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Shrinking fish

Summary

2 October 2012

Fish species around the world are expected to shrink in size by up to 24%, according to a new scientific analysis. Researchers say that rising temperatures could decrease oxygen levels in the sea and significantly reduce fish body weight.

Reporter:

Matt McGrath

Report

Although projections¹ of global temperature rises show relatively² small changes at the bottom of the oceans, the resulting impacts on fish body size are "unexpectedly large", according to this research. As ocean temperatures increase, so do the body temperatures and metabolic³ rates of the fish. This means they use more oxygen to stay alive and, according to the researchers, they have less available for growth. 

They've calculated that up to 2050, fish will shrink in size by between 14 and 24 percent, with the Indian and Atlantic Oceans worst affected⁴. The warming waters are also likely to drive fish more towards the poles, leading to smaller species living in areas like the North Sea. 

According to the scientists, their models may underestimate the potential impacts. When they looked at case studies involving North Atlantic cod⁵ and haddock, they found that recorded data on these fish showed greater decreases in actual body size than the models predicted.