Co-distribution of seabirds and their polar cod prey near the ice edge in southern Baffin Bay

• Main Authors: LeBlanc, Mathieu, Gauthier, S, Mosbech, Anders, Fortier, Louis
• Format: Conference Object
• Language: English
• Published: 2017
• Subjects: Arctic; Baffin Bay; Fulmar; Baffin; Black-legged Kittiwake; Boreogadus saida; Fulmarus glacialis; Glaucous Gull; Larus hyperboreus; Northern Fulmar; polar cod; rissa tridactyla; Sea ice; thick-billed murre; Uria lomvia; uria
• Online Access: https://pure.au.dk/portal/da/publications/codistribution-of-seabirds-and-their-polar-cod-prey-near-the-ice-edge-in-southern-baffin-bay(4eb39850-42af-4e7b-acb2-ba6cbf51bbef).html

Polar cod (Boreogadus saida) is the main prey of several arctic predators including many seabird species. Ice edges are known as important feeding locations for seabirds. How polar cod density affects arctic seabird distribution around offshore ice edges is still unclear. We tested the hypothesis that, at a large spatial scale, thick-billed murre (Uria lomvia), black-legged kittiwake (Rissa tridactyla), northern fulmar (Fulmarus glacialis) and glaucous gull (Larus hyperboreus) select habitats where polar cod abundance is high. At a medium and small scale, we hypothesized that seabird abundance is positively influenced by polar cod abundance and negatively by ice concentration. A survey was conducted in June-July 2016 in southern Baffin Bay during which polar cod abundance was estimated by hydroacoustics and seabirds were counted and sampled. Polar cod was the main fish prey ingested by each seabird species, and age-1 polar cod found in bird stomachs were likely individuals associated to ice. At a large scale of hundreds of kilometers, seabirds and age-0 polar cod were more abundant in ice-covered habitats (30 to 100% ice concentration). At medium and small scale of 12.5 and 1 km respectively, spatial relationships between seabirds and age-0 polar cod were weak or nonexistent and varied among seabird species. We suggest that these weak spatial relationships are explained by the relatively uniform distribution of age-0 polar cod and by seabirds possibly targeting less abundant sympagic age-1 fish. The ongoing climate warming and the decrease in sea-ice extent may lead to the confinement of sympagic age-1 polar cod in northernmost regions of the Arctic and force seabirds to travel farther to reach more productive ice edges.