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

摘要

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.