Estimation of abundance and population dynamics of the Antarctic blue whale in the Antarctic Ocean south of 60°S, from 70°E to 170°W

Abstract The Antarctic blue whale population size has decreased due to commercial whaling, and it is listed as endangered by the International Union for Conservation of Nature. Its population status has received widespread attention and the abundance of Antarctic blue whales has been estimated through surveys conducted by international and national programs. This study estimated the abundance of Antarctic blue whales south of 60°S from 70°E to 170°W using data collected during Japanese national surveys. Furthermore, using this information and existing abundance estimates from the IDCR‐SOWER surveys conducted by the International Whaling Commission, we estimated and forecasted the population trajectory of the Antarctic blue whale since the beginning of its exploitation using Bayesian state‐space surplus production models. The abundance estimate for 2009 was 476, 95% CI [242, 972], corresponding to 0.8%, 95% CI [0.3, 1.9] of the prewhaling levels, and the intrinsic growth rate in this population was low at 0.042, 95% CI [0.009, 0.093]. This analysis suggests that the population size in this region is lower than that during prewhaling. The input of new abundance estimates in the future is expected to accurately estimate population dynamics compared with the current assessment.