Composition of polyunsaturated fatty acids in the liver of freshwater and marine ringed seals (Phoca hispida ssp.) differs largely due to the diet of the seals.

Fatty acid composition in the liver of four ringed-seal (Phoca hispida ssp.) populations, from ocean (Spitsbergen), brackish water (the Baltic Sea) and freshwater (Lake Saimaa and Lake Ladoga) were determined by gas liquid chromatography. The fatty acid compositions in liver were compared with those of the blubber of the seals, which largely reflect the fatty acid supply from marine or freshwater fish. When the ratios of 20:4n-6/20:5n-3 (arachidonic acid/eicosapentaenoic acid, AA/EPA, from 0.06 to 0.55) and n-6 PUFA/n-3 PUFA (n-6/n-3, from 0.09 to 0.35) increased from the marine to freshwater blubber, the corresponding increase in these ratios in the total lipids of the liver was 10-fold or more (AA/EPA: from 1.2 to 13.5 and n-6/n-3: from 0.9 to 3.2). Thus, when available in the diet, AA is preferentially incorporated into the lipids of pinniped liver.