Use of stable isotopes and trace elements to determine harvest composition and wintering assemblages of belugas at a contemporary ecological scale

Abstract

Stable isotopes and trace elements reflect interactions between individuals and their environment over shorter periods than genetic tracers and may capture contemporary patterns relevant to stock conservation and management. The endangered eastern Hudson Bay (EHB) belugas Delphinapterus leucas and those from the non-endangered western Hudson Bay (WHB) population are harvested during migration through Hudson Strait (HS), making protection of the endangered stock difficult. We assessed whether chemical tracers of beluga feeding ecology, i.e. carbon and nitrogen isotope ratios and concentrations of 27 trace elements, can help delineate wintering assemblages and successfully define summering stocks and their relative contributions to aboriginal harvests in HS. Skin was obtained from 1032 belugas in 9 regions of Hudson Bay, HS and southeast Baffin Island from 1989 to 2009. Isotopic signatures and trace element concentrations varied regionally and seasonally and suggest that several summering stocks and at least 3 winter assemblages exist. The use of isotopically defined summering stocks as sources in a discriminant function analysis indicates that the endangered EHB belugas account for 20 to 49% of the southern HS fall harvest. Low misclassification rates (≤10%) when using haplotypes unique to, or typical of, EHB belugas as a validation indicate that the isotopic approach is reliable. The analysis combining isotopes with trace elements is promising, although sample size is currently too small to define summering stocks. Spring signatures suggest that Cumberland Sound belugas winter in a separate area and may be differentiated from belugas found elsewhere in southeast Baffin Island, a contemporary pattern relevant to management.

Dietary plasticity and broad North Atlantic origins inferred from bulk and amino acid‐specific δ15N and δ13C favour killer whale range expansions into Arctic waters

“…Giménez et al, 2016). Prey SI sources: bowhead (Pomerleau et al, 2012); narwhal (Watt et al, 2013); beluga (Rioux et al, 2012); ringed seal (Hobson et al, 2002;Young et al, 2010); bearded seal (Young et al, 2010); harbour seals (Young et al, 2010); and Greenland shark (Fisk et al, 2002); see also Table S1.…”

Migration, Dispersal, and Gene Flow of Harvested Aquatic Species in the Canadian Arctic

“…EHB belugas migrated in groups of related individuals and their migration route seemed to be learned and shared by related individuals [99]. As they migrated in the spring and fall along Hudson Strait [100], both WHB and EHB belugas were susceptible to harvest by coastal aboriginal communities along their migration route [101].…”

The influence of biopsy site and pregnancy on stable isotope ratios in humpback whale skin

“…14 δ 15 N is also driven to some extent by primary production and nitrogen processes at the base of the food web; however, this element fractionates heavily with each increasing trophic level, making it a strong indicator of trophic position. 15,16 When paired together, δ 13 C and δ 15 N taken from tissues can provide insight into an individual's or population's biogeography, 17 foraging ecology and diet, 18 population structure, 19 drivers of stress, 20 trophic position, 16 tissue turnover rates, 21 and other key life history events such as fasting and migration. 22 While isotope ratios in animal tissues allow researchers to answer a broad range of questions, variability introduced by unknown factors (e.g., pregnancy, fasting, tissue physiology) could confuse or confound study results.…”