Climate change may shrink fish

Climate change will decrease Haddock sizes in the future.

Researchers at the University of British Columbia, Canada modelled the impact of rising temperatures on more than 600 species of fish between 2001 and 2050. The results show that warming waters could decrease ocean oxygen levels which would lead to a decrease in body weight of fish. Up to now, scientists were only concerned that climate change would alter distribution and reproductive capabilities of fish but this new finding adds a further dimension to the problems.

"Rising temperatures directly increase the metabolic rate of the fish's body function," said Dr. William Cheung from UBC. 

"This leads to an increase in oxygen demand for normal body activities. So the fish will run out of oxygen for growth at a smaller body size."

The model also predicts that fish will move polewards at a rate of up to 36 km per decade. "So in, say, the North Sea," says Dr Cheung, "one would expect to see more smaller-body fish from tropical waters in the future. The largest decreases of about 24% are predicted to occur in the Indian and Atlantic Oceans.

Dr Alan Baudron, from the University of Aberdeen, UK, who has studied changes in the growth of haddock in the North Sea said "smaller individuals produce fewer and smaller eggs which could affect the reproductive potential of fish stocks and could potentially reduce their resilience to other factors."

While the authors acknowledge some shortcomings in the research, they say it highlights a need to look at the biological implications of climate change and push for further research to be conducted. 

Read the article in Nature Climate Change here: http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1691.html