Induction and viability of tetraploids in brook trout (Salvelinus fontinalis)

Authors: Weber, Gregory - Greg; Hostuttler, Mark; SEMMENS, KENNETH - West Virginia Division Of Natural Resources; BEERS, BRIAN - Virginia Department Of Game And Inland Fisheries

Submitted to: Canadian Journal of Fisheries and Aquatic Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2015
Publication Date: 7/6/2015
Citation: Weber, G.M., Hostuttler, M.A., Semmens, K.J., Beers, B.A. 2015. Induction and viability of tetraploids in brook trout (Salvelinus fontinalis). Canadian Journal of Fisheries and Aquatic Sciences. DOI: 10.1139/cjfas-2014-0536.

Interpretive Summary: Brook trout populations are threatened by introduction of invasive species, habitat loss and degradation, and climate change in their native range; and are a problem invasive species in western Unites States and Canada, and in Europe. Stocking sterile triploids has been promoted as an approach to reduce negative effects of stocking of brook trout for recreational fishing on native fish populations. Triploid fish are fish that are treated in the hatchery to have three sets of chromosome instead of the normal two sets as in normal diploid fish. Fish with odd number sets of chromosomes are sterile. Triploidy has also been suggested for more efficient production of brook trout as food fish but they are a smaller salmonid and therefore only a minor species for farming. Brook trout are produced for stocking from a wide network of government and private hatcheries throughout the country which all would need to have the capability for triploid production. Production of triploids, however, is time consuming and can be costly if fish must be certified as triploid. We have developed an alternative approach for making triploid brook trout that may help hatcheries meet triploid brook trout production goals. We have developed a protocol to make tetraploid brook trout which have four sets of chromosomes and are fertile. We've also shown a tetraploid brook trout can be crossed with a normal diploid brook trout and all the offspring will be triploids. Development of a tetraploid brook trout broodstock has the potential to decrease the labor and cost involved in producing triploids for stocking by removing the need to induce and confirm triploidy, and increase reliability of production by eliminating the risk of failed induction efforts. Furthermore, sperm from tetraploids produced from a centralized source can be easily shipped to other hatcheries to increase the amount of hatcheries with capabilities to produce triploids.

Technical Abstract: Brook trout (Salvelinus fontinalis) populations are threatened by introduction of invasive species, habitat loss, and habitat degradation in their native range; and are a problem invasive species in western Unites States and Canada, and in Europe. Stocking sterile triploids has been promoted as an approach to reduce negative effects of stocking of brook trout for recreational fishing on native fish populations. Crossing a tetraploid with a diploid is an alternative method of triploid production that may help hatcheries meet demand. We induced tetraploidy in brook trout by application of 633 kg.cm-2 of hydrostatic pressure for 8 minutes at 70-72.5% of the first cleavage interval. Yields of above 50% tetraploid progeny at hatching were readily achieved although few animals reached one year of age. We also crossed a male tetraploid with female diploid fish and produced interploid-triploids with eyeing rates in excess of 50%, demonstrating male tetraploids are fertile and capable of siring triploid progeny. Female tetraploid fish were reared to 16 months post-hatching and possessed follicles in secondary vitellogenesis, suggesting tetraploid females are also fertile.