/wildlife/article/45002

When it comes to farm raised fish, it doesn't pay to let them be lazy. Fish like wild salmon, tuna and eel are built for the vigorous swimming required during migration.

These fish are "uniquely adapted to a physiology of high levels of exercise performance," says Tony Farrell, who studies fish physiology in the University of British Columbia Zoology department. "Therefore when we put them in constrained environments and remove predators, the consequences are they become a little more like couch potatoes."

When these fish are raised on farms in captivity, they are prone to a variety of health problems everything from heart disease to viral infections kind of like human couch potatoes. And, just like with humans, getting more active seems to make a big difference in their health.

There's at least 50 years of research on the physiological benefits of exercise to fish, demonstrating that when fish are good swimmers, they have better cardiovascular fitness, a stronger immune system and are less prone to disease and physical deformities than their sedentary brethren. Yet very few fish farms use exercise as a way to improve the quantity and quality of their product. New research and a new book, Swimming Physiology of Fish: Towards Using Exercise to Farm a Fit Fish in Sustainable Aquaculture, are trying to persuade the commercial fish farmer to give it a try.

Farmed fish currently make up nearly half of all fish consumed, and the industry is growing rapidly. While it produces a fairly cheap source of protein, disease, waste and a decreasing supply of traditional fish feed remain problems yet to be fully solved.

Increasing survival rates even just a few percent by exercising fish not only creates a healthier environment for them, but it may translate into billions of dollars for fish farms.

Fish exercise may aid the fish farming industry financially, Farrell says, but there's another lesson as well. "Exercise, in a world that is sedentary, is beneficialeven in fish."

So what does that mean to what you get on your dinner plate? Some experts suggest that bigger, stronger, and healthier fish may also produce changes in color, texture or overall appearance that make a more attractive meal to the consumer. But there's no evidence yet that the nutritional content is affected.

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Farm Raised Salmon Need to Beef Up