The Impact of Increased Accuracy in Geoduck (Panopea generosa) Age Determination on Recommended Exploitation Rates

Abstract

Exploitation rates for the Pacific geoduck commercial fishery in British Columbia are currently based on an age-structured model using geoduck age data derived from the ring-counting method. Since 2005, geoduck ages have been determined using the more accurate method of cross-dating. We assessed how the results of age-structured models are impacted by the aging method used by considering 2 data sets that were aged with both methods. Historical recruitment patterns were back-calculated and compared to examine the effect that the aging method had on trends in estimated recruitment over time. Through forward simulation, we examined the influence of alternative fishing intensities on geoduck stocks and evaluated the impact of increased accuracy in age determination on precautionary exploitation rates. Results indicate that the use of the cross-dating methodology has improved our understanding of geoduck recruitment patterns but does not suggest that a change in exploitation rates is warranted. The exploitation rates currently in use are still considered precautionary.