Abstracts Biological Sciences

Is the laboratory growth of Pacific oyster spat, Crassostrea gigas, exposed to varying salinities, predictive of their growth in the estuary?

by Christopher Brooks

Results of this study suggest that laboratory growth of full-sib families of five month old Pacific oyster spat can be predictive of growth to market size at different grow-out sites. Seven to ten millimeter spat were selected from each of fifteen full-sib families and commercially available polyploids. Each family was split into two groups and exposed to either variable salinity (V.S., 3-30 ppt) or constant salinity (C.S., 30 ppt) laboratory conditions for five months, then planted at either an upriver or downriver subtidal site in the Yaquina estuary, Oregon. After six months of growth in the estuary, the rankings of the families based on average individual weights, specific growth rates (SGR), survival and yields were compared between laboratory and estuary sites. There was a significant effect of family, laboratory treatment and site upon final individual live weights of oysters in the estuary (P=0.0001). The rankings of families based on average individual laboratory weights were correlated with average individual estuary weights at the downriver site (C.S. oysters, P=0.010, V.S. oysters, P=0.005). Tetraploid oysters grew to heavier final estuary weights than either triploids or diploids, with individual C.S. tetraploids averaging 79.4 g live weight by fifteen months of age. Laboratory family rankings based on SGRs were negatively correlated with estuary rankings of family SGRs for all treatments (P<0.0001, Rho=-0.668). Rankings of families based on laboratory yields on day 60 were correlated with standardized estuary yield rankings for all treatments, except V.S. oysters planted downriver. Laboratory yields of families were also found to be predictive of estuary yields at an intertidally planted site in Sequim Bay, Washington, indicating the potential for predicting yields across a wide range of sites and culture methods (subtidal vs. intertidal). Oyster breeding programs may realize more efficient progress from the results of this study. If family yields at grow-out sites can be predicted from spat yields in the laboratory, poor and average families could be identified early at the spat stage, eliminating the need to expend resources to plant them out at test sites.