Assessment of sea turtle nesting activity in Libya

In contrast, virtually no tumors of the oral cavity have been found among green turtles studied in Florida as the result of strandings and the live capture of free-ranging individuals (L. M. Ehrhart, University of Central Florida; B. A. Schroeder, Florida State Department of Environmental Protection; E. R. Jacobson, University of Florida; W. G. Teas, U. S. National Marine Fisheries Service, personal communications).

No demonstrable explanation currently exists to account for this notable difference in the expression of FP. Routes of exposure for the disease at various anatomic sites may not be equivalent between turtles living in Hawaii and those living in Florida. One possible significant difference may be greater numbers of ectoparasites, such as ozobranchus leeches and talitroidean amphipods in the mouths of Hawaiian green turtles. Small lesions to oral tissues caused by these organisms may serve to promote infection by the agent responsible for FP. The impact of FP to individual turtles needs to be better characterized for each population in order to adequately understand the etiology of this serious disease. The predilection for oral tumors in the Hawaiian population, as summarized here, may provide useful clues for conducting additional research.

Casey, R. N., S. L. Quackenbush, T. M. Work, G. H. Balazs, P. R. Bowser and J. W. Casey. 1996.

Identification of retroviruses associated with unaffected green sea turtles and turtles with fibropapillomas. [Abstr.] AQUAVET 20th Anniversary Conference, 14-17 November 1996.

Herbst, L. H. 1994. Fibropapillomatosis of marine turtles. Ann. Rev. Fish Dis. 4:389-425.

Herbst, L. H., E. R. Jacobson, R. Moretti, T. Brown, J. P. Sundberg and P. A. Klein. 1995.

Experimental transmission of green turtle fibropapillomatosis using cell-free tumor extracts. Dis. Aquat. Org. 22:1-12.

GEORGE H. BALAZS, National Marine Fisheries Service, Southwest Fisheries Science Center, Honolulu Laboratory, 2570 Dole Street, Honolulu, Hawaii 96822-2396 USA, A. ALONSO AGUIRRE and SHAWN K. K. MURAKAWA, Joint Institute for Marine and Atmospheric Research, 2570 Dole Street, Honolulu, Hawaii 96822-2396 USA. ASSESSMENT OF SEA TURTLE NESTING ACTIVITY IN LIBYA Prior to our recent survey (16 June to 7 July 1995), Libya was the only Mediterranean country where the abundance and distribution of sea turtle nesting remained unknown. Libya’s long, pristine and largely sandy coastline, a tradition of low fishing activity, and high levels of loggerhead sea turtle (Caretta caretta) nesting reported from the Kouf National Park (Schleich, 1987), combined to suggest that the country might host a very large loggerhead colony (Laurent, 1993). The absence of data from this country has made it impossible to define the breeding effort by loggerhead turtles in the Mediterranean Sea, precluded meaningful demographic analyses, and hindered attempts to estimate the impact of incidental catch and mortality on the regional population.

The 1995 survey was organized by the Regional Activity Centre for Specially Protected Areas (RAC/SPA-MAP-UNEP) and funded by, in alphabetical order, the Marine Biology Research Centre (Tajura, Libya), the Mediterranean Association to Save the Sea Turtles (MEDASSET), the Technical Centre for Environment Protection (Tripoli, Libya), the United 2 - Marine Turtle Newsletter, 1997, No. 76

Nations through RAC/SPA-MAP-UNEP, and the World Wide Fund for Nature (WWF International - Mediterranean Programme). The survey had three objectives: (1) to census sea turtle nesting activity by documenting signs of nesting during ground surveys of potential nesting beaches, (2) to measure crawl densities and estimate the total number of nests laid in Libya, and (3) to record threats linked to fisheries expansion and other anthropogenic factors.

Libya's coastline extends 1,785 km along the southern shore of the Mediterranean Sea, including approximately 1,144 km of sandy coastline (beaches), nearly all of which is without human installations such as towns, industrial centres or harbours. The survey focused on 1,195 km between the Egyption border and Sirte (Figure 1), an area that includes approximately 743 km or 65% of the nation's sandy coastline. Fifteen coastal areas were sampled, corresponding to 50 beaches and beach portions (totalling 141.65 km, or about 12% of the nation's sandy coastline); 48 beaches were patrolled once and two beaches were patrolled twice by foot and /or motorbike.

Most patrols were made during the day.

We recorded 342 crawls; all of them were made by loggerhead turtles. We also obtained carapace lengths for 11 nesting females: four were observed during rare night patrols, two were killed while nesting (we found remains on the beach), and five were brought to us by residents.

The average standard curved carapace length was 78.05 cm (sd= 4.01, range 71-86.3). Based on our findings, nesting by green sea turtles (Chelonia mydas) in Libya should be considered improbable.

