Estimating the abundance of Baird’s beaked whales in waters off the Pacific coast of Japan using line transect data (2008–2017)

Abstract Coastal whaling targeting Baird’s beaked whales has a long history, and more than a quarter of a century has passed since the last abundance estimation of this species was conducted for management purposes. Here, we estimated the latest and time series abundances of Baird’s beaked whales in...
Ausführliche Beschreibung

Abstract Coastal whaling targeting Baird’s beaked whales has a long history, and more than a quarter of a century has passed since the last abundance estimation of this species was conducted for management purposes. Here, we estimated the latest and time series abundances of Baird’s beaked whales in the waters off the Pacific coast of Japan since 2008 using standard line transect analyses. Sighting surveys dedicated to estimating the abundance of Baird’s beaked whales were conducted four times. Additionally, we used the Baird’s beaked whale sighting dataset from a sighting survey targeting baleen whale in 2016. Two types of detection functions with multiple covariates were fitted to sighting data from these surveys. Abundances were estimated using the half-normal model to be 1524 (coefficient of variation, CV = 0.72) in 2008, 1546 (CV = 0.81) in 2009, 1093 (CV = 0.54) in 2015, 1034 (CV = 0.51) in 2016, and 3596 (CV = 0.82) in 2017. Some of these estimates had imperfect coverage, but all estimates sufficiently represented abundances in the main habitat in the study region. Overall, our abundance estimates were smaller than past estimates from the early 1990s, implying that further monitoring of the abundance are needed to manage and conserve populations of Baird’s beaked whales in this region. Ausführliche Beschreibung