Southern Right Whale Eubalaena australis recolonizes Golfo San Matias (Patagonia, Argentina)
Magdalena Arias, Mariano A. Coscarella, M. Alejandra Romero, Nicolas Sueyro, Guillermo M. Svendsen, Enrique A. Crespo, Raul A. Gonzalez
International Whaling Commission
Historically, the distribution range of the Southern Right Whale in Argentina included winter calving grounds around Península Valdés. After the commercial whaling, Southern Right Whales have shown signs of recovery during the last few decades. They seem to be experiencing a density-dependent process and are expanding their distribution range in Patagonia. We evaluate the presence and distribution of right whales in the Golfo San Matías using coastal aerial surveys between 2007 and 2016, and we studied the effectiveness of this sampling methodology by comparing the sighting per unit of effort outside and inside of the coastal strip. Also we evaluate the trend of relative abundance in the area of greatest concentration between 2014 and 2016 using a GLMM. Whales were observed from August to October, with a peak in late August-early September, and the solitary individuals were the predominant group type along the surveyed area. We present evidence of a geographic distribution change from the west to the northern coast of the Golfo San Matías and a positive trend in the relative abundance was observed in the last years for this area. To make an analysis at a regional scale, we compared the group types and the number of whales/km survey, using a GLM, in the areas of highest concentration in Chubut province with the highest concentration area of Río Negro province. In these areas, it was observed a dominance of mother calf pairs in Chubut and solitary individuals in Rio Negro, and the number of whales/km survey was 4 times greater in the Chubut province. Finally we reported evidence of the presence of whales in Golfo San Matías previous to the commercial whaling, highlighting the recolonization process.