Greenland shark (Somniosus microcephalus) stomach contents and stable isotope values reveal an ontogenetic dietary shift

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  • Julius Nielsen, Københavns Universitet, Greenland Institute of Natural Resources, National Aquarium Denmark, UiT The Arctic University of Norway
  • ,
  • Jørgen Schou Christiansen, UiT The Arctic University of Norway, Åbo Akademi University
  • ,
  • Peter Grønkjær
  • Peter Bushnell, Indiana University South Bend
  • ,
  • John Fleng Steffensen, Københavns Universitet
  • ,
  • Helene Overgaard Kiilerich
  • ,
  • Kim Præbel, UiT The Arctic University of Norway
  • ,
  • Rasmus Hedeholm, Greenland Institute of Natural Resources

Current knowledge on the feeding ecology of the Greenland shark (Somniosus microcephalus), a potential top predator in arctic marine ecosystems, is based on small sample sizes as well as narrow size ranges of sharks. Therefore, potential size-related feeding patterns remain poorly documented. Using stomach content data (N = 88) and stable isotope values of white muscle tissue (N = 40), this study evaluates the diet of sharks ranging in size from 81 to 474 cm (total length). The importance of prey categories ("Fish," "Mammal," "Squid," "Crustacean," and "Other") was evaluated based on the reconstructed prey biomass of the stomach contents. Stable isotope values of δ 13 C and δ 15 N ranged between -14.4 to -19.9‰ and 11.8 to 17.2‰, respectively. The importance of each prey category was estimated by the Index of Relative Importance (IRI). Our findings suggest that the smallest Greenland sharks (<200 cm) feed on lower trophic level prey, predominantly squids. Larger sharks (>200 cm) mainly feed on higher trophic level prey such as seals, epibenthic and benthic fishes including gadoids (Gadidae), skates (Rajidae), righteye flounders (Pleuronectidae), lumpfish (Cyclopteridae), wolffish (Anarhichadidae), and redfish (Sebastidae). Redfish were, however, only found to be important in the largest sharks sampled (>400 cm). In addition to demonstrating ontogenetic shifts in their feeding preferences, this study supports that Greenland sharks are capable of active predation on fast swimming seals and large fishes.

TidsskriftFrontiers in Marine Science
Antal sider11
StatusUdgivet - apr. 2019

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