Effect of Microalgal Diets on Sunray Venus Clam (Macrocallista nimbosa) Production and Fatty Acid Profile

Abstract

The sunray venus (sunray) clam, Macrocallista nimbosa, is an alternative clam species reared in hard clam hatcheries in Florida. Current feeding practices follow those used for hard clam culture. This study aimed to identify whether a hard clam bi-algal Tisochrysis lutea and Chaetoceros neogracile diet was an optimal diet for post-set sunray clams or whether other microalgal dietary combinations could improve production. Six dietary bi-, tri-, or tetra-algal combinations consisting of four microalgae species (Tisochrysis lutea, Diacronema lutheri, Chaetoceros neogracile, and Thalassiosira weissflogii) were fed for 6 weeks; the growth, survival, and fatty acid profiles of post-set clams were evaluated. Clams fed equal proportions of T. lutea, D. lutheri, C. neogracile, and T. weissflogii had higher growth, while those fed equal proportions of T. lutea and C. neogracile had higher survival. The poorest-performing diet consisted solely of diatoms. A contrasting polyunsaturated fatty acid (PUFA) profile was found in post-set clams fed flagellate- or diatom-only diets. Clams fed the bi-algal flagellate diet had a higher percentage of docosahexaenoic acid (DHA) but a lower percentage of (n-6) PUFA, whereas those fed the bi-algal diatom diet had a higher percentage of arachidonic acid (ARA) and eicosapentaenoic acid (EPA) but a lower percentage of DHA. The percentages were similar and neither very high nor very low in clams fed the remaining dietary treatments. The results of this study show that sunray venus post-set clams can be successfully produced when fed a typical hard clam bi-algal flagellate and diatom diet, but they indicate that growth may be accelerated by the addition of other microalgae species.

Feasibility of Microalgal Concentrates for Production of Post Set Northern Quahogs, Mercenaria mercenaria and Sunray Venus Clams, Macrocallista nimbosa

“…As bivalves rely on a microalgal diet that is rich in FA, they are an excellent source of PUFA, particularly EPA and DHA, for human consumption (Wright et al 2018). Studies have noted changes in the FA profile of bivalve species associated with the type of phytoplankton consumed both in the natural environment (DeMoreno et al 1980, Pazos et al 1996, 2003, Laramore et al 2017) and in dietary studies (Langdon & Waldock 1981, Fernández-Reiriz et al 1998, Soudant et al 1999, Rivero-Rodríquez et al 2007, Aranda-Burgos et al 2014, Hassan et al 2023, Perri et al 2023). As expected, the two concentrates used in the present study varied in the FA profile.…”

“…Hard clams rank second in the state in terms of aquaculture production, and fourth in the nation, with over $19 million in annual sales, primarily due to the production of hard clams, with oysters and alternative clam species contributing to that total (USDA 2019). Of the alternative clam species produced in Florida, the sunray Venus clam, Macrocallista nimbosa has elicited the most commercial interest due to its larger meat size, increased wholesale price, and that culture conditions are similar to that of hard clams (Scarpa et al 2009, Sturmer et al 2009, Laramore et al 2017, Perri et al 2023). Native to Atlantic waters ranging from North Carolina to Florida, and the Gulf of Mexico, this venerid clam gets its name from the unique radiating sun pattern on its shell (Abbott 1974).…”