Data from: Seasonal shifts in feeding patterns: individual and population realized specialization in a high Arctic fish

• Main Authors: Cusa, Marine, Berge, Jørgen, Varpe, Øystein
• Format: Dataset
• Language: unknown
• Published: 2020
• Subjects: Arctic cod; Arrhis phyllonyx; Chaetognatha; Polychaeta; niche width; Sebastes sp; Themisto abyssorum; Hyperia galba; Mysidacea; Boreogadus saida; Lebbeus polaris; Polar cod; Sabinea septemcarinata; Themisto libellula; Isopoda; crustacean; Leptoclinus sp; Copepoda; Cumacean; Pandalus borealis; Teleostei; Euphausidae; Arctic; Svalbard; polar cod; Themisto; Zooplankton
• Online Access: https://zenodo.org/record/3976977; https://doi.org/10.5061/dryad.6472vq6

Species with a broad and flexible diet may be at an advantage in a rapidly changing environment such as in today's Arctic ecosystems. Polar cod (Boreogadus saida), an abundant and ecologically important circumpolar Arctic fish, is often described as a zooplankton generalist feeder, which suggests that it may cope successfully with changes in prey composition. This description is justified based on the relatively broad diet of polar cod across sites and seasons. In this case study, we used polar cod dietary data from fall and winter and from two distinct environments, dominated either by Arctic or Atlantic water masses in Svalbard. Our results point to the importance of time and space when drawing conclusions on dietary plasticity and degree of specialization. Polar cod diet differed significantly between fall and the winter and between Arctic and Atlantic domains. Polar cod from Arctic domains displayed a strong realized population specialization on T.libellua in fall, and the larger dietary niche width observed in the winter was the product of realized individual specialization, with increased feeding on fish prey. Overall, we did not observe a generalized feeding behavior. If dietary niche width is to inform conservation management, we argue it must be recognized that populations from a single species may adopt seasonally contrasting degrees of dietary specialization and that these populations may differ in their vulnerability to climate-induced changes in prey community composition. Seasonal gravimetric stomach content of Boreogadus saida from SvalbardThis file contains data from the stomach content of polar cod (Boreogadus saida) in grams. The ID number corresponds to a single individual. The dissected stomachs were examined with a dissecting microscope and prey taxa were identified to the lowest possible taxonomic level. Individuals of each prey taxa were weighed. Some taxonomic levels were grouped into broader dietary categories for the analyses. The season "FALL" corresponds to September and October, ...