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

Det første forsøket på å produsere en populasjon av bare hunnlaks ble ikke vellykket. Denne sesongen (høst/vinter 2023) har vi et større antall gytende stamfisk som kan gi opphav til avkom av bare hunnkjønn, og vi forventer resultater på dette i løpet av de neste månedene. Funksjonelle studier av alle genene/proteinene av interesse går etter planen. Vi forventer å publisere en artikkel med resultater for et av genene i løpet av våren 2024. Vaksineforsøkene går etter planen. Et av tre forsøk er avsluttet, og de to siste vil bli avsluttet i løpet av de neste månedene. Analyser er pågående.

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.