Sulfur stable isotope ratios provide further insight into movements of the fin whale, an oceanic long-range migrant.

Abstract

Stable isotope ratios have proven a valuable tool to investigate marine mammal ecology, including diet of species, distribution and migratory movements. While most studies have focused on δ 15 N and δ 13 C values, knowledge on the sources and tissue dynamics of δ 34 S values is still very limited. We examined the sequential variation of δ 15 N, δ 13 C and δ 34 S values along the baleen plates from fin whales occurring off W Iceland in summer. All baleen plates exhibited fluctuations along their growing axis. A significantly synchronic correlation was found between δ 15 N and δ 34 S values, while the relation of these values with δ 13 C was highly variable and inconsistent. These results were similar to those from previous studies in Greenland bowhead whales, although the periodicity of the oscillations was reversed. Although seasonal variations in food intake and the associated cycles of protein synthesis and catabolism, may have played a role in such fluctuations and the observed differences between species, we suggest that the main driver for the δ 15 N and δ 34 S fluctuations reflected in baleen plates is the variation of local baselines between winter and summer grounds. This offers great potential for using δ 34 S values to study migratory movements and destinations provided that the actual patterns of geographic variation of such values are clarified.