Free imidazole compounds in white and dark muscles of migratory marine fish

1. Extractive nitrogenous components were analyzed in specimens of white and dark muscles of three tunas and the Pacific saury. 2. Tunas contained high concentrations of histidine, anserine and creatine in white muscle, and of taurine, anserine and creatine in dark muscle. 3. Imidazole compounds were determined in both muscles of 11 migratory marine fish. Histidine was found in great quantities in all species except swordfish, anserine was found in relatively large amounts in tunas and swordfish, but carnosine was only present in small amounts in yellowfin and skipjack tunas. 4. The dark muscle had a lower content of imidazole compounds than white muscle.