Loggerhead nesting activity was widespread; all but two beaches showed some level of nesting (Figure 1). Crawls were classified as follows: UCT (“U” crawl track), no body pit; FCT (“false” crawl track), body pit but egg laying doubtful; NCT (“nest” crawl track), well defined Marine Turtle Newsletter, 1997, No. 76 - 3

body pit with evidence of digging and covering, egg laying likely; CT old crawl track, no classification possible; N (“nest”), no crawl track but nest opened by a predator. In total, 342 crawls were recorded, including successful and unsuccessful nesting attempts (classified as above). Crawl density (UCT+FCT+NCT+CT) ranged from 0-5.8 crawls/km; estimated nest density (NCT+N) ranged from 0-3.8 nests/km. For analysis of these densities among beaches, we excluded additional crawls and nests recorded during subsequent surveys of two beaches. The most important nesting areas,as determined by our survey, are Oum el Frais, Ras el Aweija, East Sirte, and No rth Benghazi (Figure 1). These should be considered major Mediterranean nesting sites for Caretta.

We recorded 122 NCT along the 141.65 km surveyed once. NCT densities ranged from 02.2 nests/km, for an average of 0.86 nests/km. We assumed that any nest laid seven days prior to the survey had a very low probability of being recorded as an NCT (based on a typical crawl longevity of 3-4 days; see Sofer, 1988); therefore, the total NCT was treated as an estimation of the number of nests laid on a particular beach during a one week period. Analysis of nesting distribution on a weekly basis elsewhere in the Mediterranean indicates that the number of nests laid per week during that portion of the nesting season surveyed for this study, represents, on average, 11% of the season’s total number of nests (see Margaritoulis, 1988: 10.1% at Kiparisia Bay, Greece; Broderick and Godley, 1993, 1995: 9.4% and 10.1% in N. Cyprus; Godley and Broderick, 1994: 14% in N. Cyprus). Applying this to Libya, we estimated a mean annual density of 7.82 nests/km, a density not unlike that reported in Greece, Turkey or Cyprus (Margaritoulis, 1988; Margaritoulis and Dimopoulos, 1995; Margaritoulis et al., 1995; Erk’akan, 1993; Godley and Broderick, 1994).

Assuming that our beach sample accurately reflects the overall nesting activity east of Sirte, and further assuming a consistent level of variability in nesting activity (thus a comparable average nest density) throughout the remaining 35% of nation’s sandy coastline (which is situated west of Sirte and could not be included in this survey), the total number of nests laid in Libya in 1995 is estimated at 9000. We believe that this high level of nesting is primarily related to Libya’s long sandy shoreline, the virtual absence of human habitation along this shoreline, and the underdeveloped nature of the fishing industry, especially when compared to Tunisia and Egypt.

Based on this estimate, Libya hosts the largest loggerhead colony in the Mediterranean Sea, corresponding to more than 60% of all loggerhead nesting in the region. With this information, the groundwork is laid for the first holistic estimates of the loggerhead nesting population in the Mediterranean Sea, estimates which have great value in demographic modeling exercises. Taken as a whole, it is now clear that the Mediterranean very likely supports the third largest loggerhead population in the world, after those of Oman and the United States.

As is the case in many other Mediterranean countries, nest predation in Libya is high; 44.8% of the nests we observed during single ground surveys had been depredated by carnivores (mammals) and sand crabs. Two nesting females were found killed by carnivores, probably jackals, corroborating earlier published observations (Schleich, 1987). Incidental catch is a recent phenomenon in Libya and, when compared to other Mediterranean countries, is relatively low. No commercial use of the turtles captured alive was evident. However, the impact from a population dynamics standpoint may not be negligible for two reasons. First because the incidental catch involves adults, and second because the fishing sector will develop considerably in the coming years. Human density along the coast is low and tourism is nonexistent. Most of the Libyan coast remains in a pristine state. The expanse of sandy coast seems unique in the Mediterranean, and the new Ministry of Tourism should bear in mind the fragile state of the coast as development plans proceed.

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Based on our findings, we would like to make the following recommendations. First, Libya clearly hosts a substantial proportion of the loggerhead nesting that takes place in the Mediterranean each year, and the country is duty bound to protect this heritage. This exceptional situation should be used to facilitate the creation of a Libyan Conservation Strategy for the Loggerhead Sea Turtle. Since most of the coast is completely unspoiled by human development, fishing is only slightly developed, and the tourism industry is nascent, there is potential for Libya becoming a model for conservation, management and planning with regard to its diverse coastal zone. The effective protection of sea turtle nesting beaches should be taken into account in all future planning for the coastal areas.

Secondly, the fishing community should be educated in sea turtle biology and conservation, including gear technology and other measures to reduce incidental catch. Advantage should be taken of the relatively undeveloped nature of the national fishing industry, and a serious policy of informing fishermen and involving them in conservation practices should be established as a priority. Without this effort, the well known consequences of sea turtle and fishery interactions will come to pass. With assistance from different sources, this policy should operate at all levels in the fishing sector, including vocational schooling and administration. Materials should be distributed in markets, ports, landing areas, etc. Such a program might serve as a pilot scheme for later adaptation throughout the Mediterranean. Investigations on sea turtle interaction with trawls, gill nets, fishing with dynamite, etc. should be undertaken and are indispensable for setting future action priorities.

