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

An Zerbini,Bk Rone,As Kennedy,Mf Baumgartner,Pj Clapham,Pr Wade

doi:10.3354/meps11366

Abstract

Understanding habitat use of critically endangered North Pacific right whales (NPRWs, Eubalaena japonica) is important to better evaluate the potential effects of anthro- pogenic activities and climate change on this species. Satellite transmitters were deployed on indi- vidual 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 habi- tat 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 bot- tom 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. Teleme- try 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 dif- ferent 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 anthro- pogenic activities.

Highlights

The zooplanktivorous North Pacific right whale (NPRW) Eubalaena japonica was once abundant across the North Pacific Ocean and the Bering Sea (Brownell et al 2001, Shelden et al 2005)
There were significantly more Argos locations within the National Marine Fisheries Service (NMFS) designated Critical Habitat (CH) area than expected had the animals moved at random (Monte Carlo test, p = 0.0003), which suggests that the tagged right whales exhibited a preference for the area encompassed by the CH designation
Habitat use in the Southeastern Bering Sea

Summary

Introduction

The zooplanktivorous North Pacific right whale (NPRW) Eubalaena japonica was once abundant across the North Pacific Ocean and the Bering Sea (Brownell et al 2001, Shelden et al 2005). To examine right whale movements with respect to the presence and extent of the cold pool, temperature and salinity profiles collected with conductivity-temperature-depth (CTD) instruments during 1 August to 31 October from 1973 to 2005 in the Bering Sea and the Gulf of Alaska were acquired from the World Ocean Database (Boyer et al 2009). Bottom temperature and bottom salinity data were extracted from each CTD cast; in areas where the water depth exceeded 1000 m, the temperature and salinity at 1000 m was used instead of bottom values These data were converted to a climatology (a set of longterm averages) over a regular grid with 1.260° and 0.675° resolution in longitude and latitude (respectively) producing roughly 50 × 50 km grid cells in the Bering Sea. To create the climatology, annual means were first produced for all casts that fell within the geographic limits of a single grid cell, and the grand mean of these annual means was used as the climatological value for that respective grid cell.

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Results

Conclusion