Effects of Sea Otter Foraging on Subtidal Reef Communities off Central California

Abstract

As a major predator of sea urchins, the sea otter (Enhydra lutris) plays a determining role in structuring many subtidal kelp-forest communities in the North Pacific (reviewed in Estes and Harrold, Riedman and Estes, this Vol.). In the absence of otters, patches of kelp and other erect algae survive only on shallow pinnacles, crests, and other high-relief zones of turbulence (Estes et al. 1978; VanBlaricom 1984), which are unstable platforms for sea urchins (Dayton 1985b; Laur et al. 1986). Thus, after otters return to reef habitats previously overgrazed by exposed urchins (Strongylocentrotus spp.), large stands of kelp reappear as the remaining urchins become restricted to cracks and crevices (Estes and Palmisano 1974; Dayton 1975; Estes et al. 1978; Duggins 1980; Breen et al. 1982). As otters remove the destructive grazers, furthermore, enhanced productivity creates an environment favorable for greater numbers of finfish (Simenstad et al. 1978; Estes et al. 1981, 1982; VanBlaricom 1984; Estes and VanBlaricom 1985).