)

Average discharge (m3.s-1) Reservoirs (No.) % stream straightened No. inhabitants (ths) Cities > 10,000 inhabitants (No.) Arable land (%) Number of pigs bred (ths) Number of poultry bred (ths)

TNMN site Morava: Dyje: Lanzhot Pohansko 9,883 11,165 150 155 61.1 37.5 10 28 58 36 1,363 1,395 22 12 53.0 64.3 373 652 3,078 4,800

one twelfth that of the Dyje River basin. Channel straightening has been implemented to a greater extent in the Morava RBD (ca. 57% of stream length), with barrier construction of greater importance in the Dyje basin (90% of streams). Overall, lack of fish passes has the greatest impact in the upper stretches of the rivers, with straightening and levee construction of greater importance in the lower stretches. Moreover, there is a clear difference in agricultural management for the two RBDs, with both area of arable land and number of animals bred (pigs, poultry) clearly higher in the Dyje RBD (Table 1).

Water quality development The present degraded environmental status of the lower Morava and Dyje reflects a whole range of historic anthropogenic pressures, including inadequately treated discharges from urban settlements and industry, the influence of diffuse pollution and hydromorphological alterations.

Effluent from sugar mills had a very destructive impact on benthic communities during the autumn months of each year (period of sugar beet processing) from the 1960s to the 80s. In the late 1970s, the results of saprobiological monitoring performed by the T.G.Masaryk Water research Institute (TGM WRI), Brno (unpublished), indicated very poor riverine community status along these rivers (these results have since provided a baseline for future water quality status assessments of important rivers in the basin). Because of the high levels of pollution, additional samples were collected along these rivers in addition to regular saprobiological monitoring and two Czech TNMN sites (Morava Lanžhot and Dyje - Pohansko) have also been surveyed every 3-5 years. The extremely high organic pollution levels discharged into the river system each autumn from the sugar mills resulted in an alphameso-polysaprobic status of plant and animal communities along the Morava River. Starting in the late 1980s, wastewater treatment plants were constructed for all larger cities in the RBD, resulting in a gradual improvement in water quality, not only in autumn but throughout the year. In 2007, saprobic indices that had formerly reached values of 2.8 had decreased to 2.1 in the Morava; and an even greater improvement was attained in the Dyje, where an index of 3.4 was decreased to 1.8 between 1976 and 2007. Despite the great efforts focused on decreasing point source pollution discharges in the basins, negative influences of diffuse pollution and hydromorphological alteration on benthic macroinvertebrate and fish communities remain a problem.

95

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

HISTORY OF LIMNOLOGICAL RESEARCH While some data on floodplain invertebrates of the lower reaches of the Dyje and Morava had been published even before 1900, they were mainly focused on temporary and/or permanent stagnant waters and were published in “grey literature”.

A similar priority was given to still waters until World War II with, for example, systematic studies of chironomids undertaken by Zavřel (1941, 1943) and of oligochaetes by Hrabě (1929). The first valuable information on macroinvertebrates along the lower reach of the Morava itself relates to the occurrence of the potamal mayfly Palingenia longicauda (Zavřel, 1905) and its later disappearance in the 1920s (Zavřel, 1934). Between 1950 and 1965, the running and still waters of southern Moravia were studied as part of an extensive research project supervised by the Czech Academy of Sciences and Masaryk University in Brno (Landa et al., 1997). In 1959, the lower Morava was monitored by Zelinka and Skalníková (1959) and has since been the subject of repeated studies throughout the 1990s (e.g. Soldán et al., 1998) and 2000s. Many of these projects also surveyed the River Dyje, though the study sites were situated further upstream of the JDS2 site.

Adámek and Sukop (1992) identified 118 taxa (mainly species) along the lower Dyje, while Zahrádková et al. (1995) identified 31 species or higher taxa at sites on the lower Morava. More recently, aquatic invertebrates were sampled and identified along the lower reach of the Dyje by Horsák (2001), who reported 143 taxa (not restricted to benthic fauna). Both JDS2 sites presented in this paper were included in a complex study of aquatic invertebrates of the Pálava Biosphere Reserve published by Opravilová et al. (1999), who identified 64 taxa. Větříček and Geriš (2003) reported the mayfly Baetopus tennelus (Albarda, 1878) as a new species for the Czech Republic from the River Morava near its confluence with the Dyje. Systematic research into benthic macroinvertebrates of the two river reaches near their confluence was initiated in the 1970s due the coordination of activities within (i) periodic sampling within the framework of the State Water Management (Water Quality) Balance, (ii) monitoring undertaken by the Morava River Basin Authority, (iii) project “Morava” of the TGM WRI Brno (1990-2010) and (iv) regular surveillance monitoring (2006-2010).

Fish assemblages in both running and still waters of the Morava and Dyje confluence area have been surveyed since the beginning of the 20th century (Mahen, 1927). Based on historical records, recent surveys and anglers’ reports 2 cyclostomes 96

and 55 fish species have been reported from the main channel of the Morava, 48 being indigenous and 9 exotic (Peňáz and Jurajda, 1993). Such species richness is exceptional compared with most other European rivers of similar size.

MATERIAL AND METHODS Study sites The JDS2 study of benthic macroinvertebrates was performed near the towns of Lanžhot (N 48° 41’, E 16° 59’) and Pohansko (N 48° 43’, E 16° 53’) on the rivers Morava and Dyje, respectively (Fig. 1), while the fish survey was performed along the shoreline between river km 79-76 on the River Morava (48’40’’N, 16’59’’E) and rkm 17-14 on the Dyje (48’42’’N, 16’54’’E). Channel width and depth on the Morava were 50-60 m and 0.8 m, respectively, and 30-40 m and 1.0-2.0 m on the Dyje. While the banks of the Morava consist primarily of rip-rap, the banks of the Dyje are mostly natural. Furthermore, the main channel of the Morava is completely isolated from its floodplain, whereas elements of floodplain and several backwaters remain connected along the Dyje.

Benthic macroinvertebrates With respect to the importance of potamal river stretches and to the level of their anthropogenic alterations, all available data on benthic macroinvertebrates related to the studied river stretches, including historical ones, were exploited, namely: 1) saprobiological monitoring of the TGM WRI, Brno; 2) results from the River Morava Project undertaken by TGM WRI, Brno (Zahrádková et al., 1995); 3) monitoring of transboundary rivers (TGM WRI, Brno, unpublished); 4) monitoring of the Morava River Catchment Area (Morava River Authority, unpublished); 5) collection of the Department of Botany and Zoology, Masaryk University Brno; 6) results of Horsák (2001; 7) results of JDS2 (TGM WRI, Brno, unpublished); 8) results of Opravilová et al. (1999).

Long-term data from river km 79-76 and 17-14 on the Morava and Dyje, respectively, were summarised and the data divided into several time periods, the presence and/or absence of individual species allowing a general evaluation of biodiversity alteration of each stretch over the study period. The following periods were distinguished: 1976-1995 (data sources 1 and 5), 1996-2006 (data sources 1, 2, 3 and 6), 2007 (data sources 1, 4 and 7), 2010 (data source 3 for the River Dyje only). While it was not

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

possible to assign data from source 8 to a specific time period, the information was included due to its faunistic value.

Several different methods were used for sampling benthic macroinvertebrates. The majority of data were obtained before 1995, the samples being collected according to Czech standard ČSN 757703 for the Czech saprobiological monitoring programme (data source 1 and 2). The goal of saprobiological biomonitoring is not the evaluation of ecological condition of a site but only an assessment of running water quality and oxygen condition (Forejtníková et al., 2006). A multihabitat sampling methodology, therefore, was not applied and segments with rapidly flowing water were sampled by hand sweep net preferentially, the segments with slowly flowing or standing water not being included.

Data obtained from sources 3, 4, and 7 were sampled and processed according to the Czech national multihabitat sampling method PERLA (ČSN 757701), using semi-quantitative 3-minute kick samples collected with a hand net (25 x 40 cm aperture and 500 µm mesh size). All mesohabitats (riffle, pool, macrophyte, woody debris, etc.) were sampled for a period corresponding to their total proportional area in the sampling section (Kokeš et al., 2006).

The metrics used were calculated according to formulas given in the AQEM Manual (AQEM consortium, 2002; http://www.aqem.de). The autecological characteristics used for calculation of the metrics were adopted from the online ARROW (2009) database.

According to the WFD, assessment of ecological status requires comparison with a reference status.

Due to a lack of recent potamal reference localities, relevant historical data and difficulties associated with sampling methods suitable for non-wadeable rivers in the Czech Republic, assessment of respective stream types has not yet been finished. To a certain degree, this issue can be solved through the compilation of a list of taxa typical for potamal river stretches. Such a list has already been compiled for German streams (Schöll et al., 2005). This list is, however, regionally limited and cannot be applied to any other region (river/sea catchment area). For the purposes of this publication, an ad hoc list was compiled of taxa expected at the evaluated sites and the macroinvertebrates found were compared with this. The list of typical potamal species compiled by experts (Zahrádková et al., 2007) was adopted after partial modification. Species were selected according to their known autecological characteristics (e.g. stream zonation preference, altitude and habitat preference, etc.) or according to their doc-

umented occurrence at the studied river stretches in the past, or in similar undisturbed river types in Central Europe (only species with an appropriate area of distribution were taken into account). In addition, the total numbers of all expected EPT taxa in Moravian large lowland rivers (Zahrádková et al., 2007) were compared with the numbers found in the spring samples of 2007.

Non-indigenous species were classified according to Mlíkovský and Stýblo (2006) and Panov et al.

(2008) who presented a “grey list” of species with unknown level of invasiveness, a “white list” of species with low level of invasiveness, and a “black list” of species of high invasiveness.

Fish Fish were collected quantitatively at ten 300 m stretches along the right bank of the Morava and the left bank of the Dyje by electrofishing (one handheld anode, EFKO FEG 13000, Honda 13 kW, ~ 300 V, 60 A, 50-80 Hz) from a drifting boat one to five metres from the bank. Stunned fish were collected by hand net (10 mm mesh size). Aside from bleak Alburnus alburnus, which were significantly dominant, all fish collected were measured and weighed individually. For bleak, 18-32 specimens were measured and weighed individually at each stretch and the rest bulk-weighed and counted. After surveying, all fish were released back into the river alongside the opposite bank. The F/C ratio (Holčík and Hensel, 1972), indicating the relationship between non-predatory and predatory fish, was calculated as a ratio between their biomass reported in survey catches.

Data on angling intensity and efficiency, fish species and size composition at the Dyje 2 and Morava 2 angling grounds (which correspond with the JSPD2 survey sections) were obtained from regularly summarised angling records available each year at the close of the angling season. Figures on stocking and angling catches for individual years were provided by the headquarters of the Moravian Anglers Union. As fish for stocking purposes are usually available in size and age categories that differ between years, and even between individual stocking events during one year, the appropriate ministerial instruction (Implementation Provision No.197/2004 of the Czech Fishery Law No. 99/2004) provides rules on how to convert individual size and age categories into one appropriate category, i.e. 2+ for carp and 0+ for other fish in this case study. Conversion rates were also supplied for mortality and survival rates for different species/categories compared to the fish category suggested by the stocking plan. Conversion to one age category ena97

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

bles comparability and an appropriate evaluation of stocking intensity and efficiency between years and individual water bodies. The ratio between number of fish stocked and caught is presented as a rate of return for individual species.

RESULTS Benthic macroinvertebrates

and 7.7% at the Dyje and Morava rivers, respectively (the respective percentage of potamal species was 60.3% and 79.0%). Another difference was found in proportion of active and passive filtrators both in the Dyje River (6.3 and 1.6%, respectively) and the Morava River (13.5 and 0.5%, respectively).

Concerning the microhabitat preferences, the species in the Dyje River evinced higher preferences to more course-grained substrate like akal and lithal (13.6 and 25.3%, respectively) in comparison with the Morava River (5.0 and 16.6%, respectively) where mainly the species preferring pelal (26.0%) and phytal (25.3%) occurred.

The indices of saprobity indicated middle betamesosaprobity at both sites (the Dyje River: 2.01, the Morava River: 2.15). A higher proportion of species occurring also in oligosaprobity was present in the Dyje River (23.4%) than in the Morava River (4.8%).

A comparison of species identified in the spring samples of 2007 with proposed list of typical potamal species was done (see Table 2). Of 18 expected mayfly species, 9 and 7 species were found in the Dyje River and Morava River, respectively.

Ten stonefly species should be present at the respective stream type, however, only unidentified specimen of the genus Leuctra occurred in the Morava River. The occurrence of 16 potamal caddis fly species is assumed, only 6 (and unidentified species of genus Hydroptila) and 7 species were found in the Dyje River and Morava River, respectively.

In addition to the typical potamal species, the species with less specific requirements or even ubiquitous ones usually occur in the respective stream type. A total number of at least 15 EPT species (regardless of the typical potamal species) is expected in this stream type under the good river health condition in spring season. This number was not achieved at the Dyje River (12 species) but overcame at the Morava River (20 species).

Taxonomic composition A list of taxa found since 1975 is provided in Appendix 1 (River Morava) and 2 (River Dyje).

Altogether, 262 taxa were found at the Dyje River above the confluence with the Morava River (204 species, 58 taxa were identified at genera or higher taxonomic levels). Three non-indigenous species were ascertained: Potamopyrgus antipodarum, Lithoglyphus naticoides and Dreissena polymorpha.

Twenty one species are categorised as threatened according to IUCN categories (see Appendix 1).

Caddis fly, Setodes punctatus, considered regionally extinct, was found in 2007 and Oecetis tripunctata, critically endangered species was found in 2010.

Additional species belonging to the categories “endangered” (10 species), “vulnerable” (6 species) or “nearly threatened” (3 species) were found within different periods, mainly after 1996.

The total number of taxa recorded at the Morava River stretch upstream the confluence with the Dyje River was 137 (95 species or species groups, 42 taxa identified at genera or higher taxonomic levels).

The non-indigenous species Dugesia tigrina and Dreissena polymorpha were present. Ten species are categorised as “threatened” according to IUCN categories (see Appendix 2). One species of the category “critically endangered”, mayfly Baetopus tenellus, was found in 2002. Additional species belonging to the categories “endangered” (3 species), “vulnerable” (4 species) or “nearly threatened” (2 species) were found after 1996, mainly in 2007.

Fish

Analyses of semiquantitative sampling campaign in spring 2007 The spring semiquantitative samples taken in 2007 were analysed in detail. Sixty two taxa (including 4 mayfly species and 8 caddis fly species) were found at the Dyje River (April 27) and 55 taxa (including 7 mayfly species, 1 stonefly and 12 caddis fly species) were found at the Morava River (May 2) (for species list of Ephemeroptera, Plecoptera and Trichoptera see Table 2). The lowland species slightly dominated in both samples (ca. 55% of taxa). The difference in zonation preferences was evident since the percentage of rhitral species was 21.7%

Species composition Altogether, 4396 and 2476 fish individuals (162.16 and 117.02 kg), respectively, were collected in the surveyed stretches of the Morava and Dyje rivers (Table 3). The respective numbers of species were 24 + 1 hybrid and 23 + 1 hybrid belonging to 6 identical families (Cyprinidae, Esocidae, Siluridae, Gadidae, Percidae and Gobiidae) in each river. With respect to the density, bleak was markedly the dominant fish species in both river stretches. Its proportions in the total fish numbers and biomass amounted to 75.02 and 16.71%, and 83.70 and 20.41% in the Morava and Dyje rivers, respectively.

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Table 2. Typical potamal species expected along the river stretches studied. Note: + = species observed after 1975, * species found in spring 2007

TRIChOPTERA

PLECOPTERA

EPhEMEROPTERA

Order

Species Baetis buceratus Eaton, 1870 Baetis fuscatus (Linné, 1761) Baetis nexus Navás, 1918 Brachycercus harrisella Caenis luctuosa (Burmeister, 1839) Caenis macrura Stephens, 1835 Caenis pseudorivulorum Keffermueller, 1960 Ecdyonurus aurantiacus (Burmeister, 1839) Ecdyonurus insignis Thomas & Sowa, 1970 Ephemera vulgata Linné, 1758 Ephemerella mesoleuca (Brauer, 1857) Ephoron virgo (Olivier, 1791) Heptagenia coerulans Rostock, 1877 Heptagenia flava Rostock, 1877 Choroterpes picteti (Eaton, 1871) Isonychia ignota (Walker, 1835) Palingenia longicauda (Olivier, 1791) Potamanthus luteus (Linné, 1767) Agnetina elegantula (Klapálek, 1905) Isoperla grammatica (Poda, 1761) Isoperla obscura (Zetterstedt, 1840) Isoptena serricornis (Pictet, 1881) Leuctra fusca (Linné, 1758) Marthamea vitripennis (Burmeister, 1839) Perlodes dispar (Rambur, 1842) Siphonoperla taurica (Pictet, 1841) Taeniopteryx nebulosa (Linné, 1758) Xanthoperla apicalis (Newman, 1836) Brachycentrus subnubilus Curtis, 1834 Ceraclea albimacula (Rambur, 1842) Ceraclea alboguttata (Hagen, 1860) Ceraclea annulicornis (Stephen, 1836) Ceraclea dissimilis (Stephens, 1836) Ceraclea nigronervosa (Retzius, 1783) Hydropsyche bulgaromanorum Malicky, 1977 Hydropsyche contubernalis McLachlan, 1865 Hydropsyche exocellata Dufour, 1841 Hydropsyche guttata Pictet, 1834 Hydroptila angulata Mosely, 1922 Hydroptila sparsa Curtis, 1834 Cheumatopsyche lepida (Pictet, 1834) Neureclipsis bimaculata (Linné, 1758) Psychomyia pusilla (Fabricius, 1781) Setodes punctatus (Fabricius 1793)

River Dyje: Pohansko + +* +

River Morava: Lanžhot

+* +* +

+* +* +

+ +

+ +*

+*

+*

+*

+* Leuctra sp.

+ +

+* +*

+ +*

+ +* +*

+*Hydroptila sp. +* +*

+*

+*

99

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. AdĂĄmek et al.: Zoobenthos and fish of lower Morava and Dyje

Table 3. Fish assemblage composition upstream of the confluence between the rivers Morava and Dyje, as recorded during the JDS2 survey. Note: n = total individuals, W = fish biomass in g Species B. barbus A. alburnus C. nasus C. gibelio A. aspius S. cephalus L. idus L. leuciscus R. amarus A. brama A. bjoerkna A. sapa S. erythrophthalmus R. rutilus R. rutilus x A. bjoerkna R. vladykovi G. gobio P. parva C. carpio V. vimba E. lucius S. glanis L. lota P. fluviatilis G. schraetser S. lucioperca Z. zingel Z. streber P. semilunaris

River Morava % W 3.71 27,181.7 75.02 26,123.9 1.57 1251.2 0.93 26,601.0 1.46 1,597.2 4.85 17,597.3

% 16.76 16.11 0.77 16.40 0.98 10.85

3 147 11 22 1

0.08 3.33 0.25 0.51 0.03

23.8 338.1 7,998.7 520.9 320.0

0.01 0.21 4.93 0.32 0.20

112 2 133 38 1 6 2 3 13 32 10

2.55 0.05 3.03 0.86 0.03 0.13 0.05 0.08 0.30 0.73 0.23

2,155.4 89.6 696,4 196.6 7.0 30,340.0 29.4 2,682.0 13,403.7 1,569.0 990.0

1.33 0.06 0.43 0.12 0.04 18.71 0.02 1.65 8.26 0.97 0.61

8 1

0.18 0.03

369.0 113.0

0.23 0.07

1

0.03

1.0

0.001

n 163 3,300 69 41 64 213

The proportion of other fish species in the total fish density in surveyed stretches of the Morava river did not exceed 5%, most numerous among them being chub, Squalius cephalus, barb, Barbus barbus, bitterling, Rhodeus amarus, and white-finned gudgeon, Romanogobio vladykovi, with 4.85, 3.71, 3.33 and 3.03%, respectively. Other important commercial and game fish species exceeded the level of numerical proportion of 1% only rarely (nase, Chondrostoma nasus and asp, Aspius aspius with 1.57 and 1.46%, respectively), however, some of them proved a significant proportion regarding the biomass. The highest figures were recorded for common carp, Cyprinus carpio, of which proportion in the total biomass was 18.71%, whilst only 0.13% in fish density (mean individual weight 5056.7 g), followed by barb and Prussian carp, Carassius gibelio, with 16.76 and 16.40%, respectively. Among 25 recorded fish species in the Morava River, 3 of them 100

River Dyje % W 2.87 31,975.4 83.70 23,884.3 0.36 5,020.0 1.12 1,491.0 1.35 8,330.5 0.54 4,762.0 1.26 12,985.4

% 27.33 20.41 4.29 1.27 7.12 4.07 11.10

46 94

1.84 3.81

14598.0 3,777.9

12.48 3.23

1 26 1 13 1

0.04 1.03 0.04 0.54 0.04

46.0 881.0 29.0 45.1 10.0

0.04 0.75 0.02 0.04 0.01

6 3 1 14 6 1 1 3 1

0.22 0.13 0.04 0.58 0.22 0.04 0.04 0.12 0.04

5,620.0 2,094.0 16.7 599.1 175.0 290.0 280.0 84.0 1.1

4.80 1.79 0.01 0.51 0.15 0.25 0.24 0.07 0.001

n 71 2,073 9 28 33 13 31

(Prussian carp, topmouth gudgeon, Pseudorasbora parva, and tubenose goby, Proterorhinus semilunaris) were non-indigenous. The F/C ratio of the whole fish community corresponded to 4.24 in the surveyed stretch of the Morava River.

Besides dominant bleak (83.7% of total fish density – see above), the proportion of other species occurrence was much lower in the Dyje River and only rarely exceeded the 2% threshold, like it happened in case of white bream, Abramis bjoerkna, and barb with 3.81 and 2.87%, respectively. The proportion of other important game fish was quite low with maximum values in common bream (Abramis brama), chub, ide (Leuciscus idus), asp and roach, Rutilus rutilus, with 1.84, 1.35, 1.26, 1.12 and 1.03%, respectively. With respect to biomass, the highest proportion belonged to barb (27.33%), followed by bleak, common bream and ide with 20.41, 12.48 and 11.10%. Two non-indigenous fish species were re-

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

Table 4. Stocking level, angling yield and rate of return (ind.) for the Dyje 2 (D2) and Morava 2 (M2) fishing grounds between 2006 and 2010. Note: *Herbivorous fish = grass carp, Ctenopharyngodon idella; silver carp, Hypophthalmichthys molitrix; bighead carp, Aristichthys nobilis. **Others = (R. rutilus, S. erythrophthalmus, G. cernuus, C. auratus gibelio, C. carassius, A. alburnus, L. idus and rarely others)

Species E. lucius C. carpio T. tinca A. brama L. cephalus B. barbus C. nasus V. vimba *Herbivorous fish A. aspius P. fluviatilis S. lucioperca S. glanis A. anguilla L. lota **Others TOTAL

Stocking rate individuals kg D2 M2 D2 M2 181 282 15 67 885 897 670 772

2,420 1,000 1,800 1,500

920

25 10 18 15

10

680

7

2210 463

22 10

2040 200

62 20

corded – Prussian carp and tubenose goby. The F/C ratio of the whole fish community corresponded to 3.40 in the surveyed stretch of the Dyje River.

Angling yield Both stretches, belonging to angling grounds of the Moravian Angling Union, are regularly stocked with commercial and game fish species. Common carp (2+ category) dominate with respect to stocking biomass. Carp average rates of return amount to 13.6 and 18.5% in the Dyje 2 and Morava 2 angling grounds, respectively. Predatory fish (pike, zander, Sander lucioperca, European catfish, Silurus glanis, asp) are usually released as 0+ age category, however, their rates of return do not exceed 10% (Table 4).

