Fish swim as if they were competing in a bicycle race

Jun 27, 2011, 13:48 GMT

London - Fish swimming in schools use the same technique as cyclists riding in the peloton during the Tour de France, taking advantage of the slipstream of the strongest to get ahead with less effort.

The fittest fish are to be found up front, enabling them to take the pick of the best food, according to the findings of an international research team reported in the 'Proceedings B' of the Royal Society.

Until now scientists believed that the position of individual fish within a shoal was largely equal and if anything left to chance.

The work was led by Shaun Killen of Montpellier University in France. His team placed eight juvenile golden grey mullet in a transparent swim tunnel and observed their behaviour.

After letting them swim freely for 20 minutes, the metabolic rate of the fish was measured by seeing how fast the oxygen levels in the water declined as the animals breathed.

The effort each fish was making was calculated by counting the number of beats it made with its tail. In this way the researchers could see which fish regularly held the pole position, and which ones swam in midfield or at the back of the group

The results revealed that while the fittest fish were to be found at the front and fed on the best plankton, those further back benefited from huddling together like cyclists in a race. In doing so they could swim almost as fast as the other fish without expending as much energy.