High condition index and distinct biochemical profiles in triploid Crassostrea gigas cultured at a high-energy open-water site

High-energy open-water (HEO) sites are increasingly being explored as alternatives to conventional coastal oyster farms, yet their suitability for triploid Pacific oysters remains poorly documented. This study compared the physiological condition and tissue biochemical composition of a single cohort of triploid Crassostrea gigas cultured for 7 months at three Korean grow-out environments: an independently moored HEO site located approximately 1.3 km from an operating offshore wind farm, a sheltered subtidal bay, and an intertidal flat exposed to regular emersion. Biometric observations were made on 30 oysters from three culture units per site and are reported descriptively. Biochemical analyses were based on three pooled composites per site, one from each culture unit. Oysters sampled from the HEO site showed smaller mean shell size and whole weight but greater mean soft tissue mass and the highest mean condition index (29.2%), compared with 13.9–15.0% at the coastal sites. Proximate composition differed among the three sites, with HEO oysters showing higher mean crude fat, ash, and carbohydrate fractions but a lower mean crude protein concentration. Within the diethyl ether extract, oleic acid and DHA showed their highest mean relative proportions at HEO, whereas EPA and ARA showed their highest mean relative proportions at the intertidal Gochang site. These findings provide initial site-specific evidence that independently moored HEO culture is compatible with high tissue condition in triploid oysters, and that tissue biochemical composition at this site differed from that of the two coastal sites. However, because site, culture system, and environmental conditions varied simultaneously, the findings should not be interpreted as an isolated test of hydrodynamic exposure or proximity to the offshore wind farm.