Space use patterns of the endangered North Pacific right whale Eubalaena japonica in the Bering Sea

Abstract

Understanding habitat use of critically endangered North Pacific right whales (NPRWs, Eubalaena japonica) is important to better evaluate the potential effects of anthropogenic activities and climate change on this species. Satellite transmitters were deployed on individual right whales in 2004, 2008 and 2009 to investigate whether their space-use patterns in the Southeastern Bering Sea (SEBS) were influenced by environmental conditions and to assess habitat use in areas of human interest. Whales were monitored for an average of 40 d (range 29-58 d) between July and October, a period in which they inhabited the SEBS shelf. Individuals tagged in 2008-2009 (cold years) remained in the middle shelf domain, travelled at a slower rate and showed a spatially more restricted habitat use than a whale tagged in 2004 (a warm year). Monte Carlo tests suggested that NPRWs associated with the cold pool (remnant winter water in the bottom layer of the middle shelf domain) during cold years, which is likely due to higher copepod abundance and reduced competition with other copepod predators within the cold pool. Telemetry data indicated that a Critical Habitat designated by the US National Marine Fisheries Service encompasses the main feeding range of NPRWs in the Bering Sea. Two whales briefly visited the North Aleutian Basin, an area previously considered for oil and gas development. Small sample sizes precluded conclusive comparisons of space-use patterns among years with significantly different temperature regimes, but we hypothesize that habitat use in the SEBS varies with these regimes because of concomitant changes in the abundance of the whales primary copepod prey. Long-term evaluation of space-use patterns of NPRWs is required to further understand their habits in the feeding grounds in light of global warming and the potential for increased anthropogenic activities.