Farmed salmon and trout are interbreeding with and passing genetic defects to wild-born offspring
Anne Hart
Examiner.com
07/05/2009
Farmed salmonids (hatchery-born fish) also are reducing the fitness of wild populations when they interbreed. According to the San Francisco Chronicle online, SF Gate, July 5, 2009, the article, "Warning on trout hatcheries could force changes," by Peter Fimrite, Chronicle Staff Writer, notes that, "Hatchery-raised steelhead trout pass on genetic defects that hamper survival of even their wild-born offspring, according to a study that biologists say could lead to a radical shift in the way salmon breeding programs operate on the West Coast."
Hatcheries usually have been seen as part of the solution. But a new Oregon State study released in June 2009 shows that farmed fish may instead be part of the problem.
That most recent Oregon State University study found that even hatchery fish whose parents were wild develop and pass on genetic defects severe enough to hamper the reproductive ability of their offspring. That could mean that any genetic defects created by injecting farmed fish with various retroviruses or dependent upon what the fish ate.
For example, instead of soy pellets, rendered cows, farmed fish might genetically reproduce defective fish when they interbreed with wild fish. The study noted that hatchery-produced fish can harm wild fish when they interbreed with the wild fish.
According to the article, "Warning on trout hatcheries could force changes," The implication, scientists said, "is that hatchery programs for all salmonid species, including steelhead, chinook and coho, could actually be harming the natural balance and contributing to the demise of the once plentiful salmon runs in California, Oregon and Washington."
"Past studies have always suggested that hatchery-produced fish are of lesser quality, but this study shows it is more disturbing than we thought," Tina Swanson reported in the article published in today's SF Gate. Swanson is a fishery scientist and the executive director of the Bay Institute. "This is the clearest indication that hatchery-produced fish can actually harm wild stocks. It underscores my suspicion that hatcheries are not the solution."
Aquaculture is the fastest growing form of food production in the world. It is also a significant source of protein for people in many countries, including the United States. Globally, nearly half the fish consumed by humans is produced by fish farms. This worldwide trend toward aquaculture production is expected to continue. At the same time, demand for safe, healthy seafood is also expected to gro
The issue is critically important to biologists, fishermen and water managers in California, where the commercial salmon fishing season was shut down for a second straight year after another paltry return of spawning fall run chinook. The Sacramento-San Joaquin River fall run is historically the largest run of salmon on the West Coast and the vast majority of those fish are mass produced in hatcheries.
Scientists point to a host of environmental and habitat problems, including a warming ocean, for the decline. A biological review this month by the National Marine Fisheries Service placed much of the blame on diversions by the state and federal water systems. For more information, read, "Fish Facts" at the National Marine Fisheries Service's site.
What did the latest study reveal? Michael Blouin is a professor of zoology at Oregon State and the lead author of the study that researched how well farmed and wild fish reproduce by studying the genetic fingerprints of three generations of wild and hatchery-raised fish from Oregon's Hood River, in the Columbia River system using meticulous standards.
Blouin explained to the SF Gate how the genetic fingerprints of three generations of wild and hatchery-raised fish had been studied, noting the analysis involved genetic data on thousands of fish dating back to 1991. Research revealed that, on average, Blouin said, the offspring of two hatchery-reared steelhead were only 37 percent as reproductively fit as fish whose parents were both wild.
The fish with two hatchery parents were 87 percent as fit as the offspring of one wild parent and one hatchery parent. Blouin emphasized that these differences were detectable even after a full generation of natural selection in the wild.
"What's surprising is how poorly the first generation of fish do," Blouin told the SF Gate. "There's a rapid decline in the fitness of those fish when they go out and spawn in the wild."
In the past most scientists thought genetic problems developed over several generations and only in hatcheries that were lax in their efforts to ensure genetic variability. However, the Hood River hatchery, used for conservation purposes, requires meticulously breeding the fish. It's important what the farmed fish are fed, keeping the fish food as natural as possible. The fish are regularly interbred with wild fish for the purpose of promoting genetic diversity. If the genes get too narrow on one group of fish, they can be easily attacked by viruses and bacteria, but if the fish gene pool is wide, the fish usually are more resistant to diseases.
