Dietary characteristics of co-occurring polar cod (Boreogadus saida) and capelin (Mallotus villosus) in the Canadian Arctic, Darnley Bay
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Reduction in sea ice due to climate change is expected to have a negative impact on habitat availability for Arctic marine fishes and induce range expansion of species from southern environments. Such an effect will likely be observed in the abundance of polar cod, Boreogadus saida (Lepechin, 1774), as well as interspecific interactions of this intermediate-level trophic taxon, particularly in more southerly fringing seas in the Arctic. Polar cod and capelin, Mallotus villosus (Müller, 1776), are pelagic, planktivorous forage fishes, which occupy similar dietary niches and are the primary prey of marine predators. Co-occurring polar cod and capelin were collected at seven stations in Darnley Bay, NT, during August 2013. Standard length (SL), used as a proxy for age, suggested that polar cod (mean ± 1 SD: 71.1 ± 10.3 mm) were predominantly age 1+ and capelin (96.2 ± 13.4 mm) were mostly age 2+. Stomach content analyses indicated that both species feed extensively on calanoid copepods (Calanus hyperboreus, C. glacialis, Metridia longa) and amphipods (Themisto libellula). There was high dietary overlap between capelin and polar cod, evidenced by Schoener’s index (0.80). Additionally the quantity of dietary items, biomass and energetic content consumed differed among size classes in both capelin (SL, 70.5–132.0 mm) and polar cod (SL, 42.1–114.4 mm). This study illustrates that the diets of these sympatric forage fishes in an Arctic ecosystem are very similar, indicating a high potential for interspecific competition as the sub-Arctic capelin expands its range into Arctic regions with climate change.
KeywordsPolar cod Capelin Diet overlap Calanus Climate change
We thank other members of the BREA Marine Fishes Project, S. MacPhee and S. Atchison for aid in sampling and providing analytical advice. This project is supported by Government of Canada funding (Beaufort Sea Regional Environmental Assessment, Environmental Studies Research Fund, Program on Energy Research and Development), Natural Sciences and Engineering Research Council Discovery Grant (GKD) and a University of Manitoba Faculty of Science Scholarship to DGM.
Compliance with ethical standards
Animal specimens used in this study were processed with the animal care permit under the guidelines of Fisheries and Oceans Canada.
- Ajiad AM, Gjøsæter H (1990) Diet of polar cod, Boreogadus saida, in the Barents Sea related to fish size and geographical distribution. ICES CM G:48Google Scholar
- Bradstreet MSW, Finley KJ, Sekerak AD, Griffiths WD, Evans CR, Fabijan MF, Stallard HE (1986) Aspects of the biology of Arctic cod Boreogadus saida and its importance in Arctic marine food chains. Can Tech Rep Fish Aquat Sci 1491(1):1–193Google Scholar
- Falk-Petersen S, Pavlov V, Timofeev S, Sargent JR (2007) Climate variability and possible effects on arctic food chains: the role of Calanus. In: Ørbæk JB, Kallenborn R, Tombre I, Hegseth EN, Falk-Petersen S, Hoel AH (eds) Arctic Alpine ecosystems and people in a changing environment, Springer, Berlin, pp 147–166Google Scholar
- Geoffroy M, Majewski A, LeBlanc M, Gauthier S, Walkusz W, Reist JD, Fortier L (2015) Acoustic target strength, vertical distribution and ontogenic migrations of polar cod (Boreogadus saida) in the Canadian Beaufort Sea: an annual cycle. Polar Biol. doi: 10.1007/s00300-015-1811-z
- Gjøsæter H, Loeng H (1987) Growth of the Barents Sea capelin, Mallotus villosus, in relation to climate. Environ Biol Fish 20:293–300Google Scholar
- Majewski AR, Walkusz W, Lynn BR, Atchison S, Eert J, Reist JD (in review) Distribution and diet of demersal Arctic Cod, (Boreogadus saida), in relation to habitat characteristics in the Canadian Beaufort Sea. Polar Biol.Google Scholar
- Pomerleau C, Nelson RJ, Hunt BPV et al (2014) Spatial patterns in zooplankton communities and stable isotope ratios (δ13C and δ15 N) in relation to oceanographic conditions in the sub-Arctic Pacific and western Arctic regions during the summer of 2008. J Plankton Res 36:757–775. doi: 10.1093/plankt/fbt129 CrossRefGoogle Scholar
- Welch HE, Crawford RE, Hop H (1993) Occurrence of polar cod schools and their vulnerability to predation in the Canadian high arctic. Arctic 46:331–339Google Scholar