Research Document 1997/64
Possible criteria for re-opening the northern abalone fishery in British Columbia
By A. Campbell
Abstract
This paper reviews the literature for relevant biological and fishery characteristics of different abalone species, makes yield and egg per recruit calculations and suggests biological reference points, criteria for reopening a potential fishery, and possible rehabilitation and management actions for the northern abalone, Haliotis kamtschatkana, in British Columbia.
The biology of the H. kamtschatkana makes this species vulnerable to over exploitation. The northern abalone is slow growing, relatively long lived and sedentary, and has low or sporadic recruitment with accumulations of older individuals distributed in shallow water locations easily accessible to harvesters. The high market value, reduced availability, and the difficulty of enforcing the fishery closure since 1990 in a large mostly uninhabited coastal area, has encouraged illegal harvesting of northern abalone populations, hampering attempts to rebuild stocks to a level that would allow a sustainable legal harvest. Evidence to date, from surveys in the central coast of British Columbia and Queen Charlotte Islands, indicate that there has been insufficient recruitment during the last two decades to maintain estimated fishing rates (F) during 1976-90 when the legal fishery was open (mean F about 0.5) and during the closure 1990-94 (F ranged from 0.1 to 0.7 in some locations). Samples from abalone illegally harvested during 1995 suggested that poachers removed all sizes of available abalone with no regard to the minimum size limit of 100 mm shell length that was in force during the legal fishery. Without size and fishing rate controls, egg per recruit (EPR) analyses suggested that egg production, during the closed fishery, could probably be at or less (<30% EPR) than the level when the fishery was open (30 - 50 %EPR). Many of the long-term abalone fisheries around the world that have conserved > 50%EPR have been sustained; other fisheries that conserved lower egg production have suffered poor recruitment, stocks have declined and many fisheries closed. However, because of the difficulties of showing a stock-recruitment relation, predicting how environmental / ecosystem changes influence abalone stock dynamics, and ongoing poaching problems, there are no guarantees that various rebuilding / rehabilitation strategies will work.
Criteria required to reopen a northern abalone fishery could not be fully resolved in this paper due to lack of information on the frequency and patch size of adult abalone required to maintain sufficient recruitment for a healthy abalone population. Likely criteria for reopening a sustainable northern abalone fishery would require further research to determine the optimal distribution and density of spawners and recruits, distance of larval transport, genetic stock discreteness and how these factors would effect the geographic scale of fisheries management.
Rehabilitation of northern abalone populations should include (1) continued fishery closure until stocks rebuild, (2) reduction of illegal harvest through increased publicity and adoption of new detection and enforcement methodologies (e.g., DNA analysis), and (3) experimental manipulation, in well monitored management areas, to determine the efficacy of brood stock transplant and juvenile seed restocking methodologies.
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