With the CRISPR method, researchers can cut out genes that control sexual maturation or color Photo: Erlend A. Lorentzen / Havforskningsinstituttet

Genetically edited, sterile salmon was similar to other farmed salmon in both health and omega-3

NORWAY
Thursday, August 11, 2022, 07:10 (GMT + 9)

It only differed from ordinary salmon with one obvious advantage.

By switching off a special gene with the CRISPR method, HI researchers previously created the world's first salmon without germ cells. The purpose has been to develop a farmed salmon that cannot mate with wild salmon if it escapes.

Now the researchers have followed such salmon throughout their entire lives (a so-called production cycle) to compare growth, signs of welfare and omega3 content with normal farmed salmon.

No measurable differences in growth and welfare

"We found no differences in body size, smoltification, stress markers, heart size or the occurrence of skeletal malformations", says 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, he got a bigger liver.

Photo of vertebra in crusher. The hypersensitive "bone crusher" measures the resistance in a salmon vertebra. It can reveal "bone fragility". Photographer: Erlend A. Lorentzen / Institute of Marine Research photo of an x-ray of salmon on a computer screen

Nobody wants sexually mature farmed salmon

"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", explains Kleppe.

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

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

Photo of an x-ray of salmon on a computer screen. In our own X-ray lab, researchers can inspect the skeleton of salmon. Photographer: Erlend A. Lorentzen / Institute of Marine Research

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.

The research salmon is eternally prepubertal

"The easiest thing would be to exclude sexual maturation completely in farmed salmon", says Lene Kleppe.

"Now we have shown that gamete-free salmon is largely similar to normal salmon, but has the clear advantage that it never reaches sexual maturity", she concludes.

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.

Photo of a cross-section of salmon on a cutting board. The researchers took many measurements from different parts of the salmon. Standard meat samples have provided the protein and fat composition. This is an archive picture from our sample reception, where we take such a sample from farmed salmon. Photographer: Erlend A. Lorentzen / Institute of Marine Research

The Institute of Marine Research is a world leader in developing methods for using CRISPR for gene editing of salmon. Read more on our theme pages.

Author: Erlend Astad Lorentzen / Institute of Marine Research (Havforskningsinstituttet)| Trnslated from original in Norwegian

Reference:

Kleppe, L., P. G. Fjelldal, E. Andersson, T. Hansen, M. Sanden, A. Bruvik, K. O. Skaftnesmo et al. "Full production cycle performance of gene-edited, sterile Atlantic salmon-growth, smoltification, welfare indicators and fillet composition." Aquaculture (2022): 738456
Link: https://doi.org/10.1016/j.aquaculture.2022.738456

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