IMPACTS OF CLIMATE CHANGE ON FISH
David Sims
Marine Biological Association, Plymouth
Executive Summary
There is substantial global evidence that climate change has impacted marine fish populations and communities. Significant fluctuations in fish abundance acting through reproduction, phenology, recruitment, growth and distribution have all been linked with climatic changes. Abundances of some fish species with southern distributions have increased in southern UK waters during recent warming periods (1950s, 1980s-2002), while declines were apparent during cooling episodes (1920s, 1960-70s). Effects of climate on species responses and community composition vary markedly between geographical regions however, making broad-scale predictions difficult. Renewed observations of rare fish migrants to UK waters may be related to recent sea warming, especially since climate-driven changes in timing and extent of annual migrations also occur. However, expected declines in northerly distributed species with recent warming remains equivocal. Boreal species may have retracted north in some regions but not in others. Current understanding suggests climate effects on fish reflect species-specific responses in addition to complex interactions between species (e.g. predator-prey relationships). Although climate influences marine fish assemblages, the precise mechanisms underlying most observed changes remain unclear.
Level of Confidence
Overall, we are ‘quite sure’ that climate change is affecting the abundance and community composition of marine fish.
However, we are ‘not sure’ whether recent climate changes are causing clear distributional changes, although we are ‘quite sure’ this has occurred in the historical past.
We are ‘not sure’ whether trends seen in some regions are applicable to other areas. This is due to limited datasets covering broad geographical areas, and spanning a long enough time period to assess patterns in relation to climate. Very few datasets exist that span >30 years and include non-target as well as target species, which is necessary to understand community (widespread) responses.
We are ‘not sure’ of the precise mechanisms underlying observed changes in fish populations to climate in all cases, but it is likely these operate between climate, environment and complex species interactions resulting in patterns that are difficult to predict or forecast. Our poor understanding in this area is caused by a lack of research using the few datasets in existence capable of supporting appropriate analyses.
Key sources of Information
Please acknowledge this document as: Sims, D. (2006). Impacts of Climate Change on Fish in Marine Climate Change Impacts Annual Report Card 2006 (Eds. Buckley, P.J, Dye, S.R. and Baxter, J.M), Online Summary Reports, MCCIP, Lowestoft, www.mccip.org.uk