Researchers report salmon mixing success

Lene Klepp

Research scientists in Norway have made important progress in their efforts to solve the problem of farmed salmon mating with wild salmon when they escape.

By turning off a special gene with the CRISPR method (a genetic engineering technique in molecular biology by which the genomes of living organisms may be modified), a team at the Norwegian Institute of Marine Research have created the world’s first salmon without germ cells.

The eventual purpose is to create a salmon that cannot mate with the wild variety in rivers.

Now the researchers have followed such salmon throughout their entire lives (a so-called production cycle) to compare growth, signs of welfare and omega-3 content with normal farmed salmon.

Researcher Lene Klepp (pictured) said: “We found no differences in body size, smoltification, stress markers, heart size or the occurrence of skeletal malformations.

The sterile salmon also had the same amount of healthy omega-3 fatty acids as the normal farmed salmon.

The researchers found towards the end of the experiment that normal salmon began to grow faster than sterile salmon. They also developed a larger liver.

Kleppe explained: “These are early signs of sexual maturation. You generally want to avoid that in farming, not only because sexually mature fish on the run can mate with wild fish.

“Fish that reach sexual maturity become more susceptible to disease and can thus experience poorer welfare.

“They also [have] poorer meat quality because they use more energy on sexual maturation. In farming, sexual maturation means that the salmon must be slaughtered, even if it was ahead of schedule.

“Especially in closed breeding facilities on land, early sexual maturation is a problem. But there the breeders can to some extent use light and temperature to prevent that.”

Kleppe said the easiest thing would be to exclude sexual maturation completely in farmed salmon.

“We have now shown that gamete-free salmon is largely similar to normal salmon, but has the clear advantage that it never reaches sexual maturity”, she concludes.

The Institute pointed out that the gene-edited salmon has only been produced for research in the laboratory. In Norway, it is defined as genetically modified, and strictly regulated by the Genetic Engineering Act.