MARINE LIPIDS

During the past 10 years world production of fish oil was decreasing from about 1.4 to 1.1 million tons (2004-05). Europe including Scandinavia accounted for about half of the world's consumption of fish oil, Japan being the first world producer with 0.28 million tons. About 90000 tons are used for pharmaceutical applications but half of the world production is used for aquaculture feed. Fish oil is a by-product of industrial fishing and the fish meal industry.
In fatty fish, lipid amounts depend largely on the time of their capture around the year and are localized under the skin, around the intestines or in the white muscle. The oil content varies also from species to species. In fat fish, it can reach up to 21% (herring) and 18% (sardines).

In contrast with the other fats and oils, fish oils contain large amounts of eicosapentaenoic (20:5 n-3) and docosahexaenoic (22:6 n-3) acids, respectively 14-19% and 5-8%. The proportion of polyunsaturated fatty acids depends on the fish species and on the average temperature of the water where they are  caught (the colder the water, the higher the amount of these components). Saturated fatty acids include C12 up to C24:0 components, and some branched chains (iso C16, iso C17..) are also found. Among monoenes, 16:1(n-7), 20:1(n-9) and 22:1(n-11) are present in various amounts, this last component being bioconverted from the corresponding fatty alcohol of crustacea (copepods) by the fish liver. More than 50 different fatty acids were described in marine fish oil, but 8 species frequently represent more than 80% of the total amount.
We give below the basic composition of two commercially important fish oils, that of menhaden representing about 80% of the production of north America.

To get information on the triacylglycerol structure  of these oils :

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