Climate change impacts on fish in the Baltic Sea.

The Baltic Sea is a marginal sea with strong abiotic gradients harbouring fish of both marine and freshwater origin. Here we review the empirical evidence for how changes in climate variables have impacted different fish and fish communities in the Baltic Sea. Studies on responses to temperature, salinity and hypoxia dominate the literature, with most evidence for negative influences on reproduction and feeding areas for demersal fish of marine origin. In contrast, warmer waters benefit the reproduction and growth of some smaller pelagic and many coastal fish species of freshwater origin, but responses on population or community levels are elusive. Several responses to climate change have further been mediated through changes in prey abundance and quality. Studies investigating adaptations to climate change indicate that fish are adapting, partly counteracting climate impact. A precautionary approach to management is therefore important to safeguard climate change adaptation and reduce deleterious impacts as the impact on the Baltic Sea from a changing climate likely will be even more pronounced in the coming decades.