Evaluation of health, welfare, and growth in sterile salmon after deletion of embryonic germ cells

Summary

Sterile farmed salmon would reduce the negative interactions between escapees and wild salmon and improve fish welfare and quality. The main goal of this project has been to evaluate important production traits in sterile salmon after ablation of the primordial germ cells. Transient inactivation of the embryonic germ cell factor Deadend caused lifelong loss of gametes in both males and females. The sterile salmon showed normal osmoregulatory ability and seawater tolerance. No consistent differences were shown in stress-response and immune status by cortisol measurement and qPCR quantification of multiple stress-related and pro-and anti-inflammatory factors. Sterile salmon showed robustness in seawater despite extreme weather conditions and serious sea lice attack. External wounds, fin damages and abdominal bleedings were registered in sterile and fertile salmon with only sporadic malformations. Sterile and fertile salmon showed similar growth performance in freshwater, but the comparison in sea water is uncertain due to few fertile fish left. Sex hormone synthesis was induced in both sterile and fertile males, but sex steroid levels decreased in sterile fish after seawater transfer. The project concludes that embryonic Deadend inactivation results in sterile salmon with the same phenotype as fertile fish, except for the missing gametes, and recommends that technology should be developed for large-scale production of sterile salmon in aquaculture.