Regional and temporal variation in fatty acid profiles of polar cod ( Boreogadus saida ) in Alaska

Fatty acids (FAs), the main components of lipids, are crucial for energy storage and other physiological functions in animals and plants. Dietary FAs are incorporated and conserved in consumer tissues in predictable patterns and can be analyzed to determine the composition of an individual’s diet. This study measured the variation in FA profiles of polar cod ( Boreogadus saida ) across multiple years (2010–2013) over a wide geographic area in the Beaufort and Chukchi seas. Polar cod are important prey of marine mammals, sea birds, and fishes, providing a crucial link between primary producers and higher trophic-level predators. Spatial and temporal variations in FA profiles of this important forage fish species provide insight into the transfer of lipids through the Arctic ecosystem, and inform diet studies of higher trophic-level predators on polar cod that utilize trophic mixing models based on prey FA data. FA profiles of polar cod differed between the Beaufort and Chukchi seas, and among collection years. High lipid content and elevated levels of long-chain FAs in Chukchi Sea specimens relative to the Beaufort Sea may indicate more favorable feeding conditions over the years sampled, and higher energy density for Chukchi Sea polar cod as prey. FA data provide a useful metric for examining spatial and temporal variation in the quality of prey available to higher trophic-level consumers.