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MG-05-01-005
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.
Project Start Date: June 6, 2005
Project Completion Date: December 31, 2007
For further information please contact: DFO project leader: Bénédikte
Vercaemer (VercaemerB@mar.dfo-mpo.gc.ca)
or Regional ACRDP Coordinator: Denise Méthé (E-mail:
MetheD@dfo-mpo.gc.ca).
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