Shellfish aquaculture occurs in coastal regions, where it is constrained by competition for alternative uses and by onset of the rapid environmental changes expected from global climate change. Commercial breeding programs can improve the yield of Pacific oysters, especially in regions, such as the U.S. West Coast, where farmers depend on seed produced in hatcheries. The Pacific oyster Crassostrea gigas, which has been exported from Japan to all continents but Antarctica and has had the highest production of any aquatic species for the past decade ? 4.2 Mt in 2007 (FAO 2009) ? is an obvious candidate for domestication. Genetic improvement and domestication are proven routes to increasing the efficiency of agricultural production across a range of environments, but research towards these ends in shellfish aquaculture remains in a relatively primitive state. The innovative approach employed in this project will if successful serve to significantly improve the efficiency of a commercial crossbreeding program for increasing the yield of farmed Pacific oysters. The proposal builds on previously published evidence that crossbreeding can improve yield, owing to hybrid vigor, and refines a conceptual framework for commercial crossbreeding. The work plan features the combined application of new culture technologies for replicated larval and seed rearing, molecular-based pedigree confirmation, estimation of specific and general combining abilities of inbred lines for yield, and correlation of performance at different phases of culture to determine the earliest point at which combining ability for yield can be predicted. Inefficiencies in the component processes of the program ? developing inbred lines (at least two generations), testing inbred lines for combining ability, and propagating elite inbred lines for further testing at commercial scales ? have constrained the production and distributing of hybrid oyster seed to farmers. We propose to address and eliminate or reduce several of the inefficiencies that stand in the way of progress in order to provide the basis for a time and cost efficient cross breeding approach to increasing domestication and overall value of the Pacific oyster culture industry in the western United States. Outcomes of this research have the potential to improve production efficiencies in shellfish aquaculture, generally including the potential for use of research results in other commercially important species such as clams, mussels and geoducks. OBJECTIVES: Commercial breeding programs can improve the yield of Pacific oysters, especially in regions, such as the U.S. West Coast, where shellfish farmers depend on seed produced in hatcheries. The primary goal of the SBIR proposal for Taylor Shellfish Farms, Inc. (TSF) is to increase production and yield of farmed Pacific oysters. This proposal addresses approaches to reduce several of the inefficiencies that stand in the way of progress. Using diallel crosses among inbred parent lines, TSF with funding from the Western Regional Aquaculture Center found that yield increased with general combining ability (GCA), as expected from previous responses to family selection but that specific combining ability (SCA) of certain lines resulted in high-yielding hybrids. A research and development effort has been proposed to modify existing larval and nursery culture technologies to accommodate necessary research on crossbreeding efficiencies. We propose to increase replication at the early stages of oyster production, by implementing new small-scale, high density technologies for larval and early seed rearing, and to estimate the correlation in yield among the first three phases of culture, larval rearing (Phase I), early juvenile rearing (Phase II, indoor upwelling tanks), and late seed production (Phase III, outdoor seed cages). Once these culture systems are operating and have been tested, the primary Phase I research effort will be focused on estimating specific combining ability (SCA) of inbred lines in factorial crosses. The research has these two specific goals: (1) Make two, factorial diallel crosses of first-generation inbred lines, one a 10 by 10 cross designed to estimate correlation of SCA for yield between Phases II and III of culture and the other a 5 by 5 cross designed to estimate correlation of SCA between Phases I and II. (2) Measure yield (growth and survival) of hybrid families produced in two factorial diallel mating experiments at the larval, early juvenile and late juvenile stages. The technical question that needs to be answered to establish the feasibility of the Phase I approach is: Can sufficient replication be achieved in the early phases of experimental oyster culture to permit estimation of specific combining ability for yield (biomass achieved as a product of rates of survival and growth) for a set of inbred oyster lines in a factorial diallel cross If the results of the research provide a positive answer, then the TSF crossbreeding program can be made substantially more efficient, its costs of testing inbred lines, dramatically reduced, and the rate of improvement in the yield of commercial Pacific oyster seed, increased.
