Small-scale Fisheries Increase Loggerhead and Green Turtles Death

Throughout the eastern Mediterranean there are many different marine vertebrates that have populated the coastal waters two specific marine vertebrates are the loggerhead and green turtles. In the specific area of North Cyprus there is a conservational issue that is arising. This issue is the small-scale fishery that targets siganids with the use of trammel-net gear (Figure 1). A trammel net is a mesh net used by fishermen to catch an abundance of fish by having the fish swim into the net and having the gills get caught. The holes on the net are approximately 0.81mm to 0.90mm made of monofilament.

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Figure 1. A sketch of a trammel net and the way that it is used to catch fish

These nets are becoming an increasing conservational issue because they are entangling many breeding females as  bycatch, a species that was unintentionally caught while targeting a specific species (Figure 2).

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Figure 2. An example of turtle bycatch

These trammel nets are used to catch schools of siganids (Figure 3). Siganids populate shallow benthic waters near the coastline and unfortunately have overlapping habitats with the loggerhead and green turtles.

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Figure 3. A picture of a mature adult siganid

North Cyprus has been document to have a large abundance of optimal waters conditions for nesting sites for the loggerhead and green turtules due to its shallow benthic waters (Snape T. et al. 2013). North Cyprus also has a well-established small-scale fishing fleet of 126 vessels, which ultimately is causing an increase in the mortality rates of loggerhead and green turtles from their trammel nets. This study was done to determine the amount of turtles that have been killed due to the trammel nets by surveying the amount of carcasses that wash up on shore. The study observed 16 beaches from November 1, 2009 till October 31, 2011. Data was also collected through the use of volunteer survey pertaining to their catch of turtles that were filled out by 126 captains, 42%-59% of the fishing fleet. From November 1, 2009 till October 31, 2011 there were 129 marine turtle carcasses found, 50% were Loggerhead and 46% were green turtles (Snape T. et al. 2013).  From the surveys that were filled out voluntarily by the 126 captains show that approximately 480-660 of the 800-1100 annually caught died. Therefore, the turtles had a mortality rate of approximately 60% after they had been caught in the trammel nets and released.

This study of the mortality of loggerhead turtles and green turtles can further be used to assist in the protection of the turtles and also assist in creating a better management system of the small-scale commercial fishery of the coast of North Cyprus. It provided the expose of the fishing industry and showed that even though the different species were being released after being caught, the turtles were still dying as a result of being entangled in the fisheries nets. From the knowledge gained from this study, further research could be done on the amount of turtles caught and then survived after being released and then also the amount of turtles that have been caught and released but end up dying because of the impact that the trammel nets have had on the turtles.

-by Kyle Giffen

 

Reference

Snape, Robin T., Damla Beton, Annette Broderick, Burak Çiçek, Wayne Fuller, Özge Özden, and Brendan Godley. “Strand Monitoring and Anthropological Surveys Provide Insight into Marine Turtle Bycatch in Small-Scale Fisheries of the Eastern Mediterranean.” Chelonian Conservation and Biology 12.1 (2013): 44-55. Web. 4 Sept. 2012.

 

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