Game fish (chub, barb, nase, burbot, Lota lota, and others) are also stocked for the angling purposes but their rates of return range just below 1%.

On average, altogether 489 fish (862 kg) are caught each year by anglers in the Dyje 2 angling ground, whilst in the Morava 2 angling ground these figures are twice as high (835 fish/1737 kg) (Table 4). Carp dominate in biomass comprising 49.0 and 40.4% of the total angling yield in the Dyje 2 and Morava 2, respectively. Despite low numbers of European catfish caught by anglers (12 and 30 individuals in Dyje 2 and Morava 2, respectively), their respective angling yield biomass is the second highest with 147 and 247 kg, which corresponds to the mean individual weight of 12.25 and 8.23 kg.

individuals D2 M2 12 26 120 166 1 1 67 87 6 24 8 71 6 3 4 28 6 32 3 3 35 39 12 30 <1 6 <1 7 216 308 489 835

Angling yield kg rate of return (%) D2 M2 D2 M2 32 61 6.6 9.2 422 702 13.6 18.5 2 1 46 73 22 19 0.2 17 133 0.8 7.7 6 <0.05 3 <0.05 34 217 12 59 4.7 1 1 94 74 1.8 147 247 6.5 <1 4 <1 6 0.3 50 130 154.0 862 1737

DISCUSSION Benthic macroinvertebrates Benthic macroinvertebrates have various functions in aquatic ecosystems. Analyses of some of them (e.g. an assessment of production or suitability as fish food) are difficult to evaluate without extensive quantitative data. This type of data is, however, not available. On the other hand, semiquantitative or sometimes even qualitative data generally can be exploited for bioindication and/or ecological status assessment. Also long-term changes of biotopes can be detected via comparison of taxonomic or functional structure of benthic assemblages. Nevertheless, sampling difficulties and incomplete ecological status assessment system of the Czech potamal rivers rather limited the exploration of accessible data.

The total number of taxa of certain localities is one of very simple biodiversity measures, assuming the comparable data sources. In the comparison of evaluated river stretches, the number of taxa of the Dyje River is nearly twice as that of the Morava River (262 and 137 taxa, respectively). However, the high number of taxa found at the Dyje River originated from a very precise investigation (Horsák, 2001). No such extensive and detailed study was performed at the Morava River. After excluding results of that study, the total number of taxa of the Dyje River 101

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

was evidently lower (188). The total numbers of taxa found at both stretches in 2007 (monitoring of the Morava River Authority and JDS2 results) were nearly the same (105 and 108 taxa). The comparison of numbers of taxa between periods is possible taking into account that especially in the 1st period only the riffle parts of both rivers were sampled, so lower numbers of taxa within the period of 1976-1995 are caused by a specific sampling method, as well as a higher level of anthropogenic disturbances, especially organic pollution. The decrease of this type of pollution, especially disappearing of autumn peaks caused by sugar mill campaigns, leads to partial benthic macroinvertebrate assemblage reconstruction during the subsequent period (after 1995). The occurrence of species with higher proportion of preferences to oligosaprobity was found in detailed analyses of spring samples (2007) in the Dyje River.

It is probably caused by rhithralisation (montanisation) of river stretches below large impoundments - reservoirs on the Dyje River and their tributaries, which partially changed character of rivers, mainly their temperature regime. The results correspond with a higher proportion of rhithral species in the Dyje River than in the Morava River.

The recovery of the river stretches was limited to the organic pollution decrease. No radical improvement of hydromorphological status has been performed and habitat diversity is still lost.

The environment is unfavourable for species with special habitat requirements like burrowing larvae (e.g. mayfly Ephoron virgo). Very sensitive, rare and strictly potamal species such as Isonychia ignota and Choroterpes picteti are probably extinct in the area studied hence the re-occurrence of such species at the localites studied is very unlikely. The ratio of expected, typical potamal species and species observed in the spring season of 2007 (cf. Table 2) was very similar at both samples.

The presence of non-indigenous species is relatively low, both qualitatively and quantitatively, but the occurrence of invasive amphipods is expected in the near future because they are present in the near downstream stretch of the Morava and Dyje Rivers (Mišíková-Elexová et al., 2010). It is a paradox that the snail Lithoglyphus naticoides, which is considered as an invasive species according to the results of the project ALARM (Panov et al., 2008), is mentioned as endangered species in the Czech Red List (Farkač et al., 2005).

Summarised, the Morava and Dyje river stretches under study evinced similar character and history of disturbances. The Dyje River macroinvertebrate assemblages are more influenced by a high number of reservoirs within the basin, the Morava 102

River assemblages were periodically destroyed by organic pollution in the past. Both rivers are influenced by changed river morphology. The species composition, regardless of the occurrence of some less sensitive potamal or IUCN category species, corresponds to the list of respective river type expected species only partially.

Fish In lowland rivers and their floodplains, it is always problematic to find methods that provide accurate estimates of fish communities. For example, representative sampling of adult fish in larger lowland rivers is almost impossible. Since all Czech streams are managed as angling grounds, they have been regularly stocked with fish from aquaculture since the middle of the 20th century. However, ichthyological surveys proved that the key driver to formation and sustainability of original appropriate composition of riverine fish communities (particularly in lowland rivers) is their natural recruitment (Jurajda et al., 2010). In the lowest stretches of the Morava and Dyje rivers, fish originating from the natural recruitment made the vast majority of the density and biomass (Jurajda, 1995, 1999; Jurajda and Peňáz, 1994, 1996; Jurajda et al., 2000, 2001).

Altogether 24 fish species and 1 hybrid (R. rutilus x B. bjoerkna) were recorded in the Morava river section in the JDS2 survey campaign in 2007. Despite one-time survey, the number of species recorded is almost identical with the monitoring performed by Jurajda et al. (1998) who identified 26 species from 5 families in a four-year (1991-1994) survey below and within a rocky chute on the Morava River, the upper boarder-line site of the section surveyed in 2007. In opinion of Jurajda et al. (2008), fish species richness in the Morava River increased continuously over the years 1990-2000 as a result of substantial improvement of water quality and almost reached the situation that existed 100 years ago. The up-todate assessment of the fish assemblage composition in the Morava River section under study presented 35 fish species in 1994, of which 23 were identical and one species (tubenose goby) was new. Fish assemblage composition comprising 26 species with the same species (chub and gudgeon Gobio gobio) dominating before and after the flood was recorded

by Jurajda et al. (2006). According to their survey, exceptionally extensive flood in July 1997 with water discharge peaking at 2000% of long-term average and discharge >1000 m3.sec-1 lasting for 20 days had a minor effect on the assemblage structure.

Bleak was by far the most abundant fish in both surveyed river sections. Despite its high abundance

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

amounting to 75.02 and 83.70% in the Morava and Dyje rivers, respectively, its respective contribution to the total fish biomass was quite low and corresponded to 16.11 and 20.41%. According to the survey performed by Sindilariu et al. (2006) in the Danube Delta, bleak and monkey goby (Neogobius fluviatilis) were most abundant and frequent, contributing together 61% to the total catch. Despite the fact that the rip-rap banks provide mesohabitat favored by gobids, their occurrence in this type of the Morava River bank armoring shoreline against water erosion was very rare in the survey monitoring in 1997 and actually it was limited just to sporadical record of tubenose goby individuals. Obviously, the efficiency of electrofishing in sampling gobids is quite low (Polacik et al., 2008) but their occurrence in interstitial rip-rap spaces was not very frequent anyhow. Currently, both tubenose goby and round goby (Neogobius melanostomus) are a regular part of fish assemblages both in the lower Morava and Dyje rivers, despite appearring there for the first time only in 1996 (tubenose goby, Prášek and Jurajda, 2005) and 2008 (round goby, Lusk et al., 2010), respectively.

Jurajda and Peňáz (1994) described fish community structure in the lower stretch of the Morava River in 1991-1992, ten years after the completion of regulation. Species richness and diversity depended mainly on the connectivity of the regulated section with a more natural section below the studied stretch. Bitterling, bleak, gudgeon, chub, roach and white-finned gudgeon were the most abundant species in all sections of the regulated main channel, with phytophilous species occurring in very low densities. They reported 27 fish species recorded in the section identical with our survey. Similarly, Valová et al. (2006) compared the 0+ fish communities in the regulated-channelized Morava River stretch without connection to the floodplain with non-interrupted stretches of the Morava and Dyje rivers connected with floodplains. Surprisingly, the total number of 0+ fish species in all of the three stretches recorded over three years was similar (22, 23, and 25 species, respectively), lowest diversity and highest density being documented in the regulated-channelized stretch.

In the Morava and Dyje river sections under study, also several rare and/or protected species were recorded. Two of them, ide and burbot belong among vulnerable fish species and four others, white-eye bream (Abramis sapa), striped ruffe (Gymnocephalus schraetser), streber (Zingel streber) and zingel (Zingel zingel) are considered as critically endangered species. Due to regular stocking into these two and associated angling grounds, ide and

burbot occur quite regularly in the fish assemblages of the lower Morava and Dyje rivers and recently they have even been included into the list of fishes allowed for taking into possession in angling. The occurrence of streber on the Morava-Dyje confluence was recorded for the first time again after almost a century in 2003 (Lusk et al., 2004).

The proportion of non-predatory to predatory fish biomass (F/C ratio) is a simple expression of the balance in a particular fish community (Holčík and Hensel, 1972). Values for the F/C ratio between 3.0 and 6.0 indicate optimal values, whilst values >10 demonstrate undesirable condition of fish community with strong prevalence of non-predatory fish.

The F/C ratio of the whole fish community in the surveyed stretch of the Morava River corresponded to 4.24 which is considered as a value within the optimal range. However, when excluding (rather) omnivorous chub from predatory species, its value increases to 7.87, which is already above the upper limit value of the optimal range 3.0 – 6.0 (Holčík and Hensel, 1972). In the Dyje River, the FC values amounted to 3.40 in the total community evaluation but when not considering omnivorous chub and ide as predators, it raised to 8.93 which is also above the upper limit value of the optimal range 3.0 – 6.0.

It is obvious that the latter values reflect the actual situation in equilibrium of the Morava and Dyje fish assemblages more appropriately.

Anglers’ statistics also document a substantial increase in fish catches as a result of considerable water quality improvement in the 90s of the last century (Jurajda et al., 2008). The data presented by Baruš et al. (2000) prove that the anglers´ catches in the lower Morava River (fishing ground Morava 2, 20.0 ha) rose from 23.5 to 131.0 tonnes in 1992 and 1998, respectively. Nevertheless, the rates of return in fish stocked are quite low being highest in carp as common phenomenon in the majority of fishing grounds in the Czech Republic. However, their figures are very low compared with other fishing grounds, probably due to the lotic environment and not easy accessibility (Protected Landscape Area, Czech-Austrian and Czech-Slovak border line rivers). Carp, as by far the most popular fish for Czech anglers, are usually subject to focused angling pressure resulting in considerably higher rates of return – e.g. 58.5% in the Brno reservoir (Adámek and Jurajda, 2011) or even 92.4% in the Svitava 1 angling ground located largely on the territory of the Brno City (http://brno3.momrs.cz/prehledy-ulovku). The rates of return are quite low also in predatory and game fish. Regarding predatory fishes, the reason for low rates of return is small fish size at stocking and poor accessibility of angling loca103

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

tions. Extremely low rates of game fish return are moreover caused by quite rare focus of anglers and widely applied catch-and-release approach regarding these species.

The area of the Morava – Dyje confluence represents a unique natural environment of floodplain forest and wetland meadows. The noticeable improvement of water environmental conditions particularly in the last two decades, however, concerned almost exclusively just the water quality issues, the physical habitat degradation (river channelization, limited connectivity with side arms and oxbow lakes) being de facto unchanged. As a consequence of improved water quality, the diversity of benthic macroinvertebrate and fish assemblages has been considerably increased. Thus, continuous monitoring of this area of interest is highly desired and worthwhile also in the future.

Acknowledgement The study was supported by projects MZP0002071101 (Research and Protection of Hydrosphere – research of relationships and processes in water component of the environment, focused on the impacts of human pressures, sustainable use and protection of the hydrosphere and related legislative tools) from the Czech Ministry of Environment and P505/12/G112 from the Grant Agency of the Czech Republic.

Sažetak UTJECAJ ČOVJEKA NA MAKROZOOBENTOS I IHTIOFAUNU NA DONJIM TOKOVIMA RIJEKA MORAVE I DYJE (SLIV RIJEKE DUNAVA U ČEŠKOJ) Donja Morava i rijeka Dyje pripadaju velikim nizinskim rijekama na jugoistoku Češke Republike te se 69 km nizvodno od svog ušća ulijevaju u rijeku Dunav. Unatoč njihovoj značajnoj prirodnoj vrijednosti i zaštiti okoliša, obje rijeke pretrpjele su teško zagađenje od 60-ih do 80-ih godina prošlog stoljeća.

Značajan napredak kvalitete njihove vode u posljednja dva desetljeća rezultirao je djelomičnim oporavkom makrozoobentosa i ihtiofaune. Nedavno je zabilježeno ukupno 262 taksona makrozoobentosa u rijeci Dyje te 137 taksona u rijeci Moravi. U rijeci Dyje pronađene su 3 nove i 21 ugrožena vrsta beskralježnjaka (prema IUCN kategorijama), a u rijeci Moravi pronađene su 2 nove i 10 ugroženih vrsta. Rijeka Dyje ima 23, a rijeka Morava 24 vrste te se tom broju pridodaje po jedna hibridna vrsta u objema rijekama, dok je obična uklija najza104

stupljenija riba. U dijelu istraživanja također je zabilježeno nekoliko rijetkih i/ili zaštićenih vrsta.

Dvije vrste, jez (Leuciscus idus) i manjić (Lota lota) spadaju u ugrožene vrste riba, a ostale četiri, crnooka deverika (Abramis sapa), prugasti balavac (Gymnocephalus schraetser), mali vretenac (Zingel streber) i veliki vretenac (Zingel zingel) smatraju se kritično ugroženim vrstama. Donjim tokovima rijeka Morave i Dyje trenutno prijeti invazija okrugle glavuče, Neogobius melanostomus.

Ključne riječi: makrozoobentosi, riba, raznolikost, zagađenje rijeke, riječni propisi, zajedničko ispitivanje sastava rijeke Dunava

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Mlíkovský, J., Stýblo, P. (eds) (2006): Nonindigenous species of fauna and flora of the Czech Republic. (Nepůvodní druhy fauny a flóry České republiky). ČSOP, Praha, 496 pp. (In Czech) Opravilová, V., Vaňhara, J., Sukop, I. (1999): Aquatic invertebrates of the Pálava Biosphere Reserve of UNESCO. Folia Facultatis .Scientiarum Naturalium Universitatis Masarykianae Brunensis, Biologia, 101, 279 pp.

Panov, V. E., Alexandrov, B., Arbaciauskas, K., Binimelis, R., Copp, G. H., Faunus, D., Gozlan, R. E., Grabowski, M., Lucy, F., Leuven, R. S. E. W., Mastitsky, S., Minchin, D., Monterroso, I., Nehring, S, Olenin, S., Paunović, M., RodriguezLabajos, B., Semenchenko, V., Son, M. (2008): Interim protocols for risk assessment of aquatic invasive species introductions via European inland waterways. Project ALARM - Assessing LArge scale environmental Risks for biodiversity with tested Methods. Deliverable 4.1.3.10, Annex 6: Invasive Alien Species (IAS) as significant water management issue for Danube River basin.

Peňáz, M., Jurajda, P. (1993): Fish assemblages of the Morava River – longitudinal zonation and protection. Folia Zoologica, 42, 4, 317-328.

Polacik, M., Janac, M., Jurajda, P., Vassilev, M., Trichkova, T. (2008): The sampling efficiency of electrofishing for Neogobius species in a riprap habitat: a field experiment. Journal of Applied Ichthyology, 24, 5, 601-604.

Prášek, V., Jurajda, P. (2005): Expansion of Proterorhinus marmoratus in the Morava river basin (Czech Republic, Danube R. watershed).

Folia Zoologica, 54, 1-2, 189-192.

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Schöll, F., Haybach, A., König, B. (2005): Das erweiterte Potamontypieverfahren zur ökologischen Bewertung von Bundeswasserstraßen (Fließgewässertypen 10 und 20: kies- und sandgeprägte Ströme, Qualitätskomponente Makrozoobenthos) nach Maßgabe der EUWasserrahmenrichtlinie.

Hydrologie und Wasserwirtschaft, 49, 5, 234-247.

Sindiliaru, P. D., Freyhof, J., Wolter, C. (2006): Habitat use of juvenile fish in the lower Danube and the Danube Delta: implications for ecotone connectivity. Hydrobiologia, 571, 51-61.

Schomaker C., Wolter C. (2011): The contribution of long-term isolated water bodies to flood106

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Soldán, T., Zahrádková, S., Helešic, J., Dušek, L., Landa, V. (1998): Distributional and quantitative patterns of Ephemeroptera and Plecoptera in the Czech Republic: a possibility of detection of long-term environmental changes of aquatic biotopes. Folia Facultatis .Scientiarum Naturalium Universitatis Masarykianae Brunensis, Biologia, 98, 305 pp.

Valová, Z., Jurajda, P., Janáč, M. (2006): Spatial distribution of 0+ juvenile fish in differently modified lowland rivers. Folia Zoologica, 55, 3, 293-308.

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Zahrádková, S., Opatřilová, L., Tajmrová, L., Kvardová, H., Marvan, P., Heteša, J., Grulich, V., Slavík, O., Horký, P. (2007): Stanovení referenčních podmínek ekologického stavu povrchových tekoucích vod pro potřeby implementace Směrnice 2000/60/ES v ČR. Zpráva pro MŽP ČR. (In Czech) Zavřel, J. (1905): Palingenia longicauda from Moravia.

(Palingenia longicauda z Moravy). Časopis Československé společnosti entomologické, 2, 97-98. (In Czech) Zavřel, J. (1934): Zoological memories from Hodonín (Zoologické vzpomínky na Hodonín).

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Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

Appendix 1. List of macroinvertebrate taxa recorded at the Morava River stretch upstream of the confluence with the Dyje River Taxon

Dugesia tigrina (Girard, 1850) Nematoda g. sp. div.

Bithynia tentaculata (Linnaeus, 1758) Galba truncatula (O. F. Müller, 1774) Radix auricularia (Linnaeus, 1758) Unio pictorum (Linnaeus, 1758) Pisidium sp.

Pisidium henslowanum (Sheppard, 1823) Pisidium supinum A. Schmidt, 1851 Dreissena polymorpha (Pallas, 1771)*3 Nais sp.

Nais behningi Michaelsen,1923 Tubificidae gen. sp.

Bothrioneurum vejdovskyanum Štolc, 1886 Tubifex sp.

Tubifex tubifex (O. F. Műller, 1773) Psammoryctides barbatus (Grube, 1861) Limnodrilus sp.

Limnodrilus claparedeanus Ratzel, 1868 Limnodrilus hoffmeisteri Claparède, 1862 Eiseniella tetraedra (Savigny, 1826) Propappus volki Michaelsen, 1905 Glossiphonia complanata (Linné, 1758) Helobdella stagnalis (Linné, 1758) Piscicola geometra (Linné, 1758) Erpobdella sp.

Erpobdella nigricollis (Brandes, 1900) Erpobdella octoculata (Linné, 1758) Erpobdella testacea (Savigny, 1822) Acari, Acarina Asellus aquaticus (Linné, 1758) Gammarus fossarum Koch, 1836 Gammarus roeselii Gervais, 1835 Baetis sp.

Baetis fuscatus (Linné, 1761) Baetis rhodani Pictet, 1843 - 1845 Baetis scambus Eaton, 1870 Baetis vernus Curtis, 1834 Cloeon dipterum s. lat. (Linné, 1761) Procloeon bifidum (Bengtsson, 1912) Procloeon ornatum Tshernova, 1928 Baetopus tenellus (Alabarda, 1878) Heptagenia sp.

Heptagenia coerulans Rostock, 1877 Heptagenia flava Rostock, 1877 Heptagenia sulphurea (Mueller, 1776) Potamanthus luteus (Linné, 1767)

IUCN categories

NT

NT CR EN

Data sources Periods of research (year) without time 1976-1995 1996- 2006 2007 specification 4 4 1,2 4 7 1 1 4 4 4 4 2 4 4 4 2 4 1 2 4,7 4,7 1 4,7 1 4,7 2 4 2 4 1 1 1 1,2 1 1,2 1 4,7 1,2 1 4 1,2 1 1 1 1,4 1,2 4 1 4,7 1,2 8 1 8 1 1,4 1 4 7 4 4 1 1 2 1 1,4 8 1 1 4 8

107

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

Appendix 1. Continued Taxon

Caenis sp.

Caenis horaria (Linné, 1758) Caenis luctuosa (Burmeister, 1839) Caenis macrura Stephens, 1835 Caenis pseudorivulorum Keffermueller, 1960 Calopteryx splendens (Harris, 1782) Platycnemis pennipes (Pallas, 1771) Gomphidae g. sp.

Gomphus vulgatissimus (Linnaeus, 1758) Ophiogomphus cecilia (Fourcroy, 1785) Leuctra sp.

Micronecta sp.

Sigara striata (Linnaeus, 1758) Aphelocheirus aestivalis (Fabricius, 1794) Sialis lutaria (Linné, 1758) Rhyacophila nubila (Zetterstedt, 1840) Hydroptila sp.

Hydroptila sparsa Curtis, 1834 Hydropsyche sp.

Hydropsyche angustipennis (Curtis, 1834) Hydropsyche bulgaromanorum Malicky, 1977 Hydropsyche contubernalis McLachlan, 1865 Hydropsyche exocellata Dufour, 1841 Hydropsyche modesta Navas, 1925 Hydropsyche pellucidula (Curtis, 1834) Neureclipsis bimaculata (Linné, 1758) Ecnomus tenellus (Rambur, 1842) Athripsodes sp.

Athripsodes cinereus (Curtis, 1834) Ceraclea annulicornis (Stephen, 1836) Ceraclea dissimilis (Stephens, 1836) Oecetis sp.

Oecetis notata (Rambur, 1842) Hexatoma sp. Latreille, 1809 Hexatoma bicolor (Meigen, 1818) Tipula sp.

Chironomidae g. sp. div.

Conchapelopia sp.

Natarsia sp.

Procladius (Holotanypus) sp.

Thienemannimyia sp.

Cricotopus sp.

Cricotopus bicinctus-Gr. Cricotopus sylvestris-Gr. Cricotopus tibialis (Meigen, 1804) Cricotopus tremulus-Gr. Eukiefferiella sp.

Metriocnemus sp.

108

IUCN categories

VU EN

VU

VU

Data sources Periods of research (year) without time 1976-1995 1996- 2006 2007 specification 7 4 8 4 1 4,7 4,7 4 8 4 4 1 4 4,7 4 4 1 4,7 4 4 4 4 2 1 1,4 1,2 4 4 1,2 1 1,4 8 4 1,2 1 4 8 1 4,7 4 4 4 4 4 4 4 4,7

EN 4 4.7 4 4 7 7 4 4 1,2 2 4 4 2

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

Appendix 1. Continued Taxon

Nanocladius bicolor (Zetterstedt, 1838) Orthocladius sp.

Rheocricotopus fuscipes (Kieffer, 1909) Tvetenia calvescens (Edwards, 1929) Cladopelma sp.

Cryptochironomus sp.

