Proximate Composition of Canadian Atlantic Fish: II. Mackerel, Tuna and Swordfish

Abstract

Mackerel, tuna and swordfish (order Acanthopteri) have a prominent red or dark brown fatty lateral-line tissue which, in the samples analyzed, had a lipid content varying from 6% in swordfish to 22% in mackerel. A white blubber or layer of fat tissue, almost two-thirds lipid, may also be present beneath the skin. The white meat was also fatty, from 2% in swordfish to 8% in tuna. The belly-flap muscle of mackerel contained from about 20 to 40% fat. Protein, ash and moisture percentages were lower in the fatty tissue, showing that fat replaces some protein as well as water. Non-protein nitrogen averaged 20% of the total nitrogen, higher than in halibut and the cod family. In tuna and mackerel the protein content was 19% in the white meat and 14% in the brown lateral-line tissue, similar to halibut but higher than in the cod family.