Unusual gray whale Eschrichtius robustus feeding in the summer of 2005 off the central Oregon coast

Abstract

The climate of the North Pacific underwent an unusual event in the summer of 2005 with a very late spring transition. This event had profound effects on both resident gray-whales (Eschrichtius robustus) and their food source, mysids, off Depoe Bay, Oregon. Near bottom swarms of gray whales' major prey item, Holmesimysis sculpta, were sparse until August, a marked contrast to normal years when mysid swarms are abundant all summer. A large percentage of mysid females had empty brood pouches in 2005 while in 2003 and 2004 all observed females had full brood pouches. Gray whales spent little time foraging and spent fewer days in residence than in earlier years. The 2005 resident whales also showed signs of poor body condition, reflecting a nutritional deficit. Copyright 2006 by the American Geophysical Union.