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Global Warming Could Increase Fish Parasites

GLOBAL - Parasitic worms that infect fish and have a devastating effect on fish reproduction grow four times faster at higher temperatures providing some of the first evidence that global warming affects the interactions between parasites and their hosts, writes TheFishSite editor, Charlotte Johnston.

Research from the University of Leicester shows that global warming could have serious implications for fish populations. As parasites grow faster in higher temperatures, the host's growth rate is slowed. The research suggests that parasites can influence fish behaviour - making them seek out warmer temperatures.

The results provide some of the first evidence that increasing environmental temperatures can lead to a shift in the delicate balance that exists between co-evolved hosts and parasites, increasing the speed with which parasites complete their life cycles that could lead to an increase in the overall level of parasitism in natural animal populations.

In the US, it has been proved that sockeye salmon are evolving through natural selection to deal with a warming climate.

Research from the National Oceanic and Atmospheric Administration shows that fish now migrate upstream an average of 10 days earlier than they did in the 1940s.

Evidence of an evolutionary response in Columbia River sockeye salmon is good news, because it appeared to reduce their exposure to potentially lethal river temperatures in recent years, according to Dr Lisa Crozier.

"This study gives managers insight into the multiple processes that help salmon persist in the face of a changing environment, and augments our toolbox for predicting how other species might respond to similar changes," she said.

Chris Haris

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