Pacific oysters worldwide have suffered mass mortalities from the oyster herpes virus (Ostreid herpes virus 1). In Tomales Bay in Northern California, a major shellfish growing center in the state, the virus has doubled summertime mortality rates of oysters over their 18-month culture cycle. As a waterborne pathogen activated by warmer water temperatures, all the state’s shellfish growing areas are potentially at risk should the virus spread from its current location in Tomales Bay and Drake’s Estero. The goal of this project is to protect and improve Pacific oyster farming in Tomales Bay and other parts of the state by providing a detailed understanding of the genetic, cellular and physiological mechanisms of heritable resistance to the herpes virus infection. In the project’s first year, the scientists will conduct field trials to identify oyster families with differential susceptibility to the oyster-virus infection. A second set of experiments will then examine the heritability of disease resistance from these families and whether it translates into higher survivorship and yield in the field. Assuming that it does, the researcher will employ gene-mapping and gene-expression profiling techniques to localize and identify genes and biomarkers for disease resistance. Maps of these genes will then be compared to genetic profiles of oyster families that have previously produced offspring with high rates of survivorship in Tomales Bay. Ideally, findings will advance the seed industry’s ability to selectively breed high-yield oysters with genetic resistance to the virus. This project is a collaboration with the University of Washington in Seattle, Hog Island Oyster Company, Taylor Shellfish Farms and California Department of Fish and Wildlife.