Researchers from Wageningen, together with the Koepon Foundation and WorldFish, found that genes influence the swimming fitness of tilapia. As there are indications that fitter fish are also healthier and more resilient, researchers recommend including fitness in selective breeding programs for farmed fish. 

“In humans, cardiovascular fitness is typically measured through a cycling or treadmill test,” program leader, Hans Komen, said. “In farmed animals, this is rare. We have developed a methodology for fish. Our test shows, for the first time, that physical fitness, measured through this test, is largely inherited.”

In the study, scientists have Nile tilapia swim against the flow in a carousel. By gradually increasing the flow, they were able to precisely measure when the fish reached their maximum swimming capacity. As in humans, their fitness depends on their ability to absorb oxygen and cardiovascular condition. Fast swimming fish showed slower growth. “We suspect these results from of an evolutionary principle,” said researcher Arjan Palstra. “To avoid predation, you can either swim faster to escape, or grow larger as a defense.”

There are also indications that fitter fish are healthier fish. Researchers, therefore, recommend fish breeders include the swimming test in their selective breeding programs. To date, the main focus has been increasing the growth rate. Komen and his team intend to apply their results to other fish species such as trout, salmon and sea bream. 

Check out the study here.