Feeding the world, with a catch

By Jack Suntrup

The world’s fish populations are dwindling. As a result, farm-raised fish selections are growing.

The National Oceanic and Atmospheric Administration estimates that half of the fish Americans eat are farm-raised.

Aquaculture is a growing trend, seen as essential in feeding the world as natural stocks struggle. But these fish, hand-fed and netted off from outside oceans, pose problems to wild stocks when, inevitably, some escape or are released.

Spawning sockeye salmon in a stream. Photo courtesy of NOAA

Spawning sockeye salmon in a stream. Photo courtesy of NOAA

So say Robin Waples of NOAA and  Marissa L. Baskett of the University of California Davis at the American Association of the Advancement of Science conference in Chicago on Friday. Their research points to two strategies to help cope with the problem:

  • Raise fish to be as genetically different as possible from their wild counterparts, to minimize interbreeding.
  • Raise fish to be genetically similar to their wild counterparts, to increase population numbers. The downside would be a possible decreased level of fitness for the population.

Under the different scenario, Waples says the new conspecies of fish would hardly intermingle with their wild counterparts, thus not harming the gene pool.

But because they wouldn’t become part of the population, it could be hard for the group to survive in the wild, especially when weak fish reproduce.

The second point has pros and cons. On the plus side, there would be more fish to supplement populations, and for fishermen to catch. Naturally, the similar farm-raised wild animals would reproduce. But intermingling could come with adverse side effects for the population’s fitness.

In Missouri, for example, farm-raised deer are posing a risk to wild deer throughout the state. Farms are acting as a reservoir for Chronic Wasting Disease. When deer escape the farms, government agencies fear the disease is spreading to wild populations.

Waples concluded his talk by outlining three ways captive fish would not breed with wild ones, lowering fitness:

  •  Preventing all escapes
  • Complete sterilization
  • Breeding the fish to be as different as possible from wild ones to minimize interbreeding

He said that none of these answers would be a “silver bullet.” Natural variables prevent it. What needs to be discussed, though, he said, is whether the benefits of feeding society with farm-raised fish outweigh adverse effects to native populations.

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