Abstract
Blubber blocks were collected from both a recently killed (dead whale complete sam- ples; DWCS) and several live (living whale partial samples; WPS) Mediterranean fin whales Bal- aenoptera 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 triacyl- glycerols (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 con- tent. 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 coun- terparts. Hence, the lower percentages of 20:1 and 22:1 FAs in the inner layer could reflect the struc- ture 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 through- out the body suggested that sampling live animals to describe trophic interactions may be more realistic in the Mediterranean Sea than in the Atlantic.
Highlights
Fin whales Balaenoptera physalus L. are the largest marine predator in the Mediterranean Sea, with a summer abundance estimated to be around 3500 individuals (Forcada et al 1996)
Mean lipid content for the different body parts of dead whale complete samples (DWCS) samples ranged from 33 to 69% of the wet weight and triacylglycerols (TG) represented 80 to 86% of the total lipids; 36 fatty acid (FA) were observed in all blubber layers in greater than trace amounts (> 0.2%)
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
Summary
Fin whales Balaenoptera physalus L. are the largest marine predator in the Mediterranean Sea, with a summer abundance estimated to be around 3500 individuals (Forcada et al 1996). Around 900 individuals concentrate in the Northern part of the occidental basin (Gannier 1997, Notarbartolo di Sciara et al 2003) to feed on euphausiids (mostly Meganyctiphanes norvegica) (Orsi-Relini & Giordano 1992, Notarbartolo di Sciara et al 2003). The biochemical composition of the fin whale blubber has been mainly investigated in individuals from the Atlantic Ocean, and no study has been reported for the western Mediterranean Sea. The ventral groove blubber is a fibrous and tough tissue, while the rest of. Mar Ecol Prog Ser 311: 165–174, 2006 the body, with the exception of the upper jaw, is less
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