What are the bioeconomic consequences of fishing-induced evolution?

A new article in Canadian Journal of Fisheries and Aquatic Sciences from EvoFish member Fabian Zimmermann, co-authored together with Christian Jørgensen, examines the potential bioeconomic impacts of fishing-induced evolutionary change, using a life-history model with stock dynamics based on Northeast Arctic cod. Selection in the model is driven both by size-dependent natural mortality and fishing mortality that emulates the gear selectivity of a trawl fisheries. To analyse the effects of fishing, both fishing mortality and size-selectivity of the fishing gear are varied, leading to evolutionary changes in age at maturation as well as fisheries yield.

Through the comparison of two scenarios, one allowing for evolution and one assuming that evolutionary changes do not occur, the potential impacts of fishing-induced evolution on the stock and the fishery become evident. Overall, the results show that under current size selectivity, there is little to no difference in the fishing regimes that generate maximum economic yield when evolution is considered. However, there are possible risks of ignoring evolution, because non-evolutionary harvest strategies tend to overestimate long-term catches under optimal fishing regimes and underestimates resilience to overfishing. In general, the relevance of fishing-induced evolution depends on many factors, in particular the size selectivity used in the fishery and its effects on specific traits, but also the current stock state and a previous history of adapation to fishing. Whether fishing-induced evolution should be specifically accounted for in fisheries management cannot be generalized and requires stock-specific answers. The study also reveals that possible evolutionary changes are very sensitivity to the value of discount rate, calling for a cautious use of net present value as sole criterion for management of evolving resources.