Cryptochironomus defectus (Kieffer, 1913) Dicrotendipes nervosus (Staeger, 1839) Glyptotendipes sp.

Glyptotendipes cauliginellus (Kieffer, 1913) Chironomus plumosus-Gr. Chironomus reductus-Gr. Chironomus thummi-Gr. Microtendipes chloris (Meigen, 1818) Microtendipes chloris-Gr. Parachironomus sp.

Parachironomus varus (Goetghebuer, 1921) Polypedilum aegyptium Kieffer, 1925 Polypedilum convictum-Gr. (Goetghebuer, 1931) Polypedilum cultellatum (Kieffer, 1916) Polypedilum nubeculosum-Gr. Polypedilum scalaenum-Gr. Robackia demeijerei (Kruseman, 1933) Stictochironomus sp.

Cladotanytarsus sp.

Cladotanytarsus mancus (Walker, 1856) Cladotanytarsus vanderwulpi-Gr. Micropsectra junci (Meigen, 1818) Rheotanytarsus sp.

Tanytarsus sp.

Tanytarsus brundini/curticornis Pseudorthocladius sp.

Simulium sp.

Simulium equinum (Linnaeus, 1758) Simulium erythrocephalum (De Geer, 1776) Simulium galeratum Carlsson, 1962 Simulium ornatum Meigen, 1818 Simulium paramorsitans Rubtsov, 1956 Atrichops crassipes (Meigen, 1820) Chrysopilus erythrophthalmus Loew, 1840 Chrysops sp.

Hemerodromia sp.

Limnophora sp.

IUCN categories

VU

Data sources Periods of research (year) without time 1976-1995 1996- 2006 2007 specification 4 1 4 4 4 4 7 1,2 7 4 2 7 4 1,2 2 1 7 4 1,2 7 1,2 7 7 2 4,7 4 4 4,7 2 7 7 1 2 7 7 2 4 4 4 4 1,2 1 4 4 4 4 4 4

Legend: IUCN categories: according to Farkač et al. 2005 (RE - regionally extinct, CR - critically endangered, EN - endangered, VU vulnerable, NT - near threatened); non indigenous species: * - according to Mlíkovský and Stýblo (2006), 1,2,3 Panov et al. (2008); data sources: 1 - saprobiological monitoring of the TGM WRI TGM Brno, 2 - monitoring within the Morava River Project, 3 - monitoring of transboundary rivers (TGM WRI Brno), 4 - monitoring of the Morava River Authority, 5 - collection of the Dept. of Botany and Zoology Masaryk University Brno, 6 - Horsák (1999), 7 - JDS2 results, 8 - Opravilová et al. (1999).

109

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Appendix 2. List of macroinvertebrate taxa recorded at the Dyje River stretch upstream of the confluence with the Morava River Taxon

IUCN categories

Data sources 19761995

Ephydatia fluviatilis (Linnaeus, 1758) Spongilla lacustris (Linnaeus, 1758) Dugesia polychroa (O. Schmidt, 1861) Dugesia tigrina (Girard, 1850) Nematoda g. sp. div.

Potamopyrgus antipodarum (Gray, 1843)*3 Lithoglyphus naticoides (C. Pfeiffer, 1828)3 Bithynia tentaculata (Linnaeus, 1758) Valvata piscinalis (O. F. Müller, 1774) Galba truncatula (O. F. Müller, 1774) Radix sp.

Radix auricularia (Linnaeus, 1758) Radix ovata (Draparnaud, 1805) Ancylus fluviatilis O. F. Müller, 1774) Physella acuta (Draparnaud, 1805) Unio crassus Philipsson, 1788) Unio pictorum (Linnaeus, 1758) Unio tumidus Philipsson, 1788) Anodonta anatina (Linnaeus, 1758) Anodonta cygnea (Linnaeus, 1758) Pseudanodonta complanata (Rossmaessler, 1835) Sphaerium sp.

Sphaerium corneum (Linnaeus, 1758) Sphaerium rivicola (Lamarck, 1818) Musculium lacustre (O. F. Müller, 1774) Pisidium sp.

Pisidium casertanum (Poli, 1791) Pisidium henslowanum (Sheppard, 1823) Pisidium nitidum Jenyns, 1832 Pisidium subtruncatum Malm, 1855 Pisidium supinum A. Schmidt, 1851 Dreissena polymorpha (Pallas, 1771)*3 Chaetogaster sp.

Chaetogaster diastrophus (Gruithuisen, 1828) Ophidonais serpentina (O.F. Műller, 1773) Nais sp.

Nais alpina Sperber, 1948 Nais barbata O. F. Műller, 1773 Nais behningi Michaelsen,1923 Nais bretscheri Michaelsen, 1899 Nais communis Piguet, 1906 Nais elinguis O. F. Műller, 1773 Nais pseudoobtusa Piguet, 1906 Nais simplex Piguet, 1906 Nais variabilis Piguet, 1906 Slavina appendiculata (Udekem, 1855) Stylaria lacustris (Linné, 1767)

110

EN 1

EN VU VU EN

NT

NT

EN

Periods of research (year) 1996without time 2007 2010 2006 specification 6 8 6 8 1,2,6 3 1.2 7 3 4 3 1.2 1,2,6 3 8 1,2,6 4.7 3 8 6 8 2.6 4.7 3 6 7 3 3 8 1,2,6 4 8 6 4.7 3 8 6 8 6 8 1,2,6 8 6 8 6 8 6 8 4 1,2,6 4 8 4 2 1.2 4 3 4 6 7 3 8 6 6 3 8 6 4.7 3 4 8 3 6 8 1,2,6 4 3 8 3 1,2,6 8 6 6 8 6 4 8 6 7 8 6 4 8 6 8 6 8 6 3 1.6 4 3 8

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

Appendix 2. Continued Taxon

IUCN categories

Data sources 19761995

Dero digitata (O. F. Műller, 1773) Pristina foreli (Piguet, 1906) Pristinella menoni (Aiyer 1929) Pristinella rosea (Piguet, 1906) Tubificidae g. sp.

Rhyacodrilus coccineus (Vejdovský, 1875) Rhyacodrilus falciformis Bretscher, 1901 Bothrioneurum vejdovskyanum Štolc, 1886 Potamothrix hammoniensis (Michaelsen, 1901) Potamothrix moldaviensis Vejdovský-Mrázek, 1902 Tubifex ignotus (Štolc, 1886) Tubifex tubifex (O. F. Műller, 1773) Spirosperma ferrox (Eisen, 1879) Psammoryctides albicola (Michaelsen, 1901) Psammoryctides barbatus (Grube, 1861) Limnodrilus sp.

Limnodrilus claparedeanus Ratzel, 1868 Limnodrilus hoffmeisteri Claparcde, 1862 Limnodrilus udekemianus Claparcde, 1862 Criodrilus lacuum Hoffmeister, 1845 Eiseniella tetraedra (Savigny, 1826) Propappus volki Michaelsen, 1905 Enchytraeidae g.. sp.

Enchytraeus sp.

Stylodrilus heringianus Claparcde, 1862 Rhynchelmis limosella Hoffmeister, 1843 Glossiphonia complanata (Linné, 1758) Glossiphonia nebulosa (Kalbe, 1864) Helobdella stagnalis (Linné, 1758) Caspiobdella fadejewi (Epstein, 1961) Piscicola geometra (Linné, 1758) Piscicola respirans Troschel, 1850 Erpobdella sp.

Erpobdella nigricollis (Brandes, 1900) Erpobdella octoculata (Linné, 1758) Erpobdella vilnensis Liskiewicz, 1927 Acari, Acarina Asellus aquaticus (Linné, 1758) Proasellus coxalis Dollfus, 1892* Gammarus roeselii Gervais, 1835 Siphlonurus aestivalis (Eaton, 1903) Baetis buceratus Eaton, 1870 Baetis fuscatus (Linné, 1761) Baetis nexus Navás, 1918 Baetis scambus Eaton, 1870 Baetis vernus Curtis, 1834 Cloeon dipterum s. lat. (Linnaeus, 1761) Heptagenia coerulans Rostock, 1877

1 EN

EN

1

1 1 1

Periods of research (year) 1996without time 2007 2010 2006 specification 6 6 6 6 4 3 6 4 3 6 6 4 3 2.6 4 3 4 6 4 1,2,6 8 1,2,6 4.7 3 4 3 4 6 4 8 4 3 6 4 1.6 4 4 3 4 6 1.2 2 6 8 6 1.6 6 8 1,2,6 4 3 1.2 3 2 8 1,2,6 4 3 8

1,2,6 6

4

3 3 3

1

8 8 8

6 1 1 VU

EN

8 4.7

3

6 5 1 1 1

6 6

7

8

111

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

Appendix 2. Continued Taxon

Heptagenia flava Rostock, 1877 Heptagenia sulphurea (Mueller, 1776) Potamanthus luteus (Linné, 1767) Caenis sp.

Caenis horaria (Linné, 1758) Caenis luctuosa (Burmeister, 1839) Caenis macrura Stephens, 1835 Caenis pseudorivulorum Keffermueller, 1960 Caenis robusta Eaton, 1884 Calopteryx splendens (Harris, 1782) Calopteryx virgo (Linnaeus 1758) Platycnemis pennipes (Pallas, 1771) Coenagrion puella (Linnaeus, 1758) Ischnura elegans (Vander Linden, 1820) Gomphus flavipes (Charpentier, 1825) Gomphus vulgatissimus (Linnaeus, 1758) Onychogomphus forcipatus (Fourcroy, 1785) Ophiogomphus cecilia (Fourcroy, 1785) Nepa cinerea Linnaeus, 1758 Micronecta sp.

Micronecta scholtzi (Fieber, 1860) Sigara sp.

Sigara falleni (Fieber, 1848) Sigara lateralis (Leach, 1817) Sigara striata (Linnaeus, 1758) Ilyocoris cimicoides (Linnaeus, 1758) Aphelocheirus aestivalis (Fabricius, 1794) Plea minutissima Leach, 1817 Hydrometra stagnorum (Linnaeus, 1758) Aquarius paludum (Fabricius, 1794) Gerris lacustris (Linnaeus, 1758) Sialis lutaria (Linné, 1758) Haliplus sp. Ad. Haliplus sp. Lv. Haliplus fluviatilis Lv. Aubé, 1836 Hydroglyphus geminus Ad. (Fabricius, 1792) Laccophilus sp. Ad. Laccophilus hyalinus Lv. (De Geer, 1774) Platambus maculatus Lv. (Linné, 1758) Orectochilus villosus Lv. (O. F. Müller, 1776) Helophorus sp. Ad. Hydrobius fuscipes Lv. (Linné, 1758) Limnoxenus niger Lv. (Zschach, 1788) Laccobius minutus Lv. (Linné, 1758) Berosus signaticollis Lv. (Charpentier, 1835) Hydrochara flavipes Ad. (Steven, 1808) Scirtes sp. Lv. Oulimnius tuberculatus Ad. (P. W. J. Müller, 1806)

112

IUCN categories

Data sources 19761995 1 1 5

1

Periods of research (year) 1996without time 2007 2010 2006 specification 2 4.7 3 1,2,6 6 6 1,2,6

4.7

4 4 7

3 3

8

3 3

8

3

8

3

8 8

6 1 2.6 6 6 6 1,2,6 1.2

EN VU EN EN

4

3 7

6

8 4

3

6

8 3

VU

1

6 6 6 6 1,2,6 1.2 6 6 6 6

3 3 4.7

3

3

3 4 6 6 3 6 6 1.2

4 4

NT

6 6 6 6 3 6 3

8 8 8 8 8 8 8 8

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

Appendix 2. Continued Taxon

IUCN categories

Data sources 19761995

Hydroptila sp.

Hydropsyche sp.

Hydropsyche angustipennis (Curtis, 1834) Hydropsyche bulgaromanorum Malicky, 1977 Hydropsyche contubernalis McLachlan, 1865 Hydropsyche modesta Navas, 1925 Hydropsyche pellucidula (Curtis, 1834) Neureclipsis bimaculata (Linné, 1758) Plectrocnemia conspersa (Curtis, 1834) Ecnomus tenellus (Rambur, 1842) Anabolia furcata Brauer, 1857 Athripsodes bilineatus (Linné, 1758) Athripsodes cinereus (Curtis, 1834) Ceraclea annulicornis (Stephen, 1836) Ceraclea dissimilis (Stephens, 1836) Mystacides nigra (Linné, 1758) Oecetis sp.

Oecetis notata (Rambur, 1842) Oecetis ochracea (Curtis, 1825) Oecetis tripunctata (Fabricius, 1793) Setodes punctatus (Fabricius, 1793) Hexatoma sp, Neolimnomyia nemoralis (Meigen, 1818) Pilaria discicollis (Meigen, 1818) Ellipteroides alboscutellatus (Roser, 1840) Erioptera sp.

Rhypholophus haemorrhoidalis (Zetterstedt, 1838) Scleroprocta sp. Edwards, 1938 Antocha vitripennis (Meigen, 1830) Dicranomyia modesta (Meigen, 1818) Tipula sp.

Tipula lateralis Meigen, Jungiella sp.

Psychoda sp.

Culex pipiens pipiens Linné, 1758 Ceratopogonidae g. sp.

Probezzia seminigra (Panzer, 1796) Mallochohelea setigera (Loew, 1864) Dasyhelea modesta (Winnertz, 1852) Chironomidae g. sp.

Conchapelopia sp.

Macropelopia nebulosa (Meigen, 1804) Procladius sp.

Procladius (Holotanypus) sp.

Thienemannimyia sp.

Diamesa sp.

Potthastia longimana (Kieffer, 1922) Prodiamesa olivacea (Meigen, 1818)

1

CR RE

1

Periods of research (year) 1996without time 2007 2010 2006 specification 6 4 3 1 7 3 1,2,6 4 8 6 3 1,2,6 4.7 3 8 1,2,6 4.7 3 1.2 1,2,6 4.7 3 8 1.2 1.2 4 1,2,6 4 3 8 1.2 4 3 8 1.2 6 4 3 6 3 2 4 3 6 3 4.7 1.2 4.7 3 6 6 7 7 6 1.2 2 6 4.7 3 6 7 6 6 6 2 6 6 6 4.7 3 4 3 6 1,2,6 3 6 7 1,2,6 1 6

113

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adรกmek et al.: Zoobenthos and fish of lower Morava and Dyje

Appendix 2. Continued Taxon

IUCN categories

Data sources 19761995

Cardiocladius fuscus Kieffer, 1924 Corynoneura celeripes Winnertz, 1852 Cricotopus sp.

Cricotopus albiforceps (Kieffer, 1916) Cricotopus bicinctus-Gr. Cricotopus patens Hirvenoja, 1973 Cricotopus sylvestris-Gr. Cricotopus tremulus (Linnaeus, 1758) Cricotopus tremulus-Gr. Metriocnemus sp.

Nanocladius bicolor (Zetterstedt, 1838) Orthocladius sp.

Orthocladius rubicundus (Meigen, 1818) Orthocladius wetterensis Brundin, 1956 Rheocricotopus chalybeatus (Edwards, 1929) Rheocricotopus fuscipes (Kieffer, 1909) Synorthocladius semivirens (Kieffer, 1911) Tvetenia sp.

Tvetenia calvescens (Edwards, 1929) Tvetenia discoloripes (Goetghebuer in Thienemann, 1936) Cryptochironomus sp.

Cryptochironomus defectus (Kieffer, 1913) Dicrotendipes sp.

Einfeldia gr. pectoralis Glyptotendipes sp.

Glyptotendipes cauliginellus (Kieffer, 1913) Glyptotendipes palens Harnischia sp.

Harnischia fuscimana Kiefffer, 1921 Chironomus sp.

Chironomus plumosus-Gr. Chironomus reductus-Gr. Chironomus riparius Meigen, 1804 Microtendipes chloris-Gr. Microtendipes pedellus-Gr. Parachironomus sp.

Parachironomus vitiosus (Goetghebuer, 1921) Phaenopsectra sp.

Phaenopsectra flavipes (Meigen, 1818) Polypedilum sp.

Polypedilum albicorne (Meigen, 1938) Polypedilum cultellatum (Kieffer, 1916) Polypedilum nubeculosum-Gr. Polypedilum scalaenum-Gr. Cladotanytarsus sp.

Cladotanytarsus mancus (Walker, 1856) Cladotanytarsus vanderwulpi-Gr. Micropsectra junci (Meigen, 1818)

114

1

1

Periods of research (year) 1996without time 2007 2010 2006 specification 4 6 6 4 1.2 4.7 4 3 3 4 1.2 4 6 1.2 3 2 6 6 1,2,6 4 3 6 1,2,6 4 3 1 4 1.2 1.2 7 4 1.2 4 3 6 1.2 4 3 6 7 2 6 1.2 7 4 6 6 4.7 3 1.2 1,2,6 3 2 4 6 2 3 3 7 1,2,6 4 1,2,6 4.7 3 1.6 2 4 3 4 3 1

Croatian Journal of Fisheries, 2013, 71, 93-115 Z. Adámek et al.: Zoobenthos and fish of lower Morava and Dyje

Appendix 2. Continued Taxon

IUCN categories

Data sources 19761995

Neozavrelia luteola Goetghebuer, 1941 Paratanytarsus sp.

Rheotanytarsus sp.

Tanytarsus sp.

Thienemannia sp. Kieffer, 1909 Saetheria sp.

Simulium sp.

Simulium equinum (Linnaeus, 1758) Simulium erythrocephalum (De Geer, 1776) Simulium galeratum Carlsson, 1962 Simulium lineatum (Meigen, 1804) Simulium ornatum Meigen, 1818 Chrysops sp.

Chrysops caecutiens (Linné, 1758) Atylotus latistriatus (Brauer, 1880) Tabanus sp.

Hemerodromia sp.

Liancalus virens (Scopoli, 1763) Syntormon sp.

Scatella sp.

Lispe sp.

Cristatella mucedo Cuvier, 1798 Paludicella articulata (Ehrenberg, 1831)

1

Periods of research (year) 1996without time 2007 2010 2006 specification 1 1.2 3 1,2,6 3 2.6 4.7 3 1.2 4 1.2 4.7 6 7 4 3 4 4

1 4

3

6

8 3

2 6 6 7 6 7 6 6

Legend: IUCN categories: according to Farkač et al. 2005 (RE - regionally extinct, CR - critically endangered, EN - endangered, VU - vulnerable, NT - near threatened); non indigenous species: * - according to Mlíkovský and Stýblo (2006), 1,2,3 Panov et al. (2008); data sources: 1 - saprobiological monitoring of the TGM WRI Brno, 2 - monitoring within the Morava River Project, 3 - monitoring of transboundary rivers (TGM WRI Brno), 4 - monitoring of the Morava River Authority, 5 - collection of the Dept. of Botany and Zoology, Masaryk University Brno, 6 - Horsák (1999), 7 - JDS2 results, 8 - Opravilová et al. (1999).

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Croatian Journal of Fisheries, 2013, 71, 116-123 S. O. Obasa et al.: Fermented mango seed meal in the diet of Nile tilapia

CODEN RIBAEG ISSN 1330-061X

ORIGINAL SCIENTIFIC PAPER

EVALUATION OF FERMENTED MANGO (Mangifera indica) SEED MEAL IN THE PRACTICAL DIET OF NILE TILAPIA, (Oreochromis niloticus) FINGERLINGS Samuel Olubodun Obasa*1, Segun Peter Alatise2, Isaac Tunde Omoniyi1, Wilfred Olusegun Alegbeleye1, Francisca Adebukola George1 Federal University of Agriculture, Department of Aquaculture and Fisheries Management, P. M. B. 2240, Abeokuta, Ogun State, Nigeria 2 National Institute of Freshwater Research, New Busa, Niger State, Nigeria, Tel. +2348082216684 * Corresponding Author, E-mail: samoluobasa@yahoo.com 1

ARTICLE INFO

ABSTRACT

Received: 27 November 2012 Received in revised form: 19 June 2013 Accepted: 5 July 2013 Available online: 12 July 2013

This study evaluated the use of fermented mango (Mangifera indica) seed meal (FMS) to substitute yellow maize in the practical diet for Nile tilapia, Oreochromis niloticus fingerlings (4.76Âą0.32 g). Five iso-nitrogeneous (35% crude protein) and approximately iso-energetic (3400 ME Kcal/kg) dietsin which yellow maize was replaced by FMSat 0% (FMS0/Control diet), 25% (FMS25), 50% (FMS50), 75% (FMS75) and 100% (FMS100) levels were formulated. The fish were fed on the diets at 5% body weight for 84 days. Alkaloids were highest (2.32%) among the anti-nutritional factors analyzed in FMS, while oxalate (0.84%) was lowest.

Potassium was highest (8.91 mg/g) among the minerals, while copper was lowest (0.01 mg/g). Weight gain, specific growth rate and feed conversion ratio were similar (p>0.05) in fish fed diets FMS0 and FMS50. The fish fed diet FMS0 had the highest protein efficiency ratio (1.88). Protein digestibility decreased (p<0.05) as dietary FMS increased, while carbohydrate digestibility gave an inverse relationship. Results obtained show that FMS could replace yellow maize at 50% level without affecting growth, nutrient utilization and apparent protein digestibility in diets for Nile tilapia fingerlings.

Keywords: Fermentation Mango seed Nutrient digestibility Nile tilapia Anti-nutritional factors

INTRODUCTION Fish culture production is on the increase in developing countries and the problems of the sector include lack of nutritionally balanced and low-cost feeds (Falaye, 1992; Avnimelech et al., 2008). Fish feed accounts for about 60-70% of the variable cost in fish culture. This is due to the high cost of feed ingredients, especially maize which is the conventional source of dietary energy in fish and livestock feeds. Maize is also a staple for humans in many developing countries. In view of the scarcity and escalating costs of most conventional animal feed 116

ingredients, it has become necessary to evaluate alternative nutrient sources to improve aquaculture production.

There have been some researches on various inexpensive agro-industrial by-products as substitutes for maize in fish diets with varying degrees of success. These include water fern (Lemna paucicostata) (Fasakin et al., 2001), duckweed (Azola africana) (Mbagwu et al., 1990; Youssouf et al., 2007), coffee pulp (Ulloa Rojas and Verreth, 2003) and housefly maggot (Ugwumba et al., 2001).

Mango (Mangifera indica), family Anacardiaceae, is high in probiotics, fibre, vitamin C, polyphenols,

Croatian Journal of Fisheries, 2013, 71, 116-123 S. O. Obasa et al.: Fermented mango seed meal in the diet of Nile tilapia

carotenoids and minerals (FAO 2004). The fresh kernel of the mango seed constitutes 13% of the weight of the fruit. After consumption or industrial processing of mangoes, considerable amount of mango kernels (seeds) form the discards as waste.

Waste generated approximates 40 to 60% during processing of mangoes; 12 to 15% consists of peels and 15 to 20% of kernels (Budhwar, 2002).

One of the inexpensive ways to improve the nutritive value of agricultural residues biologically is fermentation. There exists a great potential in the use of microorganisms for the production of high quality feedstuffs from the abundantly available agro-industrial wastes. Mango seed by virtue of its relative low cost and its abundance in many developing nations stands as a suitable substrate for microbial fermentation and protein enrichment (Ubalua, 2007).

Hence, this study evaluates the substitution of yellow maize with fermented mango seed meal on the growth performance and feed utilization of Nile tilapia, Oreochromis niloticus fingerlings.

