Fat metabolism in fishes

Abstract

THE Atlantic salmon, Salmo salar-an anadromous migrant-is from its spawning habits particularly suitable for studies of the mobilisation of depot fat. The maturing and adult fish feed intensively in the sea, and then, as the spawning time approaches, migrate to the rivers and commence to ascend them. It is certain that from the moment of entering the rivers, if not earlier, the salmon cease feeding entirely. The journey upstream to the spawning grounds demands the expenditure of much energy, which has to be supplied mainly by reserve fat. Moreover, considerable quantities of fat accumulate in the gonads, and this fat is probably transferred from the depots (vide infra). Continuous depletion of the latter thus takes place. Almost all the males perish in the river, presumably from weakness and starvation, but most of the females survive until they reach the sea again. Here most of them presumably die also, as only a small percentage return to spawn a second time. The fish after spawning are known as kelts, and some of these have been found with as little as 03 % of fat in the muscles, contrasted with 13-14 % of fat in a fish fresh from the sea.