Third, it is essential to continue censusing nesting activities on the whole Libyan coast in order to acquire, as rapidly as possible, a detailed map of nesting beaches, an accurate estimate of the annual number of loggerhead nests in Libya, and a baseline from which to assess future population trends.

Broderick, A. and B. Godley. 1993. Expedition Report: Glasgow University Turtle Conservation Expedition to Northern Cyprus 1993. Dept. Vet. Anat., Glasgow University Vet. School, Beardsen. 50 pp. Unpubl.

Broderick, A. and B. Godley. 1995. Expedition Report: Glasgow University Turtle Conservation Expedition to Northern Cyprus 1995. Dept. Vet. Anat., Glasgow University Vet. School, Beardsen. 21 pp. Unpubl.

Erk’akan, F. 1993. Nesting biology of loggerhead turtles, Caretta caretta, on Dalyan beach, MuglaTurkey. Biol. Cons. 66:1-4.

Godley, B. and A. Broderick. 1994. Expedition Report: Glasgow University Turtle Conservation Expedition to Northern Cyprus 1994. Dept. Vet. Anat., Glasgow University Vet. School, Beardsen. 18 pp. Unpubl.

Laurent, L. 1993. Une approche de biologie de la conservation appliquée à la population de Caouanne Caretta caretta de Méditerranée. Thèse de Doctorat de l’Université Paris VI. 195 pp.

Margaritoulis, D. 1988. Nesting of the loggerhead sea turtle Caretta caretta on the shores of Kiparissia Bay, Greece, in 1987. Mesogee 48:59-65.

Margaritoulis, D. and D. Dimopoulos. 1995. The loggerhead sea turtle Caretta caretta on Zakynthos: population status and conservation efforts during 1994. Sea Turtle Protection Society of Greece, Athens. 47 pp. Unpubl.

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Margaritoulis, D., Chr. Pappa and K. Teneketzis. 1995. Monitoring and conserving of the Caretta caretta populations nesting at Kiparissia Bay and Lakonikos Bay during 1994. Sea Turtle Protection Society of Greece, Athens. 36 pp. Unpubl.

Schleich, H. H. 1987. Contributions to the herpetology of Kouf National Park (NE-Libya) and adjacent areas. Spixiana 10(1):37-80.

Sofer, A. 1988. Survey of sea turtle nests in the Mediterranean shore between Ceasaria to Haifa, Summer 1986. Nature Reserves Authority, Jerusalem. 31 pp. Unpubl.

LUC LAURENT, WWF International-Mediterranean Programme, 5 bd Honoré de Balzac, 69627 Villeurbanne Cédex, FRANCE, MOHAMED N. BRADAI, National Institute for Marine Science and Technology (INSTM), B.P. 1035, Sfax 3018, TUNISIA, DAU A. HADOUD and HISHAM M. EL GOMATI, Marine Biology Research Centre Tajura, P. O. Box 30830 Tajura, LIBYA; Email: llaurent@net.asi.fr ON THE IMPORTANCE OF EGGS Sea turtle population models published by Crouse et al. (1987), Crowder et al. (1994) and Heppell et al. (1996a,b) have emphasized the “importance” of subadult and adult annual survival over egg and hatchling survival. Their model analyses reveal that a proportional change in the annual survival rate of older turtles has a much larger impact on the annual growth rate of a population than a similar (or in some cases much greater) proportional increase in survival during the first year of a turtle’s life. There are two primary reasons for this: 1) Many life stages for sea turtles include a large proportion of the population, as they are aggregates of several year classes. For example, the large juvenile stage specified by Crouse et al. (1987) from Frazer’s life table (1983) spanned ages 8 15. Depending on mortality rates in the pelagic phase, this could include a great many turtles.

2) As an individual approaches sexual maturity, its “reproductive value” increases.

This is an individual’s contribution to future reproduction, and is based on (i) the probability that it will live long enough to reproduce and (ii) the number of offspring it will generate.

In an age- or stage-based model, the proportional sensitivity of population growth to changes in annual survival is dependent on the number of individuals affected and their reproductive value. Because the reproductive value of eggs and hatchlings is generally much lower than that of large juveniles, subadults or adults, an increase in the annual survival in the first year of life will always have a comparatively small impact on these long lived, late maturing animals.

The results from life table-type models appear insensitive to changes in egg production because they are not really simulation models; rather than predicting fluctuations in a population through time, these models are best for comparing trends in a qualitative manner, such as comparing the overall impact of head-starting programs with the predicted impacts of turtle excluder devices (Heppell et al., 1996a). Because there is a long time lag between birth and reproduction in sea turtles and adults may be long~ lived, large variations in hatchling production may be dampened over time, producing relatively little fluctuation in the number of adults.

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