Update to estimation methods for geoduck (Panopea generosa) stock index / Dominique Bureau. : Fs70-5/2017-070E-PDF

“The stock index in the British Columbia (BC) Geoduck fishery is estimated on a by-Geoduck-bed basis and is defined as the ratio of current biomass (Bc) to unfished exploitable biomass (B’). The limit reference point (LRP) for the BC Geoduck fishery was defined as current biomass being equal to 40% of B’. When biomass is estimated for a bed, the stock index is also estimated and beds for which the stock index is below 0.4 are closed to fishing. To date, B’ has been back-calculated as the sum of current biomass and fishery landings on the bed. This method assumes no surplus production on a bed after fishing begins. The methods currently used to estimate B’ on surveyed and un-surveyed beds were reviewed. Alternative options of estimating B’ on surveyed and un-surveyed Geoduck beds were proposed and evaluated. Methods for estimating the stock index at the by-sub-bed spatial scale were presented along with advantages and disadvantages of this approach. An evaluation of the possible impact of changing the spatial scale at which the stock index is calculated was presented. A recommendation was made to implement calculation of stock index at the by-sub-bed spatial scale"--Abstract, p. viii.

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