摘要
Fleet expansion, increased gear efficiency, increased effort and the constant improvement in fishing methods have greatly contributed to the current overexploitation of many target stocks. It is therefore essential to identify and monitor the changes in fishing practices as well as the technological creep to determine their implications for the conservation of target and non-target species. The present study documents the recent technical and operational changes in a longline fishery targeting swordfish (Xiphias gladius) operating in southern Italy (Ionian Calabria). Data collected during the swordfish fishing seasons of 2007, 2010 and 2011 showed a significant change in fishing practices over the survey years, as the longline fishery switched from surface (10-100 m) to mid-water (100-500 m) depth and from 11 h to 25-30 h soak time. These modifications in fishing operations, which result in an increase and redistribution of the effort, were motivated by a drastic decrease in the swordfish catches made with the traditional surface longline. They have modified the fleet structure, catch species composition and size of the target species. Although these operational changes resulted in an increase in the swordfish size and a decrease in the sea turtle bycatch, their implications for less known and potentially more vulnerable commercial and bycatch species are unclear. Moreover, the shift of fishing effort into deeper water is a well-documented evolution of many fisheries worldwide in response to the decline in shallow coastal water resources. The change in fishing practice of the pelagic longline fishery reported in the present study could be considered an additional alarm bell of the current state of overexploitation of the Mediterranean swordfish.