A preliminary investigation of the biology and status of juvenile Chelonia mydas in Lakonikos Bay, Southern Peloponnese, Greece Konstantinos Grimanis1, Christopher Dean1, Neil Davies1, Konstantina Kostoula1, Gala Pogodnic1, Juliana Baker1, John D.Pantis2, Lily Venizelos1 1. MEDASSET – 1C LYCAVITTOY STR., GR 106 72, ATHENS , GREECE. 2. ARISTOTLE UNIVERSITY OF THESSALONIKI, SCHOOL OF BIOLOGICAL SCIENCES.
INTRODUCTION There is a severe lack of knowledge concerning the small and severely threatened Chelonia mydas metapopulation in the Mediterranean, which has received relatively little attention and inadequate protection due to the limited knowledge on local populations.. Especially for the area of Lakonikos Bay in Southern Peloponnese, Greece, very little of such research has been done and published. Because little is known about the Lakonikos population of Chelonia mydas, more data must first be collected to adequately protect this endangered species. A long-term study is proposed whereby several aspects of the biology of Lakonikos turtles will be investigated to develop a sound understanding of the correct conservation strategy for the species within this area. In addition, the interaction of Chelonia mydas with existing fisheries in the area will be investigated in order to address the impact of fisheries on the species but also to try and address how artisanal fishing in area could become more sustainable taking into account that fish stocks in the area according to anecdotal information by fishermen are steadily decreasing and that a lot of the damaged nets is caused by turtles. During the preliminary stages of the proposed study an attempt to locate and identify foraging populations of green turtles in the Lakonikos Bay area will be made through a systematic survey consisting of the following stages: 1. Questioning local sources i.e. fishermen; 2. An aerial survey; 3. A boat survey coupled with direct observation and; 4. On board collection of data from fishing vessels. WHAT HAS BEEN DONE SO FAR To this date Stage 1 of the proposed study has been completed. FISHERMEN QUESTIONNAIRES In July 2011 a MEDASSET team comprising of four people visited Lakonikos Bay for a week and conducted interviews with local fishermen along the entire Laconicos Gulf in Southern Peloponnese. Margaritoulis et al., demonstrated that from 1997-2000 (3 fishing seasons) 40.4% of incidental captures of marine turtles were green turtles. Of those, beach seines were responsible for most of the captures. Beach seines is a type of fishing gear that has been abandonded as of 2010, thus, the project team focussed their efforts on interviews with artisanal fishermen that use two types of gear, namely gill/tramel nets and bottom longlines.
BACKGROUND INFORMATION
• In the Mediterranean Chelonia mydas have been afforded an IUCN status of Critically Endangered (Corbett K. & Kasparek M., 2001). •Lakonikos Bay is an important nesting area for loggerhead sea turtles in the Mediterranean with 200nests/year recorded and protected by ARCHELON.(Margaritoulis D., Teneketzis K. & Sioris I., 1999). • Lakonikos Bay is considered a sea turtle wintering area due to the frequent occurrence of loggerhead (Caretta caretta) and green (Chelonia mydas) turtles during the winter (Margaritoulis et al., 1992). •The broader area of the Evrotas delta comprises an important feeding ground for sea turtles. Lakonikos also seems to be a significant site of a specific developmental stage in the life cycle of the green turtle. Further research is required in order to confirm the above indications (Margaritoulis et al., 1999). •Spatial distribution of captures in the water column showed that preferred depth by Chelonia is up to 36m (Margaritoulis et al., 2001). In the months of October and November Green turtles predominate. However, both species are present in the area throughout the winter. •Analysis of stomach content of two juvenile greens revealed almost exlusive consumption of seagrasses of Cymodosea nodosa & Zostera marina (Margaritoulis et al., 2001).
Interviews with 24 fishermen were carried out. Copyright Neil Davies.
RESULTS-CONCLUSIONS The 24 interviews revealed the following: •Most fishermen that were interviewed were professionals (19) and only few amateurs (5). 10 of artisanal fishermen have other occupations. •Longlines: average number of hooks is 480 & average length is 13,221m. •Nets: average size of eye is 25mm and average length is 2,250m. •70 % of fishermen use both types of gear, 20% use only longlines and nearly 8% only nets. •Lakonikos Bay was divided into 5 distinct fishing zones based on the areas that most fishermen fish and based on the frequency of sightings of marine turtles (loggerheads and greens). •Information was collected regarding the time of year fishermen fish and what type of gear they use. About 80% of respondents said they fish throughout the year and during night time using both types of fishing gear. •Information on fishing depths in relation to the type of fish they catch and type of gear that they use was also collected. Information on fish species they catch was collected in order to investigate if diet of juvenille greens is in anyway related to commercial fish species. •Fishing depth varies from 10m to 125m. •Fishing effort is more intense in Zones 1 (Gythio to Elia) and 2 (Skoutari to Elia). •All of the respondents said that they observe more turtles mainly from May to October. However, all of them said that turtles are present throughout the year.
18 small fishing harbors were visited (indicated in red circle) and fishermen were interviewed on the spot. The entire marine area of Lakonikos Gulf was divided into 5 distinct zones based on the fishing effort and the frequency of marine turtle sightings.
•Only 37.5% of respondents said that they can distinqush loggerheads from greens.
WHAT WE ARE AIMING TO DO NEXT – FURTHER STEPS.
•80% of respondents said that most turtles are usually observed in Zone 1 (Gythio to Elia) mostly from May to October. This area corresponds to the observation made by Margaritoulis et. al. (2001) that the Evrotas delta is potentially an important foraging site for green turtles.
In the long-term, further data will be collected to build a better understanding of the status of the Chelonia mydas population in Lakonikos Bay. This includes:
• 46% of respondents said that they catch turtles in their gear, mainly from May to October. •37.5% said that most strandings occur up to 20m depth.
1) A satellite telemetry study. The aim is to attach 3 to 5 satellite tags on captured green turtles. 2) Dive patterns, length of time at what depths, implications for fishing practices. 3) Assess feeding habits, stomach contents. 4) Determine sex ratios of juvenile population in the feeding ground and blood sampling.
•58.3% of fishermen said that turtles are usually alive when caught. Those strandings that result in death are associated with net use.
5) Origins of green turtles from stable isotope analysis and DNA.
• 8 Fishermen replied that they are willing to collect more information on strandings and all of them would be willing to work with MEDASSET personnel on their vessel and record more information.
6) Identify heavy metals in sea turtles. The proposed study will contribute to a better understanding of relevant aspects about the conservation and biology of Chelonia mydas in general, as well as the Mediterranean metapopulation and their feeding grounds.
ACKNOWLEDGEMENTS
7) Mapping of sea grass beds in the area.
We are grateful to all the fishermen from Lakonikos Bay,
8) Proposal of protective zones in the marine area.
the Port Authorities and the Municipality of Gytheion, Takis Daveros, Dimitris Demetriades, Nikos Koussias, Kostas Teneketzis, and the local ENGO Peripolos.
COMMENT The continuation of this study is highly dependent on the co-operation of local artisanal fishermen, local authorities and NGOs active in the area for years such as Peripolos and ARCHELON. A systematic survey on the status and biology of Chelonia mydas is vital for the protection of the species and a means to enable local artisanal fishermen to work together and protect their area and consequently their livelihoods.