The dynamic relationship between foraging gray whales (Eschrichtius robustus) and their mysid prey (Mysidae), along the Southwest coast of Vancouver Island, British Columbia

Date

2008-03-20T22:54:17Z

Authors

Pasztor, Christopher J

Journal Title

Journal ISSN

Volume Title

Publisher

Abstract

Gray whales (Eschrichtius robustus Lilljeborg) forage predominantly on hyper-benthic mysids (Mysidae) along the southwest coast of Vancouver Island, British Columbia. The role of mysids in the abundance and distribution of foraging gray whales prompted interest in this study. I relate the inter- and intra-annual foraging behaviour of gray whales to the number of mysid patches and biomass through boat based surveys of foraging whales, and the application of acoustic techniques for estimating mysid prey. I examine the spatial pattern of foraging gray whales and the 10 m isobath. The abundance and distribution of mysid patches are more common at a water depth of 10 m, and the likely mechanism driving the spatial pattern between foraging gray whales and the 10 m isobath. I examine whale abundance and distribution patterns during three consecutive foraging seasons. More whales forage in years when mysid prey are more abundant, and mysid patches are of larger size and higher in biomass. Whales have a considerable top-down effect on mysid populations. Years of heavy whale predation depletes mysid stocks. Mysid populations tend to increase in years of low whale activity. I examine whale abundance and distribution patterns of habitat use during a foraging season along the southwest coast of Flores Island and Nootka Sound. The abundance of mysid patches and biomass in Nootka Sound does not influence the whales’ use of Flores Island; rather the whales exploited both areas concurrently. This study expands the understanding of gray whale habitat use along the southwest coast of Vancouver Island, British Columbia.

Description

Keywords

Gray Whales, Foraging, Mysids, Vancouver Island

Citation