Impact d'une débâcle hâtive des glaces sur le régime alimentaire des jeunes morues arctiques (Boreogadus saida)

• Main Author: Caissy, Pascale
• Other Authors: Maps, Frédéric, Bouchard, Caroline
• Format: Thesis
• Language: French
• Published: Université Laval 2021
• Subjects: envir; geo; Arctic; Arctic Ocean; Pivot; Arctic cod; Arctique*; banquise; Boreogadus saida; Climate change; polar cod; Sea ice; Zooplankton
• Online Access: https://hdl.handle.net/20.500.11794/71289

Due to climate change, the whole Arctic Ocean could become free of ice during the summer as early as the 2030s. For now, sea-ice breakup already happens earlier almost year after year. Arctic cod (Boreogadus saida), a pivotal species of Arctic marine trophic networks, must cope with this lengthening of the ice-free season. Earlier studies suggest that age-0 Arctic cod recruitment is enhanced with an early sea-ice breakup. This could be explained by warmer temperatures promoting survival and by higherzooplankton biomass in areas of early sea-ice breakup. For this study, over 300 guts of larval and juvenile polar cod from various ecoregions of the Arctic were analyzed. I tested the hypothesis that young polar cods benefit from the lengthening of the ice-free season, optimal temperatures and higher abundance of nutritious preys by increasing their feeding success in those areas, which could in turn results in higher recruitment. Despite high inter-individual variability, feeding success increased with fish length and zooplankton abundance. Even though time since ice breakup and temperatures were not good predictors of feeding success, extreme temperatures as high as 10 °C led to a state close to starvation. Additionally, feeding success increased in fish feeding extensively on Calanus spp., while the consumption of cyclopoids such as Oithona similis decreased feeding success, raising concerns on the future adaptability of Arctic cod. Changes in sea ice regimes may not have a direct impact on age-0 Arctic cod feeding success on a short timescale, but they will eventually have important impacts on the phenology of key zooplankton species and their co-occurrence with age-0 Arctic cod. The feeding success of the vulnerable early life stages of Arctic cod could thus be jeopardized. Le réchauffement accéléré de l'Arctique mène à une débâcle de plus en plus hâtive de la banquise. La morue arctique (Boreogadus saida), une espèce pivot du réseau trophique, semble déjà répondre au rallongement de la période libre de ...