Southern right whale mortalities at Península Valdés, Argentina: updated information for 2010-2011

SIRONI, MARIANO; ROWNTREE, VICTORIA J.; DI MARTINO, MATÍAS; CHIRIFE, ANDREA; BANDIERI, LUCAS M.; BELTRAMINO, LUCAS; FRANCO, MARCELO; UHART, MARCELA

2010-06-01/2010-11-30

1-5

Biológica

Prom.Gral.del Conoc.-Cs.Agropec.y Veter.

Southern right whales (Eubalaena australis) continue to experience high mortalities at Península Valdés, Argentina. Systematic efforts to study the strandings began in 2003, when the Southern Right Whale Health Monitoring Program was established by a consortium of NGOs. A total of 482 dead whales were recorded on the Península Valdés nursery ground and an additional nine at other sites along the Argentine coast between 2003 and 2011, with a peak in 2008 when 100 whales died. Previous reports to the IWC included information through 2009. Here we report data for the 2010-2011 seasons. Fifty five whales died in 2010 and 61 died in 2011. As in previous years, the vast majority of strandings were calves of the season. However, an unusually high proportion of juveniles (6) and adults (7) died in 2010. In both years, most deaths were recorded in October (43) followed by August (29), September (20) and November (18). Strandings were evenly distributed in both gulfs of the peninsula (26 -47%- in Golfo San José, 26 -47%- in Golfo Nuevo, one -2%- in the Outer Coast and two -4%- outside of the peninsula) in 2010, but many more whales died in Golfo Nuevo (49 or 80%) than in Golfo San José (12 or 20%) in 2011. Two calves were alive when they stranded, and both died a few hours after they were found. The remaining whales were dead when reported or found, and post mortem examinations were performed. Hundreds of biological samples have been collected and analyzed since 2003. However, a common cause of the high mortality rates in this southern right whale population remains to be found.