Culture performance and physiology of triploid eastern oysters (Crassostrea virginica) in their northern range

Triploid oysters have become a crucial tool for aquaculture because of their rapid growth rates and reduced reproduction compared to diploids. While extensively adopted in temperate regions along the U.S. East Coast, limited research has evaluated triploid oyster performance in the colder waters of the Northwest Atlantic where the growing season is shorter. This study investigated the growth performance, morphology, and physiology of cultured triploid and diploid Crassostrea virginica in their northern range. Environmental conditions as well as oyster shell and tissue growth were monitored over a 17-month period at two farm sites in Maine. Triploids averaged 22 % greater for shell height and 53 % greater for tissue mass compared to diploids. The effects of ploidy and environmental factors (temperature, chlorophyll-a, and particulate organic matter) on shell growth were examined using generalized additive models. Triploids exhibited a significant growth advantage in temperatures above 17 °C and at higher food concentrations with minimal advantage outside these conditions. In a laboratory experiment, tissue loss and oxygen consumption rates were examined over a ten-week period along with cell size measurements. Although triploids had larger cell sizes, standardized oxygen consumption rates during starvation did not differ significantly between ploidies, suggesting similar maintenance needs after contributions to feeding, growth, and reproduction are removed. Diploids, however, experienced faster tissue loss during starvation, indicating potential energetic disadvantages. These findings highlight the culture potential of triploid C. virginica in their northern range, provide insight into optimal environmental conditions for triploid advantage, and contribute to refining mechanistic triploid oyster growth models.