Abstract
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. By contrast, males produce large numbers of motile spermatozoa capable of fertilizing wild salmon eggs. However, compared with diploids, reproductive development and survival rates of eggs fertilized 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 than in 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: (i) escaped triploid farm salmon are very unlikely to reproduce in the wild and (ii) if able to match diploid fillet lipid content, triploid farm salmon could achieve better fillet quality in terms of essential fatty acids.
Highlights
Triploidy could prevent escaped farm salmon breeding in the wild, while improving nutrient quality within farmed fillets
We found that sperm from triploid male farm salmon could fertilize eggs from diploid wild females under in vitro hatchery conditions, but these eggs showed a much-reduced survival rate, with,1% of the wild salmon eggs exposed to triploid milt reaching the eyed stage of development, compared with an average of greater than 60% for diploid male equivalents
Our study confirms that spermatogenesis and some reproductive and fertile function are present within triploid farm male Atlantic salmon, but no gametogenesis was observed in female triploid salmon
Summary
Triploidy could prevent escaped farm salmon breeding in the wild, while 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. Produced triploids carrying three sets of chromosomes usually differ from diploids in three fundamental ways: (i) they are generally more heterozygous, (ii) they have larger but fewer cells in most tissues, and (iii) their gonadal development is often reduced, making adults infertile [14] This latter impact on reproductive potential can be used to prevent breeding by escaped farm fish [11], and this has been successfully applied to prevent introgression of farm-strain rainbow trout (Oncorhynchus mykiss) and grass carp (Ctenopharyngodon idella), following stocking into rivers and lakes for recreational fishing, and to control invasive aquatic weeds [15,16]
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