Oyster size and morphology affect individual oyster physiology, reproductive biology, and habitat production as well as population ecological services and availability for commercial harvest. Options for oyster restoration and fishery facilitation for eastern oyster (Crassostrea virginica) populations in the Chesapeake Bay include the use of disease resistant diploid eastern oysters (DEBY strain), triploid eastern oysters, and triploid Suminoe oysters (Crassostrea ariakensis) with the objective of providing a marketable product in a reasonable time frame. Shell height-at-age, growth in shell height in relation to environmental conditions, ontogenetic changes in morphology, and changes in biomass for groups of triploid Suminoe, triploid eastern, and diploid DEBY eastern oysters held at identical grow out conditions for the first two years of their lives were evaluated.
Triploid Suminoe oysters reached shell heights of 76 mm (market size in Virginia of 3 in) at 1.1 y with triploid eastern oysters and diploid DEBY oysters attaining the same size at 1.2 y and 1.5 y, respectively. Increases in shell height were positively correlated with water temperature and salinity with the largest increases in shell height typically occurring in warmer months. Holding density significantly affected ratios of shell height (SH) to shell width (SW) and SH to shell inflation (SI) for all three oyster populations. Oysters at lower densities showed a decrease in SH:SI ratio indicative of increased cupping as well as a reduction in SH:SW indicating a trend toward more discoid or rounded form. Tissue dry weight (g) and ash free dry tissue weight (g) increased nonlinearly with size within each population and were statistically different across the three populations examined. Triploid Suminoe oysters had higher tissue weights than either triploid or diploid DEBY eastern oysters of similar ages. Both triploid eastern and Suminoe oysters had higher tissue weights than diploid DEBY oysters of similar age. Observed differences in growth rates and morphology between these groups of oysters affect both the ecological services they provide (filtration rates as well as habitat) as well as their fishery potential (time to market size).