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Impact of 21st century climate change on the Baltic Sea fish community and fisheries

Authors

  • BRIAN R. MACKENZIE,

    1. Department of Marine Ecology and Aquaculture, Danish Institute for Fisheries Research, Technical University of Denmark, Kavalergården 6, DK-2920 Charlottenlund, Denmark,
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  • HENRIK GISLASON,

    1. Department of Marine Fisheries, Danish Institute for Fisheries Research, University of Copenhagen, Charlottenlund Castle, DK-2920 Charlottenlund, Denmark,
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  • CHRISTIAN MÖLLMANN,

    1. Department of Marine Fisheries, Danish Institute for Fisheries Research, Technical University of Denmark, Charlottenlund Castle, DK-2920 Charlottenlund, Denmark
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    • 1Present address: Institute for Hydrobiology and Fisheries, University of Hamburg, Hamburg, Germany.

  • FRIEDRICH W. KÖSTER

    1. Department of Marine Fisheries, Danish Institute for Fisheries Research, Technical University of Denmark, Charlottenlund Castle, DK-2920 Charlottenlund, Denmark
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Brian R. MacKenzie, tel. +45 3396 3403, fax +45 3396 3434, e-mail: brm@difres.dk

Abstract

The Baltic Sea is a large brackish semienclosed sea whose species-poor fish community supports important commercial and recreational fisheries. Both the fish species and the fisheries are strongly affected by climate variations. These climatic effects and the underlying mechanisms are briefly reviewed. We then use recent regional – scale climate – ocean modelling results to consider how climate change during this century will affect the fish community of the Baltic and fisheries management. Expected climate changes in northern Europe will likely affect both the temperature and salinity of the Baltic, causing it to become warmer and fresher. As an estuarine ecosystem with large horizontal and vertical salinity gradients, biodiversity will be particularly sensitive to changes in salinity which can be expected as a consequence of altered precipitation patterns. Marine-tolerant species will be disadvantaged and their distributions will partially contract from the Baltic Sea; habitats of freshwater species will likely expand. Although some new species can be expected to immigrate because of an expected increase in sea temperature, only a few of these species will be able to successfully colonize the Baltic because of its low salinity. Fishing fleets which presently target marine species (e.g. cod, herring, sprat, plaice, sole) in the Baltic will likely have to relocate to more marine areas or switch to other species which tolerate decreasing salinities. Fishery management thresholds that trigger reductions in fishing quotas or fishery closures to conserve local populations (e.g. cod, salmon) will have to be reassessed as the ecological basis on which existing thresholds have been established changes, and new thresholds will have to be developed for immigrant species. The Baltic situation illustrates some of the uncertainties and complexities associated with forecasting how fish populations, communities and industries dependent on an estuarine ecosystem might respond to future climate change.

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