Fish in which the main reserves of fat are in the body tissues, e.g. Herring (Clupea harengus). Fatty fish with a seasonally low fat content may be referred to as lean fish or spent fish. See White fish. Feedy fish Fish that have been feeding heavily such that the gut is full of food when caught. Consequently, the gut enzymes are very active and such fish are liable to belly burst unless they are gutted.