This project seeks to develop tools and knowledge for developing a high-yield Pacific oyster for commercial culture. In work to date, scientists have been crossing oyster lines and studying how different oyster genotypes affect various physiological, metabolic and proteomic processes. The basic premise is that genes are responsible for hybrid vigor (high growth rates) and that this superior growth will be reflected in other biological processes, such as protein metabolism. A main goal of this project is to identify, from the millions of possibilities, genes, proteins or metabolites that might serve as biomarkers for detecting desired characteristics during an oyster’s larval stage. Such a tool would enable researchers to screen oyster genotypes rapidly, without having to wait for shellfish to mature to adult size to show their traits. In parallel with laboratory experiments, California Sea Grant Extension has led and now completed field tests of an experimental “double cross hybrid” Pacific oyster seed produced by Taylor Shellfish Farms, the project’s industry collaborator. This experimental seed was raised alongside seed, selectively bred for growth and high survivorship, at Hog Island Oyster Company in Tomales Bay, Grassy Bar Oyster Company in Morro Bay and Carlsbad Aquafarm in northern San Diego County. The double-hybrid seed was shown to increase yields by 2 percent, 6 percent and 8 percent at the three farms. Oyster culture is an $84-million-a-year industry on the West Coast, and the increased yields observed with the experimental seed could add approximately $21 million to the industry’s value over a decade.