Incidental mortality of patagonian dusky dolphins in mid-water trawling: retrospective effects from the early 80?s

DANS SILVANA LAURA; CRESPO ENRIQUE ALBERTO; GARCÍA NÉSTOR ANÍBAL; REYES, LAURA MARINA; PEDRAZA SUSANA NOEMI; KOEN-ALONSO MARIANO

Aberdeen, Escocia

Workshop; Scientific Committee International Whaling Commission; 1996

International Whaling Commission

The highest rates of incidental catches of dusky dolphins off the Patagonian coast mostly ocurr in mid-water trawling for shrimp, At present, This fishery is declining in use, but it was widely used during the 198Os, The objetives of this paper are to estimate the number of the dusky dolphins annually caught in this fishery during the period 1982-1995 and to analyse the structure of the catches and possible effects on the population. The use of this gear for shrimp bcgan in 19R2. During 19R4, the fishing effort reached a peak and the number of dolphins caught was estimated at between 442-560. decreasing during the following years. The use of mid-waler nets for shrimp was recorded up lo 1994, when mortality estimated a minimun value equal to 36 dolphins per year. The sample recovered from the fishery seems to biased toward females and young matures. Half of the females were matures and half of these were pregnant. The total number of dusky dolphins in the fishing area was recently estimated to be close to 7.252 individuals. Thus incidental mortality would have been significant al least during 1984-86, leading to a maximunn annual mortality close to 8% the present estimated population size, The effect on the population would have beem severe considering that the catches affected mostly females of the highest reproductive value.