Initiation of a Bras d'Or Lakes oyster breeding program for resistance to MSX
The American oyster (Crassostrea virginica) is an economically, ecologically and culturally important species in Cape Breton, Nova Scotia, but populations have been in decline due to over-fishing, degradation of habitats and by the appearance of the MSX parasite (Haplosporidium nelsoni) in the Bras d'Or Lakes (Pitupa'q) in 2002. Rejuvenation of depleted private leases and public beds through seeding and cultivation programs has been proposed as part of the solution by DFO, Eskasoni Fish and Wildlife Commission (EFWC) and other stakeholders. Importation of oysters from outside of the Bras d'Or Lakes is not permitted to protect the native oysters from exposure to Malpeque Disease. Furthermore, there is recent molecular evidence that the Bras d'Or Lakes oyster is a genetically discrete population from oysters found in the Gulf of St. Lawrence. Therefore, aquaculture and the commercial resource must rely solely on resident populations for future culture and enhancement activities.
Since the onset of the MSX oyster disease, the Shellfish Health Unit, DFO Moncton and the Nova Scotia Department of Agriculture and Fisheries have worked intensely on the testing of shellfish for MSX to provide scientific advice for disease management within Nova Scotia. Based on the results to date, the Bras d'Or Lakes is considered positive for MSX. However, within the Lakes there remain areas where MSX has not yet been detected and it is unknown whether these populations harbour a natural resistance or have not yet been exposed to the disease.
Breeding for disease resistance/tolerance is seen by the different stakeholders (DFO, oysters growers, Mi'kmaq elders) as a long term strategy for the recovery of the Bras d'Or oyster. After 3 years of disease challenge in the Bras d'Or Lakes, the timing for the initiation of a selection program is opportune. The oysters still surviving in the MSX affected areas are exhibiting a level of tolerance and should be considered as prime broodstock for initiating a MSX resistance breeding program. In addition, they are physiologically adapted to the particular environment of the Bras d'Or Lakes and would at this point be the likeliest candidates for such a program.
The goal of this R&D project is to initiate a breeding program for MSX resistance in the Bras d'Or Lakes oyster population with the following objectives:
- initiate a rotational breeding plan with oysters from specific sites within the Bras d'Or Lakes
- perform crosses in parallel at the UINR in Eskasoni and at the BIO Quarantine
- test the progenies in field sites
- consider impacts of future breeding in Quarantine to obtain hybrids with Bras d'Or Lakes oysters and oysters from the Gulf region and from the US, the latter showing MSX resistance
- make recommendations for an expansion/ continuation of the breeding program and for future restoration programs.
2005 - 2007
Atlantic: Gulf of Maine, Scotian Shelf
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