Spatial‐temporal patterns in intra‐annual gray whale foraging: Characterizing interactions between predators and prey in Clayquot Sound, British Columbia, Canada

Abstract

In Clayquot Sound, British Columbia, gray whales (Eschrichtius robustus) forage primarily on mysids (Family Mysideae) and also on crab larvae (Family Porcellanidae) that are constrained to specific habitat, which relate to bathymetric depths. In this paper we characterize the interactions of gray whales and their prey by analyzing fine scale spatial-temporal patterns in foraging gray whale distribution within a season. Kernel density estimators are applied to two seasons (1998 and 2002) of highresolution data on foraging by gray whales. By partitioning data from each foraging season into several time periods (12 in 1998 and 11 in 2002), using a temporal autocorrelation function, and generating kernel density estimated surfaces for each time period, it is possible to identify discrete areas of increasing and declining foraging effort. Our results indicate that gray whales forage on mysids throughout a season and opportunistically forage on crab larvae. The episodic crab larvae feeding may reduce, but not eliminate, pressure to mysid populations enabling mysids to reassemble swarms and continue to support gray whale foraging in the latter part of the season. Results suggest that when managing marine environments, gray whale populations require multiple and connected habitats for summer foraging. 356 NELSON ET AL.: GRAY WHALE FORAGING PATTERNS 357

Predatory disturbance and prey species diversity: the case of gray whale (Eschrichtius robustus) foraging on a multi-species mysid (family Mysidae) community

“…1). The primary feeding sites are bounded by the 30-m depth contour, as prey surveys perpendicular to the shoreline indicate that mysids do not occur beyond this depth (Nelson et al, 2008;Laskin et al, 2010).…”

Análise do padrão de distribuição de baleia franca austral na costa sul brasileira

“…This method is an efficient tool for mapping and analysing the spatial distribution of species in ecological research (Worton, 1989;Seaman and Powell, 1996;Righton and Mils, 2006;Nelson et al, 2008). In this context, this tool was used to identify the southern right whales distribution patterns off the southern Brazilian coast.…”

Quantifying Wildlife Home Range Changes

“…A method of change detection designed specifically for use with kernel density estimated surfaces is well suited to characterizing change in the intensity of habitat use within home ranges (Nelson et al, 2008). Kernel density estimation change detection identifies locations of statistically significant positive and negative changes, and enables the rate of change, considered significant, to vary spatially (Bowman & Azzalini, 1997, pp.…”