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What advantages do warm-blooded fish have?

Warm bloodedness – the ability to maintain a body temperature higher than the surrounding environment – is costly. Precious calories are used to keep up a warmer body. Over long periods, there must be a benefit associated with this cost or else, it would be weeded out by natural selection. 

This leads to a question – why are some fish like the bluefin tuna or great white sharks warm-blooded when so many other fish are not? Scientists have two basic hypotheses as to what benefit is derived from being a warm-blooded fish. 

First, it’s quite possible that fishes with the ability to regulate their body temperatures may live or travel through a greater range of climates and possibly even be better adapted to climate change. Sharks for instance have lived through large changes in climate before. 

The second theory is that warm-blooded fish are able to swim faster, this seems especially important for prey species or fish that travel long distances. The idea is simple – warm muscles function better than cool ones, something to keep in mind when considering skipping a warm up before your next workout. 

A new study led by PhD student Lucy Harding at the Trinity College Dublin leads this question to rest. The researchers used biologgers attached to a variety of fish and a close look at previous research to investigate the advantages of being warm-blooded. 

The data logging devices recorded the temperatures that the fish swam through as well as the speeds at which they traveled. 

Ultimately, the experts found that warm-blooded fish do not travel through a greater range of temperatures than their cold-blooded kin. They do, however, travel an average of 1.6 times faster than cold-blooded fish. 

According to the researchers, this means sharks and other warm-blooded fish are just as vulnerable to climate change as any other marine animal.     

“The faster swimming speeds of the warm-blooded fishes likely gives them competitive advantages when it comes to things like predation and migration. With predation in mind, the hunting abilities of the white shark and bluefin tuna help paint a picture of why this ability might offer a competitive advantage,” said study co-author Nick Payne.

“Additionally, and contrary to some previous studies and opinions, our work shows these animals do not live in broader temperature ranges, which implies that they may be equally at risk from the negative impacts of ocean warming. Findings like these – while interesting on their own – are very important as they can aid future conservation efforts for these threatened animals.”

The study is published in the journal Functional Ecology.

By Zach Fitzner, Staff Writer

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