Elasmobranch bycatch in a bottom trawl fishery in the Iskenderun Bay, northeastern Mediterranean

Abstract

Total biomass, species composition, depth distribution, seasonal distribution and abundance of elasmobranchs were examined by commercial bottom trawls between 2009 and 2010 from Iskenderun Bay, Turkish coast of the northeastern Mediterranean. From 52 bottom trawl surveys, it was estimated that elasmobranchs represented 23% (190.1 kg.km(-2)) of total fish biomass (840.8 kg.km(-2)) in Iskenderun Bay. Dasyatis pastinaca, Gymnura altavela, Raja clavata and Rhinobatos spp. (Rhinobatos rhinobatos and Glaucostegus cemiculus) showed high occurrence and represented each between 11.10 and 38.46% of the whole elasmobranch biomass. The other species, Dipturus oxyrinchus, Raja miraletus, Torpedo marmorata and Torpedo torpedo, represented each between 0.12 and 2.82% of the total elasmobranchs biomass. Shark species, Mustelus mustelus, Scyliorhinus stellaris, Scyliorhinus canicula, Galeus melastomus and Squatina squatina, represented each between 0.45 and 1.7% of the whole elasmobranchs biomass. When seasonal distribution was examined, total catch of fish were 32.38, 23.24, 10.71 and 33.65%, of which elasmobranchs species constitute 24.11, 34.12, 20.42 and 21.34% in autumn, winter, spring and summer respectively. Single or sporadic captures were also recorded for Isurus oxyrinchus, Carcharhinus plumbeus, Carcharhinus altimus, Oxynotus centrina, Raja radula, Rhinoptera marginata and Pteromylaeus bovinus.