Using movement, diet, and genetic analyses to understand Arctic charr responses to ecosystem change

D Cote,I Bradbury,K Layton,Jb Dempson,J Angnatok,M Piersiak,S Roul,R Laing

doi:10.3354/meps13775

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https://doi.org/10.3354/meps13775

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Abstract

Arctic charr Salvelinus alpinus are a commercially and culturally valued species for northern Indigenous peoples. Climate shifts could have important implications for charr and those that rely on them, but studies that evaluate responses to ecosystem change and the spatial scales at which they occur are rare. We compare marine-phase habitat use, long-term diet patterns, and trends in effective population size of Arctic charr from 2 areas (Nain and Saglek) of Nunatsiavut, Labrador, Canada. Tagged charr in both areas frequently occupied estuaries but some also used other habitats that extended to the headland environments outside of their natal fjords. Despite the relatively small distances separating these study areas (<200 km), we observed differences in habitat use and diet. Northern stocks (including Saglek) were more reliant on invertebrates than southern stocks (e.g. Nain), for which capelin and sand lance were important prey. The use of coastal headlands also varied, with Saglek charr occupying these environments more frequently than those from Nain, which only used these habitats in 1 year of the study. Long-term commercial catches also indicate that the tendency for Nain charr to stay within fjords varies annually and relates to capelin availability. Despite the demonstrated capacity to alter diet and habitat use to changing environmental conditions, notable declines in effective population size were associated with the regime shift of the 1990s in the northwest Atlantic. Collectively, these results demonstrate that behavioral plasticity of Arctic charr may be insufficient to deal with the large environmental perturbations expected to arise from a changing climate.

Highlights

Arctic charr Salvelinus alpinus are an iconic Arctic species native to a wide latitudinal gradient (Johnson 1980) that extends from the Arctic to north temperate regions (Reist et al 2013)
Our study was conducted in the coastal waters of the Nunatsiavut region of Labrador, Canada, a land claim area established for the Labrador Inuit
We examined temporal and spatial variation in charr diet using long-term monitoring data collected from 5680 individuals harvested in the northern Labrador charr fishery (1982−2008)

Summary

Introduction

Arctic charr Salvelinus alpinus are an iconic Arctic species native to a wide latitudinal gradient (Johnson 1980) that extends from the Arctic to north temperate regions (Reist et al 2013). & Nilssen 2000, Klemetsen et al 2003, Spares et al 2015, Moore et al 2016, Harris et al 2020), occupy a variety of thermal habitats (Rikardsen et al 2007a, Spares et al 2012, Harris et al 2020, Mulder et al 2020), and consume diverse prey often dominated by pelagic fish and plankton (e.g. amphipods), and items such as insects and benthic organisms (Dempson et al 2002, Klemetsen et al 2003, Rikardsen et al 2007b, Spares et al 2012, Davidsen et al 2020) Despite this plasticity, marine habitat use within populations can remain stable across years, even during changing environmental conditions (Harris et al 2020). Such information is important to detect and interpret the responses of Arctic charr to the rapidly changing Arctic (Reist et al 2006, Power et al 2012, Dallaire et al 2021, Layton et al 2021)

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