Contemporary Diet of Bowhead Whales (<i>Balaena mysticetus</i>) from the Eastern Canadian Arctic Inferred from Fatty Acid Biomarkers

Abstract

The diet and feeding ecology of Eastern Canada – West Greenland bowhead whales were examined using fatty acid (FA) composition of the outer blubber layer of 50 individuals sampled during the summers of 2008 and 2009. Bowhead blubber was rich in the following FAs: 14:0, 16:0, 16:1n – 7, 18:0, 18:1n – 11, 18:1n – 9, 18:1n – 7, 20:1n – 11, 20:1n – 9, 20:1n – 7, 20:5n – 3, 22:1n – 11, 22:1n – 9, 22:5n – 3, and 22:6n – 3, which together accounted for 91% of total FAs identified. Four groups of bowhead whales were identified from their FA signatures using multivariate analysis. Long-chain monounsaturated fatty acids (MUFAs) (20:1n – 9, 20:1n – 11, 22:1n – 9 and 22:1n – 11) and polyunsaturated fatty acids (PUFAs) (20:5n – 3, 22:5n – 3, 22:6n – 3) accounted for most of the variance among groups. Whales from a single sampling site segregated into different groups, some of which included whales from other sampling sites, suggesting summer mixing of whales from different wintering areas and prey assemblages, or alternatively, selective feeding. FA composition was similar in males and females and among whales of different age classes, which suggests that these different groups shared foraging areas and had similar diets. The blubber of bowhead whales from the eastern Canadian Arctic was composed of high proportions of calanoid copepod markers (20:1n – 9 and 22:1n – 11), especially compared to the adipose tissue of western Arctic bowhead whales. This finding suggests that Calanus spp. were likely a major prey item. Given the expected change in Arctic zooplankton assemblages with climate warming, bowhead whales, through their FA biomarkers, may serve as sentinels of change in Arctic ecosystems.