David A. Methven John F. Piatt 1992 <p>We conducted hydroacoustic surveys for capelin <i>Mallotus villosus</i> in Witless Bay, Newfoundland, Canada, on 61 days during the summers of 1983 to 1985. On 32 of those days in whlch capelin surveys were conducted, we observed a total of 129 baleen whales - Including 93 humpback <i>Megaptera</i> <i>novaeangliae</i>, 31 minke <i>Balaenoptera</i> acutorostrata and 5 fin whales <i>B. phvsalus</i>. Although a few whales were observed when capelin schools were scarce, the majority (96%) of whales were observed when mean daily capelin densities exceeded 5 schools per linear km surveyed (range of means over 3 yr: 0.0 to 14.0 schools km^-1). Plots of daily whale abundance (no. h^-1 surveyed) vs daily capelin school density (mean no. schools km^-1 surveyed) in each summer revealed that baleen whales have a threshold foraging response to capelin density. Thresholds were estimated using a simple itterative step-function model. 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).</p> application/pdf 10.3354/meps084205 en Inter-Research Science Publisher Threshold foraging behavior of baleen whales article