Understanding carbon flow through ocean food webs is fundamental in biogeochemistry, ecosystem ecology, and fisheries science. We analyzed radiocarbon content (Δ¹⁴C) and nitrogen isotopic compositions (δ¹⁵N) of individual amino acids (AAs) in 27 species of benthic fish collected from off Tohoku (Pacific coast), northeastern Japan. The Δ¹⁴C values of fish varied from –42‰ to +41‰, consistent with Δ¹⁴C of dissolved inorganic carbon found in the cold Oyashio Current and the warm Kuroshio Current. Trophic positions (TPs) of fish calculated from the δ¹⁵N values of AAs increased from 3.1 to 4.5 with increasing of the body size. We also found a negative relationship in some species between Δ¹⁴C and TP (n = 50, r² = 0.28, p < 0.001). In this talk, we will discuss the Δ¹⁴C and TP of benthic fish to understand carbon flow in seafloor ecosystems, which is controlled by multiple factors, including ocean current, terrestrial input, species, body size, and recycling of old organic matter.