Updated information for 2012-2013 on southern right whale mortalities at Península Valdés, Argentina

SIRONI, MARIANO; ROWNTREE, VICTORIA J.; DI MARTINO, MATIAS; BELTRAMINO, LUCAS; RAGO, VIRGINIA; FRANCO, MARCELO; UHART, MARCELA

Eslovenia

Encuentro; Scientific Committee Anual Meeting 2014; 2014

Internacional whaling commission

Southern right whales (Eubalaena australis) are experiencing high mortality rates at Península Valdés, Argentina. In2003, the Southern Right Whale Health Monitoring Program was established by a consortium of NGOs to monitor thehealth status of this population by post-mortem examinations. Previous reports to the IWC included information through2011. Here we update information for the 2012-2013 seasons. A total of 672 dead whales were recorded on thePenínsula Valdés nursery ground and surrounding areas along the Argentine coast between 2003 and 2013. At least 116whales died in 2012, which represents the highest number of southern right whale deaths ever recorded in one calvingand nursing season (June ? December). The number of dead whales was 67 in 2013. As in previous years, most of thedead whales were newborn calves (97% of strandings in 2012 and 94% in 2013). More deaths were recorded in GolfoNuevo (86% in 2012 and 79% in 2013) than in Golfo San José (12% in 2012 and 21% in 2013), with two strandings(2%) in the outer coast of the peninsula in 2012. Most whales died in August ? October (77%) in 2012 and in September? October (70%) in 2013. Only one calf was alive when it stranded in 2012, and died a few minutes after it was found.The remaining whales were dead when reported or found, and post mortem examinations were performed when and tothe extent that carcass condition allowed. Biotoxins, infectious diseases and malnutrition are three hypotheses that havebeen proposed to explain the recurring high mortalities in this southern right whale population. Preliminary observationssuggest that nutritional status and body condition could play a role in the differential mortality observed in differentyears. A fourth hypothesis, the physiological and behavioral effects of kelp gull attacks on newborn calves has beenconsidered more recently. A common cause to explain the high mortality rates in this southern right whale populationremains to be found.