Threshold foraging behavior of baleen whales

Abstract

The authors conducted hydroacoustic surveys for capelin Mallotus villosus in Witless Bay, Newfoundland, on 61 days during the summers of 1983-1985. On 32 of these days they observed a total of 129 baleen whales, including 93 humpback Megaptera novaeangliae, 31 minke Balaenoptera acutorostrata and five fin whales B. physalus. The majority (96%) of whales were observed when mean daily capelin densities exceeded five schools per linear km surveyed (range of means over 3 yr 0-14 schools km-1). Foraging thresholds of baleen whales (7.3, 5.0, and 5.8 schools km-1) varied between years in relation to the overall abundance of capelin schools in the study area during summer (means of 7.2, 3.3, and 5.3 schools km-1, respectively). -from Authors