The Herpetological Journal

pp. 25-30
Authors: Echwikhi, Khaled; Jribi, Imed; Bradai, Mohamed Nejmeddine & Bouain, Abderrahmen

Abstract: Some gillnets used in the south of Tunisia (Gulf of Gabes) target shark species (Mustelus sp., Carcharhinus plumbeus) and guitarfish (Rhinobatos cemiculus, Rhinobatos rhinobatos). These artisanal nets interact with sea turtles. Here we present an analysis of the bycatch of loggerhead sea turtles Caretta caretta in these gillnets in the Gulf of Gabes, an important Mediterranean wintering and foraging area for this threatened species. We quantified mean catch per unit effort (CPUE) in three ways to account for uncertainty and found high levels of interaction in each case. The number of turtle captures per km² of gillnet per day, the number of turtle captures per km of net and the number of turtle captures per set were 0.527 (0.403–0.649), 0.339 (0.250–0.438) and 0.800 (0.654–0.904), respectively. Captured loggerheads were mainly juveniles (mean = 56.6cm CCL_n-t) and direct mortality was estimated as 69.4% (n=25). These are the first estimates of sea turtle interactions with artisanal fisheries for northern Africa, and one of very few estimates of turtle mortality in set gillnets in the Mediterranean. Our results indicate a need for research into ways for fishermen to avoid turtle captures and to raise awareness of this problem throughout the Mediterranean Sea. The following specific actions are recommended: 1) management of gillnet fisheries in the Mediterranean Sea, 2) minimizing gear soak time, particularly in foraging and inter-nesting habitats and along the migration pathways of sea turtles, 3) technical modifications of the gear by reducing the number of floats, and 4) carrying out an awareness campaign with fishermen to reduce post-release mortality.

Keywords: GILLNET, CATCH RATE, CARETTA CARETTA, BYCATCH, MORTALITY