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Abstracts
Workgroup: Aquaculture and Hatchery Issues
Cooperative Regional Oyster Selective Breeding (CROSBreed) Project
Principal Investigator(s):
Standish K. Allen, Jr., Haskin Shellfish Research Lab, Rutgers University, ska@vims.edu
Co-Investigator(s):
Ximing Guo, Susan E. Ford, Gregory A. DeBrosse, HRSL, Rutgers
Patrick M. Gaffney, Center for Marine Studies, University of Delaware
Eugene Burreson, Mark Luckenbach, Virginia Institute of Marine Science, College of William and Mary
Kennedy Paynter, Dept. of Biology
Donald Meritt, Horn Point Environmental Lab, University of Maryland
Patrick M. Gaffney, Center for Marine Studies, University of Delaware
Eugene Burreson, Mark Luckenbach, Virginia Institute of Marine Science, College of William and Mary
Kennedy Paynter, Dept. of Biology
Donald Meritt, Horn Point Environmental Lab, University of Maryland
Funding Period: 1995 - 1997
Transition from institutional to regional program
The origin of CROSBreed oyster strains is rooted in experiments by Dr. "Hal" Haskins of Rutgers University from the late 1950s onward. He developed a number of lines resistant to MSX-disease caused by Haplosporidium nelsoni. Using these lines as founder stock, new synthetic strains of disease resistant oysters were established in 1992 at Rutgers (under PI-Allen while he was there). This development gave Rutgers the opportunity to subject their MSX resistant lines to constant Dermo-disease pressure, therefore avoiding the need to start a dual resistance selection program with wild type stock. Since 1992, the synthetic lines have been on a three-year breeding cycle. Until 1995, this breeding program was a local one, supported entirely by Rutgers.
ODRP support for our regional project began in 1995 for the continued development and testing of these new synthetic lines; from that time, the strains have been known as the CROSBreed (XB) lines. There are two key differences between the original Haskin derived lines and the XB strains. First, the XB project is a well managed selection program designed for long-term maintenance of healthy brood stock with systematic exposure to both major oyster parasites on the East Coast, H. nelsoni and Perkinsus marinus. XB lines have had about 21/2 generations of selection to this latter parasite. Second, the project is regional, with New Jersey, Delaware, Maryland, and Virginia participating.
That CROSBreed has truly made the transition from institutional to regional program was evident during a 1998 Spring workshop of CROSBreed participants. The project was due to end in September of 1998 with the final task of spawning the third generation of XB lines and their controls. However, ODRP suffered a funding hiatus and no RFP was issued that year. That meant that CROSBreed participants were faced with a new generation of test stocks (8 in all, deployed in replicate at three regional testing sites). All participants agreed to undertake this work for a year until a new RFP (this one) was issued in 1999. This request, in part, is for completing the field and disease testing portions of XB selective breeding for the remaining two years of our three-year breeding cycle. The project would end in 2001 with the creation of XB 4x progeny. Regional cooperation not only means the addition of new talent to the breeding effort but also an expanded impact for the XB lines.
Among growers - gardeners and commercial start ups alike - an awareness is building that seed is not just seed, but that there are choices out there, whether they be XB strains, natural stocks such as from Tangier Sound, or other select lines such as the DEBY strain developed and maintained by Burreson's group at VIMS. And people are starting to request what they want from hatcheries.
Some XB oysters are destined for reef programs, where juveniles grown by gardeners are planted on reef sanctuaries. XB strains have been used for the Virginia Marine Resources Commission seaside oyster growers project, and a derivative of the XB line will be used this year again. XB lines have been requested for the Wilson Bay Water Quality Initiative in Jacksonville, NC. Because requests for XB brood stock are mounting constantly, the Aquaculture Genetics and Breeding Technology Center (ABC) now maintains an inventory of XB brood stock for distribution to prospective users. In addition, XB stocks are being used in a score of other research projects, some funded (or proposed for funding) by ODRP.
During the last three year period, XB lines performed as well or better than local controls in all three testing sites: low, medium, and high salinity. Superior performance obtained in disease prevalence and often growth, depending on the line. Ironically, the last three year period was one characterized by relatively low disease pressure, so the full benefit of XB lines are yet to be demonstrated, that is, their performance versus controls against heavy disease challenge.
We have to remember that XB lines were produced from MSX-resistant lines, and that Dermo resistance, if it indeed occurred, was only under selection for 1-2 generations. The fact the lines contracted Dermo is not surprising. It may be that "resistance' to Dermo involves resisting death at a high infection level rather than resisting infection per se. In any event, we speculate that if MSX were present, XB performance would be more remarkable. Other good news is that XBs were about equivalent to local controls in all sites, indicating that the stock seems genetically robust and may be useful across a number of environments.
IMPACTS and/or BENEFITS:
CROSBreed stocks have been released to commercial hatcheries and are in use by oyster restoration programs in the Chesapeake Bay, including the Oyster Recovery Partnership in Maryland and the Chesapeake Bay Foundation.
The project results are applicable to the entire range of the eastern oyster, i.e., where ever brood stock may be multiplied to production levels through aquaculture. MSX/ Dermo resistant strains could be especially valuable in the northeast where both MSX and Dermo seem to be expanding its range and where aquaculture represents the major form of oyster harvesting. The end users of the brood stock development are the oyster aquaculturists, both the hatchery and grow out industries. Already available to growers are the MSX resistant lines and excess production of the XB lines. The Dermo resistant varieties will undoubtedly spark further interest once we have clearly demonstrated that cross breeding with a naturally resistant population accelerates resistance.
The need for a strain of oysters resistant to both MSX and Dermo is critical on the East coast. Testing methods to accelerate disease resistance using C. virginica races is attractive because it avoids strategies that involve non-native species. The regional significance of this project is to foster oyster aquaculture by providing culturists with disease resistant strains. Oyster hatchery and grow out programs for C. virginica are under development in other areas of the country as well, such as Florida and Louisiana. Dermo resistance is of considerable interest in these regions. Of national significance is the demonstration of improved shellfish performance through breeding.
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