A group of studies says that salmon raised in man-made hatcheries can harm wild salmon through competition for food and habitat. Salmon, which survived millions of years of evolution, are in danger from...salmon.

The studies provide new evidence that fast-growing hatchery fish compete with wild fish for food and habitat in the ocean as well as in the rivers where they return to spawn and even raises questions about whether the ocean can supply enough food to support future increases in hatchery fish while still sustaining wild salmon. 

"This isn't just an isolated issue," says Pete Rand, a biologist at the Wild Salmon Center and a guest editor of the publication. "What we're seeing here in example after example is growing scientific evidence that hatchery fish can actually edge out wild populations."

Hatchery salmon are, of course, bred to be hearty while wild salmon are more randomly selected.  The scientists are concerned that a drop in wild fish would mean losing the genetic diversity that has allowed salmon to survive for centuries - we'd basically end up with an English Royal Family of salmon.

Wild salmon populations have a range of highly specialized adaptations to the natural environment, adaptations that help them return to their home streams to spawn and increase their ability to withstand environmental changes like increases in ocean temperature and extreme variations in stream flows. Hatchery fish, as the name implies, are hatched from eggs fertilized in a controlled environment and raised in captivity until they are big enough to release into the natural environment.

Given that advantage, why wouldn't wild salmon be the fitter of the two?  One of the new studies indicates that chum salmon (a type of Pacific salmon) released from hatcheries in Asia, mostly from Japan, have played a significant role in causing declines in a wild chum salmon population in remote western Alaska, 2500 miles away.  

"With billions of hatchery chum released each year, the abundance of adult chum salmon from hatcheries is now much greater than wild chum salmon, so it is not all that surprising that we are seeing evidence of competition in the North Pacific,"  says author Greg Ruggerone of Natural Resources Consultants.

This competition is likely to get tougher with predicted changes in ocean conditions. Recent climate patterns have made ocean conditions temporarily favorable enough to support large populations of salmon, but if these patterns shift, the amount of food in the ocean available for salmon could drop significantly, making it even harder for wild populations to survive. 

Some are calling for a new international agreement or treaty to address the expansion of hatchery salmon in the open waters of the North Pacific.  A relook certainly makes sense. As the health community has recognized the benefits of salmon, the industry has grown.  Hatcheries have been used for many years in an attempt to increase catch in the $3 billion Pacific salmon commercial fishing industry and keep it sustainable without decimating wild populations. 

Since the mid-1970s, large increases in hatchery programs in the U.S., Canada, Russia and Japan have released billions of fish into the water. And the increasing global demand for salmon has resulted in calls to further expand hatchery production, especially in Russia and Alaska. In a 2010 open letter to Alaska hatcheries, seafood processors proposed increasing pink salmon hatchery returns by 25%-115% over the next five years. Similarly, Russian hatchery managers stated in 2010 that Russia is planning to build 23 new hatcheries that would increase the country's hatchery production by 66% or 680 million fish. 

"These studies suggest that even more caution is needed to make sure hatchery programs keep wild salmon safe, and don't inadvertently hurt the long term potential of salmon runs," says Rand.  "The scale and magnitude of our current hatchery production system is enormous. Five billion juvenile salmon are released each year worldwide, and the prospect of additional increases in hatchery production is worrisome for the long-term survival of wild salmon."

Published in Environmental Biology of Fishes