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The Southwestern Atlantic Southern Right Whale, Eubalaena australis, population is growing but at a decelerated rate

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Enrique Crespo and Mariano Coscarella

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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 Península Valdés. The number of whales counted tripled from 1999 to 2016. 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 7% in 2007 to a 0.5% and 2.40% for total number of whales and number of calves, respectively for 2017. Trends in the rates of increase for total number of whales and number of calves were negative (-0.732% and -0.376%, respectively). We conclude that whales are still increasing their abundance, while the rate of increase is decreasing. Differences in the rates of increase of the group types and changes in habitat use are thought to be consequence of a density dependence process.

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