The Southwestern Atlantic Southern Right Whale, Eubalaena australis: updated population rate of increase
Enrique Alberto Crespo and Mariano Alberto Coscarella
International Whaling Commission
This paper reports on aerial surveys conducted to estimate the relative abundance and trend in growth of the southern right whale (Eubalaena australis) population from Pen??nsula ValdǸs. The number of whales counted tripled from 1999 to 2019. The year 2018 was the year in which we counted the highest number of whales ever recorded, totaling 1605 wales in a 4 hours coastal flight. We modelled number of whales, number of calves, number of Solitary Individuals and number of individuals in Breeding Groups using as predictive variables the Year, the Julian day and Julian day2 by means of generalized linear models. The rate of increase decreased from near 8% in 2007 to 0.61% for the total number of whales and from 7.5% in 2007 to 3.09% for number of calves, respectively for 2019. Trends in the rates of increase for total number of whales and number of calves were negative (-0.706% and -0.399%, respectively). We conclude that whales are still increasing their abundance, while the rate of increase starting to fluctuate near zero for the total number of whales and it continues to be positive for the calves. Additionally the solitary individuals and the mating groups are decreasing in the area, Differences in the rates of increase of the group types and changes in habitat use are consequence of a density dependence process.