MATERIALS AND METHODS Experimental fish and system 150 Nile tilapia fingerlings (4.76±0.32 g) were kept in a 250 L fibre tank, fed with a commercial feed twice daily to acclimatize for one week and starved for 24 h before the feeding trial. This was followed by

randomly distributing the fingerlings into five treatments of ten fish each in triplicate and stocked in net hapa (0.5 m x 0.5 m x 1.0 m). The net hapa (15) were suspended in an outdoor concrete tank (8 m x 5 m x 1.5 m) to 75% of their volume with kuralon twine (No. 15) tied to bamboo poles. The concrete tank was filled to 5/6 of its volume (40 m3) and was continually supplied with fresh water to sustain an optimal environment and to preclude primary productivity.

Feed preparation The mangoes used consist of mixed varieties of ripe mangoes obtained locally from a market in New Bussa, Niger state, Nigeria. Next was the removal of seeds from the kernels, washing, sun drying, milling to powder (595 µm) and fermentation for 48 h at room temperature. Fermented mango seed meal was prepared by mixing the mango seed meal (in an airtight polythene bag) with water at a ratio of 1:1 (wt. /vol.). Fermentation took place at room temperature (28-30 °C) for 48 h, after which the pH decreased to a stabilized level (3.7). The temperature of the fermented mango seed meal was taken at 12 h intervals using mercury in glass thermometer model 2751-K. (Lonner et al., 1986). The fermented meal was sundried, milled and sieved using a 595 µm sieve. The resultant meal was packed in air tight container and stored in a cool dry place at room temperature.

Table 1. Gross composition of experimental diets Feed stuff Yellow maize (%) 1 FMS (%) Fish meal (%) Soybean meal (%) Groundnut cake (%) Vegetable oil (%) Vitamin premix (%) L-Methionine DL-Lysine (%) 2 DCP (%) Chromic oxide (%) Sodium chloride (%) 3 Met. Energy (kcal/100g) Energy/protein ratio

FMS0 35.58 0.00 23.27 23.27 11.63 7.00 1.00 0.5 0.5 0.5 0.5 0.5 310.11 9.68

FMS25 25.74 8.25 23.51 23.51 11.75 6.00 1.00 0.5 0.5 0.5 0.5 0.5 310.72 9.82

FMS0 16.20 16.20 23.74 23.74 11.87 5.00 1.00 0.5 0.5 0.5 0.5 0.5 303.98 9.87

FMS75 9.96 23.89 23.97 23.97 11.98 3.00 1.00 0.5 0.5 0.5 0.5 0.5 310.59 9.87

FMS100 0.00 34.28 24.19 24.19 12.09 2.00 1.00 0.5 0.5 0.5 0.5 0.5 304.68 9.49

RADAR VIT. PREMIX supplies per 100 g diet. Palmitate (A) 1000 IU; cholecaciferol (D) 1000 IU; a- tocopherol acetate (E) 1.1 mg; Menadione (K) 0.2 mg; Thiamine (BI) 0.63 mg; Riboflavin (B2) 0.5 mg; panthothenic acid, 0.9 mg; Pyridoxine (B6) 0.15 mg; Cyanocobalamine (B12), 0.001 mg: Nicotinic acid 3.0 mg; Folic acid 0.1 mg; Choline 31.3 mg; Ascobic acid (C), 2.5 mg; Fe, 0.05 mg; Cu 0.25 mg Mn 6.0 mg; Co, 0.5 mg; Zn 5.0 mg; I, 0.2 mg; S, 0.02 mg.

1 Fermented mango seed meal 2 Di-calcium phosphate 3 Metabolizable energy, calculated using Atwater’s calculation as described by Foster and Smith (1997).where 1g of CP/ Crude ProteinLipid/EE and NFE (Carbohydrate) yields 3.5, 8.5 and 3.5 kcal/g, respectively.

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Croatian Journal of Fisheries, 2013, 71, 116-123 S. O. Obasa et al.: Fermented mango seed meal in the diet of Nile tilapia

Five iso-nitrogenous (35% crude protein) and approximately iso-energetic (3400 ME Kcal/kg) diets in which fermented mango seed meal protein replaced yellow maize at varying levels of 0% (Control diet /FMS0), 25% (FMS25), 50% (FMS50), 75% (FMS75) and 100% (FMS100) were formulated and prepared. Added to the diets were DL-lysine, L–methionine (0.5% each as fortification) and chromium III oxide (Cr2O3) at 0.5% as the external digestibility marker (Table 1). The feed ingredients were milled, weighed, mixed, pelleted, sun dried, packed in labeled air tight polyethylene bags and stored in a dry place at room temperature.

by Matheson (1974). The essential amino acids of the experimental diets were calculated from the analyzed values of the mango seed and NRC (1993) values for feedstuffs.

Growth performance and nutrient utilization parameters were expressed as the mean weight gain (MWG), percentage weight gain (%WG), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER) and apparent net protein utilization (ANPU) and were calculated as follows:

Experimental procedure

SGR (%day-1) = 100(In (Final mean weight – Ln (Initial mean weight.) x 100/time (days)

The experimental fish were fed the test diets twice daily at 5% of total biomass at 07:00 – 08:00 and 16:00 – 17:00 for 84 days. Fish were batch-weighted weekly with a sensitive electronic balance (METTLER TOLEDO, PB602). Mortality was monitored daily.

Water temperature (°C) was monitored daily using mercury-in glass thermometer; dissolved oxygen (DO) was measured using Jenway DO meter model 9071, while the pH was measured using glass electrode pH meter (E520) metrolin model. Ammonia was determined by the methods described by Thomas and Lynch (1960), while conductivity was measured using a model CMD 80 TYPEWPA conductivity metre (WPA, Cambridge, UK).

Chemical analysis At the beginning of the feeding trial, composite samples of ten whole fish were analyzed and a random sample of five fish per net hapa were analyzed for proximate composition at the end of the 84-day feeding period. Nitrogen, fat, fibre, ash and moisture content of the diets and composite fish samples were analyzed using A.O.A.C. (1990) method.

Determination of anti-nutritional factors such as the total phenolics and condensed tannins followed the spectrophotometric methods of Makkar et al. (1993), while phytic acid estimation followed the modified photometric procedure of Vaintraub and Lapteva (1988). In addition, the alkaloids determination followed the gravimetric method of Harborne (1973), total flavonoid content, colorimetric assay (Bonvehi et al., 2001), while oxalate followed the method of Dye (1956). The total saponin content followed the methods of Hiai et al.

(1976). The Hydrolysis of fermented mango seed proteins took place in a sealed tube Technicon TSM-1 Model DNA 0209 with 6NHCl for 22 h at 110 °C. Tryptophan was determined as described 118

MWG (g) = Final mean weight – Initial mean weight. %WG = Final body weight – Initial body weight x 100/ Initial body weight

FCR = (Total dry feed fed)/(Wet weight gain) PER = Mean Weight Gain/Mean Crude Protein Fed ANPU (%) = Final carcass protein – Initial carcass protein x 100/ Protein fed (g) where Protein fed (g) = % protein in feed x Total weight of diet consumed/100 Digestibility study commenced after the fish had fed for four days. Feaces were collected within each net hapa by hand stripping the fish and were oven-dried at 105 °C to a constant weight. Protein and carbohydrate contents of feaces were analyzed using AOAC (1990) methods. Determination of the chromium III oxide content of the feed and feacal samples in triplicates followed the method of Furukawa and Tsukahara (1966). ADCs calculation followed the following formula: ADC nutrient (%) = 100(1- ((% Cr2O3 indiet)(% nutrient or energy in feaces)/(% Cr2O3 in feaces) (% nutrient or energy in diet)

Statistical analyses Statistical comparisons of growth performance, protein utilization and nutrient digestibility values were made using analysis of variance (ANOVA) test (SAS 1988). Differences among means were also tested for significance (P<0.05) using Duncan Multiple Range Test (DMRT).

RESULTS Water quality parameters did not differ significantly among the experimental compartments.

Temperature ranged between 29.0 - 30.5 °C, pH, 7.6 – 8.7, dissolved oxygen, 6.5 – 8.4 and ammonia as ammonia - N (NH3-N) (0.25 - 0.45mg L1).

Croatian Journal of Fisheries, 2013, 71, 116-123 S. O. Obasa et al.: Fermented mango seed meal in the diet of Nile tilapia

Results of proximate analysis, anti-nutritional factors and minerals of the FMS (Table 2) showed that the nitrogen free extract (NFE) was highest, while the ash content was lowest. Alkaloids were highest while flavonoids were lowest. The minerals assay showed that copper was lowest and potassium had the highest value.

Table 2. Proximate composition, anti-nutritional factors and mineral content of fermented mango seed meal Nutrient Moisture content (%) Crude protein (%) Ash (%) Crude fat (%) Crude fibre (%) NFE (%) Tannin (%) Phenols (%) Alkaloids (%) Flavonoids (%) Saponin (%) Phytic acid (%) Oxalate (%) P (mg/g) Ca (mg/g) Na (mg/g) K (mg/g) Mg (mg/g) Zn (mg/g) Fe (mg/g) Mn (mg/g) Cu (mg/g)

Mean±sd 5.17±0.08 9.57±0.10 1.97±0.08 11.10±0.13 1.99±0.12 70.14±0.42 1.89±0.02 0.56±0.02 2.32±0.01 0.50±0.02 2.30±0.02 1.14±0.00 0.84±0.02 1.91 0.75 1.67 8.91 0.18 0.05 0.07 0.02 0.01

Fig 1. Growth performance of Oreochromis niloticus fed experimental diets Table 3 presents the essential amino acid (EAA) profiles of maize, soybean meal, fishmeal (calculated values of NRC 1993) and FMS (analyzed).

Leucine was highest while tyrosine was lowest.

Table 4 shows the proximate composition of the experimental diets. There was no significant difference (p>0.05) in the crude protein, moisture and ether extract. The calculated Metabolizable energy was highest in diet FMS25 and lowest in diet FMS50. The calculated EAA composition of the experimental diets (Table 5) increased as fermented mango seed meal increased in the diets. Fig 1 shows the growth of Nile tilapia fed the experimental diets. The highest increase took place between week 0 and 1. The highest increase in growth took place in fish fed the control diet (FMS0).

Table 6 shows growth, feed utilization, nutrient digestibility and survival of fish fed the experimental diets. The fish readily accepted the feeds and all fish fed actively throughout the duration of the trial.

Table 3. Essential amino acid profile of the experimental feed ingredients Ingredient *Maize (%) *Soybean meal (%) *Fish meal (%) Fermented mango seed meal (%)

Arg 0.43 3.39 4.54 3.79

his 0.26 1.19 1.65 1.60

Iso 0.35 2.03 3.13 2.23

Leu 1.21 3.49 5.19 5.67

Lys 0.25 2.85 5.57 2.69

Met 0.17 0.57 2.08 0.64

Phe 0.48 2.22 2.71 3.05

Thr 0.35 1.78 2.90 1.80

Try 0.08 0.64 0.77 0.52

Val 0.44 2.02 4.30 2.64

*NRC (1993) values

Table 4. Proximate composition of experimental diets Parameter Moisture (%) Crude protein (%) Ash (%) Ether extract (%) Crude fibre (%) 1NFE (%)

MSM0 10.21±0.12 35.85±0.88 11.65±0.60a 10.31±0.14 4.27±0.10b 27.71±0.96

MSM25 10.23±0.12 35.35±0.21 10.59±0.31b 10.83±0.27 5.89±0.02a 27.11±0.20

MSM50 10.53±0.14 34.63±0.18 11.19±0.09a 10.50±0.25 5.93±0.04a 26.72±0.60

MSM75 11.12±0.16 35.21±0.38 10.09±0.06b 10.77±0.40 5.44±0.07a 27.37±0.62

MSM100 10.60±0.23 35.42±0.47 11.74±0.36a 10.06±0.37 5.98±0.09a 27.20±0.21

a or b superscript shows significant differences (p<0.05) across rows Values are means of three replicates with standard deviation 1 Nitrogen free extract

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Table 5. Essential amino acid composition of the experimental diets Amino acids Arginine (%) Histidine (%) Isoleucine (%) Leucine (%) Lysine (%) Methionine (%) Phenylalanine (%) Threonine (%) Tryptophan (%) Valine (%)

FMS0 1.91 1.21 1.66 2.03 2.61 0.77 1.91 1.59 0.40 1.94

FMS25 2.22 1.33 1.83 2.42 2.75 0.82 2.14 1.72 0.44 2.14

FMS50 2.51 1.45 1.99 2.79 2.97 0.86 2.36 1.88 0.48 2.33

FMS75 2.79 1.56 2.15 3.15 3.18 0.91 2.57 1.98 0.52 2.51

FMS100 3.06 1.67 2.30 3.50 3.38 1.95 2.78 2.09 0.55 2.69

Tilapia requirement* 1.18 0.48 0.87 0.95 1.43 0.91 1.56 1.05 0.33 0.78

Calculated from the analyzed values for fermented mango seed meal and (NRC, 1993) values for feedstuffs; *Tilapia requirement (Santiago and Lovell, 1988)

Table 6. Growth performance, nutrient utilization, nutrient digestibility and survival of O. niloticus fingerlings fed varying dietary levels of fermented mango meal-based diets (Number of fish per net hapa = 10; Replicates = 3; Total fish sample/treatment = 30; MWG = Mean weight gain; % WG = Percentage weight gain SGR = Specific growth rate; FCR = Feed conversion ratio; PER = Protein efficiency ratio; ANPU = Apparent net protein utilization; ADCCarbohydrate = Apparent digestibility coefficient; ADCProtein = Apparent digestibility coefficient) Parameters Initial mean wt. (g) Final Mean wt. (g) MWG (g) %WG Mean feed intake (g) SGR (%/day) FCR PER ANPU (%) ADCCarbohydrate ADC Protein Survival (%)

Diet 1 4.75±0.11 24.30±3.18a 19.55±1.24a 412.21±17.9a 29.72±2.52a 1.94±0.07a 1.52±0.21c 1.88±0.13a 79.61±3.45a 64.95±5.62c 72.55±7.14a 95.3±7.86

Diet 2 4.76±0.25 20.50±3.90ab 15.74±31.65ab 330.67±65.9ab 25.65.26±2.00a 1.74±0.30a 1.63±0.57bc 1.65±0.87a 60.62±8.74a 72.91±3.33ab 59.14±9.21ab 93.5±6.43

DIETS Diet 3 4.76±0.26 18.61±3.09b 13.85±38.30ab 290.97±81.31ab 23.82±3.98a 1.62±0.35ab 1.72±0.53bc 1.49±0.21ab 52.82±5.90b 68.00±4.27b 60.62±8.07a 95.7±8.22

Diet 4 4.76±0.18 15.51±2.18c 10.75±22.16c 225.84±46.70b 21.02±1.04b 1.41±0.21bc 1.95±0.44a 1.46±0.60b 30.49±5.20bc 70.06±3.23b 54.37±8.23b 90.6±5.75

Diet 5 4.76±0.10 14.34±2.00 9.58±27.00d 201.26±2.00b 20.10±2.73b 1.31±0.29c 2.10±0.41a 1.36±0.77c 11.46±3.01c 78.58±3.22a 49.40±5.23c 93.2±6.33

a, b, ab, bc or c superscript shows significant differences (p<0.05) across rows Values are means of three replicates with standard error.

Table 7. Carcass composition of O. niloticus fingerlings fed experimental diets containing different levels of fermented mango seed meal (Number analyzed at initial = 10, while number analyzed at the end of the trial = 5/net hapa net) Nutrients Moisture (%) Crude protein (%) Ash (%) Ether extract (%)

Initial 12.22 57.95 12.70 7.85

FMS0 11.65±1.11 62.05±0.93a 13.23±2.58ab 8.25±0.12a

FMS25 12.82±2.07 61.29±0.12a 13.50±3.15ab 7.01±0.06b

FMS50 12.97±3.12 60.67±0.12ab 15.93±3.03a 7.76±0.05b

FMS75 11.00±1.08 59.52±0.31b 12.51±2.26b 8.20±0.08a

FMS100 11.15±2.06 58.04±0.16c 12.83±4.16b 9.52±0.24a

a, b, ab or c superscript shows significant differences (p<0.05) across rows Values are means of three replicates with standard error.

There was a significant reduction (p<0.05) in mean weight gain, mean feed intake, specific growth rate, feed conversion ratio, apparent net protein utilization, apparent protein and carbohydrate digestibility in fish fed diets above 50% inclusion of FMS. 120

Survival was high in all treatments (90 – 95%) with no significant difference (p>0.05).

Table 7 shows the carcass composition of Nile tilapia at the beginning and the end of the experiment. Carcass composition differed significantly

Croatian Journal of Fisheries, 2013, 71, 116-123 S. O. Obasa et al.: Fermented mango seed meal in the diet of Nile tilapia

(p<0.05) within the treatments, except the moisture content (p>0.05). Crude protein decreased significantly (p<0.05) as FMS increased in diets.

DISCUSSION Throughout the feeding trial, water quality in all treatments stayed within the favorable range required by tilapia (Balarin and Hatton, 1979; Mataka and Kang’ombe, 2007). The results of this trial demonstrated significant differences (p<0.05) among fish fed varying levels of fermented mango seed meal based diets. Growth and feed utilization decreased significantly (p<0.05) in fish fed diets above 50% FMS inclusion level. Although the essential amino acid profile of diets increased as fermented mango seed increased in the diet, protein digestibility significantly decreased while carbohydrate digestibility assumed an inverse relationship. This decrease might be due to a number of factors. These include the presence of anti-nutritional factors such as tannins, phytates and oxalate, which may not have pronounced interference with carbohydrate bioavailability as in protein. Mole and Waterman (1987) and Enujiugha and Ayodele-Oni (2003) observed that these anti-nutrients form complexes with protein thereby reducing the digestibility and consequently biological availability of this nutrient.

Also, Olaofe and Sanni (1988) and Dendougui and Schwedt (2004) stated that the anti-nutritional activity of oxalates and phytin lies in their ability to form complexes with metals like Ca, Zn, Mg and Fe, while phytic acid acts as a strong chelator, forming protein and mineral-phytic acid complexes thereby reducing protein and mineral bioavailability. Van Egmund et al. (1990) and Fasasi et al. (2003) observed that tannins interfere with digestion by displaying anti-trypsin and anti-amylase activity, forming complexes with vitamin B12 and interfering with the bioavailability of proteins.

The lower feed intake recorded in this study as FMS inclusion increased above 50% in the diet might be due to lowering palatability. This could result from the presence of tannin in the FMS. Azaza et al. (2009) reported that the presence of 2.4% tannin in faba beans (Vicia faba L. var. minuta) might be responsible for low palatability and consequently low feed intake in Nile tilapia.

The level of anti-nutritional factors in the FMS was rather high, compared to that obtained in fermented African breadfruit seed (Treculia africana) (Fasasi et al., 2003). However, fermentation improved the nutritional quality considerably. It completely removed hydrocyanic acid, significantly reduced the phytates, tannin and oxalate and in-

creased the phosphorus content of African breadfruit seed (T. africana) significantly (Fasasi et al., 2003). Olaofe and Sanni (1988) also reported that it improves the nutritional value of weaning foods, converts insoluble proteins to soluble components and increases the levels of lysine as well as of vitamins B and C. The high ash contents recorded in all the experimental diets, in spite of the low observed in mango seed meal, were expected. This is due to the high ash contents of some key ingredients like fishmeal and groundnut cake as observed by Sogbesan and Ugwumba (2008) and Akintayo et al. (2008), respectively.

The higher value of essential amino acid composition of FMS protein in this study than that of maize, and comparable to that of soybean meal, was expected. Augustine and Ling (1987) and Ahmed et al. (2007) reported that mango seed protein contains high values of essential amino acids. The presence of deficiency in methionine requirement for Nile tilapia in the first three diets might be due to a higher level of methionine in the protein of FMS than in the proteins of other plant-based ingredients in the diets. This is in agreement with Jackson et al. (1982) and Iqbala et al. (2006) who reported that methionine and lysine are the most limiting amino acids in plant protein sources, frequently causing reduced growth.

Therefore, we concluded that fermented mango seed meal could replace maize at 50% inclusion level in the diet of Nile tilapia as a carbohydrate source. This could also reduce the price of feed and consequently the cost of production of Nile tilapia.

At above 50% inclusion level, growth, feed utilization and apparent nutrient digestibility significantly reduced due to the presence of anti-nutritional factors present in the fermented mango seed meal. These factors were also responsible for the reduction in palatability and low feed intake in Nile tilapia.

Sažetak UPOTREBA SJEMENA FERMENTIRANOG MANGA (Mangifera indica) U HRANIDBI MLAđI TILAPIJE (Oreochromis niloticus) Ovim istraživanjem prikazana je upotreba sjemena fermentiranog manga kao zamjene za žuti kukuruz u hrandibi mlađi tilapije, Oreochronis niloticus (4,76±0,32g). Žuti kukuruz zamijenjen je s pet izoazotnih (35% sirovih bjelančevina) i približno toliko izoenergetskih (3400 ME Kcal/kg) oblika hranidbe sjemenom manga u sljedećim postocima: 121

Croatian Journal of Fisheries, 2013, 71, 116-123 S. O. Obasa et al.: Fermented mango seed meal in the diet of Nile tilapia

FMS 0% (FMS0/kontrolna skupina), 25% (FMS25), 50% (FMS50), 75% (FMS75) and 100% (FMS100).

Hranidba riba eksperimentalnom hranom vršena je 84 dana na razini od 5% njihove tjelesne težine.

Alkaloidi su bili najbrojniji (2,32%) od štetnih prehrambenih faktora analiziranih u FMS-u, dok je postotak oksalata bio najmanji (0,84%). Analiza je pokazala kako je kalij najzastupljeniji od minerala (8,91%), dok je bakar najmanje zastupljen (0,01 mg/g). Omjer povećane težine, specifične stope rasta i utjecaja promjene prehrane bio je sličan u FMS0 i FMS50 oblicima novih načina hranidbe (p>0,05).

Oblik hranidbe riba FMS0 imao je najveći omjer djelotvornih bjelančevina (1,88). Probavljivost bjelančevina smanjila se povećanjem dijetetskog FMS-a, dok se probavljivost ugljikohidrata povećala. Dobiveni rezultati pokazuju mogućnost zamjene žutog kukuruza sjemenom fermentiranog manga u hrandibi tilapija do 50% bez da taj oblik hranidbe utječe na rast, iskoristivost nutritivnih sastojaka i probavljivost bjelančevina prilikom hranidbe mlađi tilapije.

Ključne riječi: fermentacija, sjeme manga, probavljivost nutrijenata, tilapija, neprehrambeni faktori

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Croatian Journal of Fisheries, 2013, 71, 124-130 S. A. Uddin et al.: Probiotic use in seed production of Penaeus monodon

CODEN RIBAEG ISSN 1330-061X

ORIGINAL SCIENTIFIC PAPER

STUDY OF PROBIOTICS ON THE SEED PRODUCTION OF BLACK TIGER SHRIMP Penaeus monodon Sheikh Aftab Uddin1*, M. Abdul Kader1, M. Nurul Azim Sikder1, M. Abdul Hakim2, M. Mahbub Alam3, Ashraful Haque Azad4, Chowdhury Kamrul Hasan5 Institute of Marine Sciences and Fisheries, University of Chittagong, Chittagong-4331, Bangladesh Department of Microbiology, University of Chittagong, Chittagong-4331, Bangladesh 3 Marine Fisheries Discipline, Marine Fisheries Academy, Fish harbour, Chittagong-4000, Bangladesh 4 Bangladesh Fisheries Research Institute, Marine Station, Coxâ&#x20AC;&#x2122;s Bazar, Bangladesh 5 Department of Environmental Science, School of Environmental Science and Management, Independent University, Bangladesh, Plot 16, Block B, Bashundhara R/A,Dhaka, Bangladesh * Corresponding Author, E-mail: aftabims@yahoo.com 1 2

ARTICLE INFO

ABSTRACT

Received: 13 March 2013 Received in revised form: 15 June 2013 Accepted: 5 July 2013 Available online: 7 July 2013

Currently, antibiotics are widely used in shrimp hatcheries to control bacterial infections. Appearance of antibiotic resistant pathogens and restriction on the use of antibiotics have led to the development of alternatives to antibiotics in hatchery systems. In light of this, an attempt was undertaken to investigate the effects of probiotics on the larval rearing of Penaeus monodon, compared with the control tanks (without probiotics). The results showed that several issues significantly improved with administering probiotics in the experimental tanks compared with the tanks without probiotics. For example, the concentration of ammonia was estimated to be 1.25 mg/L which was less than a half of what was measured in the control tanks. The size variation was observed more in the control tanks than in the experimental tanks.

