New approach to produce all-female salmon avoids the use of hormones and can be combined with vaccination to achieve sterility

The first attempt to produce all-female salmon was not successful. However, we now have a larger group of spawning broodstock that may produce all-female offspring. We expect to see the results from this experiment during the next few months. Functional studies of the genes/proteins of interest are proceeding according to the plan. We expect to publish an article focusing on one of the selected genes during spring 2024. The vaccination experiments are proceeding according to the plan. One out of three experiments have been finalized, and the two remaining experiments will be finalized during the next few months. Analyses are ongoing.

In salmon aquaculture, sea lice infections and farmed escapees are currently preventing production increases and causing concerns about genetic introgression with wild populations, respectively. One way to reduce lice infections is to produce large smolts on land, thereby decreasing the time spent in sea cages where infections occur. Yet, land-based production comes with the risk of an increased incidence of precocious male maturation, which negatively effects fish welfare, somatic growth and filet quality. However, since precocious maturation of Atlantic salmon is mainly a problem in males, using all-female populations could solve this problem. The currently established way to mass-produce monosex fish involves hormone treatment to sex-reverse the broodstock. With a trend towards increased production on land, the use of hormones as part of the production protocol is neither consumer nor environmentally friendly. Alternative hormone-free protocols for producing all-female salmon will be evaluated in this project. Genetic introgression of farmed escapees into wild salmon populations can be avoided by using sterile fish in the sea cages. One way to induce sterility is to target proteins essential for germ cell formation or survival. Such candidates have been identified by us and others. Preliminary results suggest that fertilized eggs from broodstock mutated in one such candidate gene have no or low survival, suggesting a role of this candidate in the production of functional gametes, and/or in embryonic development in salmon. In this project we will elucidate the possibility to vaccinate (all-)female salmon against proteins essential for fertility. Overall, a hormone-free protocol for all-female salmon production may eradicate precocious maturation problems in land-based aquaculture systems in a sustainable way. Furthermore, a novel sterilization vaccine may reduce the negative effect of salmon farming on wild populations.