Assessing the Environmental Risks of Genetically Engineered Salmon

Risk assessment research on genetically engineered salmon

by Department of Fisheries and Oceans (DFO, Canada)

Discoveries in the last century gave humankind new understanding of the mechanisms by which genes can control characteristics of organisms, such as growth and development. In the 1970's, "recombinant DNA" technology provided the ability to manipulate gene structure, by joining DNA sequences from different sources into new combinations.

In the plant world, genetically-engineered foods such as corn, soybeans, and canola with modified production traits entered the marketplace approximately ten years ago. While they have caused significant controversy, an even higher degree of reluctance has slowed acceptance of genetically engineered organisms in the animal world, including fish.

Early research on genetically-engineered fish was undertaken at Fisheries and Oceans Canada (DFO)'s Centre for Aquaculture and Environmental Research (CAER) where Dr. Robert Devlin and colleagues developed salmon that can grow faster than normal by introducing growth hormone genes from salmon into the strains. The strains developed by Fisheries and Oceans Canada are not for commercial application, but rather Dr. Devlin's lab has focused on assessing the risks genetically engineered fish would pose should they be commercially utilized and escape to the natural environment. The scientists aim to understand the potential of the genetically engineered organism to survive and reproduce in nature, and the effects that it might have on ecosystems.

Worldwide, more than thirty species of fish have now been genetically engineered in laboratory studies, including species used in aquaculture such as Atlantic and Pacific salmon, carp, tilapia, and catfish. Tropical species such as zebrafish and Medaka have also been genetically engineered for use as models in medical and other scientific research. A primary objective in aquaculture species has been to increase production efficiency. However, no genetically engineered fish species have been approved in Canada.

"There are many questions and great complexities," Dr. Devlin says. "A chief issue is, could one keep genetically engineered salmon out of the natural environment? If they're grown in sea pens near wild salmon and other fish, there's always the potential of escapes and interaction with wild fish and other organisms in the ecosystem."

One can sterilize farmed salmon by inducing a condition known as "triploidy." Subjecting newly-fertilized eggs to pressure or other treatments can result in fish carrying three instead of the normal two (diploid) sets of chromosomes, which takes away the ability to reproduce.

"In experiments designed to assess the reliability of triploidy as a sterilization method, we've reached a 99.8 per cent success rate," Dr. Devlin says. "But if an escape of 50,000 fish occurred from a farm, even that small percentage of diploids could still represent the introduction of a hundred fertile fish, with the potential to reproduce in nature.

"Fertile escapees raise a whole set of issues. Would they survive? Would they mate with their own kind or produce hybrids with wild salmon? Would they displace the natural fish and other organisms?"

Dr. Devlin and his colleague Dr. Fred Sundstrom have designed experiments to seek answers to these questions, using artificial contained landscaped streams that partly replicate nature, complete with streams, rocks, gravel, vegetation, and predators. Salt water contained "mesocosms" are also currently being developed to examine variables affecting marine survival and consequences.

One CAER experiment monitored naturally occurring and genetically engineered salmon competing for food. When it was plentiful, the two groups co-existed well. As food got scarcer, though still available, the ever-hungry genetically engineered salmon took dominance, out-competed the naturally occurring salmon for food, and ultimately affected their survival.

On the other hand, CAER research has also shown that growth-enhanced genetically engineered salmon, which have greater appetites and thus are often foraging for food, in doing so expose themselves more to predators and lessen their chance for survival. And, at low levels of food availability, naturally occurring fish have been observed to survive better.

Bob Devlin says that "we're examining different characteristics of the fish, monitoring such things as swimming speed, food requirements, and disease resistance. Most characteristics we have examined seem to be affected to some degree by the genetically engineered condition.

"But our research has also shown the limitations of laboratory research for risk assessments. We can't release genetically engineered fish into the wild and monitor them; that would be too risky. But we're also unable to accurately re-create an ocean or river in the lab. That means we are finding it difficult to predict with confidence what would happen with genetically engineered salmon in nature, with all its variables."

Based on modeling exercises, an introduction, he notes, has the potential to affect the whole future of a species, as well as other aspects of the ecosystem.

Dr. Devlin says, "Because of current uncertainties in our ability to provide accurate risk assessments, a very important area of research is the development and assessment of new bio-containment technologies for genetically engineered fish, through enhanced triploidy or other methods."

Proponents importing or developing genetically engineered fish for purposes other than contained research are subject to regulation under the Canadian Environmental Protection Act, 1999, in order that any potential adverse environmental and human health effects may be assessed and appropriately managed.