Research Document - 1999/113
Review of the fishery and assessment of the green sea urchin stocks in British Columbia, with quota recommendations for 1999/2000.
By R.I. Perry and B.J. Waddell
Abstract
This paper (i) reviews the green sea urchin (Strongylocentrotus droebachiensis) fishery in British Columbia since its inception in 1987, with emphasis on recent years (post-1995); (ii) updates a biomass dynamic model to determine green urchin stock status in British Columbia; and (iii) presents initial results of fishery-independent surveys for green urchins. The green urchin fishery in B.C. developed rapidly from 1987 to 1991, and peaked in 1992 with landings of 1042 t. Declining landings and catch per unit of effort followed and management restrictions were implemented in 1992. In 1995, an individual quota system with dockside validation was implemented. In 1997/98, coastwide landings (all in the South Coast) were 160 t, approximately equal to the quota. The principal Pacific Fishery Management Areas for green sea urchins are 12, 13 (Queen Charlotte and Johnstone Straits) and 18, 19, 20 (Gulf Islands - Juan de Fuca Strait). Harvest logbook information is collected as a condition of licence, and verified against quota validation records. Median catch per unit of effort (CPUE) was calculated from the harvest logbook data to provide an index of changes in stock size. Analyses are conducted on a fishing season basis (1 October of year i to 31 March of year i+1). Biomass dynamic models were developed for the South Coast - inside waters northern region (PFMA 11,12,13) and South Coast - inside waters southern region (PFMA 17-20,28). Total allowable catches in the range of 25-50% * MSY are recommended to account for uncertainties in the input data and assumptions in the dynamic production models. Recommended yield options for the South Coast range from 144-289 t. A TAC calculated for PFMA 4 on the North Coast of B.C., based on a fishery-independent survey, is 6.1 t (calculated as a 10% exploitation rate applied to the surveyed biomass). Seven fishery-independent surveys were conducted in a core fishing area of PFMA 12 in eastern Queen Charlotte Strait. The lower 95% confidence bound of the mean annual legal-sized (³ 55 mm test diameter) biomass for PFMA 11,12,13 from these surveys is similar to the biomass estimated by the dynamic production model. Information from the biomass dynamic model results, fishery-independent surveys, and reports from fishermen suggest that the stock in the South Coast - northern region is relatively abundant with recent good recruitment, whereas the status of the stock in the South Coast - southern region is more uncertain.
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