Spatial segregation and similar trophic-level diet among eastern Canadian Arctic/north-west Atlantic killer whales inferred from bulk and compound specific isotopic analysis

• Published in: Journal of the Marine Biological Association of the United Kingdom
• Main Authors: Matthews, Cory J.D., Ferguson, Steven H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2013
• Subjects: Arctic; Newfoundland; Beluga; Beluga*; narwhal*; North West Atlantic
• Online Access: http://dx.doi.org/10.1017/s0025315413001379; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0025315413001379

Killer whales in the Eastern Canadian Arctic (ECA) prey on narwhal, beluga, bowhead whales and seals, while further south in the north-west Atlantic (NWA), killer whales off the coast of Newfoundland and Labrador prey on both marine mammals and fish. Bulk and amino acid (AA) specific isotopic composition of dentinal collagen in teeth of 13 ECA/NWA killer whales were analysed to assess the degree, if any, of dietary specialization of killer whales across the region. Dentine was sampled from within annual growth layer groups (GLGs) to construct chronological profiles of stable nitrogen (δ 15 N) and carbon (δ 13 C) isotopic compositions for individual whales spanning 3–25 years. Interannual isotopic variation across GLGs was less than that among individuals, and median bulk δ 15 N values differed by up to 5‰ among individuals. Significant correlation between bulk δ 15 N values and baseline (source AA) δ 15 N values indicates much of the observed isotopic variation among individuals reflects foraging within isotopically distinct food webs, rather than diet differences. This interpretation is supported by consistent differences in bulk δ 13 C values between the two individuals with lowest source AA δ 15 N values and the remaining whales. After accounting for baseline isotopic variation, comparable δ 15 N values among individuals indicates similar trophic-level diet, although uncertainties in relative trophic 15 N enrichment of individual AAs currently limits trophic position estimates for top consumers. Further research is required to clarify seasonal movement patterns and possible diet shifts of ECA/NWA killer whales to better define their role in marine ecosystems across the region.