Moreover, the muscle gut ratio of PL15 was about 85 to 92% in the probiotic treated tank and 70 to 80% in the control tank during the eight cycles of production. The fouling organisms were more in the control tank compared to the experimental tanks.

The average length of PL15 was maximum when reared in the experimental tanks compared to the control tanks. The final survival rate of PL15 from the control and experimental tank was 35 and 52%, respectively. The present investigation indicated that probiotics played an important role in the growth, survival and health status of P. monodon larvae.

Keywords: Probiotics Shrimp health Penaeus monodon Seed production Bangladesh

INTRODUCTION The decline of global shrimp production along with the outbreak of different diseases, causing mass mortalities of shrimps in hatcheries (Lavilla-Pitogo et al., 1990; Jiravanichpaisal and Miyazaki, 1994; Karunasagar et al., 1994), has led to the indiscriminate use of antibiotics and a variety of other disinfectants (Aftabuddin and Kader, 2006; Walker and Mohan, 2009; Boonthai et al., 2011). Consequently, 124

the shrimp industry is frequented by multiple drugresistant bacteria such as Aeromonas hydrophila, A. salmonicida, Edwardsiella tarda, E. ictaluri, Vibrio anguillarum, V. salmonicida, Pasteurella piscida, Yersinia ruckeri (De Paola et al., 1995; Weston, 1996; Cabello, 2006) which are becoming increasingly difficult to control and eradicate (Vine et al., 2006). As some of the antimicrobial agents have been banned in some countries (Robert et al., 1995; FAO, 2002) considering the threat to environment and human health

Croatian Journal of Fisheries, 2013, 71, 124-130 S. A. Uddin et al.: Probiotic use in seed production of Penaeus monodon

(Samuelsen et al., 1992; Graslund et al., 2002), probiotics, including Bacillus spp., have been recognized as an alternative and beneficial method of controlling the microbial environment (Ringø and Gatesoupe, 1998; Gatesoupe, 1999; Ringø and Birkbeck, 1999; Verschuere et al., 2000, Irianto and Austin, 2002).

A number of studies have focused on the use of Bacillus spp. in shrimp industry as a useful probiotic (Wang, 2007; Far et al., 2009; Zhou et al., 2009; Sundarapandian and Babu, 2010), which may increase P. monodon productivity and improve water quality by decreasing the concentration of ammonia and nitrite (Shariff et al., 2001) and by increasing dissolved oxygen (Wang et al., 2005). Moreover, the Bacillus spp. have the ability to potentially inhibit Vibrio spp. in shrimp culture facilities (Rengipipat et al., 1998; Moriarty, 1999; Gatesoupe, 1999). Based on the previous study on probiotics, it is evident that probiotics have good ability to stimulate appetite, improve the nutrient absorption and strengthen the host immunity. Therefore, the present study was undertaken to examine the effect of commercial probiotics on the growth, survival and water quality of hatchery reared seed of black tiger shrimp, P. monodon in Bangladesh.

MATERIALS AND METHODS The present investigation was carried out at the Prime Shrimp Hatchery Limited, located on the southeastern coast of Bangladesh (Fig 1) during

Fig 1. Location of the investigated hatchery at Kolatoly, Cox’s Bazar (star in the map)

April 2009-March 2011. Over the last decade, the hatchery, having state-of-the-art facilities, has been producing around 400-500 million of P. monodon seeds per year in its 5 production units.

Larval rearing operation Five larval rearing tanks (30 ton capacity) were filled with 25 ton UV treated seawater. Three tanks were kept as experimental tanks treated with probiotics and another two were kept as control tanks.

Both experimental and control tanks were inoculated with 10 ppm EDTA and 0.05 ppm treflan (fungicide) two hours before stocking. Just before stocking, algae (Skeletonema sp.) were added to the tanks at a density of 100,000 cells/ml. The tank water was sufficiently aerated throughout the culture operation. The nauplii (N5 /N6) were harvested from the hatching tanks and were released into the larval rearing tanks (LRT) slowly in small quantities at different points of the control tank at 100,000 nauplii/ ton. The similar procedure was applied while stocking the experimental tanks, except prior to stocking, they were inoculated with 0.5 ppm probiotics top 10 (containing Lactobacillus acidophilus, Bacillus spp. and Saccharomyces cerevisiae). Each experiment was carried out once in each cycle, continuing up to eight cycles.

Twenty four hours after stocking, the nauplii converted into protozoea I (called zoea I) stage.

First feeding was started when the zoea I appeared.

The zoeal stages (I to III) were fed with Skeletonema sp. thrice daily both in the control and in the experimental tanks. The mysis stages (I to III) were fed with algae at a density of 4 x 105 cells/ml both in the control and in the experimental tanks. In addition to algae, mysis stages were fed with commercially available microencapsulated feed like CAR, CD-2 etc. three times a day. These were supplemented with 1 ppm of probiotic mysis stages in the experimental tanks. Newly hatched Artemia nauplii were also given as a live feed in mysis III stage. Post larval stages were fed exclusively with freshly hatched live Artemia nauplii at 4 individuals per PL (nos. of Artemia increased with PL onwards) and artificial feed shrimp flakes three times a day. Probiotics top 10 was also added at 1.5 ppm daily in the experimental tanks with PL. Continuous aeration was maintained at a level appropriate for each larval stages to provide sufficient oxygen and to keep feed and larvae in suspension. Siphoning was done routinely (daily from mysis stage onwards) to clean the unconsumed food and fecal materials on the tank bottom. Water exchange was done from the mysis III stage on125

Croatian Journal of Fisheries, 2013, 71, 124-130 S. A. Uddin et al.: Probiotic use in seed production of Penaeus monodon

wards using mesh size of 0.5 mm and reducing 50% of the water. Once post larvae appeared, salinity was reduced slowly and maintained to 20 ppt.

Microbiological analysis was done routinely (using TCBS and/or Marine agar) to assess the evolution of the bacterial populations in each tank.

The water quality parameters of the probiotic and control tanks were regularly monitored. Water quality parameters such as salinity, temperature, pH, dissolved oxygen and ammonia were estimated daily in the morning hours. Water salinity was measured by using a hand refractometer (ATAGO, Japan). The pH of the water was measured by using electronic pen pH meter manufactured by Hanna Instrumental Company (Singapore). Water temperature was measured by using a digital thermometer (DT801, China). Dissolved oxygen (mg/L), alkalinity (ppm) and ammonia (mg/L) were measured by HANNA instruments products, Singapore, Model no. HI 3810, HI 3811 and HI 3826, respectively.

Total length and size variation To know the size variation, the length of 50 postlarvae were measured individually. The mean length and standard deviation was calculated according to Madhukiran et al. (2009).

Muscle gut ratio (MGR) A microscopic examination of the relative thickness of ventral abdominal muscle and the gut in the 6th abdominal segment of the tail of the post larvae was conducted to determine the muscle to gut ratio (Madhukiran et al., 2009). To know the MGR at least 20 PL15 were examined, indicating the nutritional status of the shrimp. High muscle to gut ratio (4:1) was preferable.

Stress test A stress test was conducted once they reached PL12-15.

Randomly selected sample of about 100 individuals were taken in a beaker containing rearing water salinity with 20 ppm formalin (0.2 ml/L) and allowed for 60 minutes. After 60 minutes, the PL that were still active or which moved when prodded with a needle were counted as a percentage of survival, following the formula: survival (%) = (no. active PL/total PL in beaker) x 100.

Fouling organisms Randomly selected PL12-15 of about 50 individuals were examined by a compound microscope to ob126

serve any fouling organisms attached with the PL (Madhukiran et al., 2009). The percentage of fouling was calculated following the formula: fouling (%) = (no. of PL attached with fouling organisms/total no. of PL counted during the observation) x 100.

Monodonbaculo virus (MBV) Baculoviruses were detected in whole or squashed (stained with malachite green for Monodonbaculovirus) preparations of hepatopancreas or fecal strands from larger-sized larvae, using a high powered light microscope to spot the characteristic viral occlusion bodies (Lightner, 1996).

Test for WSSV WSSV test was performed by IQ Plus system, which was a new technology based on insulated isothermal PCR that was a compact and portable system. The instrument could detect WSSV within 1 hour. The extraction procedure and others were performed according to the instruction manual of IQ Plus system, GeneReach Biotechnology Corp.

Taiwan.

RESULTS AND DISCUSSION The percentage of survival rate of P. monodon larvae of various stages are given in Table 1. The result showed that the survival rate of the nauplii exhibited similar trend both in the control and experimental tanks. The survival rate of Zoea 1 stage in the probiotic treated tanks (PTTs) and control tanks (CTs) was 90% and 80%, respectively. The survival rate of the mysis was maximum (81%) in PTTs and minimum in CTs (66%). The survival rate of all the post larval stages (PL1- PL15) was higher in PTTs than that of the CTs (Table 1). The survival rate of the PL15 stage in PTTs was 52%, while it was only 35% in the control. The findings of present investigation accorded closely with the works of Krishnaprakash et al. (2009) and Soundarapandian and Babu (2010).

Table 1. Percentage of larval survival (average percentage calculated by 8 cycles) Stages Zoea 1 Mysis 1 PL1 PL5 PL10 PL15

% survival in control tank 80 66 50 44 40 35

% survival in probiotic treated tank (PTT) 90 81 72 64 56 52

Croatian Journal of Fisheries, 2013, 71, 124-130 S. A. Uddin et al.: Probiotic use in seed production of Penaeus monodon

% Stress test

% fouling organisms

Presence of LB

Presence of MBV

Presence of WSSV

Cycle 1 Control tank Experimental tank Cycle 2 Control tank Experimental tank Cycle 3 Control tank Experimental tank Cycle 4 Control tank Experimental tank Cycle 5 Control tank Experimental tank Cycle 6 Control tank Experimental tank Cycle 7 Control tank Experimental tank Cycle 8 Control tank Experimental tank

% MGR

Production cycles

% size variation

Table 2. Health status of P. monodon post larvae during the investigation period (April 2009-March 2011, 8 production cycles)

17 11

72 85

80 90

25 12

-

-

-

20 11

70 85

80 95

30 15

+ -

-

-

15 11

75 85

82 95

20 10

-

-

-

16 12.5

80 90

80 95

25 12

-

-

-

20 10

78 92

75 96

30 15

+ -

-

-

25 15

75 88

73 90

30 15

+ +

-

-

14 10

76 90

78 96

28 10

-

-

-

20 12

80 92

73 90

20 15

-

-

-

Table 2 demonstrates the various health check assessment of P. monodon post larvae. The percentage of size variation was low in PTTs, compared to CTs. In PL15, the muscle gut ratio was about 85 to 92% in PTTs and 70 to 80% in CTs during the eight cycles of production. This implied that the intake of feed in CTs was lower than that of the PTTs. This was due to high stress, which was substantiated by the works of Krishnaprakash et al. (2009), stating that in PL16, the muscle gut ratio was 98% in the experimental tanks (with probiotics containing

Table 3. The average length of P. monodon post larvae reared in both control and experimental tanks Stages

Cycle 1 PL1 PL5 PL10 PL15 Cycle 2 PL1 PL5 PL10 PL15 Cycle 3 PL1 PL5 PL10 PL15 Cycle 4 PL1 PL5 PL10 PL15 Cycle 5 PL1 PL5 PL10 PL15 Cycle 6 PL1 PL5 PL10 PL15 Cycle 7 PL1 PL5 PL10 PL15 Cycle 8 PL1 PL5 PL10 PL15

Length (mm) Control tank (n=20) Probiotic treated tanks(n=20) 4.78±1.2 5.68±0.8 7.98±0.4 9.84±0.5

5.38±0.5 6.83±0.5 8.84±0.2 11.80±0.2

4.68±1.0 5.78±0.6 7.70±0.3 9.40±0.4

5.48±0.5 6.90±0.6 8.75±0.2 11.40±0.4

5.00±0.8 5.80±0.6 8.0±0.5 10.02±0.4

5.38±0.2 7.83±0.4 9.84±0.2 11.81±0.5

5.10±0.6 5.90±0.6 7.90±0.5 9.82±0.4

5.38±0.3 7.85±0.4 9.85±0.5 11.48±0.6

4.90±0.5 5.70±0.6 7.75±0.6 9.58±0.5

5.28±0.4 7.76±0.3 9.72±0.5 11.35±0.6

4.82±0.3 5.60±0.4 7.63±0.4 9.45±0.4

5.25±0.4 7.65±0.3 9.60±0.4 11.25±0.3

4.98±0.4 5.80±0.5 7.85±0.4 9.88±0.5

5.48±0.4 7.80±0.2 9.82±0.3 11.65±0.3

4.92±0.5 5.78±0.6 7.75±0.6 9.68±0.5

5.38±0.4 7.72±0.3 9.75±0.5 11.38±0.4

Bacillus sp. and Streptococcus spp.) and 75% in the control tanks.

The fouling organisms were more in the control tanks than in the experimental tanks. Fouling organisms, like filamentous bacteria and Zoothamium spp., might be commonly seen in the hatcheries, causing less harm to the shrimps than other diseas127

Croatian Journal of Fisheries, 2013, 71, 124-130 S. A. Uddin et al.: Probiotic use in seed production of Penaeus monodon

es. The minimum damage to the shrimps due to the presence of fouling organisms might be attributed to the moulting process. In some cases, they spread all over the tanks, subjected to the chemical treatment with 10-25 ppm Formalin. The percentage of fouling organisms in the probiotic treated tanks ranged from 10-12, whereas in the control tanks, it fluctuated from 20-30 during all production cycles.

The average length of all post larvae (PL1-PL15) was maximum when reared in the experimental tanks compared to the control tanks (Table 3).

At PL15, the total length of the larvae ranged from 12.12 to 11.22 mm in the antibiotic treated tank (ATT) and 11.81 to 11.25 mm in PTT; whereas in the control tank, it ranged from 10.02 to 9.40 mm.

Krishnaprakash et al. (2009) found that during PL12, PL14 and PL16 stages, total lengths of the larvae in the experimental tanks were 11.68 mm, 11.98 mm and 12.17 mm, respectively, whereas in the control tank, the growth rates were 11.05 mm, 11.38 mm and 11.79 mm, respectively, which was in close agreement with the present investigation. All tanks were free from Monodon Baculu Virus and White Spot Syndrome Virus disease.

Water quality parameters Water quality parameters, namely temperature (°C), salinity (ppt), pH, dissolved oxygen (mg/L), ammonia (mg/L) and alkalinity (ppm), are shown in Table 4.

Water temperature was probably the most important environmental variable for larval rearing of P. monodon because it directly affected metabolism, oxygen consumption, growth, moulting and survival. The optimum range of temperature for the black tiger shrimp larval rearing is between 28 to 32 °C (Kannupandi et al., 2002), which coincided with the present investigation showing a range from 29 °C - 30 °C. There was no marked difference in temperature between the control and experimental tanks.

P. monodon can tolerate a wide range of salinity. For a shrimp hatchery, the recommended salinity range is 28-35 ppt (Kannupandi et al., 2002).

In the present study, salinity was maintained at 29-31 ppt for both control and experimental tanks.

Krishnaprakash (2007) also reported almost similar salinity (31 ppt) for the larval rearing of P. monodon.

In the present study, the pH level was lower in the control tank (6.4-6.8) which was in congruence with the Law (1988), demonstrating that P. monodon could tolerate pH down to 6.0 to 6.5. On the other hand, in the experimental tanks, pH was considerably high (7.8-8.3), which conformed with the findings of Kannupandi et al. (2002) and Krishnaprakash (2007), stating that the suitable pH for the shrimp larval culture ranged from 8.2-8.5.

The results indicated that probiotics maintained a desired level of pH in the experimental tanks.

In the present study, the maximum dissolved oxygen (DO) content in the experimental tank was 4.8 mg/L and in the control tank it was 4.2 mg/L, which was in close agreement with the works of Liao and Murai (1986), Krishnaprakash (2007), Krishnaprakash et al. (2009). Surfacing response was first observed when DO reached 1.5-2.1 mg/L. Oxygen levels in the culture tanks were maintained in the desired range by aeration. Continuous aeration was done during the present investigation and therefore the oxygen level did not vary significantly between the control and experimental tanks.

Ammonia exists in water in both ionized (NH4+) and unionized (NH3) forms. Unionized ammonia is considered a more toxic form of ammonia due to its ability to diffuse readily across the cell membrane (Fromm and Gillette, 1968; Emerson et al., 1975). In the present study the higher concentration of ammonia (2.5 mg/L) was observed in the control tank and in the probiotic tank it was 1.25 mg/L, which agreed with the results (0-2.1 ppm) of Krishnaprakash (2007) and disagreed with that of

Table 4. Recorded water quality parameters for both control and probiotic treated tanks Temp (°C) Cycle 1 2 3 4 5 6 7 8

CT 29 30 29.5 29 29.5 29 30 30

PTT 29.5 29.5 30 29.5 29 29.5 29.5 30

Salinity (ppt) CT 30 31 29 30 30.5 31 29 29.5

CT=control tank, PTT=probiotic treated tank

128

PTT 30.5 30 30 30.5 30.5 30.5 30 30

ph CT 6.5 6.8 6.55 6.5 6.4 6.6 6.7 6.5

DO (mg/L) PTT 8.1 8 7.9 8 7.9 7.8 8.2 8.3

CT 4 3.9 4.2 4 4.1 3.9 4.1 3.9

PTT 3.9 4 4.8 4.02 4.5 4.3 4 3.8

Alkalinity (ppm) CT PTT 135 150 132 155 125 150 135 140 128 150 125 145 135 150 128 155

Nh4(ppm) CT 1.8 1.45 1.65 1.55 1.9 2.5 1.7 2.1

PTT 1 0.9 0.95 1.1 1.2 1.25 1 0.95

Croatian Journal of Fisheries, 2013, 71, 124-130 S. A. Uddin et al.: Probiotic use in seed production of Penaeus monodon

Das et al. (1996). The alkalinity of both control and experimental tanks ranged from 125-135 ppm and 140-155 ppm, respectively, which was approximated to the values of 140-160 ppm in the larval rearing tank, reported by Krishnaprakash (2007).

Sažetak PROBIOTICI U PROIZVODNJI POTOMSTVA TIGRASTE KOZICE (Penaeus monodon) U mrijestilištima kozica trenutno je vrlo rasprostranjena upotreba antibiotika za sprečavanje bakterijskih infekcija. Pojavom otpornih patogenih svojstva antibiotika i ograničenja njihove upotrebe, razvili su se drugi načini sprečavanja infekcija patogenima u mrijestilištima. Sukladno tome je provedeno istraživanje učinkovitosti probiotika u uzgoju ličinki Penaeus monodon te su dobiveni rezultati uspoređeni s onima iz kontrolnih spremnika bez probiotika. Rezultati su pokazali znatno unapređenje nekih odrednica uzgoja u eksperimentalnim spremnicima s dodatkom probiotika (u odnosu na spremnike bez probiotika). Primjerice, koncentracija amonijaka procijenjena je na 1,25 mg/L, što je manje od polovice izmjerene vrijednosti u kontrolnim spremnicima.

Veća varijacija veličine zabilježena je u kontrolnim, a manja u eksperimentalnim spremnicima. Štoviše, tijekom osam faza proizvodnje, omjer crijevnih mišića PL15 bio je otprilike 85-92% u spremnicima s probioticima, a 70-80% u kontrolnim spremnicima.

Obraštajnih organizama bilo je više u kontrolnim nego u eksperimentalnim spremnicima. Prosječna dužina PL15 bila je maksimalna za jedinke koje su mriještene u eksperimentalnim spremnicima (u odnosu na kontrolne). Konačna stopa preživljavanja PL15 je 35% u kontrolnim i 52% u eksperimentalnim spremnicima. Ovim istraživanjem dokazana je važna uloga probiotika u rastu, preživljavanju i održavanju zdravlja ličinki P. monodon.

Ključne riječi: probiotici, zdravlje kozica, Penaeus monodon, proizvodnja potomstva, Bangladeš

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FAO (2002): The State of World Fisheries and Aquaculture (SOFIA).FAO, Rome, 150 pp.

Far, H. Z., Saad, C. R. B., Daud, H. M., Harmin, S. A., Shakibazadeh, S. (2009): Effect of Bacillus subtilis on the growth and survival rate of shrimp (Litopenaeus vannamei). African Journal of Biotechnology, 8, 3369-3376.

Fromm, P. O., Gillette, J. R. (1968): Effect of ammonia on blood and nitrogen excretion of rainbow trout (Salmogairdneri). Comparative Biochemistry Physiology, 26, 887-896.

Gatesoupe, F. J. (1999): The use of probiotics in aquaculture. Aquaculture, 180, 147-165.

Graslund, S., Karin, K., Wongtavatchai, J. (2002): Responsible use of antibiotic in shrimp farming.

Aquaculture Asia, 7, 17.

Irianto, A., Austin, B. (2002): Probiotics in aquaculture. Journal of Fish Diseases, 25, 633-642.

Jiravanichpaisal, P., Miyazaki, T. (1994): Histopathology, biochemistry and pathogenicity of Vibrio harveyi infecting black tiger shrimp Penaeus monodon. Journal of Aquatic Animal Health, 6, 27-35.

Kannupandi, T., Soundarapandian, P., Anantharaman, P. (2002): Hatchery operation manual for Penaeus monodon Fabricius.

Annmalai University, CAS in Marine Biology Parangipettai, 1-99.

Karunasagar, I., Pai, R., Malathi, G. R., Karunasagar, I. (1994): Mass mortality of Penaeus monodon larvae due to antibiotic resistant Vibrio harveyi infection. Aquaculture, 128, 203-209.

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Krishnaprakash, R., Saravanan, R., Murugesan, P., Rajagopal, S. (2009): Usefulness of Probiotics in the Production of High Quality Shrimp (Penaeus monodon) Seeds in Hatcheries. World Journal of Zoology, 4, 2, 144-147.

Lavilla-Pitogo, C. R., Baticados, M. C. L., CruzLacierda, E. R., de la Pena, L. D. (1990): Occurrence of luminous bacterial disease of Penaeus monodon larvae in the Philippines. Aquaculture, 91, 1-13.

