Fatty acid composition of Mediterranean fin whale Balaenoptera physalus blubber with respect to body heterogeneity and trophic interaction

Diane Ruchonnet (1, 2) , Marc Boutoute (1) , Christophe Guinet (3) , Patrick Mayzaud (1)

1 LOV - Laboratoire d'océanographie de Villefranche
2 Environmental Research Institute
3 CEBC - Centre d'Études Biologiques de Chizé

Blubber blocks were collected from both a recently killed (dead whale complete samples; DWCS) and several live (living whale partial samples; WPS) Mediterranean fin whales Balaenoptera physalus and analyzed for their lipid and fatty acid (FA) composition. Mean lipid content for the different body parts of DWCS samples ranged from 33 to 69% of the wet weight and triacylglycerols (TG) represented 80 to 86% of the total lipids; 36 FAs were observed in all blubber layers in greater than trace amounts (>0.2%). Multivariate correspondence analysis showed that the major variation in FAs structure was related to body position (dorsal versus ventral and lateral) and to a lesser extent to the blubber stratification. Dorsal blubber TG could be distinguished from the other locations by the relative levels of 20:0 and 20:1 FA, whereas polyunsaturated fatty acids (PUFA) were the main descriptors of the lateral and ventral blubber. Stratification resulted in a slight increase in monoenoic fatty acid (MUFA) content from the inner to the outer layers and a decreasing PUFA content. The 6 biopsies from living whales showed a similar FA composition and displayed FA profiles similar to those of the dorsal outer blubber blocks. Comparison of blubber FA structure with fin whales from the North Atlantic showed major differences, with a far lower percentage of 22:1 FA for the Mediterranean individuals and smaller differences in long chain MUFA between the inner and outer layer. Fin whales feed on the euphausiid Meganyctiphanes norvegica. Ligurian Sea M. norvegica appeared to have lower percentages of 20:1 and 22:1 FAs than their North Atlantic counterparts. Hence, the lower percentages of 20:1 and 22:1 FAs in the inner layer could reflect the structure of the prey assimilated. The slightly higher values in the outer layer could reflect the previous fall and winter feeding periods in Atlantic waters. The relative homogeneity of the blubber throughout the body suggested that sampling live animals to describe trophic interactions may be more realistic in the Mediterranean Sea than in the Atlantic.

Mots clés: Balaenoptera physalus; Blubber; Fatty acid; Trophic interaction

Domaines: Biodiversité et Ecologie; Environnement et Société

Diane Ruchonnet, Marc Boutoute, Christophe Guinet, Patrick Mayzaud. Fatty acid composition of Mediterranean fin whale Balaenoptera physalus blubber with respect to body heterogeneity and trophic interaction. Marine Ecology Progress Series, 2006, 311, pp.165-174. ⟨hal-00184479⟩