The skeleton of a salmon being inspected in the IMR's X-ray lab. Photographer: Erlend A Lorentzen / IMR, Norway.

Gene-edited sterile salmon ‘similar to standard salmon in health and omega 3’

Gene-edited, sterile salmon is similar to other farmed salmon in terms of both health and omega 3, a study by Norway’s Institute of Marine Research showed.

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By turning off a special gene with the CRISPR method, IMR researchers previously created the world’s first salmon without germ cells so that it cannot mate with wild salmon if it escapes.

Now the researchers have followed such salmon throughout a production cycle to compare growth, signs of welfare and omega 3 content with normal farmed salmon.

Lene Kleppe examined gene-edited sterile salmon throughout a full production cycle and found no differences with standard salmon, except for the advantage of avoiding sexual maturation and the problems it brings. Photo: IMR.

Much the same

“We found no differences in body size, smoltification, stress markers, heart size or the occurrence of skeletal malformations,” said researcher Lene Kleppe.

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

What the researchers saw, however, was that normal salmon began to grow faster than the sterile salmon towards the end of the experiment. In addition, it got a bigger liver.

Maturation problems

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

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 energy on sexual maturation. In farming, sexual maturation means that the salmon must be harvested, even if it was ahead of schedule.

Early sexual maturation is a particular problem in closed farming facilities on land, although farmers can to some extent use light and temperature to prevent it.

A clear advantage

“The easiest thing would be to exclude sexual maturation completely in farmed salmon,” said Kleppe.

“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.”

So far, 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.