It’s big. It grows 4 to 11 times faster than its ordinary relatives. And it’s coming to a plate near you as soon as its developers can get approval.

It’s a transgenic salmon with a gene from a cold-water species so that it continues to grow during cold periods. It may not grow any bigger than existing fish, but it reaches its commercial weight far faster.

“Growth rates have already been improved by 10-23 percent per generation simply through selective breeding,” says Devin Bartley, FAO’s fish genetics expert. “Modifying genes can intensify the process. The first impacts will be commercial, probably in developed countries. But in the end, modified fish may increase food security.”

Aquaculture has expanded massively in the last 25 years, providing a wonderful new source of protein. Most of the progress has been in developing countries using conventional animal breeding technologies. New research is on transgenic varieties of species that are widely farmed in the developing world – for example, tilapia and carps.

Will the fish be safe to eat?

“I think the technology is less important than the end result,” says Dr Bartley. “Thorough testing is crucial for all novel foods, but in the end, food safety should be assessed on the basis of what’s actually on your plate, not how it got there.”

The call of the wild

But the environmental implications of genetically modified fish are even more pressing than those of terrestrial animals. Because the life cycles of fish are so much shorter and they are so much more numerous, genetically modified fish would have a faster impact.

And farmed fish don’t always stay where they’re meant to. About 30 percent of the salmon in Norway’s rivers are escaped farm fish, and in some regions the escape rate is higher. In the Canadian province of New Brunswick, around 33 percent of salmon are thought to be escapees. Farmed fish in the wild are already associated with the spread of pests and diseases such as sea lice.

But the escape of transgenic salmon and other farmed transgenic fish would raise more troubling questions.

• Being bred for the plate, they probably won’t survive in the wild – but what if they were to survive just long enough to breed? Their ‘soft’ characteristics could enter the wild population, compromising their descendants’ ability to survive.

• Transgenic fish may be stronger, not weaker, and may compete for food, reducing the wild population – and then they could die out because of their inability to breed.

• Transgenic fish are already being bred for resistance to disease and pests. In the wild, resistant fish could act as hosts for organisms that would normally kill them. Those organisms could then attack ‘real’ wild fish.

Reducing the risks

These risks will be reduced through insertion of an extra set of chromosomes to prevent transgenic fish from breeding. But a very small percentage may accidentally have the normal two sets of chromosomes, allowing them to reproduce.

However, some of these dangers could also arise from any breeding method that produces a fish different from wild species. Moreover, although there are now legally binding international standards concerning genetically modified organisms (the Cartagena Protocol – see links), alien species seem to get less attention – although there has been more proven damage from such species.

Genetically modified fish are a real prospect. The fast-growing salmon awaits approval from the US Food and Drug Administration and the Canadian Department of Fisheries and Oceans. Further ahead, Canadian scientists are working on tilapia that will produce insulin for diabetics, while scientists elsewhere are developing tilapia with human growth hormone and disease-resistant shrimp.

Meanwhile, fish genes are finding their way onto dry land. The anti-freeze protein gene from the Arctic flatfish used in the Canadian salmon is being transferred to food crops. In Britain a salmon gene that controls calcium loss is being transferred into rabbits. This work is experimental, but it’s clear that fish are caught up in the gene revolution in a big way.

March 2003