Data available for an assessment of North Pacific blue whales
Trevor A. Branch, Robert L. Brownell Jr, Phillip J. Clapham, Yulia V. Ivashchenko, Koji Matsuoka, Sally Mizroch, Cole C. Monnahan, Paula Olson, Ana Å iroviÄ‡
Blue whales in the North Pacific comprise at least two populations, and possibly three, based largely on song type. The best studied is the eastern North Pacific population that has a reliable catch time series and previous assessment. For the less-studied central and western North Pacific population there are recent surveys and catch data, and many locations where their song type has been recorded including off Hokkaido. Assessments of the central and western population, will be possible once abundance estimates are obtained from the POWER and JARPN/JARPNII cruises. There is also a possible third Japanese population west of 145-155Â°E, and a unique third song type recorded off Hokkaido at 145Â°E. This area around Japan was the basis of substantial whaling, followed by a lack of sightings west of 155Â°E in JSV data in the 1960s to 1980s, and no catches for several decades, leading to the possibility of extirpation being raised. Blue whales have since been regularly sighted in the 145-155Â°E region during the JARPN/JARPNII cruises, forming a continuous distribution that spans from the site where the new song type was recorded eastwards into the area off Kamchatka. More hydrophones are needed in the region 130-155Â°E zone to determine the extent of whales making the new song type, to determine the extent and status of this possible Japanese population.