Distribution and diet of the bottom dwelling Arctic cod in the Canadian Beaufort Sea Wojciech Walkusz a, b, ⁎, Andrew Majewski a , James D. Reist a a Freshwater Institute, Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB, Canada R3T 2N6 b Institute of Oceanology, Polish Academy of Sciences, Powstancow Warszawy 55, 81-712 Sopot, Poland abstract article info Available online 17 April 2012 Keywords: Arctic cod Beaufort Sea Distribution Zooplankton Feeding Demersal Distribution and diet of bottom-dwelling Arctic cod were studied in the nearshore Canadian Beaufort Sea in summer of 2006–2009 using a 3 m benthic beam trawl. In total, 82 stations were visited ranging in depth from 8 to 128 m. Fish densities were generally low for benthic habitats; pelagic fish occurrence was not assessed. We observed a gradual increase in both the biomass of daily food rations and their energetic content over fish age. Overall, fish were able to obtain high food rations indicating that the Beaufort Sea Shelf has sufficient food resources for them. Demersal Arctic cod fed mainly on copepods (Pseudocalanus spp., Calanus glacialis, Calanus hyperboreus, Limnocalanus macrurus and Jaschnovia tolli), amphipods (Apherusa glacialis and Themisto libellula) and mysids (Mysis oculata). Further studies, particu- larly focused on combined pelagic/benthic sampling, are needed to fully assess ecology of the Arctic cod population in the Canadian Beaufort Sea. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. 1. Introduction Arctic cod (Boreogadus saida) is considered to be a key element of Arctic marine ecosystems given its wide distribution and integral role in overall biomass and energy pathways (Bradstreet et al., 1986). Its importance is gauged as a result of its role both as a con- sumer of zooplankton (Orlova et al., 2009; Walkusz et al., 2011) and as a food source for higher trophic animals such as seals (Bradstreet, 1982; Finley et al., 1990; Weslawski et al., 1994a), birds (Cairns, 1987; Lønne and Gabrielsen, 1992; Weslawski et al., 1994b) and whales (Welch et al., 1993). Due to its significance in the ecosystem, Arctic cod has received considerable attention from the scientific community in the recent years, resulting in a number of papers de- scribing its basic biology and ecology (e.g., Bradstreet et al., 1986; Craig et al., 1982; Lønne and Gulliksen, 1989). Arctic cod spawns under the ice in winter, and is primarily pelagic throughout its larval and early juvenile life (Sameoto, 1984). It feeds on a broad range of organism, mainly crustaceans, and although is considered a gene- ralist it modifies its diet along with its growth and gape size (Ajiad and Gjøsæter, 1990; Walkusz et al., 2011). In some location Arctic cod creates large schoolings that create apparent feeding hot-spots for predators (marine birds, seals and whales) which enhance over- all transport of energy and biomass up the food chain (Crawford and Jorgenson, 1996; Welch et al., 1993). It has also been shown in the Franklin Bay (Beaufort Sea) that the fish aggregate during winter, particularly in the deeper layers to avoid predation from seals, and that these aggregation are large enough to cover requirements of predators (Benoit et al., 2008). The majority of papers on Arctic cod distribution are devoted to pelagic (larval and early juvenile) life-stages, however, there has been some indication that Arctic cod may also spend part of their life associated with demersal habitats (Lønne and Gulliksen, 1989; Sameoto, 1984). Mecklenburg et al. (2007) reported catches of de- mersal Arctic cod in Chukchi Sea and Bering Strait; during their study the species was found mainly on the soft bottom (mud, sand) but clearly avoided hard substrate (gravel, rock). Recent studies from the Alaskan Beaufort Sea (Logerwell et al., 2011; Rand and Logerwell, 2011) show that Arctic cod was by far the most abundant bottom dwelling fish. Although it was virtually found at all stations, Arctic cod displayed the affinity to cold waters found in the offshore Beaufort Sea (depths > 100 m). The aim of this paper is to describe the ecology of demersally asso- ciated Arctic cod in the Canadian Beaufort Sea, including their distri- bution, meristics and feeding assessed by stomach content analysis. We furthermore infer on the potential impacts of direct anthropo- genic (industrial) and indirect (climate change) stressors on Beaufort Sea Arctic cod. 2. Material and methods Arctic cod were sampled during four cruises to the Beaufort Sea in summer 2006–2009 (mid-July to mid-August) by the CCGS Nahidik, as part of Fisheries and Oceans Canada's Northern Coastal Marine Studies (NCMS) programme. In total, 82 stations were sampled between the Canada/Alaska border and the Eastern extent of Amundsen Gulf Journal of Marine Systems 127 (2013) 65–75 ⁎ Corresponding author at: Fisheries and Oceans Canada, Freshwater Institute, 501 University Crescent, Winnipeg, MB, Canada R3T 2N6. Tel.: + 1 2049845541; fax: + 1 2049842403. E-mail address: walwo@iopan.gda.pl (W. Walkusz). 0924-7963/$ – see front matter. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jmarsys.2012.04.004 Contents lists available at ScienceDirect Journal of Marine Systems journal homepage: www.elsevier.com/locate/jmarsys