Sea otters, abalone, kelp forests and snails: Should changes in life history strategies be considered in recovery strategies?

Jane Watson1, Leah Saville2 and Gina Lemieux3

1Malaspina University-College, 900 Fifth Street, Nanaimo, BC V9R 5S5, Marine Mammal Unit, University of British Columbia, < [email protected] >, Ph: 250-753-3245 local 2317. 21631 McKenzie Ave, Victoria BC V8N 5M3. 3Golder Associates, 220-174 Wilson Street, Victoria, BC V9A 7N6

In Canada the Sea Otter (Enhydra lutris) and Northern Abalone (Haliotis kamtschatkana) are listed as threatened. Sea otters were extirpated from Canada in a commercial fur trade that lasted from 1778 until1911, but were successfully reintroduced from 1969 to1972. In the absence of predation by sea otters, northern abalone and other invertebrate species increased in abundance and size and came to support commercial and recreational fisheries. However, by 1990 both commercial and recreational harvest of abalone had been prohibited, and the northern abalone was declared threatened because of declining abundance. Ironically, even if poaching, the principle threat to abalone recovery is removed abalone abundance is expected to decline as the sea otter recovers and predation on abalone increases. Prior to commercial exploitation sea otters and abalone coexisted. Using the red turban snail (Lithopoma gibberosa) as a model for abalone, we examined how the life history strategies of a species alter in response to changes in community structure and levels of predation. Our results show that although the biomass of red turban snails differs in areas with and without sea otters, the abundance of snails is not different. These results suggest that changes in life history strategies, particularly growth and reproduction, may occur in response to sea otter predation. Such results have implications in setting recovery goals for species at risk, especially predator/prey species, which have co-evolved.

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