Sex control in cod

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Aquaculture is the world's fastest growing food production sector. In Canada, where capture fisheries have declined from historic highs in the late 1980s, aquaculture production has increased more than ten-fold in the last decade. Most of Canada's aquaculture production comes from salmon farmed in British Columbia and New Brunswick. However, salmon are not well suited for aquaculture in most of Atlantic Canada and salmon aquaculture as a whole has had difficulty remaining profitable in Canada. As a result, there is a concerted effort by industry and government to diversify aquaculture in Atlantic Canada. Atlantic cod is seen as a prime alternative aquaculture species for the region, and Atlantic Canada's largest aquaculture company (Cooke Aquaculture Inc.) has recently made significant investments into cod aquaculture. Their preliminary production trials have highlighted early maturation of production fish as a key constraint to commercial viability, because mature fish cease growing, have reduced flesh quality and have high mortality rates. This problem is compounded by the fact that cod will eadily spawn in cages, thereby potentially releasing large numbers of fertilized eggs into the wild. We propose to develop practical approaches for the production of single-sex populations of cod, in order to take advantage of sex-related differences in age and size at maturity, and to link into a parallel research program currently underway on the production of triploid (sterile) cod. Our research will determine the genetic basis to sex determination in Atlantic cod and will lead to the development of treatment regimes for functional sex reversal in this species. The genetic mechanism of sex determination will be determined y gynogenesis, whereby expression of the paternal genome in viable embryos is prevented and the maternal genome is duplicated. Examining sex ratios of the offspring from gynogenetic populations helps to identify the genetic basis of sex determination and informs the decision on best approaches for producing single-sex populations. Endocrine sex reversal will then be used to create broodstock capable of generating single-sex progeny. Two graduate students will be funded to conduct this research.