Vulnerability of elasmobranchs as longline bycatch in the gulf of Gabes (Southern Tunisia, central Mediterranean sea)

Abstract

A survey of the bottom and pelagic longlines fisheries targeting groupers and swordfish was performed in the Gulf of Gabes in 2016 and 2017 in order to evaluate the elasmobranch catches. In the benthic longline fishery, the elasmobranchs represented about 50 % of the total catch (Batoids 25,6%, Sharks 24,5%) and the main species were the blackchin guitarfish (Glaucostegus cemiculus) and the hound sharks (Mustelus spp.). In the pelagic longline fishery, the elasmobranchs represented 91% of the total catches (Batoids 2,24%, Sharks 89,57%), and the main species was the sandbar shark (Carcharhinus plumbeus) with 82,5% of the total catch. The frequency distributions of TL showed that the catches of these species were mostly composed of juveniles, and few mature specimens, including some gravid females.