The coexistence between offshore wind and fisheries has raised questions about potential impacts on species that are fished. We systematically evaluated the offshore wind farm (OWF) literature for evidence of effects leading to impacts on commercial fisheries species. First, we collated evidence of environmental effects of OWFs on fisheries species and then determined whether these could be interpreted as impacts using fishery-scale and organism-scale parameters for pelagic finfish, demersal and reef-associated roundfish, demersal flatfish, elasmobranchs and shellfish. We appraised consistency and level of agreement of direct evidence and explored the body of indirect evidence. A total of 1268 documents featured evidence of OWF effects on fisheries species, with only 60 documents (274 species records) providing direct evidence. Evidence on finfish far outweighed that for shellfish. Demersal and reef-associated roundfish were the best-studied group, while elasmobranchs were poorly evidenced. Most studies considered population rather than stock parameters. There was limited evidence of impacts, owing to inconclusive results and inconsistent effects within the parameters assessed—illustrating the importance of looking across the evidence base rather than focussing on individual studies. Hence, there is currently insufficient direct evidence to confidently determine OWF impacts on fisheries species. Overwhelmingly, the evidence deals with indirect effects, although these should not be disregarded as they can highlight plausible impacts on fisheries species, which could guide research and monitoring targeted at understanding the impacts of OWF—a pressing concern given the increased policy commitment of many nations to these two marine sectors sharing marine space.
Modern management of fish stocks is based on integrating the precautionary approach with the maximum sustainable yield framework. It relies on accurate estimation of precautionary limits, defined as levels of spawning biomass where a stock has reduced reproductive capacity, and harvesting targets aimed to maximise future yields. Therefore, it is heavily depending on productivity assumptions. Most fish stocks are managed assuming that productivity will increase as the stock size decreases (i.e., density dependent compensatory stock and recruitment relationship). However, several biological and ecological processes will result in a decreased productivity below a certain population size, referred to as the Allee effect or depensation. Through a meta-analysis of 81 Northeast Atlantic fish stocks, we investigated the impact of assuming compensatory recruitment in the presence of depensation in fisheries management. Across life histories, depensation results in a 22% reduction of the fishing mortality rate leading to extinction. On average, the maximum reproductive rate per spawning biomass was found at 35% of BMSY, which was also the biomass where stocks have a 5% risk of extinction without fishing. Finally, the presence of depensation resulted in increased rebuilding times when stock spawning biomass falls below the limit reference point. When depensatory effects are present, assuming increasing productivity at low biomass will generally result in over-optimistic perceptions of rebuilding and stock status at biomass below 25% and 45% of BMSY in general, and for pelagic stocks respectively. When not accounted for, depensation will potentially lead to unsustainable harvesting practices of marine living resources.
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