Fish may be evolving to swim faster and evade capture in trawler nets, according to research.

Scientists at the University of Glasgow found that fitter fish are better at evading nets and believe that, over time, it could lead to physiological changes in future fish populations. The group used simulated trawling with schools of wild minnows to investigate whether some individual fish were consistently more susceptible to capture by trawling and if that related to swimming performance and metabolism.

The researchers measured the swimming ability, metabolic rate, and indicators of aerobic and anaerobic physical fitness of 43 fish.

They then placed them in a tank with a simulated trawling net to identification those most susceptible to capture.

There is a lot of concern on how overfishing is affecting the abundance of wild fish

Shaun Killen of the Institute of Biodiversity, Animal Health and Comparative Medicine, led the study.

He said: “There is a lot of concern on how overfishing is affecting the abundance of wild fish, consequences for the economy, employment and the ecosystem as a whole.

“But one aspect that is often overlooked is that intense fishing pressure may cause evolutionary changes to the remaining fish that are not captured.”

The study is published in the journal Proceedings of the Royal Society B and the researchers want to carry out a similar study on fish in the wild. Killen said: “Humans are effective predators, and selective harvest of animals by humans probably represents one of the strongest drivers of evolutionary change for wild animal populations.