Interannual variability in the lipid and fatty acid profiles of east Australia-migrating humpback whales (Megaptera novaeangliae) across a 10-year timeline

Abstract

Southern hemisphere humpback whales are classified as high-fidelity Antarctic krill consumers and as such are vulnerable to variability and long-term changes in krill biomass. Evidence of heterogeneous feeding patterns of east coast of Australia migrating humpback whales has been observed, warranting a comprehensive assessment of interannual variability in their diet. We examined the lipid and fatty acid profiles of individuals of the east coast of Australia migrating stock sampled between 2008 and 2018. The use of live-sampled blubber biopsies showed that fatty acid profiles varied significantly among all years. The two trophic indicator fatty acids for Antarctic krill, 20:5ω3 and 22:6ω3 remained largely unchanged across the 10-year period, suggesting that Antarctic krill is the principal prey item. A distance-based linear model showed that 33% of the total variation in fatty acid profiles was explained by environmental variables and climate indices. Most of the variation was explained by the Southern Annular Mode (23.7%). The high degree of variability observed in this study was unexpected for a species that is thought to feed primarily on one prey item. We propose that the observed variability likely arises from changes in the diet of Antarctic krill rather than changes in the whale’s diet.

First evidence of bubble‐net feeding and the formation of ‘super‐groups’ by the east Australian population of humpback whales during their southward migration

“…For example, while feeding off Eden, whales have been observed to form larger group sizes and feed at a higher rate when targeting krill at the surface than fish at depth (Owen et al, 2015; Owen et al, 2016). It is also possible that changes in the availability of krill in the Southern Ocean feeding grounds in the previous summer influence the extent to which whales rely on opportunities to feed along the migratory route, with fatty acid profiles of humpback whales in this population recently linked to changes in the Southern Annular Mode (Groß et al, 2020).…”

Assessing the effects of lipid extraction and lipid correction on stable isotope values (δ13C and δ15N) of blubber and skin from southern hemisphere humpback whales

“…14 Southern hemisphere humpback whales are highfidelity Antarctic krill (Euphausia superba) consumers. [26][27][28] Thus, they have a simpler diet than northern hemisphere humpback whales and also feed at a lower trophic level. 29 These differences in feeding ecology warrant the separate assessment of the impact lipids have on stable isotope values of different populations of the same species.…”

Multi-Omics Approaches and Radiation on Lipid Metabolism in Toothed Whales

“…Several factors, such as genes, environmental factors, and gene and environment interactions, can also affect the synthesis of the endogenous lipid profiles in mammals. Therefore, the lipid profile of toothed whales can be changed with dietary lipids, de novo lipogenesis, enzymes, desaturation, physical forces, and the incorporation of fatty acids into more complex lipid molecules [11,16,17]. In addition, changes in lipid metabolism in animals can occur due to anthropogenic or natural factors like radiation [18].…”