03032nas a2200337   4500008004100000050008300041245011900124210006900243260000900312300001200321490000700333520201800340653001302358653001302371653002602384653001302410653001402423653001602437653003902453653001402492100001402506700001502520700001502535700001302550700001402563700001602577700001502593700001502608700001602623856005502639       2004                        eng d  aOSU Libraries: Valley SH370.A1 J61, Guin SH370.A1 J61, Electronic Subscription00aImprovement of disease resistance and understanding of summer mortality in Pacific oyster <i>Crassostrea gigas</i>0 aImprovement of disease resistance and understanding of summer mo  c2004  a284-2850 v233 aPacific oyster (Crassostrea gigas) summer mortalities are a recurring problem in the United States, Japan, France, and Mexico. During the 2002 to 2003 growing season, for example, farmers in Carlsbad, CA, Netarts Bay, OR, and Willapa Bay and south Puget Sound, Washington reported up to a 50% loss of market-ready oysters occurring over a brief 2 to 3 week span. Research findings indicate genetic pedigree, ploidy, culture practice, and prior exposure to environmental stress have varying influences on the expression of the summer mortality disease in Pacific oysters. Key facets of research to date include (1) the ability of oysters to survive episodes of summer mortality is in part genetically determined and perhaps can be enhanced through selective breeding of families showing high survival traits. Pedigreed lines of oysters with different genetic histories, produced by the Oregon State University Molluscan Broodstock Program (MBP), displayed markedly differential survival, yields, and growth rates during episodes of summer mortality at project study locations in California and Washington. There is a strong and consistent genetic response of families to environmental stress that is independent of when the families were produced and planted. In addition, prior inconsistent mortalities occurring across large culture plots can, at least in part, be explained by differential genetic backgrounds of the oyster crops. (2) Triploid and diploid oysters appear to have different optimal environments and definition of their respective requirements and response is essential for maximizing their survival and productivity. Field experiments and grower observations have demonstrated sporadic high triploid mortalities and wide variation in survival compared with diploid oysters planted at the same locations. Overall, triploid oysters grown at Puget Sound test sites in 2000 to 2002 experienced a cumulative mortality of 8%-28% above the mortality rates of diploid oysters planted in comparable plots.10abivalves10agenetics10ahuman use and impacts10amolluscs10amortality10aNetarts Bay10aPacific oyster = Crassostrea gigas10ashellfish1 aCheney, D1 aBurnett, L1 aChristy, A1 aDavis, J1 aElston, R1 aFriedman, C1 aGriffin, F1 aLangdon, C1 aSuhrbier, A  uhttps://netarts.library.oregonstate.edu/node/13721