Broad Whitefish (Coregonus nasus) isotopic niches: Stable isotopes reveal diverse foraging strategies and habitat use in Arctic Alaska

PLoS One. 2022 Jul 26;17(7):e0270474. doi: 10.1371/journal.pone.0270474. eCollection 2022.

Abstract

Understanding the ecological niche of some fishes is complicated by their frequent use of a broad range of food resources and habitats across space and time. Little is known about Broad Whitefish (Coregonus nasus) ecological niches in Arctic landscapes even though they are an important subsistence species for Alaska's Indigenous communities. We investigated the foraging ecology and habitat use of Broad Whitefish via stable isotope analyses of muscle and liver tissue and otoliths from mature fish migrating in the Colville River within Arctic Alaska. The range of δ13C (-31.8- -21.9‰) and δ15N (6.6-13.1‰) across tissue types and among individuals overlapped with isotope values previously observed in Arctic lakes and rivers, estuaries, and nearshore marine habitat. The large range of δ18O (4.5-10.9‰) and δD (-237.6- -158.9‰) suggests fish utilized a broad spectrum of habitats across elevational and latitudinal gradients. Cluster analysis of muscle δ13C', δ15N, δ18O, and δD indicated that Broad Whitefish occupied four different foraging niches that relied on marine and land-based (i.e., freshwater and terrestrial) food sources to varying degrees. Most individuals had isotopic signatures representative of coastal freshwater habitat (Group 3; 25%) or coastal lagoon and delta habitat (Group 1; 57%), while individuals that mainly utilized inland freshwater (Group 4; 4%) and nearshore marine habitats (Group 2; 14%) represented smaller proportions. Otolith microchemistry confirmed that individuals with more enriched muscle tissue δ13C', δD, and δ18O tended to use marine habitats, while individuals that mainly used freshwater habitats had values that were less enriched. The isotopic niches identified here represent important foraging habitats utilized by Broad Whitefish. To preserve access to these diverse habitats it will be important to limit barriers along nearshore areas and reduce impacts like roads and climate change on natural flow regimes. Maintaining these diverse connected habitats will facilitate long-term population stability, buffering populations from future environmental and anthropogenic perturbations.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alaska
  • Animals
  • Carbon Isotopes / analysis
  • Ecosystem*
  • Lakes
  • Nitrogen Isotopes / analysis
  • Salmonidae* / physiology

Substances

  • Carbon Isotopes
  • Nitrogen Isotopes

Grants and funding

This research was funded in-part by the National Science Foundation [Awards Alaska EPSCoR OIA-1208927; ARCSS-1722572] and the state of Alaska in the form of funds to MSWi and by the U.S. Bureau of Land Management [Interagency Agreement Number L15PG00216] in the forms of funds to MSWh. The Wilderness Society provided support in the form of a salary for JCL, the U.S. Geological Survey in the form of a salary to MSWi, the U.S. Bureau of Land Management in the form of a salary to MSWh, and the U.S. Fish and Wildlife Service in the form of a salary to DJR. The specific roles of these authors are articulated in the ‘author contributions’ section. In-kind support such as borrowed equipment and staff assistance was provided by the U.S. Fish and Wildlife Service and the Native Village of Nuiqsut Tribal Council. The funders had no role in the study design, data collection, and analysis, decision to publish, or preparation of the manuscript.