The fatty acid composition of body lipids was deternfined by GLC for 14 species of saltwater fish, three species of freshwater fish and four species of shellfish. In addition, liver lipids of two species and egg lipids of one species were analyzed for comparison with the fish body lipids. The various species ranged from lean to fatty and contained from 0.7-15.5% oil in the tissues. Certain majorfatty acids were found to vary widely among the species, as follows: 1.6-8.0.% myristie, 9.5-33.4% palmitie, 2.0-11.2% palmitoleic, 5.2-29.1% oleic, 0.7-10.5% eicosenoic, 5.0-21.5% eicosapentaenoic, 0.2-11.6% docosenoic and 5.9-26.2% docosahexaenoic acids. Analyses of two separate mullet-oil samples illustrated the wide differences that are possible for a single species caught during different seasons. Significant differences in the amt of particular fatty acids were found in comparing freshwater-fish analyses with analyses for marine fish. Oysters and scallops showed large amt of pentaenoic and hexaenoic acids in their oils.

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Off odors and flavors in fish oils arise from contamination from metabolites, from the spoilage of fish protein, or from oxidation products of the oil itself. The resulting odors and flavors can render the oil less desirable for many applications. Odors or flavors in the flesh of animals or poultry fed fish oil come more from the polyunsaturated nature of the fish oil than from the oxidation products or flavor and odor of the oil that is fed. Odors and flavors can be removed by refining methods or in some cases, masked by use of certain additives.

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Data reveal a very large variation in fatty acid pattern of oil from the same species of fish even when each batch of oil represents many thousands of individual fish. The necessity for using samples involving a much larger number of fish for studies to determine fatty acid patterns for a given species is emphasized. Other sources of error are considered briefly.