GRAY WHALE OCCURRENCE AND FORAGE SOUTHEAST OF KODIAK, ISLAND, ALASKA

Abstract

Although the Bering and Chukchi seas are commonly cited as the principal summer feeding grounds of Eastern North Pacific (ENP) gray whales (e.g., Highsmith et al. in press, Swartz et al. 2006), records indicate that this population actually feeds opportunistically throughout its range from the lagoons of Baja California, Mexico, to Alaskan waters (Nerini 1984). Specifically, recent reports suggest that whales may routinely feed in the Gulf of California (Sanchez-Pacheco et al. 2001) and Bahia Magdalena, Baja California Sur (Caraveo-Patino and Soto 2005), whereas Clapham et al. (1997) noted that feeding gray whales occurred offshore California even in the 1920s when population numbers were very low. The dynamic nature of foraging in this population is best described from coastal study sites along the southeastern shore of Vancouver Island, Canada, where whales shift among pelagic, epi-benthic, and benthic prey within and between years (Darling et al. 1998; Dunham and Duffus 2001, 2002). In the 1980s the southern Chukchi Sea and the Chirikov Basin in the northern Bering Sea were considered the primary feeding grounds for ENP gray whales, based on reported high densities of both whales (Braham 1984, Kim and Oliver 1989, Moore et al. 2000) and their ampelicid amphipod prey (Grebmeier et al. 1989, Highsmith and Coyle 1990). However, by 2002, benthic productivity in the Chirikov Basin had declined precipitously, due to either whale foraging (Highsmith et al. 2006), ecosystem change (Grebmeier et al. 2006), or both, and only the southern Chukchi Sea supported dense aggregations of gray whales (Moore et al. 2003). Indeed, the