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Research Document - 1999/163

A Review of the Biology and Fisheries for Purple Sea Urchin (Strongylocentrotus purpuratus, Stimpson, 1857) and Discussion of the Assessment Needs for a Proposed Fishery.

By G. Workman

Abstract

In accordance with the phased approach to providing scientific advice for new and developing fisheries, the following paper has been prepared as the "Phase 0: Review of existing information" assessment for the purple sea urchin Strongylocentrotus purpuratus. This paper consists of a review of the relevant literature on the biology of S. purpuratus, and describes urchin fisheries on the west coast of North America. Relevant management measures, and their data requirements, that should be applied to any fishery for purple sea urchins are discussed. Interest was first expressed in starting a fishery for this species in the late 1980s, a small experimental fishery ran between 1989 and 1992, when concerns over compliance with the terms of the experimental harvest permit and local depletion lead to a closure of the fishery. Since 1992, nine proponents have requested a re-opening of the fishery.

Intertidal S. purpuratus have been studied extensively in Oregon and in California. This species is characterized by long life, greater than 50 years, patchy distribution, slow and variable growth, low and periodic recruitment, is sedentary and displays density dependant spawning success (Allee effect). The above characteristics are indicative of a species susceptible to over-exploitation, which in turn dictates a very cautious approach to fisheries development.

Small fisheries for S. purpuratus exist in Oregon and California. The fisheries for purple sea urchin are of limited success because of this urchin's small size, variable gonad quality and the harsh conditions under which it must be harvested. Other urchin fisheries on the west coast of North America include S. franciscanus, the giant red sea urchin, which is harvested from South-east Alaska to Baja California, Mexico and S. droebachiensis, the green sea urchin, which is harvested from Kodiak, Alaska to Washington State. Red sea urchin fisheries in Oregon and Northern California have collapsed under excessive fishing pressure, the green sea urchin fishery in British Columbia likewise peaked and crashed. These are examples of "Boom and Bust" fisheries where rapid development of a commercial fishery decimates the virgin biomass prior to assessment of the resource.

Suggested management measures include quotas, size limits, seasonal closures, a rotational fishery and limited entry. The data requirement for the first of these measures could be met by an extensive survey and bio-sampling program, designed to ascertain the abundance, and life history parameters of purple urchins and the appropriate spatial scale on which to implement these management actions.

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