Forecasting fish distribution dynamics under climate change: insights from a rapidly warming arctic

Temperatures in the Arctic are rising three times faster than the global average, resulting in a rapid decline in sea-ice, and lengthening of the ice-free season. As sea ice retreats, fishing grounds that were previously not accessible will inevitable open up and shipping activities in the Arctic will increase together with the potential of accidental oil spills into the marine ecosystem. Environmental changes, together with increased development and economic interest in the region, are altering the Arctic marine ecosystem and putting pressure on the cold-adapted species inhabiting them. One of those species is polar cod (Boreogadus saida), an abundant circumpolar marine gadid inhabiting both open and ice-covered waters of the Arctic Ocean and adjacent seas. Polar cod plays a central role in the Arctic marine ecosystem as key species channelling nearly 75 % of zooplankton production to marine vertebrate predators. Changes in its abundance, distribution and trophic ecology will have consequences for the energy flow and community dynamics throughout the entire marine ecosystem. In this PhD, I study the population structure, connectivity patterns and feeding ecology to investigate the resilience of polar cod in a rapidly changing Arctic Ocean. In the first part, I focus on the population structure and genetic connectivity of polar cod using microsatellites and single nucleotide polymorphisms. In the second part, investigate the trophic and feeding ecology of polar cod through the study of the diet, and gut microbial diversity and composition at an unprecedented taxonomic resolution using DNA metabarcoding. Gained insights will support decision-making regarding ecosystem-based management, future fishery grounds and exploitation regulations.