Development of a broodstock genetic program for the European Oyster (Ostrea edulis) in Nova Scotia
The European oyster (Ostrea edulis) was introduced to the Nova Scotia aquaculture industry 30 years ago. The stocks were imported from naturalized populations in Maine, whose ancestors originated from the Netherlands. In past years, Nova Scotian hatcheries have successfully produced Ostrea edulis spat, but in 2001 and 2002 the two remaining hatcheries in the province suffered 100% larval mortality. One of the factors that may have contributed to the collapse is a suspected loss of genetic diversity due to the limited number of individuals used to establish the Maritimes stocks, and the inevitable subsequent inbreeding during propagation of these populations. Using microsatellites, we found that some genetic erosion has occurred in the Maritime populations, with the largest loss of alleles found in the hatchery stocks. In spite of this loss, genetic diversity and heterozygosity in the Maritimes populations are still relatively high.
While the impact of inbreeding and heterosis on performance (survival, growth, settlement success) could not be evaluated in this project due to mortalities, we found no evidence of selfing (self-fertilization) but did find evidence that mass spawning is dominated by a few individuals.
The impact of grading spat was also evaluated. Smaller oysters (normally discarded as "runts") showed increased growth rate (% mass and size) when competition from larger oysters was removed and when density was lower.
Recommendations for broodstock management of Ostrea edulis and the direction of future studies of this species are summarised at the end of this report.
2003 - 2004
Atlantic: Gulf of Maine, Scotian Shelf
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