Variability in the summer diets of juvenile polar

Authors: Benjamin P Gray Brenda L Norcross Arny L Blanchard Anne H Beaudreau Andrew C Seitz

Publish Date: 2015/10/14

Volume: 39, Issue: 6, Pages: 1069-1080

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Abstract

Polar cod Boreogadus saida is an important link between top predators and lower trophic levels in highlatitude marine ecosystems Previous findings describe differences in its diet throughout the western Arctic however the causes of this variation are not well known This study examined the diets of juvenile polar cod collected via demersal trawling methods over three summers in the northeastern Chukchi Sea 2010–2012 and one summer in the western Beaufort Sea 2011 to determine the amount of variability explained by biological spatial and interannual factors Prey were identified measured for length and aggregated by percent mean weight into taxonomically coarse prey categories for analysis Within seas variation in juvenile polar cod diet composition was significantly related to body size latitude longitude depth and interannual Chukchi Sea only factors Canonical correspondence analysis indicated body size was the most important factor contributing to the total variance in juvenile polar cod diet in the Chukchi and Beaufort Seas Body sizebased diet differences between the Chukchi and Beaufort Seas were evaluated using nonmetric multidimensional scaling This method revealed that similarsized polar cod consumed similarsized prey in both seas but their diets were more benthically influenced in the Chukchi Sea and more pelagically influenced in the Beaufort Sea Juvenile polar cod diet compositions vary by body size and region of inhabitance throughout their distribution Here we show that body size was the primary factor explaining variation in the summer diet of juvenile polar cod within the Chukchi and Beaufort SeasWe thank the crewmembers aboard the R/V Alaska Knight and R/V Norseman II for their help and fishing expertise along with all past and present UAF Fisheries Oceanography Laboratory technicians for their help in processing fish stomach contents We also thank Crystal Cano Max Hoberg Hillary Nichols and Chris Stark for their assistance in prey identification This study was funded in part with qualified outer continental shelf oil and gas revenues by the Coastal Impact Assistance Program Fish and Wildlife Service US Department of the Interior It was also funded by the Bureau of Ocean and Energy Management BOEM Award M10AC20004 and BOEM Award M12PG00018 The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the US Government Mention of trade names or commercial products does not constitute their endorsement by the US Government

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