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Croatian Journal of Fisheries, 2013, 71, 131-135 V. O. Eyo et al.: Fecundity and biometric indices of the silver catfish

CODEN RIBAEG ISSN 1330-061X

ORIGINAL SCIENTIFIC PAPER

RELATIONSHIP BETWEEN FECUNDITY AND BIOMETRIC INDICES OF THE SILVER CATFISH Chrysichthys nigrodigitatus (Lacepede) IN THE CROSS RIVER ESTUARY, NIGERIA Victor Oscar Eyo1*, Albert Philip Ekanem1, George Eni2, Asikpo Patience Edet3 Institute of Oceanography, University of Calabar, P.M.B.1115 Calabar, Nigeria Zoology and Environmental Biology, University of Calabar, Nigeria 3 Zoology and Environmental Biology Programme, University of Calabar, Nigeria * Corresponding Author, E-mail: sirvick2003@yahoo.com, Tel.: +2348065162221 1 2

ARTICLE INFO

ABSTRACT

Received: 1 May 2013 Received in revised form: 18 May 2013 Accepted: 5 July 2013 Available online: 10 July 2013

The relationship between fecundity and biometric parameters of silver catfish, Chrysichthys nigrodigitatus from the Cross River estuary was studied between July and October 2012. A total of 120 gravid female fish were examined. The results show that fecundity of C. nigrodigitatus ranged between 975 eggs for fish of total length 23.2 cm, total weight 99 g, ovary weight 15 g and mean egg diameter 2.43 mm to 11,280 eggs for fish of total length 50.0 cm, total weight 1420.0 g, ovary weight 80.0 g and mean egg diameter 3.44 mm. There was a positive significant relationship between fecundity (F) and total length (TL), total weight (TW), ovary weight (OW) and mean egg diameter (MED) as follows: F = 2.457TL1.9225 (r = 0.8457 and r2 = 0.7152, P<0.05), F = 61.51TW0.6098 (r = 0.890, r2 = 0.7921, P<0.05), F = 28.162OW1.2468 (r = 0.9457, r2 = 0.8943, P<0.05), F = 704.44MED1.0624 (r = 0.2128, r2 = 0.0453, P<0.05).

Fecundity and mean egg diameter increases with total weight (TW). This finding is essential for evaluating the aquaculture strategies required to intensify commercial production and management of C. nigrodigitatus stock since it is a valuable source of protein in Nigeria.

Keywords: Fecundity C. nigrodigitatus Cross River estuary Biometric parameters Ovary weight

INTRODUCTION Silver catfish, Chrysichthys nigrodigitatus commonly called â&#x20AC;&#x153;Inaghaâ&#x20AC;? by the Efik and Ibibio tribes in Nigeria, is an important food fish for the inhabitants of the Cross River estuary. It is appreciated by consumers for its taste and meat quality and is mostly smoked and used in traditional and continental dishes. According to Enin (2007), C. nigrodigitatus is known to be the most dominant fish in trawl catches accounting for a considerable frequency of occurrence in both artisanal and trawl fishery of Cross River estuary. Offem et al. (2008) reported that C. nigrodigitatus is a highly valued food-fish included among the dominant commercial catches exploited

in major rivers of Africa. It is exploited mainly by hook and line and the gillnet fisheries in the Cross River estuary, Nigeria (Holzlohner et al., 1998). It forms 10.0% of the catches of the gillnet fishery in the central Cross River estuary, Southern Nigeria (Holzlohner et al., 1998).

Fecundity is an index which measures the number of eggs carried by a gravid female fish or shrimp. It is one of the various reproductive characteristics of fish species, thus fecundity estimate is of great importance for fisheries science (Hunter and Goldberg, 1980). In fisheries science, fecundity is important in the following areas: stock assessment, eggs and larval survival studies, standing stock size estimates, exploited stock prediction, re131

Croatian Journal of Fisheries, 2013, 71, 131-135 V. O. Eyo et al.: Fecundity and biometric indices of the silver catfish

cruitment of back shell and fin fish species (Shalloof and Salama, 2008) and formulation of management strategies (Komolafe and Arawomo, 2007). In aquaculture, fecundity is used as an important criterion in the selection of aquaculture candidates (Mayer et al, 1989). Several scientists have researched the reproductive biology of C. nigrodigitatus, including Offem et al. (2008), Aransiola (1989), Ekanem (2000), Ezenwa et al. (1986), Fagade and Adebisi (1979) etc.

Investigation into the possibility of culturing C. nigrodigitatus to meet the demand is ongoing (Ezenwa, 1982 and Ekanem, 1992). Presently, fish farmers in the southern part of Nigeria who embarked on trial culture and breeding of this species have failed due to lack of information on various aspects of its reproductive biology. The objective of the present study is to determine the relationship between fecundity and biometric indices such as total weight (F/TW-g), total length (F/TL-cm), egg diameter (F/ ED-mm) and ovary weight (F/OW-g) of C. nigrodigitatus from the Cross River estuary, Nigeria.

MATERIALS AND METHODS Study area description The study area for this research is the Cross River estuary, Nigeria, which lies approximately between latitude 4° and 8° N and longitude 7° 30 and 10° E in the southern part of Nigeria. It takes its rise from the Cameroon Mountain and meanders westwards into Nigeria and then southward through high rainforest formation before discharging into the Atlantic Ocean at the Gulf of Guinea. The study area has a mangrove forest vegetation (Ama-abasi et al., 2004) with climate characterized by long wet season from April to October and a dry season from November to March. Mean annual rainfall is about 2000 mm (Akpan and Offem, 1993). A short dry period known as August break occurs in August. There is usually a cold, dry and dusty period between December and January, referred to as the harmattan season. Temperatures generally range from 22 °C in the wet to 35 °C in the dry seasons. Relative humidity is generally above 60% at all seasons, with close to 90% during the wet season (Akpan and Offem, 1993; Ama-abasi et al., 2004).

Collection and identification of C. nigrodigitatus species and their sexes One hundred and twenty freshly caught gravid females of C. nigrodigitatus were collected between July and October 2012 from the catches of the artisanal fisheries at Nsidung beach, Calabar, a major 132

landing point of the artisanal fisheries of the Cross River estuary. Samples were transported in icepacked containers to the Fisheries and Aquaculture laboratory, Institute of Oceanography, University of Calabar, for further analysis.

Identification of C. nigrodigitatus was based on the identification key given by Fischer et al. (1981).

Differentiation of sexes was based on external features (anal opening) and internal features such as gonad.

Measurements of biometric indices The following biometric parameters were measured for each specimen: Total length (TL), Total weight (TW) and Gonad weight (GW). Total length was measured from snout to the base of the caudal fin rays. Measurements were taken to the nearest 0.1 cm and 0.1 g using measuring board for length and Metlar-2000D electronic weighing balance for weight.

Procedures for fecundity estimation and measurement of egg diameter Eggs from each specimen were removed by cuttingopen the abdominal part of the fish with a sharp pair of scissors. Each specimen was cut-opened through the cloaca.

Eggs were washed in distilled water and weighed using Metlar-2000D electronic weighing balance to the nearest 0.1 g (Ama-abasi, 2006).

The eggs removed from each sample were fixed in Gilson fluid in order to loosen the tissues surrounding the eggs (Davenport, 1960).

Fecundity (F) was determined as the product of total weight of eggs in the ovary and count in 1 g of egg mass as shown below: F = total weight of eggs in the ovary x count in 1 g of egg mass The diameters of 30 eggs per fish were measured according to Lampert et al. (2004); Mesa et al. (2007) using a stereo microscope with an ocular micrometer eye piece.

Statistical analysis Values of regression coefficient ‘b’ intercept ‘a’ and coefficient of correlation ‘r’ in relationship between fecundity and body parameters (F/TL-cm, F/TWg, F/OW-g and F/MED-mm) for C. nigrodigitatus from the Cross River estuary were determined by linear and power regressions.

Croatian Journal of Fisheries, 2013, 71, 131-135 V. O. Eyo et al.: Fecundity and biometric indices of the silver catfish

RESULTS Fecundity of C. nigrodigitatus from the Cross River estuary Fecundity was determined for one hundred and twenty (120) specimens of C. nigrodigitatus collected from the Cross River estuary. Fecundity of C. nigrodigitatus ranged between 975 eggs for fish of total length (TL-cm) 23.2 cm, Total weight (TW-g) 99 g, ovary weight (OW-g) 15 g and mean egg diameter (MED-mm) 2.43 mm to 11,280 eggs for fish of total length (TL-cm) 50.0 cm, Total weight (TW-g) 1420 g, ovary weight (OW-g) 80 g and mean egg diameter (MED-mm) 3.44 mm.

Relationship between biometric indices and fecundity of C. nigrodigitatus from the Cross River estuary Fecundity of C. nigrodigitatus from the Cross River estuary showed a linear relationship with the total length (cm). Power regression equation for fecundity and total length as shown in Figure 1 is as follows:

Fecundity of C. nigrodigitatus from the Cross River estuary showed a linear relationship with the Ovary Weight (g) (Figure 3). Power regression equation for fecundity and ovary weight as shown in Figure 3 is as follows: F = 28.162OW1.2468 (r = 0.9457, r2 = 0.8943, P<0.05)

Fig 3. Power regression of Fecundity against Ovary Weight (OW-g) of C. nigrodigitatus from the Cross River estuary Fecundity of C. nigrodigitatus from the Cross River estuary showed a linear relationship with the mean egg diameter (MED-mm) (Figure 4). Power regression equation for fecundity and mean egg diameter as shown in Figure 4 is as follows: F = 704.44MED1.0624 (r = 0.2128, r2 = 0.0453, P<0.05)

F = 2.457TL1.9225 (r = 0.8457 and r2 = 0.7152, P<0.05)

Fig 4. Power relationship between Fecundity and Mean Egg Diameter (MED-mm) of C. nigrodigitatus from the Cross River estuary Fig 1. Power relationship between Fecundity and Total Length (TL-cm) of C. nigrodigitatus from the Cross River estuary Fecundity of C. nigrodigitatus from the Cross River estuary showed a linear relationship with the total weight (g) (Figure 2). Power regression equation for fecundity and total weight (g) as shown in Figure 2 is as follows: F = 61.51TW0.6098 (r = 0.890, r2 = 0.7921, P<0.05)

Fig 2. Power relationship between Fecundity and Total Weight (TW-g) of C. nigrodigitatus from the Cross River estuary

DISCUSSION The use of fecundity as a criteria for estimation of population parameters and maintenance of C. nigrodigitatus fishery in Cross River estuary cannot be overemphasized in fisheries science. Fecundity is necessary to evaluate the reproductive capacity of individual fish species. In the present study, C. nigrodigitatus showed a significant (P<0.05) positive correlation between fecundity and total length, total weight, ovary weight and mean egg diameter.

Fecundity ranged between 975 eggs for fish with total length 23.2 cm, total weight 99.0 g, ovary weight 15.0 g and mean egg diameter 2.43 mm to 11280 eggs in fish with total length 50.0 cm, total weight 1420.0 g, ovary weight 80.0 g. This result indicated that bigger sized C. nigrodigitatus contributed a higher number of eggs and smaller fish had a smaller number of eggs. These findings are lower than the results obtained by Abraham and Akpan (2012) 133

Croatian Journal of Fisheries, 2013, 71, 131-135 V. O. Eyo et al.: Fecundity and biometric indices of the silver catfish

who estimated the highest fecundity for uninfected gravid females of C. nigrodigitatus to be 28,676 eggs.

Also, fecundity results from the present study were found to be lower than 28,086 eggs reported

by Ekanem (2000) for Cross River population but higher than 2,884 eggs reported by Fagade and Adebisi (1979) for Lake Adejire as the highest fecundity estimated for Chrysichthys nigrodigitatus.

In this study, the range of mean egg diameter observed (2.43 mm to 3.44 mm) falls within the range reported by Imevbore (1970), Ekanem (2000) and Abraham and Akpan (2012) for gravid females of C. nigrodigitatus from the Cross River system.

Offem et al. (2008) reported that the growth of eggs has a course similar to that of the entire ovaries. In this study, egg diameter of C. nigrodigitatus which varied in fish of the same length or weight agrees with Isa et al., 2012. However, this observation corroborates the findings of Domagala and Trzebiatowski (1987) who have shown that as a rule older and larger females produce larger eggs.

Begenal (1957) observed that environmental factors and food supply might affect the fecundity of fish.

It is possible that the variation in fecundity of C. nigrodigitatus in the Cross River estuary may be due to environmental conditions and food availability in the estuary. This type of variation was also reported by some previous studies of other fish (Doha and Hye, 1970).

CONCLUSION The result of this study showed that C. nigrodigitatus from the Cross River estuary is highly fecund with positive correlation between fecundity and total length, total weight, ovary weight and mean egg diameter. Fecundity and egg diameter was found to increase with fish total weight. Knowledge about fecundity of C. nigrodigitatus is essential for evaluating the aquaculture strategies required to intensify commercial production and management of its stock since it is a valuable source of protein in Nigeria.

Sažetak ODNOS PLODNOSTI I BIOMETRIJSKIH INDEKSA KOD SREBRNOG SOMA Chrysichthys nigrodigitatus (Lacepede) U ESTUARIJU RIJEKE CROSS U NIGERIJI Odnos plodnosti i biometrijskih parametara srebrnog soma, Chrysichthys nigrodigitatus iz estuarija rijeke Cross, proučavan je od srpnja do listopada 2012. godine. Pregledano je ukupno 120 gravidnih 134

ribljih ženki. Rezultati pokazuju sljedeće kretanje plodnosti C. nigrodigitatus: od 975 jajašca kod ribe dužine 23,2 cm, ukupne težine 99 g, težine jajnika 15 g i promjera jajašca 2,43 mm do 11280 jajašca kod ribe ukupne dužine 50,0 cm, ukupne težine 1420,0 g, težine jajnika 80,0 g i promjera jajašca 3,44 mm. Pozitivna je i značajna veza između plodnosti (F) i ukupne dužine (TL), ukupne težine (TW), težine jajnika (OW) i promjera jajašca (MED): F = 2,457TL1.9225 (r = 0,8457 i r2 = 0,7152, P<0,05), F = 61,51TW0.6098 (r = 0,890, r2 = 0,7921, P<0,05), F = 28,162OW1.2468 (r = 0,9457, r2 = 0,8943, P<0,05), F = 704,44MED1.0624 (r = 0,2128, r2 = 0,0453, P<0,05).

Plodnost i promjer jajašca povećavaju se zajedno s ukupnom težinom (TW). Ovakvi rezultati važni su za ocjenjivanje strategija u akvakulturi radi povećanja komercijalne proizvodnje i stoka srebrnog soma (C. nigrodigitatus), budući da je riječ o vrlo vrijednom izvoru bjelančevina u Nigeriji.

Ključne riječi: plodnost, C. nigrodigitatus, estuarij rijeke Cross, biometrijski indeks, težina jajnika

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Isa, M. N., Mohd, N. S., Yahya, N. K., Md Nor, S. A. (2012): Reproductive biology of estuarine catfish, Arius argyropleuron (Siluriformes: Ariidae) in the northern part of Peninsular Malaysia. Journal of Biology, Agriculture and Healthcare, 2, 3, 14-28.

Komolafe, O. O., Arawomo, G. A. O. (2007): Reproductive Strategy of Oreochromis niloticus (Pisces: Cichlidae) in Opa Reservoir Ile Ife, Nigeria. International Journal of Tropical Biology and Conservation, 55, 2, 595-602.

Lampert, V. R., Azevedo, M. A., Fialho, C. B. (2004): Reproductive biology of Bryconamericus iheringgii, from Rio Vacacai, RS, Brazil. Neotropical Ichtyology, 2, 46-54.

Mayer, I., Shackey, S. E., Witthames, P. R. (1989): Aspects of reproductive biology of bass, Decentrarchus Labrax L. Fecundity and pattern of oocyte development. Journal of fish Biology, 3, 141-148.

Mesa, L. M., Caputo, V., Eastman, J. T. (2007): Gametogenesis in the Dragonfishes, Akarotaxis nudiceps and Bathydraco marrii (Pisces, Notothenizidae: Bathydraconidae) from the Ross Sea. Antarctic Science, 19, 64-70.

Offem B. O, Akegbejo-Samsons, Y., Omoniyi, I. T. (2008): Diet, size and reproductive biology of the silver catfish, Chrysichthys nigrodigitatus (Siluformes: Bagridae) in the Cross River, Nigeria. Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN0034-7744), 56, 4, 1785-1799.

Shallof, K. A., Salama H. M. (2008): Investigation on some aspects of reproductive biology in Oreochromis niloticus (Linnaeus, 1957) in inability Abu-zabal Lake, Egypt. Global Veterinariae, 2960, 351-359.

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CODEN RIBAEG ISSN 1330-061X

PREThODNO PRIOPĆENJE / PRELIMINARY COMMUNICATION

GOSPODARSKI RIBOLOV NA DUNAVU U REPUBLICI HRVATSKOJ KROZ FOXOV I SCHAEFEROV MODEL Dinko Jelkić1, Anđelko Opačak*1, Tomislav Treer2, Ivica Aničić2, Roman Safner2 Poljoprivredni fakultet u Osijeku, Kralja Petra Svačića 1d, 31000 Osijek/University of Josip Juraj Strossmayer in Osijek, Faculty of Agriculture, Department of Wildlife, Fishery and Beekeeping, Kralja Petra Svačića 1d, Osijek, Croatia 2 Agronomski fakultet u Zagrebu, Svetošimunska cesta 25, 10000 Zagreb/University of Zagreb, Faculty of Agriculture, Department of Fisheries, Apiculture and Special Zoology, Svetošimunska cesta 25, 10000 Zagreb, Croatia * Autor za korespodenciju / Corresponding Author, E-mail: aopacak@pfos.hr 1

STATUS ČLANKA / ARTICLE INFO

SAŽETAK

Primljeno/Received: 28 May 2013 Korigirano/Received in revised form: 19 June 2013 Prihvaćeno/Accepted: 5 July 2013 Dostupno na internetskoj mreži/Available online: 10 July 2013

Za analizu gospodarskog ribolova Foxovim i Schaeferovim modelom na rijeci Dunav u Republici Hrvatskoj, u razdoblju 2004. – 2009. godine, korištena je službena evidencija ulova Ministarstva poljoprivrede, Uprave ribarstva. U promatranom razdoblju prosječan godišnji ulov ribe na Dunavu iznosio je 39.088,05 ± 7.450,06 kg. Broj odobrenih i realiziranih povlastica bio je u rasponu od 19 do 25, od 30 mogućih. Utvrđen je visok udio ribara (32,28 ± 7,55%) koji nisu dostavili potpune podatke o ostvarenom ulovu i korištenim ribolovnim alatima, iako im je to zakonska obveza. Ulov po jedinici napora (CPUE) imao je velike oscilacije u promatranom razdoblju te prosječno iznosi 0,985 ± 0,290 kg·alat·sat-1. Foxov i Schaeferov model maksimalnog održivog ulova ribe u Dunavu ukazuje na relativno nisku ribolovnu kvotu (42,0 – 44,0 t) od predviđene (101,9 – 130,5 t). Radi boljeg ribolovnog gospodarenja Dunavom bilo bi potrebno pojačati edukaciju i kontrolu i ribara i ribiča, kao i osnovati zajedničko tijelo s Republikom Srbijom.

Ključne riječi: Maksimalni održivi ulov Ribolovna kvota Ribolovno gospodarenje

UVOD Gospodarski ribolov u slatkovodnom ribarstvu na području Republike Hrvatske provodi se samo na dvije granične rijeke, Savi i Dunavu, što je regulirano odredbama Zakona o slatkovodnom ribarstvu i posebnim podzakonskim propisima (Suić i sur., 2011). Za potrebe utvrđivanja stanja ihtiofaune, zaštitnih mjera i utvrđivanje ribolovnih kvota, 2002. godine Ministarstvo poljoprivrede pokrenulo je program „Praćenja stanja u slatkovodnom ribarstvu“. Program se u cijelosti financira dijelom sredstava ostvarenih prodajom (broja prodanih) godišnjih i dnevnih dozvola ribiča. Svake godine Ministarstvo poljoprivrede otvara javni natječaj na koji se mogu prijaviti samo ustanove registrirane za stručna i znanstvena istraživanja iz područja slatkovodnog ribarstva i ekologije kopnenih voda (NN, 136

2005). Ustanove rezultate istraživanja dostavljaju Ministarstvu poljoprivrede (tj. Upravi ribarstva) u obliku stručnih studija, uz obvezu njihove javne prezentacije. Na temelju stručnih studija određuje se model gospodarenja za sljedeću godinu. Isto tako, Ministarstvo poljoprivrede, odnosno Uprava ribarstva, kontinuirano prikuplja službene podatke mjesečnog i godišnjeg ulova ribe fizičkih i pravnih osoba, koje love na temelju povlastice za gospodarski ribolov i kojima je propisana obveza dostavljanja podataka (Suić i sur., 2011). Broj povlastica za obavljanje gospodarskog ribolova utvrđuje se naredbom ministra. Iako broj povlastica varira iz godine u godinu iz različitih razloga (Suić i sur., 2011), Naredbom o broju povlastica za obavljanje gospodarskog ribolova (NN, 2003, 2006, 2010) određeno je ukupno 30 povlastica za ribolovno područje rijeke Dunava i 10 povlastica za ribolovno područje

Croatian Journal of Fisheries, 2013, 71, 136-141 D. Jelkić i sur.: Gospodarski ribolov na Dunavu u Republici Hrvatskoj D. Jelkić et al.: Commercial fisheries on River Danube in Republic of Croatia

rijeke Save. Količina dopuštenog ulova iz područja gdje dopušten gospodarski ribolov smije iznositi 50% dopuštenog ulova određenog gospodarskom osnovom, tako da nositelji povlastice (ribari) ravnomjerno dijele kvotu ulova s ovlaštenicima ribolovnog prava (ribičima) za određeno područje, odnosno zonu (Suić i sur., 2011). Jedan od glavnih problema prilikom procjene maksimalnog održivog ulova je nedostatak preciznih podataka o ulovu ribe gospodarskih ribara, ali i ribiča u Dunavu, pa je uloga znanstvenih institucija tim značajnija u prikupljanju i obradi podataka vlastitih istraživanja putem monitoringa. Maksimalni održivi ulov (MSY – maximum sustainable yield) je teoretski najveći ulov koji se može uzeti iz populacije riba tijekom neograničenog perioda, bez narušavanja dugoročne produktivnosti populacije. Cilj takvog modela je održavanje veličine populacije na razini maksimalne stope rasta, tako da se jedinke koje bi bile dodane populaciji izuzimaju, omogućavajući tako produkciju populacije na maksimalnoj stopi rasta u neograničenom vremenskom periodu. Imajući u vidu dugu tradiciju gospodarskog i športskog (rekrecijskog) ribolova, prirodno bogatstvo i ribarski potencijal, Dunav predstavlja najznačajniju ribolovnu vodu nizinskog tipa na području Republike Hrvatske. U ovom području zakonski je predviđena koegzistencija sportskog i gospodarskog ribolova koji povremenim sukobljavanjima gospodarskih ribara i ribiča dovode i do ozbiljnijih antagonizama (Holoker, 1999; Timarac, 1999). Ovim radom se stoga pokušava ukazati na probleme koji generiraju analizom službenih podataka o ulovu ribe gospodarskih ribara na hrvatskom dijelu Dunava i njihovom vjerodostojnom tumačenju, kako bi se pronašao optimalan (održiv) model gospodarenja ribljim resursima ove rijeke. Radi komparacije nekadašnjeg i sadašnjeg stanja ihtiofaune rijeke Dunava te načina gospodarenja ribiča i gospodarskih ribara ovim nacionalnim bogatstvom, potrebno je razmotriti određene povijesne argumente (rezultate istraživanja) koji značajno mogu doprinijeti potpunijem razumijevanju ove problematike, ali i donošenju budućih valjanih odluka. Tako Pažur (1962) navodi kako je 1960. godine u NR Hrvatskoj ukupno bilo 2.930 privrednih ribara (570 društvenih, 549 zadružnih i 1.820 privatnih), upozoravajući da bi broj gospodarskih ribara trebalo svesti na realnu mjeru, odnosno omogućiti gospodarski ribolov samo onima kojima je to glavno (jedino) zanimanje. Između 1945. i 1977. godine postoje službeni podaci o ulovu ribe u Dunavu i pripadajućem plavnom području. Prosječan godišnji ulov u rijeci Dunavu i pripadajućem plavnom području na prostoru Hrvatske u razdoblju 1953.

