Geology topics

Research about Witless Bay

Source-linked reports with geographic coverage including Witless Bay.

3 recordsLinked to original sources

USGS1992

Threshold foraging behavior of baleen whales

We conducted hydroacoustic surveys for capelin Mallotus villosus 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 Megaptera novaeangliae , 31 minke Balaenoptera acutorostrata and 5 fin whales B. phvsalus . 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).

Newfoundland↗

USGS1990

The aggregative response of common murres and Atlantic puffins to schools of capelin

I studied the aggregative responses of Common Murres and Atlantic Puffins to schools of capelin during three summers (1982-1984) at Witless Bay, Newfoundland, by conducting hydroacoustic surveys for capelin in synchrony with seabird censuses. Murres and puffins foraged offshore prior to the arrival inshore of spawning schools of capelin. Both species were abundant during peak periods of capelin abundance from late June to late July, but only puffins continued to forage inshore after capelin schools dispersed in August. On individual surveys, murre and puffin flocks were significantly correlated with capelin schools at fine and coarse spatial scales. Aggregation intensity and spatial correlations peaked at measurement intervals of 2-6 km. At that scale, murres and puffins exhibited sigmoidal (Type III) aggregative responses to capelin schools. Inflection points (thresholds) in sigmoidal aggregative response curves occurred at higher densities of capelin for murres than for puffins and foraging thresholds for both species varied daily with overall capelin abundance in Witless Bay. Murres probably foraged on denser schools of capelin than puffins because of their larger body size and associated higher food demands. The implications of differing foraging thresholds for population ecology of alcids are discussed.

Newfoundland↗

USGS1989

Seasonal and annual variation in the diet of Atlantic cod ( Gadus morhua ) in relation to the abundance of capelin ( Mallotus villosus ) off eastern Newfoundland, Canada

The importance of capelin as prey for cod has long been known (Thompson, 1943; and see Lilly (1987) for a review); however, no studies have been conducted on how the highly dynamic seasonal and yearly variations in capelin abundance affect cod diet. We studied the occurrence of capelin in cod stomachs in relation to the relative abundance of capelin at Witless Bay, Newfoundland (47°15’N 52°46’W), during June, July and August, 1982-1984. The mean number of capelin per stomach and the per cent occurrence of stomachs containing capelin were determined for each collection of stomachs. A total of 680 stomachs were examined. Cod were sampled from those caught in gillnets by fishermen and averaged 66 cm ± 8 (s.d.) in 1983 and 62 cm ± 8 (s.d.) in 1984. Relative abundance of capelin in the local habitat was determined by conducting hydroacoustic surveys around Gull Island in Witless Bay, the same area where cod were collected for stomach content analysis. Only hydroacoustic surveys conducted within three days of cod stomach collections were analyzed. Further details of hydroacoustic surveys including quantifications of acoustic echograms are described in Piatt (1989).

Newfoundland↗