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Dryad

Isotopic values of sea otters (modern and archaeological) from Southeast Alaska and Northern Oregon and potential prey items from Southeast Alaska

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Dec 18, 2024 version files 31.89 KB

Abstract

Integrating pre-industrial datasets into management frameworks is critical for establishing ecologically relevant baselines for conservation. Here, we use isotopic analysis of archaeological and modern sea otter (Enhydra lutris) specimens to anticipate future impacts of recolonization. We focus on Southeast Alaska (SEAK) and northern Oregon, where sea otter populations are recolonizing and competing with macroinvertebrate fisheries or remain extirpated with translocations being considered, respectively. We measured bulk bone collagen δ13C and δ15N and essential amino acid δ13C values of archaeological sea otters, and bulk isotopic values of vibrissae from modern SEAK sea otters. We compare these results with data of potential prey and archaeological samples from California. Isotopic data from SEAK reveal pre-industrial populations consumed infaunal bivalves and utilized both soft-sediment (33%) and kelp forest habitats (67%), with variation among sub-regions. If contemporary populations expand into this historical niche, conflict with Indigenous subsistence fisheries (bivalves) is likely to persist. Isotopic data of archaeological sea otters from northern Oregon suggest past consumption of low trophic level invertebrates, and a reliance on kelp forests (88%) rather than soft-sediment habitats, underscoring the significance of kelp forests for future translocations. Our work provides important perspectives on the potential future ecology of a recovering keystone predator.