Proceedings 2021/036

Proceedings of the Pacific regional peer review on the Update to estimation methods for Geoduck (Panopea generosa) stock index; March 15-16, 2017

Chairperson: Julia Bradshaw

Editors: Sylvia Humble, Julia Bradshaw and Dominique Bureau

Summary

The BC Geoduck fishery is managed at the sub-bed spatial scale. The limit reference point (LRP) is defined as current biomass being equal to 40% of estimated unfished exploitable biomass (Zhang and Hand 2007). The stock index, defined as the ratio of current biomass (B^c) to estimated unfished exploitable biomass (B’) on a bed, is calculated for each bed. Beds with a stock index below 0.4 are closed to fishing. If surplus production is occurring, the current method of estimating unfished exploitable biomass in the Geoduck stock assessment framework (Bureau et al. 2012) is likely to be biased and lead to biased estimates of stock index and consequently lead to all harvested Geoduck beds reaching the LRP erroneously. This may be an artefact of the method currently used to estimate unfished exploitable biomass and not be reflective of true stock status. Fisheries and Oceans Canada Fisheries and Aquaculture Management Branch has requested that Science Branch provide a review of the method currently used to estimate Geoduck unfished exploitable biomass and provide alternative Geoduck unfished exploitable biomass estimation methods.

The specific objectives of this review, as outlined in the terms of reference are to:

1. Provide a review of the method currently used to estimate Geoduck unfished exploitable biomass, for surveyed and un-surveyed Geoduck beds.
2. Describe alternative methods for estimating Geoduck unfished exploitable biomass for both surveyed and un-surveyed Geoduck beds, including evaluation of the relative advantages and disadvantages of each method.
3. Provide methods for calculating Geoduck stock index on a by-Geoduck-sub-bed basis. Describe the advantages and disadvantages associated with this approach.
4. Identify and discuss uncertainties and knowledge gaps in the available data and proposed estimation methods.

These proceedings summarize the relevant discussions and key conclusions that resulted from a Fisheries and Oceans Canada (DFO), Canadian Science Advisory Secretariat (CSAS) Regional Peer Review meeting held on March 15-16, 2017 at the Pacific Biological Station in Nanaimo, BC. A working paper describing and evaluating alternative methods to estimate unfished exploitable biomass intended to address the concerns with biased stock indices was presented.

Participation included Fisheries and Oceans Canada Science and Fisheries and Aquatic Management Sectors staff, the commercial fishing sector and the Washington Department of Fish and Wildlife.

The conclusions and advice resulting from this review will be provided in the form of a Science Advisory Report (SAR) providing advice to improve the current methods of estimating unfished exploitable biomass.

The Science Advisory Report and supporting Research Document will be made publicly available on the Canadian Science Advisory Secretariat website.

Proceedings 2021/036 (PDF, 616 KB)

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