Retrospective bioeconomic analysis of Fraser River sockeye salmon fishery management

摘要

We analyzed past management performance in the Fraser River sockeye salmon fishery, examining how much more profitable the fishery could have been under different harvest rules than those that were applied historically. There has been uncertainty about what management regime would be optimal because of (1) large cycles in the abundance of the stocks, the cause(s) of which are unknown, and (2) past underestimates of the capacity of the ecosystem to produce sockeye. We used historical stock-recruitment data and variation in productivity as the basis for retrospective biological dynamics using two different biological models, each model corresponding to a hypothesized cause of the cyclic population dynamics. We then used prices, fishing costs and discounting to incorporate the economics of the fishery, and simulated the fishery under several different harvest rules. We found that the fishery could have been 20-200% more profitable than it was historically if relatively simple harvest rules (fixed exploitation rate or target escapement) had been implemented. However, we found that there would have been relatively little increase in profit above the level attained by these simple rules if managers had also know in advance the so-called recruitment anomalies, i.e., the deviation of actual recruitment from that predicted by the deterministic model. The results suggest that, if this fishery is to be managed to maximize long-term profit given conservation constraints, research would be better directed at discovering management-related parameters (optimal exploitation rate and optimal escapement) and finding ways to reach management goals than at predicting recruitment anomalies.