Diet of capelin ( Mallotus villosus ) in the Eastern Canadian Arctic inferred from stomach contents and stable isotopes
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ORIGINAL PAPER
Diet of capelin (Mallotus villosus) in the Eastern Canadian Arctic inferred from stomach contents and stable isotopes Wesley R. Ogloff1,2 · Steve H. Ferguson1,2 · Ross F. Tallman1 · Gail K. Davoren2 Received: 8 July 2019 / Revised: 22 May 2020 / Accepted: 23 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Capelin (Mallotus villosus), a sub-Arctic forage fish, has become abundant in the Canadian Arctic in recent decades, with consistent spawning documented; however, the trophic role of capelin in these systems is unknown. We investigated the diets of small, immature (70–129 mm), medium, mature (130–174 mm), and large, mature (175–219 mm) capelin in Pangnirtung Fjord, Nunavut during and prior to spawning in June–July, 2015–2016 using stomach contents and stable isotopes, respectively. Ontogenetic niche shifts were observed in both cases. Small, immature capelin consumed predominantly small copepods (primarily Clausocalanidae) and had a narrow isotopic niche (SEAC: 0.11 ‰2). In contrast, medium-sized, mature capelin consumed a mix of Calanus copepods, amphipods, and mysids and had a broad isotopic niche ( SEAC range: 0.23–0.51 ‰2), while large, mature capelin consumed higher proportions of large prey types (primarily Calanus hyperboreus and amphipods) and had a narrower isotopic niche ( SEAC range: 0.09–0.26 ‰2). A higher percentage (by dry biomass) of capelin eggs (73–100%) were consumed by mature capelin in 2016, when ice cover in the fjord delayed the initiation of sampling by ~ 10 days after spawning had begun, relative to 2015 (0–9%). Non-egg prey types primarily consisted of amphipods (77–100% by dry biomass, mostly ice-associated Apherusa glacialis) in 2016 and primarily pelagic Calanus copepods (64–99%) in 2015. As capelin diet was broadly similar to other Arctic forage fishes, such as polar cod (Boreogadus saida), high dietary overlap may occur. Findings provide baseline data to examine future changes in capelin diet as well as their trophic interactions in the Canadian Arctic. Keywords Foraging ecology · Range shifts · Forage fish · Cumberland sound · Copepods
Introduction As a result of a warmer ocean and a longer open-water period (Stroeve et al. 2014), temperate and sub-Arctic species are now able to extend the high-latitude margins of their ranges and thrive in regions in which they were historically rare or absent (Moore and Huntington 2008; IPCC 2014). Capelin (Mallotus villosus) is one such sub-Arctic species that was historically rare (Carscadden et al. 2013), but has recently become Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00300-020-02707-1) contains supplementary material, which is available to authorized users. * Wesley R. Ogloff [email protected] 1
Fisheries and Oceans Canada, Winnipeg, MB R3T 2N6, Canada
University of Manitoba, Winnipeg, MB R3T 2N2, Canada
2
abundant, in Arctic regions. Capelin are small (
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