Impacts of climate change on fish, relevant to the coastal and marine environment around the UK.

The appearance of warm-water (Lusitanian) fish species in UK watersalong with local declines of some cold-affinity species provides themost compelling evidence of a climate-change effect.• Distinguishing between climate-induced effects on fish distributionand other drivers is a key challenge. Some past studies have notaccounted for geographic attachment and population structure instudies of distributional shifts in species including Atlantic cod andmackerel.• The synchrony between winter–spring hatching fish larvae (e.g. cod,sole, sandeel) and their plankton prey appears to be changing, withconsequences for recruitment. These changes reflect both changes inthe timing of fish reproduction as well as that of their plankton prey.• Temperature changes are affecting fish growth and age at maturation.Rising temperatures also decrease oxygen solubility and increasemetabolic costs and there is now considerable debate as to whetherthis is limiting the maximum size that fish species can attain.• Fin-fish larvae may be sensitive to expected changes in oceanacidification, but species have shown a variety of responses inexperiments. For example, the use of end-of-century CO2concentration under the IPCC RCP 8.5 scenario resulted in a doublingof daily mortality rates in Atlantic cod larvae, but only had a minoreffect on European seabass and herring larvae.Advances in both statistical and mechanistic models have increased ourability to provide future projections for climate change impacts on fish.Scientists have started to provide ‘forecasts’ for some species at the seasonalto decadal time horizon, but there have been insufficient runs to yet beconfident in these projections.