Can Selective Breeding Reduce the Heavy Metals Content of Pacific Oysters (Crassostrea Gigas), And are There Trade-Offs with Growth Or Survival‪?‬

ABSTRACT Oyster producers in the Pacific Northwest region of the United States export large quantities of oysters to international markets. Proposed changes to international limits for heavy metals content in shellfish could drastically curtail exports and impact the viability of this environmentally-friendly industry. "Supply-side" solutions such as moving oyster farms to uncontaminated sites or short-term depuration would incur substantial costs in terms of labor and infrastructure and displace workers in already economically challenged coastal communities, whereas selective breeding could benefit both producers and consumers within the current infrastructure. We studied the feasibility of selective breeding to reduce heavy metal content through a quantitative genetic analysis of heavy metals accumulation in the Pacific oyster, Crassostrea gigas by opportunistically sampling a factorial mating experiment initiated in 2000 to study the effects of parent size on offspring growth and survival. The experiment consisted of all possible crosses among six males (sires) and five females (dams). At harvest, we measured four performance traits (yield, survival, whole oyster live weight and shucked meat dry weight) and the accumulated levels of four heavy metals (copper, lead, zinc and cadmium). Analyses of variance testing for sire and dam effects and bootstrap estimates of heritability showed that all of these traits have a genetic basis. Further, half-and full-sib family means correlations revealed genetic trade-offs between copper and cadmium content and performance traits. Preliminary indications are that selective breeding to reduce heavy metals accumulation is possible, but that genetic trade-offs between metal content and performance should be taken into account in designing any program of selective breeding in this species. KEY WORDS: Crassostrea gigas, cadmium, copper, lead, zinc, heavy metals contamination, depuration, quantitative genetics, genetic correlation