Sea ice, temperature, and prey effects on annual variations in mean lengths of a key Arctic fish, Boreogadus saida, in the Barents Sea

Nicolas Dupont,Harald Gjøsæter,Leif Christian Stige,Joël M Durant,Øystein Langangen

doi:10.1093/icesjms/fsaa040

Nicolas Dupont, Harald Gjøsæter + Show 3 more

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https://doi.org/10.1093/icesjms/fsaa040

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Abstract

Abstract Oceanographic conditions in the Arctic are changing, with sea ice cover decreasing and sea temperatures increasing. Our understanding of the effects on marine populations in the area is, however, limited. Here, we focus on the Barents Sea stock of polar cod (Boreogadus saida). Polar cod is a key fish species for the transfer of energy from zooplankton to higher trophic levels in the Arctic food web. We analyse the relationships between 30-year data series on the length-at-age of polar cod cohorts (ages 0–4) and sea surface temperature, sea ice concentration, prey biomasses, predator indices, and length-at-age the previous year using multiple linear regression. Results for several ages showed that high length-at-age is significantly associated with low sea ice concentration and high length-at-age the previous year. Only length-at-age for age 1 shows a positive significant relationship with prey biomass. Our results suggest that retreating sea ice has positive effects on the growth of polar cod in the Barents Sea despite previous observations of a stagnating stock biomass and decreasing stock abundance. Our results contribute to identifying mechanisms by which climate variability affects the polar cod population, with implications for our understanding of how future climate change may affect Arctic ecosystems.

Highlights

The largest changes in temperature are recorded in the Arctic areas at the northernmost part of the northern hemisphere (Hansen et al, 2006)
The multilinear regression for age 1 showed that length at age 1 was not significantly associated with the mean length of the same year class the previous year and that length was negatively associated with winter sea ice concentration and positively associated with the amphipod index
Our results show the associations between environmental variables and length-at-age of polar cod in the Barents Sea

Summary

Introduction

The largest changes in temperature are recorded in the Arctic areas at the northernmost part of the northern hemisphere (Hansen et al, 2006). (1978–2010), the observed sea ice cover and sea ice period, as well as the modelled sea ice thickness, have decreased in the Arctic marginal seas often associated with increased net primary production (Stroeve et al, 2012; Arrigo and van Dijken, 2015; Laidre et al, 2015). Sea ice cover is projected to continue shrinking and thinning, leading to changes in the VC International Council for the Exploration of the Sea 2020.

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