June 8, 2011

Biologists Compare School Of Fish To Peloton Of Cyclists

Biologists found resemblances between a peloton of cyclists in the Tour de France and a school of fish, reports the Guardian.

Fish swim as though they were cyclists, where as fish at the back of a school use the slipstream created by the stronger fish out in front to swim with less effort.

The study found that the position of a fish in the school depends on how physically fit it is.  The fittest swim at the front, where they get the pick of the best food.

The less-fit fish swim towards the back of the school, but what they lose in quality food they make up for by swimming in the slipstream created by the fish in front of them.

"Animals moving in coordinated groups, such as birds flying in formation or humans riding bicycles in a peloton, are often found to have reduced energetic costs of locomotion owing to various mechanisms allowing individuals to exploit areas of reduced drag created by more forward individuals," the researchers wrote in Proceedings of the Royal Society B.

Researchers filmed schools of eight juvenile golden grey mullet in a swim tunnel for the study.  They estimated the metabolic rate of the fish by measuring how fast the oxygen levels in the water were declining as the animals breathed and worked out the effort each fish was making by counting the number of beats it made with its tail.

The team found that trailing fish required fewer tail beats to swim the same speed as individuals at the front of schools.

"Fish with higher rates of tail movement would have been working harder to propel themselves forward and therefore spending more energy," Dr. Shaun Killen, a biologists at the University of Glasgow, told guardian.co.uk. "An analogy would be human runners: those taking the most steps each minute are those having to spend the most energy."

The researchers believe that when the school was swimming at 30 centimeters per second, trailing fish were having to work 12 percent less hard compared with the fish they were following.

"One of the most interesting things that these results hint at is that there may be differences in energy demand or performance capacity between schools in the wild. It wouldn't be smart for a fish to join a school with others that are much slower or faster than it is," Killen said in a statement.

"Again, this is a bit similar to human runners. If a group of friends are going for a run it makes the most sense if they are all at a similar performance level: a slower person might find it difficult to keep up, while a person who is much faster would be limited by running with a slower group."


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