Nutritional Profiles of Ruditapes philippinarum and the Complementary Food-Resource Potential of the Warm-Water Clam Ruditapes variegatus.

The sustained decline in Japanese Manila clam landings has increased interest in complementary bivalve food resources. This descriptive study compared one pooled soft-tissue analytical sample from each of four sources: Ruditapes philippinarum from Akkeshi, Mangoku-ura, and a commercial Chinese-origin source, and the warm-water clam Ruditapes variegatus from Ishigaki Island. Each pooled sample comprised approximately 250 g of soft tissue from at least 40 individuals; independent lot-level biological replication was not available, so no inferential statistical comparisons were made. Proximate composition, amino acids, taurine, vitamin-related compounds, minerals, and fatty acids were analyzed, and mitochondrial cytochrome c oxidase subunit I (COI) sequencing together with morphology confirmed the Ishigaki material as R. variegatus. Wet-weight total amino acid contents were 8.670, 6.800, 6.135, and 5.555 g/100 g in the Akkeshi, Ishigaki, Mangoku-ura, and Chinese-origin pooled samples, respectively. After normalization, total amino acid contents ranged from 507.0 to 559.4 mg/g dry matter and from 829.1 to 850.0 mg/g protein, indicating that much of the wet-weight contrast reflected differences in tissue moisture and protein concentration. Adult-reference amino acid scores ranged from 97.1 to 100 across the four composites. The Akkeshi pooled sample also showed comparatively high taurine and vitamin A-related values. Sea surface temperature and satellite chlorophyll-a data were used only to document source-region environmental context and were not treated as causal predictors of composition. Within the limits of this pooled-sample survey, the food-composition profile of taxonomically verified Ishigaki R. variegatus supports further replicated evaluation of this species as a complementary clam-like food resource.