Sea otter (Enhydra lutris) COSEWIC assessment and status report 2007L chapter 11

Special Significance of the Species

Once on the verge of extinction, sea otters have made a remarkable recovery, largely because of protective legislation, an abundance of suitable unoccupied habitat, and successful reintroductions (Mason and MacDonald 1990). Although sea otter populations have demonstrated a capacity to recover, the dramatic declines in Western Alaska illustrate that populations can decline rapidly and unexpectedly.

Sea otters are considered a keystone species exerting significant ecological effects on nearshore marine communities and upon the life history of their prey (Estes and Palmisano 1974; Estes et al. 2005). They reduce grazing pressure by preying on herbivorous invertebrates, particularly sea urchins. This allows kelp to grow, thereby altering the community from one dominated by grazers with little kelp to one that supports kelp and associated communities of fish and invertebrates (Breen et al. 1982; Watson 1993; Estes and Duggins 1995). Research in the Aleutian Islands indicates that communities dominated by sea otters are up to 2 to 3 times more productive than systems without sea otters because of the kelp-derived carbon (Duggins et al. 1989), furthermore these communities support a greater abundance and diversity of fish species (Reisewitz et al. 2006).

The “teddy-bear-like” appearance of sea otters, their near brush with extinction, role in structuring rocky nearshore communities, historical importance, and their vulnerability to oil spills have endeared otters to the general public. Sea otters are of increasing interest to the wildlife-viewing tourism industry in Canada as people have become more aware of their presence on Canada’s west coast. Sea otters do well in captivity (although they do not breed well in captivity) and are popular in zoos and aquaria. Sea otters are the only mammals other than primates to use tools to break open hard-shelled invertebrate prey.

Sea otters feed on invertebrates and can control the abundance of many invertebrate species. As the sea otter population grows, controversy over sea otters and the availability of invertebrate stocks to First Nations, commercial and recreational harvesters will increase (Watson and Smith 1996).

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