Bib and chips may be on future menus
Fears that global warming is threatening fish stocks were confirmed with the publication of a new study in the international journal Science.
The new research reveals that 21 species of fish have shifted their distributions with the rise in sea temperature. Eighteen species have moved up to hundreds of kilometres northward over the past 25 years – at nearly four times the rate of land-based birds, butterflies and alpine herbs.
As the temperature of the North Sea continues to rise – having already warmed 1°C over the past 25 years – populations of fish such as cod have responded by moving northwards. Cod’s centre of population has shifted 117km towards the Arctic while the haddock’s southern boundary has also moved 105km north. At the same time, species that normally inhabit warmer waters are encroaching on the North Sea. The northern boundary of the bib, for example – a cod-like fish – shifted 342km during the study period.
University of East Anglia PhD student Allison Perry led the research in collaboration with Professor John Reynolds and scientists at the Centre for Environment, Fisheries & Aquaculture Science.
The scientists measured the shift in the geographic distribution centres and range boundaries of 36 North Sea fish species using long-term government trawl surveys. The team compared the year-to-year changes in fish ranges with year-to-year changes in sea temperatures, Gulf Stream position, and zooplankton communities.
North Sea fishes are responding faster to climate change by moving further each year than other well-studied species. On average, birds, butterflies and alpine plants have shifted half a kilometre per year, whereas the studied North Sea fishes have travelled northwards at a speed of just over 2km per year.
Allison Perry says: ‘We were very struck by the extent and scale of these shifts, particularly by the fact that the rates of movement are nearly four times as fast as climate-driven shifts in terrestrial species. This could have significant impacts on an ecosystem which is already under heavy pressure.’
The study raises concerns that some over-exploited fish stocks face a further threat from climate change. However, the detailed consequences of the changing fish distributions for biodiversity, fishery yields and the UK fishing fleets is unknown.
Clive Fox, Cefas fisheries biologist, adds: ‘These results emphasise the value of long-term monitoring programmes, such as those run by Cefas, in detecting the effects of environmental change on marine bio-resources.’
The scientists predict that blue whiting and redfish will have left the North Sea by 2050 and will be replaced by bib.
Fish with faster life cycles and smaller body sizes are more likely to respond to continued changes in sea temperature. However, larger fish – which are already more vulnerable to over-fishing – respond less strongly to climate change. It is unclear whether larger-bodied species, such as cod and haddock, will be able to adapt to the new North Sea conditions. They may, in fact, be left out in the cold
‘Climate Change and Distribution Shifts in Marine Fishes’ by Allison Perry, Paula Low, Jim Ellis and John Reynolds was published in Science on 13 May 2005.
For further information:
- About Cefas’ climate change-related work, contact: Anne McClarnon at the Cefas Press Office, 01502 524370 / a.mcclarnon@cefas.co.uk
