Bycatch of the pelagic ray Dasyatis violacea in Uruguayan longline fisheries and aspects of distribution in the southwestern Atlantic

Abstract

The presence of the pelagic ray Dasyatis violacea (Bonaparte, 1832) in Uruguayan waters has been monitored since April 1998, the beginning of the National Observer Programme on board the Uruguayan tuna fleet (PNOFA). These are the first records of these species for the South Atlantic off Uruguay. Its distribution within the area is analysed, based on 13 trips made from April 1998 to September 2001 from 26 to 37°S. Five hundred and twenty five specimens were caught during this period. The presence of the species appears to be closely associated with the highest values of surface water temperature, with CPUE being relatively low below 20°C. The southern border of its distribution is around 36°S. Dasyatis violacea is part of a well-defined warm water fauna that reaches Uruguayan and northern Argentinean waters following warm subtropical waters. The incidental capture of D. violacea in the area reaches significant levels; the species is always discarded. We suggest that this bycatch is important and should be monitored from a conservation point of view.