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Abstracts
Workgroup: Genetics and Oyster Populations
Cooperative Regional Oyster Selective Breeding (CROSBreed) Project: Comprehensive strategy for genetic rehabilitation and conservation of oysters.
Principal Investigator(s):
Standish K. Allen, Jr., Virginia Institute of Marine Science, ska@vims.edu
Co-Investigator(s):
Eugene Burreson, Mark Camara, Kimberly Reece, Mark Luckenbach, VIMS, College of William and Mary; Patrick M. Gaffney, College of Marine Studies, U. Delaware; Ximing Guo, Gregory A DeBrosse, HSRL, Rutgers; Matthew Hare and Kennedy Paynter, Dept. of Biology, Donald Meritt, Horn Point Environmental Lab, U. Maryland
Funding Period: 2001 - 2003
Breeding
the Aquaculture Genetics and Breeding Technology Center (ABC) of VIMS has been developing and implementing strategies to genetically invigorate the CROSBreed and DEBY stocks and to produce new ones that build upon previous gains -- namely, line expansion. Line expansion consists of outcrossing the DB and XB lines to other oyster stocks that have demonstrated superior disease resistance when compared to wild control stocks in field experiments: Louisiana Grande Terre (LGT), Tangier Sound and Mobjack Bay (MB). In 2000, the DB line was crossed with MB to produce the DMO line, with LGT oysters to produce the DBLA line, and with the XB line to produce the DXB line. In 2002, under ODRP funding, these 3 lines were perpetuated. In addition, the LGT line was continued. These stocks have been deployed for testing. We expect some "slippage" of the previously realized selective gains, but the augmented genetic variation should promote a rapid recovery and increased scope for long-term improvement in subsequent generations of selection.
Deployment
Much of the restoration effort for Chesapeake Bay oysters is based on reef habitat construction and seeding with natural and selectively bred disease-resistant oyster strains. The extent to which reproduction on seeded reefs will supplement surrounding oyster populations depends on the average age of first reproduction and the geographic extent of oyster larval dispersal. Also, the benefits of genetic enhancement through introgression of disease-resistant alleles into natural stocks depends on the level of inbreeding in selected strains and on the rate of interbreeding between selected strains and natural oysters. We are using the unique genetic signature of disease-resistant strains in Maryand and Virginia subestuaries to measure dispersal from restored reefs the rate of interbreeding and introgression. With cooperation from the Oyster Recovery Partnership and the Chesapeake Bay Foundation we established study populations of DEBY-strain oysters one year ahead of schedule. Genetic analysis of wild adults and juveniles settling near the restored reefs during 2002 has been used to demonstrate better than 95% accuracy in assigning individual oyster recruits to a source population, wild or DEBY-strain. Most benefits from this research are expected in later years as reproductive output of DEBY oysters increases. Ongoing analysis of 2002 spat will indicate to what extent the 2002 DEBY planting in the Great Wicomico River (averaging 6 cm total length) contributed to the relatively high level of recruitment observed.
IMPACTS and/or BENEFITS: ongoing
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