Hypoxic conditions are avoided by bottom trawl fisheries

Oxygen depletion in marine ecosystems, known as hypoxia, is an escalating form of marine pollution driven by eutrophication and climate-induced warming that threatens coastal ecosystems worldwide. Although the ecological impacts of hypoxia are well documented, its broader environmental consequences remain less understood, including how oxygen stress alters human use of marine habitats. Based on an extensive oxygen monitoring dataset integrated with bottom-trawl activity and catch records from the Western Baltic Sea (2010-2023), we assess how fisheries respond to varying levels of hypoxia as an indicator of ecosystem degradation and its consequences for fishing activities. Fishing activity declined to 20% of baseline levels under moderate hypoxia (2-4 mg/L) and to 10% under severe hypoxia (<2 mg/L). Fishers also delayed their return to previously hypoxic areas by an average of 1.9 to 2.7 weeks, respectively. These behavioral shifts mirror known ecological responses of demersal fish and benthic invertebrates to sublethal oxygen stress. While the resumption of fishing activity suggests some short-term recovery, likely reflecting the return of some fish species to affected areas, long-term degradation of benthic communities may further compromise habitat quality and fish stock productivity. Our findings highlight the importance of incorporating oxygen dynamics into environmental and fisheries management, pollution mitigation, and marine spatial planning, particularly as hypoxia intensifies under the combined pressures of climate change and nutrient loading. • We linked measured oxygen data (n = 2117) to prevailing bottom trawl activity • Fishing activity dropped to 20% and 10% under moderate and severe hypoxia • Fishers’ return to these areas was delayed by 1.9 (moderate) and 2.7 (severe) weeks • Sub-lethal hypoxia (<4 mg/L) strongly altered fish and fishers behaviour • As hypoxia intensifies globally, fisheries management should consider oxygen stress