– 1963. iznosio je 877,90 ± 236,66 t (Basioli, 1964), s

evidentiranim najmanjim ulovom od 584 t (1963.) te maksimalnim ulovom od 1.196 t (1957.). U sljedećem desetogodišnjem razdoblju (1964. – 1974.) prosječni godišnji ulov je smanjen na 132,45 ± 92,86 t.

Najmanji ulov od 47 t evidentiran je 1974. godine, a maksimalni ulov od 302 t ostvaren je 1965. godine (Basioli, 1976). Prema Đisalovu (1967), prosječan godišnji ulov ribe u Apatinskom području, (oko 6.000 ha), kojem pripada i hrvatski tok Dunava od 133 km i dunavci, u razdoblju 1945. – 1962. iznosio je 722 tone ili 122,7 kg/ha. Prosječni desetogodišnji ulov ribe u gospodarskom ribolovu u Dunavu na teritoriju bivše države, kako navodi Đisalov (1972), iznosio je 1.400 t godišnje, dok je prosječni desetogodišnji ulov športskim ribolovom iznosio 137 t godišnje. Ukupan ulov ribe gospodarskim ribolovom u odnosu na športski iznosio je 90,7% : 9,3%.

Ukupan prosječni godišnji ulov po jednom ribaru iznosio je 2.569 kg, a po ribiču u prosjeku 5,5 kg ribe.

Pujin i sur. (1977) navode kako je područje Dunava I (1430 rkm – 1347 rkm) vrlo produktivno područje s prosječnom godišnjom ihtioprodukcijom (desetogodišnji prosjek) od oko 750 t ili oko 112 kg/ha ribe. U jugoslavenskom dijelu Dunava, u razdoblju 1978. – 1997. godine, ulov ribe se kreće oko 900 t godišnje (Maletin i Djukic, 1998). Izražen po jedinici površine, ulov iznosi 60 – 70 kg.ha-1.god-1. Ove su vrijednosti znatno iznad procijenjenog prirasta u ovom području. On prema Mikuski (1988) iznosi 25 kg.ha-1.god-1, a prema Hristiću (1982) 20 – 45 kg.ha-1. god-1. Ihtiofauna Dunava (korito i plavne zone) zastupljena je s utvrđenih 55 slatkovodnih vrsta riba svrstanih u 16 familija (Đisalov, 1972), dok Pujin i sur. (1977) smatraju kako ih ima oko 60 vrsta, a Mrakovčić i Kerovac (1997) navode kako je utvrđeno 68 vrsta u 16 porodica. Treer i sur. (1999) navode kako je u posljednjih 20 godina uočen višegodišnji drastični pad razine vode, povezan s usporenim tokom rijeke i smanjenjem poplavnih zona (npr. u području Apatina i Koviljskog rita). Sve ovo uzrokovalo je smanjenje područja za mrijest i prehranu riba. Istovremeno su unošene alohtone riblje vrste i vršen prelov postojećih ihtiopopulacija. Opačak i sur. (2006) su inventarskim uzorkovanjem 2003. i 2004. u ribolovnom području Drava – Dunav utvrdili 25 vrsta slatkovodnih riba, s time da se abundanca kretala od 63 do 645 kom·ha-1, a ihtiomasa preračunata iz CPUE od 40,6 do 247,4 kg·ha-1.

Kasnija evidencija uključuje prikaz ulova športskog i gospodarskog ribolova na čitavom području Republike Hrvatske te otežava ozbiljniju analizu.

Na sadašnji status ihtiocenoze na hrvatskom dijelu Dunava najveći utjecaj imaju: unos alohtonih vrsta, onečišćenje, regulacija vodotoka i degradacija staništa (Mrakovčić i sur., 2006). Izgradnjom brane 137

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Đerdap I 1972. godine, i Đerdap II 1984. godine, onemogućena je migracija jesetrovki (Acipenseridae): sim (Acipenser nudiventris), pastruga (Acipenser stellatus), atlanska jesetra (Acipenser sturio), moruna (Huso huso) i dvije vrste haringi, dunavska (Alosa caspia) i crnomorska (Alosa immaculata) iz Crnog mora.

ribolovnog napora (CPUE) bio je u opadanju od 2004. do 2006. godine, od kada bilježi porast, ali u 2009. godini utvrđen je najniži ribolovni napor (0,587 kg/alat·sat) u promatranih šest godina (slika 2).

MATERIJAL I METODE Korišteni su službeni podaci Uprave ribarstva o evidenciji ribolovnih alata i ulova slatkovodnih vrsta riba za rijeku Dunav u razdoblju 2004.–2009. godine. Ribolovni napor svakog gospodarskog ribara (alat · sat) izračunat je kao umnožak broja korištenih alata s 12 sati. Za izračun maksimalnog održivog ulova (MSY) korištena su dva matematička modela: Y(i) / f(i) = a + b*xf(i) (Schaefer,1954) i ln (Y(i)/f(i)) = c + d*f(i) (Fox, 1970), gdje je Y masa ulova, dok je f ribolovni napor.

Slika 1. Zastupljenost (%) gospodarskih ribara bez potpunih podataka po godinama Fig 1. Representation (%) of commercial fishermen without complete data by year

REZULTATI Ukupni ribolovni napor, kao i ulov po jedinici napora, za sve gospodarske ribare jako varira tijekom promatranog razdoblja (tablica 1). Ukupni ulov slatkovodne ribe kreće se između 27.665 i 47.693 kg, odnosno u promatranom razdoblju prosječno je iznosio 39.088,05 ± 7.450,06 kg. Prijavljeni ukupni ulov slatkovodne ribe je znatno niži od dozvoljene ribolovne kvote koja je za razdoblje 2004. – 2009. službeno iznosila 101.983,00 kg, iako je temeljem programa „Praćenja stanja u slatkovodnom ribarstvu“ predlagano povećanje ulovnih kvota na 130.500 kg (Opačak i sur., 2010).

Broj gospodarskih ribara koji nisu dostavili potpune podatke tijekom promatranog razdoblja iznosi 32,28 % ± 7,55 %, bez trenda smanjivanja takve prakse (slika 1). Izračunati ulov po jedinici

Slika 2. Prosječni godišnji CPUE u gospodarskom ribolovu na rijeci Dunav u Republici Hrvatskoj u razdoblju 2004. – 2009.

Fig 2. Average annual CPUE in commercial fishing on the Danube in Croatia for 2004 – 2009

Tablica 1. Sumirani podaci za ukupni ribolovni napor i ukupni ulov na rijeci Dunav u razdoblju 2004. – 2009.

Table 1. Summarized data for the overall fishing effort and total catch in the Danube during 2004 – 2009

* *

Godina/ Year

Broj povlastica/ Number of fishing licenses

Broj aktivnih ribara*/ Number of active fishermen*

2004 2005 2006 2007 2008 2009

19 25 23 21 22 25

15 18 13 14 15 16

Ukupni ribolovni napor (alat sat)/ Total fishing effort (gear hour) 40.212 46.464 39.000 29.328 30.096 70.140

Gospodarski ribar s dostavljenim potpunim podacima o korištenim ribolovnim alatima i ulovu ribe Commercial fisherman who delivers full data on the catch and fishing gear used

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Ukupni ulov/ Total catch (kg) 47.693,3 44.652,95 27.665,15 33.063 40.312,9 41.141

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Prema službenim podacima ostvarenog ulova i ribolovnog napora na rijeci Dunav (tablica 1), procijenjeni maksimalni održivi ulov iznosi između 42.543,6 kg (Foxov model) i 43.901,7 kg (Schaeferov model) (Slika 3).

Slika 3. Grafički prikaz krivulja Schaeferovog i Foxov modela za gospodarski ribolov Fig 3. Graphical representation of curves for the Schaefer and Fox models for commercial fishing

RASPRAVA Prikazani ulovi slatkovodne ribe gospodarskim ribolovom na Dunavu u Republici Hrvatskoj, u razdoblju 2004. – 2009., su ispod dopuštene kvote, koja se na godišnjoj razini u navedenom razdoblju kretala oko 101,9 t (Suić i sur., 2011), a u 2013. godini iznosi 130,5 t ribe (Opačak i sur., 2012). Ukupna ribolovna kvota na rijeci Dunavu nikada nije ispunjena iznad 44,0 %, na što ukazuju i drugi autori (Jahutka i sur., 2005, 2006, 2007; Suić i sur., 2008, 2009, 2011).

Jedino je prekoračena kvota ulova šarana 2009. godine, i to 20,26 % na Dunavu (Suić i sur., 2011), što je prema Zakonu o slatkovodnom ribarstvu nedopušteno. Analiza rezultata gospodarskog ulova ribe na rijeci Dunavu varira i o autorima koji izrađuju godišnja izvješća. Tako Jahutka i sur. (2007) navode kako je gospodarski ulov na rijeci Dunav u 2006. godini iznosio 39.965,15 kg, dok Suić i sur. (2008) za istu godinu utvrđuju prijavljeni ulov od 27.552,15 kg. Prema izvornim podacima prijavljenog ulova u 2006. godini, ukupan ulov iznosi 27.665,15 kg.

Kako Foxov i Schaeferov model ukazuju na relativno nisku ostvarenu ribolovnu kvotu (42,0 t – 44,0 t), očekivano je kako će se broj gospodarskih ribara smanjivati jer ova aktivnost, prema navedenim rezultatima, više nije gospodarski isplativa. Međutim broj zahtjeva za izdavanje povlastice za obavljanje gospodarskog ribolova je u porastu. Opravdanje za ovaj paradoks može se pronaći u slabom nači-

nu kontrole obavljanja gospodarskog ribolova, što omogućava razne manipulacije ribom, netočnim prijavljenim podacima, kao i u rastu nezaposlenosti u Republici Hrvatskoj. Ribarski inspektori su jedini nadležni za kontrolu gospodarskog ribolova temeljem Zakona o slatkovodnom ribarstvu. Isto tako, utvrđeno je kako 32 % gospodarskih ribara ne dostavlja službene podatke, što upućuje kako se ti podaci Uprave ribarstva o gospodarskom ribolovu na rijeci Dunav ne mogu koristiti za ozbiljnu stručnu analizu niti se na temelju njih mogu donositi valjane odluke. Također, na temelju tih podataka ne može se izračunati vjerodostojan maksimalni održivi ulov korištenjem Schaeferovog i Foxovog modela.

Jedini dugoročni način gospodarenja ovim ribolovnim resursom je održivo gospodarenje (Safner i sur., 2002). U izgradnji bolje politike upravljanja ribolovnim resursima naših rijeka, potrebno je uvažiti i značaj temeljnih socioloških čimbenika koji utječu na ponašanje ribara i ribiča u slatkovodnom ribarstvu (Čaldarević, 2006). Gospodarski ribolov na slatkim vodama je dio hrvatske tradicije te se stoga ne bi trebao ukinuti. Jedino ga je potrebno prilagoditi postojećem stanju ihtiocenoze i mogućem godišnjem prirastu. Međutim, postojeći način gospodarenja slatkovodnom ribom u Dunavu nije dugoročno primjenjiv i održiv. Kontrola mora biti bolja, a prekršaji se moraju sankcionirati. Uz to je potrebna dodatna edukacija ribara (ali i ribiča, čija točnost podataka je također znatnim dijelom upitna), kako bi obje skupine bile svjesne da je korektna dostava podataka ne samo njihova obveza, nego je prvenstveno u njihovom interesu radi pravilnog gospodarenja (Treer i sur., 2012). Ovaj problem uočen je i u susjednim državama na Dunavu, u Srbiji i u Mađarskoj (Treer i sur., 2013). S obzirom na to da je Dunav granična rijeka na kojoj bi model gospodarenja trebale prihvatiti obje države, potrebno je uspostaviti suradnju s nadležnim ministarstvom u Republici Srbiji radi osnivanja zajedničkog tijela za ribarsko gospodarenje Dunavom, u koje bi ušli predstavnici svih zainteresiranih stana (ribari, ribiči, znanstvenici te tijela lokalne i državne uprave).

Očekivane skorašnje izmjene postojećeg Zakona o slatkovodnom ribarstvu u prometu ribom (iskrcajna mjesta, prva prodaja, prvi kupac i dokumentirani put ribe do krajnjeg kupca) pomoći će u sprječavanju crnog tržišta, krivolova, boljoj evidenciji, nadzoru ulova i otkupa ribe, ali bez pojačanog nadzora i edukacije i ribiča i ribara, organiziranog otkupa ulovljene ribe za tržište te ekonomske opravdanosti ovoga posla, na Dunavu ne treba očekivati značajne promjene.

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Croatian Journal of Fisheries, 2013, 71, 136-141 D. Jelkić i sur.: Gospodarski ribolov na Dunavu u Republici Hrvatskoj D. Jelkić et al.: Commercial fisheries on River Danube in Republic of Croatia

Abstract COMMERCIAL FISHERIES ON THE DANUBE IN THE REPUBLIC OF CROATIA ANALYZED BY THE FOX AND SCHAEFER MODELS Official data of the Ministry of Agriculture, Directorate of Fisheries was used in order to analyze commercial fisheries on the Danube in the Republic of Croatia between 2004 and 2009 (average annual catch was 39,088.05 kg ± 7,450.06 kg).

The number of approved and used licenses varied between 19 and 25, out of a possible 30. A high percentage of fishermen (32.28% ± 7.55%) who ignored the legal obligation to deliver full data on the catch and tools used was determined. Catch per unit effort (CPUE) varied greatly with an average of 0.985 ± 0.29 kg · tool · hour-1. The Fox and Schaefer models of maximum sustainable yield in the Danube indicate a relatively low fishing quota (42.0–44.0 t) in comparison to the anticipated (101.9–130.5 t). In order to improve fishery management, it is necessary to enhance the education and control of recreational and commercial fishermen, as well as to form a joint administrative body with the Republic of Serbia.

Keywords: maximum sustainable yield, fishing quota, fishery management

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Croatian Journal of Fisheries, 2013, 71, 142-146 S. O. Adeyemi: Fish production estimates for Gbedikere lake

CODEN RIBAEG ISSN 1330-061X

ShORT COMMUNICATION

FISH PRODUCTION ESTIMATES FOR GBEDIKERE LAKE, BASSA, KOGI STATE, NIGERIA Samuel Olusegun Adeyemi Department of Biological Sciences, Faculty of Natural Sciences, P.M.B.1008, Kogi State University, Anyigba, Kogi State, Nigeria Corresponding Author, E-mail: sadeyemi2003@yahoo.com

ARTICLE INFO

ABSTRACT

Received: 16 November 2012 Received in revised form: 11 April 2013 Accepted: 15 May 2013 Available online: 6 July 2013

Annual estimates of the fish caught by local fishermen in randomly selected fishing villages adjacent to Gbedikere Lake were determined using Catch Assessment (CAS). The studies were carried out within two seasons of low water (February) and high water (September) periods between 2006 and 2008. Annual fish catch varied from 537.4 mts to 576.9 mts at high water. Mean catch per boat ranged from 7.40 kg to 10.60 kg among the landing sites. A total of 12 fish species were identified belonging to ten families. The catches were dominated by cichlids with Orechromis niloticus dominating the overall catch compositions.

Production estimate was compared with the catches obtained through experimental gill-net sampling and potential fish yield estimates using Ryderâ&#x20AC;&#x2122;s Morpho - Edaphic Index (MEI) as modified by Henderson and Welcomme (1974). Contributions of the gears in use were also done with cast nets ranking above others (29%), followed by the set net (25%), hook and lines (16.6%), traps (16.6%), clap net (8.3%). Management measures were suggested.

Keywords: Gbedikere Lake Fish productions Catch assessment Fishermen Fish landings Fish yield

INTRODUCTION Lakes are invaluable ecological resources that serve many human needs and, therefore, enhance our lives by providing a lot of opportunities. This explains why a large proportion of Nigeria population lives near water bodies such as lakes, reservoirs, rivers, swamps and coastal lagoons. Many depend heavily on the resources of such water bodies as their main source of animal protein and family income (Haruna et al., 2006).

Catch Assessment Surveys (CAS) are conducted to obtain reliable current estimates of the total quantity of the fish harvested by fishers. Species composition and fishing effort involved in the catch are considered as secondary objectives while frame surveys among other things provide reliable estimates of changes in the size and structure in the fishing industry over time. Bazigos (1972) studied the yield pattern at Kainji Lake using CAS just as Moses et al. (2002) also used catch assessment meth142

od to estimate catches for the artisanal fisheries of south-eastern Nigeria.

CAS could also reveal whether a lake has been overfished or is being underfished. Coulter (1988) found that Lake Tanganyika was underfished in his assessment of the pelagic fish biomass of the lake.

Ryder and Henderson (1975) also estimated the potential fish yield for Nasser Reservoir in Egypt using catch assessment and found little evidence to support overexploitation of the stock.

This study describes the fish production in five communities located along the shores of Gbedikere Lake, as well as the contribution of various gears employed for fishing.

MATERIALS AND METHODS Frame surveys were carried out involving the count of all the fishing villages, number of fishermen, boats and fishing gears after the methods described in Apeloko and du Feu (1995) and Bankole and

Croatian Journal of Fisheries, 2013, 71, 142-146 S. O. Adeyemi: Fish production estimates for Gbedikere lake

Mbagwu (2000). Physico-chemical parameters for the lake were obtained using standardized methods as given in APHA (1980). Fish production was estimated using CAS (Bankole and Mbagwu, 2000).

The catch assessment surveys were carried out six times. These were conducted in 3 randomly selected villages among the ones identified from the frame survey. Daily records of catches for six fishermen for 3 days each were obtained once for a low water period and a high water period of 1998, 1999 and 2000. This was done to determine fish abundance by species, weight, catch per boat and overall fish production for the entire lake as stated earlier.

Production estimate was compared with catches obtained through experimental gill-net sampling, as well as potential fish yield estimates using Ryder’s Morpho-Edaphic Index (MEI) as modified

by Henderson and Welcomme (1974) using conductivity, Toews and Griffith (1979) using conductivity and Schlesinger and Regier (1982) using Total Dissolved Solids (TDS) in the MEI models. These are given by:

is grossly underexploited with only one fisherman given the 11/2 or 2 fishermen per km2 recommendation by Henderson and Welcomme (1974).

Table 1. Physical characteristic of Gbedikere lake (ADP, 1995) PARAMETER Average annual run – off (m3) Type of lake Crest elevation(m) Crest length (m) Dead storage level (mAMSL) Top width (m) Maximum base width (m) Maximum height (m) Total storage capacity (m3) Dead storage capacity (m3) Active storage capacity (m3) Surface Area (ha) Spillway width (m) Spillway level (m) Spillway type Mean depth (m)

VALUE 1.50 x 1.08 Natural lake 31.50 1.0 50 4.50 15.0 1.50 0.50 x 1.08 1.50 x 1.06 0.70 x 1.08 @50m AMS 6.75 0.70 x 2 50.10 Free flow 12.00-15.00

(1) Henderson and Welcomme (1974) Y = 14.3136 MEI 0.4681

Table 2. Monthly water quality parameters for Gbedikere Lake from 2006 to 2008

Where MEI is

Parameter Mean±sd Range Surface Water Temperature °C 27.50 ± 0.05 26.00 -29.00 pH 6.55 ± 0.12 5.08 - 8.02 Conductivity (µmhos/cm) 14.07 ± 11.08 0.04 - 49.19 Dissolved Oxygen (DO2) mgL-1 8.65 ± 1.08 6.10 - 19.85 Total Dissolved Solid (TDS) 19.33 ± 10.09 13.00 - 45.00 mgL-1 Water Transparency(cm) 26.60 ± 8.17 8.00 -68.7

(2) Toews and Griffith (1979) Log Y = 1.4071 + 0.3697 Log MEI – 0.00004565 A0 Where A0 = Lake area in km2 (3) Schlesinger and Regier (1982) Log Y = 0.050 Tm + 0.280 Log MEI + 0.236 Where Tm = Mean Temperature.

RESULTS Physical and chemical parameters of Gbedikere Lake are provided in Table 1 and 2. Water quality parameters of temperature, pH, oxygen, conductivity, total dissolve solids and transparency showed that the lake exhibits a nutrient fair system.

The fish landing identified around Gbedikere Lake was Biroko, being the only location where all the fishermen landed their respective catches.

Generally, fewer numbers of fishers and boats were recorded between 2006 and 2008.

Fishers’ population was 55, 50 and 48 in 2006, 2007 and 2008, respectively (Table 3). This shows a declining trend. The general decline could be attributed to the tenancy nature of the lake coupled with the migratory nature of the fishers. The fishers are constantly on fishing migration when informed of an improved fishing ground. The lake (6.75 ha)

In the fishermen’s landings fish from 10 families were recorded. These include Osteoglossidae, Heterotis niloticus (Linnaeus, 1762); Cichlidae, Oreochromis niloticus (Linnaeus, 1758) and Tilapia zilli (Gervais, 1848); Clariidae, Heterobranchus bidorsalis (Geoffrey Saint – Hilaire, 1809; Citharnidae, Citharinus citharus (Geoffrey Saint – Hilaire, 1809); Gymnarchidae, Gymnarchus niloticus (Linnaeus, 1758); Protopteridae, Protopterus annectens (Owen, 1883); Mochokidae, Synodontis nigrita (Valenciennes, 1840); Clariidae, Clarias gariepinus (Burchell, 1822); Cyprinidae, Labeo senegalensis; Mormyridae, Mormyrus rume (Valenciennes, 1846); and Malapteruridae Malapterurus electricus (Gmeiin, 1789).

