Edinburgh, Fife & East Scotland

Warm-bodied fish 'swim twice as fast as cold-bodied species'

Shark speed sensor Image copyright St Andrews University
Image caption The team collected their own data by attaching speed sensors to sharks in Alaska, the Bahamas and the central Pacific

Warm-bodied fish, such as the Great White shark, can swim more than twice as fast as cold-bodied species, according to new research.

It is thought their warmer muscle temperatures enhance power output.

St Andrews University was part of a team which found that the increased swim speeds allowed warm-bodied fish to migrate large distances in a shorter time.

This means they can take advantage of seasonal changes in food supplies.

Warm-bodied fish were found to be able to swim at cruising speeds 2.7 times faster than other similar sized cold-bodied species.

The scientists compared the Great White shark with cold-bodied species of shark such as the Oceanic Grey Reef shark and the Oceanic White Tip shark.

Image copyright St Andrews University
Image caption The Great White shark is warm-bodied

The findings are published in the Proceedings of the National Academy of Sciences.

Dr Yuuki Watanabe of the National Institute of Polar Research in Japan, who led the study, said they had been trying to establish why the "unique evolution" of the warm-bodied species had taken place.

"In other words, what kind of advantages do the fish gain from being warm-bodied?" he said.

Dr Yannis Papastamatious of the University of the St Andrews' Scottish Oceans Institute was one of the researchers involved in the study.

Image copyright St Andrews Univerisity
Image caption The Oceanic Grey Reef shark is cold-bodied

The team gathered and analysed data from previous studies as well as collecting their own data by attaching speed sensors to sharks in Alaska, the Bahamas and the central Pacific, to compare swim speeds of warm and cold-bodied fish.

Dr Papastamatious said: "Fishes are generally considered cold-bodied in that their body temperatures are very similar to that of the water they reside in.

"However, amazingly a small number of tunas and sharks, including white sharks, have evolved the ability to maintain their body temperatures higher than the surrounding water - sometimes up to 20C warmer.

"We found that on average, warm-bodied fishes can swim almost 2.7 times as fast as cold blooded species, likely because the warmer muscle temperatures enhances power output.

"As such these animals can swim to distant locations and back again which may allow them to take advantage of seasonal pulses in food or other resources.

"Our study provides a potential explanation for the evolution of endothermy (being warm-bodied) in fishes."

Image copyright St Andrews University
Image caption The Oceanic White Tip shark is cold-bodied

Related Internet links

The BBC is not responsible for the content of external Internet sites