To study the influence of different ocean currents on the trophic spectra found in a sympatric fish community, we analyzed the radiocarbon contents (<italic>Δ</italic>¹⁴C) and stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic compositions in their bulk muscle tissues and the δ¹⁵N of individual amino acids in 26 species of demersal fish collected from off Tohoku (Pacific coast), northeastern Japan. The <italic>Δ</italic>¹⁴C values of the fish varied from –42 to +41‰, consistent with the <italic>Δ</italic>¹⁴C of the dissolved inorganic carbon in the cold Oyashio Current (typically about –50‰) and the warm Kuroshio Current (typically about +50‰). The trophic positions (TPs) of the fish estimated from the δ¹⁵N values of amino acids increased from 3.1 to 4.5 with increasing snout length. A negative correlation was observed between <italic>Δ</italic>¹⁴C and TP in gadiform fish and flatfish, suggesting that the Oyashio Current delivers a high TP diet to these fish groups. These results suggest that the trophic ecology of marine fish in the coastal western North Pacific is primarily controlled by the two major surface water currents, but is also significantly influenced by a combination of species-specific feeding and migration strategies.