Evaluating the sustainability of a de facto harvest strategy for British Columbia's Spot Prawn (Pandalus platyceros) fishery in the presence of environmental drivers of recruitment and hyperstable catch rates

TL;DR

This study evaluates the sustainability of British Columbia's Spot Prawn fishery management strategy, showing that the current conservative approach maintains stocks effectively despite environmental variability and hyperstability in catch rates.

Contribution

Develops a management strategy evaluation framework to assess the real-world performance of the de facto harvest rule in BC's Spot Prawn fishery, accounting for environmental effects and hyperstability.

Findings

De facto catch rate rule maintains stocks near or above 0.8 BMSY.

Abundance indices exhibit strong hyperstability, with fishing efficiency 1.5 to 3.0 times higher at low biomass.

The conservative management approach is effective in sustaining the fishery.

Abstract

The Spot Prawn trap fishery off the west coast of British Columbia (BC) is managed using a fixed escapement strategy that aims to prevent recruitment overfishing while maximizing expected long-term yield by closing the fishery when the catch rate of spawners, projected to the following spring, drops below 1.7 spawners per trap (the de jure rule). We develop a management strategy evaluation framework for BC's Spot Prawn fishery that examines the expected performance of the management procedure implemented in practice (the de facto rule), which was significantly more conservative than the de jure rule, usually closing the fishery when spawner catch rates were at least twice as high as specified by the de jure rule. Simulations indicate that the de facto spawner index rule using average empirical March 31st targets from 2000 to 2019 maintains most stocks near or above 0.8 BMSY with or without accounting for environmental effects and/or increasing future SST on recruitment. Abundance indices were found to be strongly hyperstable, with fishing efficiency 1.5 to 3.0 times higher under low biomass than high biomass.