Consequences of climate-induced low oxygen conditions for commercially important fish

Oxygen availability is key in determining habitat suitability for marine fish. As a result of climate change, low oxygen conditions are predicted to occur more frequently and over a greater geographic extent. Studies assessing the long-term chronic effects and impacts for commercially important fish are rare. To assess the potential effects of climate-induced low oxygen on fisheries, physiological data, such as critical thresholds, derived from laboratory experiments on 5 commercial fish species were integrated with hindcast and future oxygen projections from the hydrodynamic-biogeochemical model GETM-ERSEM. By using this approach, changes in habitat suitability from the 1970s to 2100 were identified. In the North Sea, the current extent of areas with the lowest oxygen levels is smaller than during the 1970s, with improved oxygen conditions having less impact on species' critical thresholds. Oxygen levels are expected to decrease again in the coming century due to climate change, although not to the minima of previous decades. In affected areas and years, intermediate oxygen levels could have temporary impacts in late summer on swimming, growth, ingestion and metabolic scope of adult fish. These results demonstrate that although physical model oxygen projections help to provide insight, they are insufficient by themselves to predict the full potential impacts of climate change on fish distribution and fisheries. Such modelling requires underpinning through experimentation, particularly of the physiological effects of climate change on different life stages so that effects on reproduction, growth and commercial catches can be determined and tailored, and robust management measures put in place.