Bycatch of the piked dogfish Squalus acanthias Linné, 1758 (Chondrichthyes, Squalidae) in semi-pelagic longline fisheries at the Patagonian Shelf

the piked dogfish squalus acanthias is part of the bycatch of several south american longline fisheries, although in argentina, it was only reported in the bycatch of benthic and demersal fisheries operating bottom nets. this communication represents the first record of s. acanthias bycatch in a commercial semi-pelagic longline fishery within argentinean waters. in october-november 2005, 185 piked dogfish were captured (122 females and 63 males). the estimated mean catch rate was 0.37 sharks/1000 hooks (544,320 hooks deployed). nearly half of the captured females and over 50% of captured males were morphometrically mature. the piked dogfish bycatch could have been influenced by the use of the argentine shortfin squid illex argentinus as bait; this squid is part of the shark？s natural diet. although s. acanthias is abundant in the region, we believe that the bycatch species could be more vulnerable than the targeted ones since the signs indicating a declining population of non-target species in commercial catches and collapses in bycatch populations go unnoticed