Understanding feeding ecology of Minke whale (Balaenoptera acutorostrata) in East Sea using fatty acids and stable isotopes

Abstract

In order to understand the feeding ecology of minke whale (Balaenoptera acutorostrata) in the East Sea, lipid contents and compositions with compound specific stable isotopes were examined in blubbers. Lipid content in blubber was 70% of wet weight with the dominance of triacylglycerols (94 to 99% of total lipids). The stratification pattern of lipid content appeared in their blubber layers. Relative abundance of some fatty acids (e.g. 14:1, 16:0, 18:1n-7, 18:0, 20:1n-11 and 20:2) were significantly different. These differences might be related with their diets because bulk stable isotope ratios (δ13C, δ15N) in the skin of marine mammals indicated minke whale mainly feeds on the krill and anchovy. However, we found the significant shift of FA compositions within blubber layers for both species. While monounsaturated FAs (MUFA) gradually increased from inner (near muscle) to outer layer (near skin), polyunsaturated FAs (PUFA) decreased from inner to outer layer. These compositional shifts in the blubber could be related with their physiological needs (i.e. thermoregulation, streaming, buoyancy and energy storage). With the addition of compound-specific stable isotope analysis, the detailed information on lipid metabolism and the diet history of marine mammals would be disclosed.