The highest fish landing was 21,721.5 kg recorded in January 2007, 21,655.4 kg in February 2007 and 20,216.3 kg in December 2006. These form 38.6%, 38.5% and 35.9%, respectively. Cichlidae dominated the catches constituting 30.91%, followed by H. niloticus (15.56%) and C. gariepinus (13.16%), while 143

Croatian Journal of Fisheries, 2013, 71, 142-146 S. O. Adeyemi: Fish production estimates for Gbedikere lake

Table 3. Frame assessment result showing the distribution of fishermen’s boats and gears along the shores of Gbedikere Lake in September 2006, 2007 and 2008 Landing Type of fishing site village

Biroko

Village Fishing camp Fishing camp Village Village

Total

No. of fishermen

Types of gears

Boat owners Assistants Cast net Set net Hook and line 2006 2007 2008 2006 2007 2008 5 3 3 10 7 7 x x 5 3 2 11 9 10 x x x 5 2 3 12 10 9 x x 4 3 3 12 12 11 x x 4 3 2 10 12 11 x x 55 50 48

Traps Clap nets x x x

x

Table 4. Estimated landings (kg) from fishermen’s catches for Gbedikere Lake for the low water period of 2006 –2007, February 2008 Species Jan Feb Mar Apr Heterotis niloticus 27.6 22.6 30.3 24.5 Oreochromis niloticus 38.5 38.3 44.4 36.4 Tilapia zilli 10.2 10.7 13.4 11.3 Heterobranchus bidosarlis 7.3 15.4 23.2 19.5 Citharinus citharus 5.7 4.6 3.9 5.4 Gymnarchus niloticus 13.2 15.3 14.7 15.9 Protopterus annectens 6.3 4.7 5.1 5.0 Synodontis nigrita 7.9 5.7 6.9 7.4 Clarias gariepinus 19.8 14.2 29.8 22.6 Labeo senegalensis 2.3 3.9 2.0 3.5 Mormyrus rume 2.9 3.9 1.2 3.1 Malapterurus electricus 0.0 0.0 1.6 2.2 Total 141.7 139.3 176.4 156.8 No. of boats sampled/ 6 6 6 6 day No of boats 18 18 18 18 sampled for 3days Catch per boat (kg) 7.9 7.7 9.8 8.7

May June Jul Aug Sept Oct 24.4 28.4 20.5 31.3 30.0 54.4 28.6 29.2 24.6 20.2 18.2 29.9 13.6 15.7 17.3 16.5 14.4 13.2 15.4 12.8 22 19.6 17.9 20.8 4.3 7.5 8.3 7.7 10.3 14.4 15.3 8.3 6.2 6.0 5.2 4.5 4.8 2.5 2.2 1.7 2.3 2.7 9.6 7.8 9.3 7.8 8.7 9.2 18.7 16.7 25.8 23.7 18.6 20.3 4.1 3.2 4.5 5.7 5.9 7.8 1.1 1.0 2.0 2.6 5.1 4.3 1.1 1.0 1.5 2.6 2.8 3.0 140.9 134 144.2 145.4 139.4 184.5

Nov Dec Total 46.7 50.3 391.0 22.6 26.6 357.5 14.6 11.3 162.2 23.6 18.6 216.1 12.5 11.1 95.7 3.3 2.1 110.0 1.8 2.1 41.2 5.8 6.3 92.4 17.3 17 244.5 6.3 5.8 55.0 3.4 4.2 34.8 1.1 2.1 19.0 159 157.5 1819.1

6

6

6

6

6

6

6

6

72

18

18

18

18

18

18

18

18

216

7.8

7.4

8

8.1

7.7

10.3

8.8

8.8

101

Table 5. Estimated Landings (kg) from fishermen’s catches for Gbedikere Lake for the high water period of 2006-2008 Species Heterotis niloticus Oreochromis niloticus Tilapia zilli Heterobranchus bidosarlis Citharinus citharus Gymnarchus niloticus Protopterus annectens Synodontis nigrita Clarias gariepinus Labeo senegalensis Mormyrus rume Malapterurus electricus Total No. of boats sampled/day Total No of boats sampled for 3 days Catch per boat (kg)

144

Jan 53.2 34.7 10.2 15.9 9.4 6.6 2.1 6.0 18.9 4.5 4.0 1.0 166.5 6.0

Feb 51.4 45.3 9.6 12.6 14.9 8.9 3.2 8.9 13.3 3.5 2.7 1.0 175.3 6.0

Mar 27.8 40.4 13.6 11.8 8.9 14.8 2.6 5.8 20.6 3.3 2.3 0.0 151.9 6.0

Apr 23.7 42.1 9.8 19.8 8.2 18.6 2.9 6.2 23.2 2.6 3.1 0.9 161.1 6.0

May 21.7 41.9 12.8 18.0 7.3 20.4 3.7 6.4 20.3 2.1 4.4 1.1 160.1 6.0

Jun 30.2 34.8 14.6 20.9 11.7 20.9 3.9 8.7 20.0 4.5 3.5 1.0 174.7 6.0

Jul 28.7 40.9 12.9 25.7 13.3 14.5 4.1 9.3 23.6 3.8 6.4 2.0 185.2 6.0

Aug 26.4 42.3 18.4 23.0 12.6 12.5 4.0 8.6 28.1 4.9 7.7 2.6 191.1 6.0

Sept 18.9 38.2 17.9 21.6 16.3 10.4 3.7 8.8 22.4 6.9 6.9 2.0 174.0 6.0

Total 282.0 360.6 119.8 169.3 102.6 127.6 30.2 68.7 190.4 36.1 41.0 11.6 1539.9 54.0

18.0

18.0

18.0

18.0

18.0

18.0

18.0

18.0

18.0

162.0

9.3

9.7

8.4

9.0

8.9

9.7

10.3

10.6

9.7

85.5

Croatian Journal of Fisheries, 2013, 71, 142-146 S. O. Adeyemi: Fish production estimates for Gbedikere lake

the rest altogether form 40.37%. The mean catch per month was 24.4% for Gbedikere Lake (Table 4 and 5).

Estimated landings for the whole lake during the low water period were 11.913.3 mts of fish, recorded in 2006. This declined to 6.449.2 mts in 2007 and 2008. For the high water periods the estimated landings were 7.580.3 mts in 2007, followed by 6.923.2 mts in 2008. In general, about the same amount of fish seemed to have been landed for both periods.

These are evident in the mean catches for both 537.4 mts for low water and 576.9 mts for high water. A closer observation reveals that the trend for low water (February) showed a steady decline. The landing for low water of 2007 was 2165.5 mts, while in 2008 it was 1000.1 mts. These show a decline from 27.3% to 14.8%, respectively. The trend for high water (September) showed a sharp decline between 2006 and 2008. The trend is 16.6% in 2006 to 15.8% decline in 2008 due to poor catches within this period. Generally, small sized fish were caught at this time which could be attributed to growth overfishing. Growth overfishing occurs when the effort is so high that the total yield decreases with increasing effort. Thus the fish are caught before they can grow to a sufficiently large size that can substantially contribute to the fishery. Thus the mean annual yield obtained through Catch Assessment Surveys during the study was 240.2 mts. Catch per unit of effort was 24.4 kg ha-1 for the experimental gillnets.

Estimated total catch from the experimental gillnets was 326.6 metric tons.

DISCUSSION The result shows that the lake is overfished based on the statistics recorded for the year 2006, 2007 and 2008, as well as low fish catch. Catches are lower both quantitatively and qualitatively. This general decline observed in fish abundance on the lake could thus be attributed to the declining fish catch coupled with the declining number of fishermen.

The fishermen are constantly on the move once they receive information about improved catches anywhere; they migrate to such a new â&#x20AC;&#x2DC;greener pastureâ&#x20AC;&#x2122;. Reproduction is very vital to the sustenance, replenishment and progeny maintenance of every living organism. Fish stock is a renewable natural resource which gets replenished from incessant cropping by fishermen through reproduction. The conversation and survivability of any fish species depend more importantly on its reproductive potential. The Gbedikere Lake species are exposed to a

daily vigorous harvesting regime by the fishermen.

Yet the fish stock had been able to sustain itself even in the face of such onslaught through its resilience.

This resilience is made possible through its reproduction potentials.

The number of fishermen recorded for the lake varied from 48-50. This is more than expected; the reservoir with a surface area of 9.6 km2 ought not to have more than 1 fisherman at the recommended rate of 2 fishermen per square kilometer (Henderson and Welcomme, 1974).

The yield result obtained from experimental gill net catches was observed to constitute above 60% of the landings by all gears on the lake pooled together.

Thus the landings on the lake could be in the range of 326.6 metric tons of fish. This is not far from the overall mean landing of 240.2 metric tons obtained from CAS. It could therefore be said that the fish landing on the lake could be between 300 and 400 metric tons. This would fetch the lake a modest estimate of N24, 000,000.00 yr-1 at the rate of N80.00 per kg of fish. This is much lower than the earlier estimates of 870 mt yr-1 obtained in Bankole and Mbagwu (2000). However, this production is more than the predicted potentials obtained using the various predictive models above.

In a similar study around the southeastern area of Nigeria, Moses et al. (2002) obtained a mean catch per boat of over 6000 kg from the artisanal fisheries. However, the study by Moses et al (2002) covered a much wider area and included tributaries of major rivers.

The catches on Gbedikere Lake showed a dominance of cichlids, particularly T. zillii and O. niloticus. These were followed by H. niloticus and C. gariepinus in abundance. Apart from the C. gariepinus that reflected promising sizes, the catches generally showed small sized fish, even though most of the species could attain bigger sizes.

To conserve the fish resources, there is the need for intervention through enforcement of the state fishery edict, especially in the area of harvesting small sized (juvenile) fish. This could be done through a community based management approach. This approach will engender/involve a close cooperation among the stakeholders, i.e. the government of the state, the fisher folks and the local community. Once this cooperation is achieved it would be easier to manage the fishery at a sustainable level and the anticipated contribution of the lake to the fish production of the North Centre zone of Nigeria would be achieved.

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Croatian Journal of Fisheries, 2013, 71, 142-146 S. O. Adeyemi: Fish production estimates for Gbedikere lake

Sažetak PROCJENA PRODUKCIJE RIBA U JEZERU GBEDIKERE (BASSA, DRŽAVA KOGI, NIGERIJA) Godišnja procjena ulova lokalnih ribara za slučajno odabrana ribarska sela iz obližnjeg jezera Gbedikere izvršena je CAS metodom. Istraživanja su provedena u dvama razdobljima tijekom niskog vodostaja (u veljači) i visokog vodostaja (u rujnu) u periodu od 2006. do 2008. godine.

Godišnji ulov kretao se između 537,5 t i 576,9 t pri visokom vodostaju. Prosječan ulov po ribarskom brodu kretao se od 7,4 kg do 10,6 kg između mjesta iskrcaja. Ukupno je identificirano 12 vrsta koje pripadaju u 10 porodica. U ulovu su dominirale vrste iz skupine Ciclidae, od kojih je Orechromis niloticus bila najzastupljenija u ukupnom ulovu. Procjena produkcije je uspoređena s eksperimentalnim ulovom mrežama i potencijalnom procjenom prirasta upotrebom Morpho-Edaphic indeksa (MEI), kako su odredili Henderson i Welcomme.

Doprinos je napravljen i međusobnom usporedbom ribolovnih alata, a najčešće su korištene mreže sačmarice (29%), zatim stajačice (25%), udice i parangali (16,6%), vrše (16,6%) te povlačne mreže (8,3%). Predložene su daljnje mjere gospodarenja.

Ključne riječi: jezero Gbedikere, produkcija, procjena ulova, ribari, ulov, prirast

REFERENCES ADP (1995): Survey of Agricultural Developments Projects in Kogi State, Nigeria 186 p.

Apeloko, F., du Feu, T. A. (1995): Frame Survey, Kainji Lake National Institute for Freshwater fisheries Research (NIFER) Annual Report, 177-180.

APHA (1980): Standard methods for examination of water and waste water. 15th ed. American Public Health Association, Washington D.C., 1134 p.

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Bankole, N. O., Sule, O. D., Okwundu E. C., Umoru, I., Balogun. I. (1994): Preliminary investigation on the frame and Catch Assessment Survey of Alau Lake, Maiduguri, Borno State. N.I.F.F.R., Annual report, 134-147.

Bankole, N. O., Mbagwu, I. G. (2000): Aspects of the Fisheries of Alau Lake, Maiduguri ,BornoState, North Eastern Nigeria. African journal of tropical hydrobiology and fisheries, 1-2, 49–62.

Bazigos, G. P. (1972): Frame survey at Kanji Lake Nigeria FAO/UNDP/SF/NIR/24/ST.1.

Coulter, G. W. (1988): Production dynamics in Lake Tanganyika. In; Predator prey relationships, population dynamics and Fisheries productivity of large African Lakes (Ed. by D. Lewis). CIFA Occass, Pap. 15, 18–25.

Haruna, A. B., Abubakar, K. A., Ladu, B. M. B. (2006): An assessment of physico-chemical parameters and productivity status of Lake Geriyo, Yola, Adamawa state, Nigeria. Biological and Environmental Sciences Journal for the tropics, 3, 1, 18-23.

Henderson, H. F., Welcomme, R. C. (1974): The relationship of yield to morpho-edaphic Index and numbers of fishermen in African Inland Fisheries. FAO, Rome. CIFA Occassional Paper, 1, 19 p.

Moses, B. S., Udoindiong, O. M., Okon, A. O. (2002): A statistical survey of the artisanal fisheries of south- eastern Nigeria and the influence of hydroclimatic factors on catch and resource productivity. Fisheries Research, 57, 267-278.

Ryder, R. A., Henderson, H. F. (1975): Estimates of potential Fish yield for Nasser Reservoir, Arab Republic of Egypt. Journal of the Fisheries Research Board of Canada, 32, ii, 2131–2157.

Schlesinger, D. A., Regier, H. A. (1982): Climatic and morphoedaphic indices of fish yields from natural lakes. Transactions of the American Fisheries Society, 111, 141-150.

Toews, D. R., Griffith, J. S. (1979): Empirical estimates of potential fish yield for the Lake Bangwelu system, Zambia, Central Africa. Transactions of the American Fisheries Society, 108, 241- 252.

Croatian Journal of Fisheries, 2013, 71, 147-148 J. I. Robalo et al.: Threatened fishes of the world: I. almacai

CODEN RIBAEG ISSN 1330-061X

ShORT COMMUNICATION

THREATENED FISHES OF THE WORLD: Iberochondrostoma almacai COELHO, MESQUITA & COLLARES-PEREIRA, 2005 (Cyprinidae) Joana Isabel Robalo*1, Carla Sousa-Santos1, Maria Manuela Coelho2, Vítor Carvalho Almada1 Unidade de Investigação em Eco-Etologia, Instituto Superior de Psicologia Aplicada, 34. 1149-041 Lisboa, Portugal Universidade de Lisboa, Faculdade de Ciências, Centro de Biologia Ambiental/Departamento de Biologia Animal, Campo Grande, 1749-016 Lisboa, Portugal * Corresponding Author, E-mail: jrobalo@ispa.pt

1 2

ARTICLE INFO

ABSTRACT

Received: 25 Juny 2013 Received in revised form: 12 July 2013 Accepted: 22 July 2013 Available online: 3 September 2013

Iberochondrostoma almacai is an endemic cyprinid fish from the southwest of the Iberian Peninsula, with a distribution area restricted to three independent Portuguese river basins. This species is critically endangered due to water abstraction, pollution, habitat destruction and introduction of exotic species. Captive breeding for restocking purposes is already being conducted.

Keywords: Iberochondrostoma almacai Endemic species Conservation Restocking

COMMON NAME Boga do Sudoeste (Portuguese) (Fig 1).

lateral line and 3.5-5.5 scales below the lateral line (Coelho et al., 2005).

DISTRIBUTION This species is endemic to the southwest Portuguese drainages of the Mira, Arade and Bensafrim (Ribeiro et al., 2007).

ABUNDANCE Fig 1. Iberochondrostoma almacai sampled at the River Arade (Scientific illustration by Clara Almada)

CONSERVATION STATUS Critically Endangered (Portuguese Red Data Book Cabral et al., 2005).

IDENTIFICATION This small cyprinid (up to 148 mm TL) presents 4553 scales in the lateral line, 10.5-12 scales above the

The species is highly fragmented and has a small distribution range. Genetic data indicate a population decrease in the last 100 to 2400 years, probably as a result of anthropogenic disturbance (range of estimated effective population size 25-163) (Sousa et al., 2010).

HABITAT AND ECOLOGY This fish lives in small or medium-sized Mediterranean-type streams surviving the summer in small pools under the shade of vegetation.

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Croatian Journal of Fisheries, 2013, 71, 147-148 J. I. Robalo et al.: Threatened fishes of the world: I. almacai

REPRODUCTION

Sažetak

I. almacai breeds from January to April. Both sexes mature at age 2. This species presents high fecundity. A female with 100 mm may release more than 3000 eggs (Magalhães, 2002).

UGROŽENE VRSTE RIBA U SVIJETU: Iberochondrostoma almacai COELHO, MESQUITA & COLLARES-PEREIRA, 2005 (Cyprinidae)

THREATS

Iberochondrostoma almacai je endemska vrsta ribe s jugozapada Iberijskog poluotoka, nastanjena u ograničenom području triju nezavisnih portugalskih riječnih slivova. Ova vrsta posebno je ugrožena zbog raznih vodozahvata, zagađenja, uništavanja staništa i uvođenja egzotičnih vrsta. U tijeku je uzgoj ove vrste za daljnje provođenje poribljavanja.

Water abstraction and pollution affect fish directly and lead to severe habitat destruction. Additionally, the construction of dams and the introduction of exotic species are thought to contribute to the decrease of sub-populations, mainly in the River Arade.

CONSERVATION Ex-situ reproduction is already being implemented (http://exsitu.quercusancn.pt/) and the River Mira was already restocked in 2013 with more than 900 captive bred individuals (descendants from a brood stock captured in the same river basin to preserve the gene pool of the original population).

CONSERVATION RECOMMENDATIONS Riparian habitat recovery and digging pools where fish can survive extreme summer droughts are imperative river rehabilitation measures. Selective removal of exotic species should also be implemented as they compete with endemic species and prey on them. Since the genetic diversity index values obtained for the cytochrome b gene are moderately low (Sousa-Santos et al., 2013), measures to implement gene flow within the two described conservation units (mainly represented by the Mira and Arade rivers) are recommended to enhance genetic diversity (Sousa et al., 2010).

ACKNOWLEDGMENTS This study was funded by FCT – Portuguese Foundation for Science and Technology (partially FEDER funded), under the pluriannual financing programme UI&D 331/94 and the project PTDC/ AAC-CLI/103110/2008. C. Sousa-Santos was supported by a Post-doctoral grant from FCT (SFRH/ BPD/29774/2006).

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Ključne riječi: Iberochondrostoma almacai, endemske vrste, konzervacija, poribljavanje

REFERENCES Cabral, M. J., Almeida, J., Almeida, P. R., Dellinger, T., Ferrand, N., Oliveira, M. E., Palmeirim, J. M., Queiroz, A. I., Rogado, L., Santos-Reis, M. (eds).

(2005): Livro Vermelho dos Vertebrados de Portugal. Instituto de Conservação da Natureza, Lisboa (in Portuguese), 659 p.

Coelho, M. M., Mesquita, N., Collares-Pereira, M. J. (2005): Chondrostoma almacai, a new cyprinid species from the southwest of Portugal, Iberian Peninsula. Folia Zoologica, 54, 1–2, 201–212.

Magalhães, M. F. (2002): Gradientes espaciais, variabilidade ambiental e estrutura de comunidades piscícolas em rios de tipo mediterrânico. PhD thesis, University of Lisbon (in Portuguese with English summary), 171 p.

Ribeiro, F., Beldade, R., Dix, M., Bochechas, J. (2007): Carta Piscícola Nacional. Direcção Geral dos Recursos Florestais-Fluviatilis, Lda. Online publication (version 09/2007). Electronic version available at http://www.cartapiscicola.org, downloaded on 25/06/2013. (In Portuguese) Sousa, V., Penha, F., Pala, I., Chikhi, L., Coelho, M. M. (2010): Conservation genetics of a critically endangered Iberian minnow: evidence of population decline and extirpations. Animal Conservation, 13, 162-171.

Sousa-Santos, C., Robalo, J., Santos, J. M., Branco, P., Ferreira, T., Sousa, M., Ramos, A., Castilho, R., Doadrio, I., Almada, V. (2013): Atlas Genético Nacional dos peixes ciprinídeos nativos. Electronic version available at http://www. fishatlas.net, downloaded on 25/06/2013. (in Portuguese with English summary)

Prilozi ribarstvenoj struci / Supplement to fishing profession

DR. SC. ZLATICA TESKEREDŽIć – MARLJIVA I POŽRTVOVNA GLAVNA UREDNICA ČASOPISA „CROATIAN JOURNAL OF FISHERIES“ („RIBARSTVO“) Desetogodišnje razdoblje od 2003. do 2012. godine obilježeno je izuzetnim zalaganjem glavne urednice dr. sc. Zlatice Teskeredžić u približavanju časopisa „Croatian Journal of Fisheries“ svjetskim ihtiološkim i biološkim znanstvenim zajednicama. Tijekom tog napornog i nimalo lakog perioda, potrebno je konstatirati da je dr. sc. Teskeredžić u svom naumu uspjela.

Njezino zalaganje dovelo je do znatnog povećanja broja baza podataka u kojima je časopis indeksiran te je tako postao vidljiv i međunarodnoj znanstvenoj zajednici. Osim toga, Hrvatska gospodarska komora je zahvaljujući dr. sc. Teskeredžić prihvatila posao tiskanja časopisa, a ta praksa je nastavljena do danas.

Upravo za vrijeme mandata dr. sc. Teskeredžić, časopis dobiva i vlastitu web-stranicu s online prijavama, što rezultira znatno većim brojem pristiglih kvalitetnih radova. Promjenom imena časopisa iz

„Ribarstvo“ u „Croatian Journal of Fisheries“, časopis postaje koristan i zanimljiv i znanstvenicima međunarodnih krugova.

Razina časopisa, na koju ga je dr. sc. Zlatica Teskeredžić podigla, pokušava se održati i danas kada je časopis postao moderni znanstveni časopis kakvom je Zlatica uvijek i težila. Časopis „Croatian Journal of Fisheries“ danas je važan za znanstvenike iz cijelog svijeta za objavljivanje najnovijih dostignuća u području ribarstva. Osim toga, omogućuje brz protok informacija te na taj način pomaže razvoju ribarskih stručnjaka.

Naša draga Zlatica se međutim nije potpuno povukla, nego i dalje svojim savjetima sudjeluje u kreiranju časopisa kao iskusna članica uredništva.

Možemo joj stoga poželjeti zaslužene mirne, ali i aktivne umirovljeničke dane.

Doc. dr. sc. Tea Tomljanović

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Number 3

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Original scientific paper THE RESPONSE OF BENTHIC MACROINVERTEBRATE AND FISH ASSEMBLAGES TO HUMAN IMPACT ALONG THE LOWER STRETCH OF THE RIVERS MORAVA AND DYJE (DANUBE BASIN, CZECH REPUBLIC) Zdeněk Adámek, Světlana Zahrádková, Pavel Jurajda, Ilja Bernardová, Zdenka Jurajdová, Michal Janáč, Denisa Němejcová

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EVALUATION OF FERMENTED MANGO (Mangifera indica) SEED MEAL IN THE PRACTICAL DIET OF NILE TILAPIA, (Oreochromis niloticus) FINGERLINGS Samuel Olubodun Obasa, Segun Peter Alatise, Isaac Tunde Omoniyi, Wilfred Olusegun Alegbeleye, Francisca Adebukola George STUDY OF PROBIOTICS ON THE SEED PRODUCTION OF BLACK TIGER SHRIMP Penaeus monodon Sheikh Aftab Uddin, M. Abdul Kader, M. Nurul Azim Sikder, M. Abdul Hakim, M. Mahbub Alam, Ashraful Haque Azad, Chowdhury Kamrul Hasan RELATIONSHIP BETWEEN FECUNDITY AND BIOMETRIC INDICES OF THE SILVER CATFISH Chrysichthys nigrodigitatus (Lacepede) IN THE CROSS RIVER ESTUARY, NIGERIA Victor Oscar Eyo, Albert Philip Ekanem, George Eni, Asikpo Patience Edet Preliminary communication COMMERCIAL FISHERIES ON THE DANUBE IN THE REPUBLIC OF CROATIA ANALYZED BY THE FOx AND SCHAEFER MODELS Dinko Jelkić, Anđelko Opačak, Tomislav Treer, Ivica Aničić, Roman Safner Short communication FISH PRODUCTION ESTIMATES FOR GBEDIKERE LAKE, BASSA, KOGI STATE, NIGERIASCHAEFER MODELS Samuel Olusegun Adeyemi THREATENED FISHES OF THE WORLD: Iberochondrostoma almacai COELHO, MESqUITA & COLLARES-PEREIRA, 2005 (Cyprinidae) Joana Isabel Robalo, Carla Sousa-Santos, Maria Manuela Coelho, Vítor Carvalho Almada Supplement to fishing profession DR. SC. ZLATICA TESKEREDŽIĆ - DILIGENT AND DEVOTED EDITOR IN CHIEF OF THE “CROATIAN JOURNAL OF FISHERIES” Tea Tomljanović