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Last updated at 12:13 BST, Wednesday, 03 October 2012

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

Cod

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Report

Although projections of global temperature rises show relatively 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 metabolic 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 affected. 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 cod and haddock, they found that recorded data on these fish showed greater decreases in actual body size than the models predicted.

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Vocabulary

projections

predictions based on studies or evidence

relatively

comparatively

metabolic rates

the amounts of energy used over a certain period of time

oxygen

a chemical element which is essential for life

calculated

worked out

shrink

get smaller

warming waters

seas which are getting hotter

poles

the most northerly and southerly points on the Earth's axis

underestimate

misjudge

case studies

specific examples