Potential future climate change effects on Swedish fish and fisheries

Abstract

Oceans have been warming at an unprecedented rate over the last few decades and climate change is having profound effects on biodiversity and other ecosystem services that oceans provide for human well-being. The motivation for this report is a strong need to understand the consequences of climate change on aquatic ecosystems to develop strategies to minimize the impact on fished species, fisheries and society. The introduction and first chapters of the report are based on a literature review, which summarizes the current state of knowledge about climate change in the Swedish marine and coastal areas, patterns emerging from the main climate scenarios, and potential effects on fish and fisheries. This is followed by an analysis of species environmental limits and tolerances to a warming environment, focusing on selected fish and invertebrate species of commercial relevance. Thermal safety margins show a smaller buffer for species of boreal origin including the northern shrimp, the gadoids and vendace, among others. Analyses of preferred spawning temperatures and depths enable a preliminary overview of the potential sensitivities of species to a warming environment, showing inter alia that species requiring shallow and cold waters for reproduction are likely more sensitive to the effect of warming. The report also includes a specific analysis of how changes in temperature, salinity and oxygen may affect the availability of suitable spawning and nursery habitats in the Baltic Sea. Using information from recently updated maps of potential spawning and recruitment areas in the Baltic Sea, the potential loss of reproductive grounds is evaluated in an ensemble analysis based on multiple climate scenarios. Finally, the report includes a climate risk analysis, which integrates information on the stocks' specific susceptibilities to climate change (hazard), with information on the vulnerabilities of the evaluated systems and their exposure to climate change. The integration is carried out at the level of different fishing segments (fleets) and at the level of the different coastal administrative regions in Sweden. Thus, the risk analysis aims to identify the relative distribution of climate risk among fishing fleets and geographical regions, and explores how this may develop under alternative climate scenarios. The results show that the risk ranks higher for the salmon, vendace and shrimp fisheries, while geographically, the northern Baltic Sea ranks higher in risk compared to other regions. Most importantly, the analyses show that the risk is not equally driven by hazard, vulnerability and exposure for the different fleets and regions, suggesting that no single risk-reducing approach is sufficient and appropriate across all areas and fleets. The report concludes with a gap analysis together with suggestions for next steps to improve the state of knowledge and enable more precise risk analyses in the future, as well as with summary conclusions.