Triploidy could prevent escaped farm salmon breeding in the wild, while also improving nutrient quality within farmed fillets. Despite these potential advantages, triploid Atlantic salmon have not been widely used in aquaculture, and their reproductive function has yet to be fully evaluated. Here, we compare reproductive function and fillet composition between triploid and diploid farm salmon under standard aquaculture rearing conditions. We show that female triploids are sterile and do not develop gonads. In contrast, males produce large numbers of motile spermatozoa capable of fertilising wild salmon eggs. However, compared with diploids, reproductive development and survival rates of eggs fertilised by triploid males were significantly reduced, with less than 1% of eggs sired by triploid males reaching late eyed stages of development. Analyses of fillets showed that total lipid and fatty acid quantities were significantly lower in triploid compared to diploid Atlantic salmon fillets. However, when fatty acids were normalized to total lipid content, triploid fillets had significantly higher relative levels of important omega-3 Long Chain Polyunsaturated Fatty Acids. Our results show that: (1) escaped triploid farm salmon are very unlikely to reproduce in the wild; and (2) if able to match diploid fillet lipid content, triploid farm salmon could achieve better fillet quality in terms of essential fatty acids.

Comparisons between diploid and triploid Atlantic salmonExcel file containing all the data collected during the investigation into the reproductive maturation of triploid Atlantic salmon, their fatty acid biochemistry and how they compare to diploid conspecifics