CHANGES IN SUBTIDAL COMMUNITY STRUCTURE ASSOCIATED WITH BRITISH-COLUMBIA SEA OTTER TRANSPLANTS

Sea otters, E. lutris, were re-introduced into the coastal waters of British Columbia, in 1969-1972, after being hunted to extinction in the previous 2 centuries. In 1979, an area was visited where 55 individuals had been seen in 1978; subtidal observations were made of the abundance and distribution of red sea urchins, other grazers and kelps. Earlier observations, made in the area before sea otters were re-introduced, confirmed that changes had taken place in subtidal communities since the re-introduction. Where sea otters had been observed feeding, sea urchins Strongylocentrotus franciscanus were scarce and restricted to crevices or beneath boulders, other grazers were scarce, and kelps colonized the bottom to 10-m depths. The algal communities in these areas appeared to be simple downward extensions of sublittoral fringe communities. Where sea otters had not fed, kelps were limited to shallow water by abundant sea urchins. The observed differences between the 2 types of areas were caused by early elimination of sea urchins by sea otters, as reported in Alaska and California [USA]. From the pattern of sea urchin abundance in the general area of the transplant, the feeding range of this small population of sea otters was delineated.