Triploid oysters have become a cornerstone of oyster aquaculture due to their faster growth and reduced reproductive effort compared to diploids. While extensively used in the southern and mid-Atlantic U.S., their performance in the colder waters of the northeast remains under-investigated since their development in Maine ~40 years ago. This study evaluated both the culture performance and oxygen consumption of triploid and diploid oysters in Maine’s Damariscotta River Estuary to inform farmer seed choices and improve bioenergetic models of triploid growth.
Two-millimeter triploid and diploid seed oysters were deployed at two sites along a natural temperature gradient with a warmer, upper estuary farm site, Pemaquid Oyster Company (POC), and a cooler middle estuary site, the Darling Marine Center’s (DMC) experimental farm. Shell and tissue growth was monitored over two summer seasons. Environmental variables such as temperature, chlorophyll, and particulate organic matter were recorded. In the winter between growing seasons, we conducted a 60-day starvation experiment coupled with oxygen consumption trials to explore if basal metabolism was different between ploidy after other contributions to oxygen demand were eliminated.
Triploids had significantly faster growth than diploids at both sites, reaching market size up to three months earlier at POC. At POC, nearly 100% of triploids reached market size by the end of the study compared to only 50% of diploids. Almost no DMC diploids reached market. Triploids starved significantly slower than diploids. However, oxygen consumption rates between triploids and diploids were not significantly different at any time point. These results indicate a strong advantage of triploid oysters, particularly at colder NE sites where product could reach market size before another season of overwintering. Additionally, triploids may handle starvation better than diploids, however it is unlikely due to metabolic needs.