The Southwestern Atlantic Southern Right Whale, Eubalaena australis: updated population rate of increase
Enrique Alberto Crespo, Mariano Alberto Coscarella
This paper reports on aerial surveys conducted to estimate the relative abundance and trend in the growth of the southern right whale (Eubalaena australis) population from PenÃnsula ValdÃ©s. The number of whales counted tripled from 1999 to 2018. 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 modeled the 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 7% in 2007 to 1.03% and 3.38% for the total number of whales and number of calves, respectively for 2018. Trends in the rates of increase for the total number of whales and the number of calves were negative (-0.757% and -0.397%, respectively). We conclude that whales are still increasing their abundance, while the rate of increase is starting to fluctuate near zero for the total number of whales and it continues to be positive for the calves. Differences in the rates of increase of the group types and changes in habitat use are consequence of a density dependence process.