The Eastern oyster Crassostrea virginica is a major aquaculture species in the United States. Genetic improvement of cultured stocks is essential for the sustainable development of Eastern oyster aquaculture. Rutgers University has been breeding Eastern oysters for disease resistance since 1960 and produced several lines of selected oysters. In this study, a hybrid cross (21D2) between two selected lines (21D1 and 21D4) was produced and evaluated along with the two pure-line crosses and a wild control (21DW). The four groups were spawned at the Rutgers Cape Shore Facility in June 2021 and were deployed in four replicate bags on Cape Shore flat once the individuals reached 4 millimeters in length. All groups were sampled (25 per replicate, 100 per group) and measured in November 2021 to compare the relative growth of the four groups. No difference in mortality was observed, which was low (1 – 2.4%) in all groups.
The hybrid cross 21D2 showed significantly higher whole weights, with a mean of 5.47g . The wild control 21DW and the selected 21D4 showed significantly lower whole weights, with means of 3.01g and 3.35g, respectively . The same patterns can be seen in the mean meat weights , with the hybrid 21D2 having a mean of 1.17g, the selected line 21D1 having a mean of 0.81g, the wild control 21DW and 21D4 having means of 0.63g and 0.67 g, respectively. These results are consistent with the sampled mean heights, lengths, and widths of each group. These results indicate that heterosis exists between the two selected lines and crossing between selected lines is an effective approach for genetic improvement of the Eastern oyster.