Research Document - 2011/121
Stock Assessment Framework for the British Columbia Geoduck Fishery, 2008
By D. Bureau, C.M. Hand, and W. Hajas
Abstract
The stock assessment framework for the British Columbia (BC) geoduck fishery is described. Quota calculations rely on estimates of current biomass and use regional harvest rates. Biomass is calculated as the product of geoduck bed area, density and mean weight. The sources of data and of uncertainties are discussed for each parameter. Density categorization, based on qualitative information on geoduck bed densities from harvesters and On-Ground Monitors, is now used to extrapolate densities to un-surveyed beds. Sea otters have a progressively larger impact on the BC geoduck fishery as their range expands. The Limit Reference Point (LRP) currently in use in the BC geoduck fishery is to close a bed to harvest once biomass is reduced to 40% of pre-fishery biomass; which requires the calculation of pre-fishery biomass which is fraught with problems. An alternative to the current LRP is required and options are discussed. A system of reserves may be an effective conservation measure. Estimation of geoduck biomass outside of commercially harvested areas should be conducted to determine what proportion of the geoduck biomass in BC already exists in de-facto reserves.
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