Fish and fisheries

Abundances of warm-water fish species (e.g. red mullet, john dory, triggerfish) have increased in UK waters during recent decades, while many coldwater species have experienced declines.
There has been a massive influx of snake pipefish to UK waters since 2004, but unusual fish occurrences or sudden proliferations of species cannot definitively be attributed to climate change.
A number of commercial and non-commercial fish species are suggested to have exhibited shifts in mean latitude over the past 25 years.
Poor ‘recruitment’ in traditional fishery target species such as cod, plaice and herring may be related to a shift in the composition of zooplankton, which are a key prey for developing larvae.
In some parts of the southern North Sea, cold-water species, such as cod and eelpout, have been shown to experience metabolic stress during warm years, as evidenced by slower growth rates and difficulties in supplying oxygen to body tissues.
Climate change will have far-reaching impacts on the dynamics of fish populations, however knowledge of underlying mechanisms is rather limited, especially in non-commercial species.
Excessive fishing pressure has caused fish populations to become more vulnerable to short-term natural climate variability by removing the oldest individuals, and making such populations less able to ‘buffer’ against occasional poor year classes.
In the short term, climate change will have little influence on fish stock recovery, which depends instead upon reducing fishing effort to allow existing year classes to survive to maturity.
Climate-related shifts in species distribution, behavior and depth preference may affect the ‘catchability’ of certain stocks to fishing fleets.
Long-term climate change may affect the overall productivity of fish stocks in a given area. Some species may be adversely affected leading to reductions in sustainable yield whilst others, for example seabass, red mullet and John Dory, may be positively affected leading to enhanced fishing opportunities.