Foraging ecology and population structuring of baleen whales in the western South Atlantic and eastern South Pacific

Buss, Danielle Lia 

Change log

Baleen whales are highly mobile marine predators that are still recovering from unsustainable exploitation between the 18th and 20th centuries. There remain considerable gaps in our understanding of the migration, foraging localities, prey choice and population connectivity of whales in the Southern Hemisphere as they recover, the impact of these populations on marine ecosystems, and how they are likely to respond to the ongoing climate crisis. Historic information on population connectivity, distribution and diet prior to exploitation provides a baseline and idealised endpoint against which to assess present-day whale populations. In this thesis, I taxonomically identified historic whalebone assemblages using biomolecular techniques, conducted stable isotope analysis of bone collagen and baleen, and analysed whaling catch locality data to: (i) provide a baseline on the isotopic niches of baleen whales across the western South Atlantic and eastern South Pacific; (ii) document historic patterns of resource partitioning between whale species; and (iii) identify whether sulfur isotopes can be used to infer site fidelity to feeding grounds. In addition, (iv) I combine DNA metabarcoding, population genetics and stable isotope analysis to compare foraging patterns, genetic diversity, and population structure of present-day and pre-exploited populations of the sei whale, Balaenoptera borealis, in the western South Atlantic. Historic isotopic niches and latitudinal feeding ground ranges suggest whale species partition resources in their western South Atlantic and eastern South Pacific feeding grounds. Fin and humpback whales appear to be ecological generalists relative to Antarctic blue whales and sei whales, thus potentially less vulnerable to ongoing environmental change. Historic and present-day populations of sei whales in the western South Atlantic were similar in terms of diet, genetic diversity, and population structure, with isotopic analyses and distribution inferred from historic catch patterns suggesting these whales may be more ecologically specialised than first thought, and therefore vulnerable to environmental perturbations. These inferences provide an important contribution to inform priority assessments for conservation management.

O'Connell, Tamsin
Cetacea, Marine Ecology, Conservation, Biogeochemical, Molecular, Animal diet, Stable Isotope, Population structure, Genetic diversity
Doctor of Philosophy (PhD)
Awarding Institution
University of Cambridge
NERC (1940085)
Natural Environment Research Council (1940085)
This research was funded by the Natural Environment Research Council (NERC) as a NERC-Cambridge ESS Doctoral Training Partnership studentship (NE/L002507/1). D.L.Buss was awarded additional funding to expand laboratory analyses including: (i) grant-in-kind (£5,960) from the NERC biomolecular analysis facility (NBAF) ref NBAF1162 to conduct molecular work of historic sei whale samples; (ii) grant-in-kind (£12,435) from the National Environment Isotope Facility (NEIF) ref (2266.0320) to conduct sulfur isotope analysis of whale bones. Funding was awarded to Falklands Conservation by the Royal Society for the Protection of Birds (RSPB) to conduct the molecular and isotopic analyses of present-day sei whale samples from the Falkland Islands included in this thesis. This research was conducted as a contribution to the Ecosystems component of the British Antarctic Survey Polar Science for Planet Earth Programme, funded by the Natural Environment Research Council.