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Marine Ecology Progress Series

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MEPS 744:147-160 (2024)  -  DOI: https://doi.org/10.3354/meps14669

Ontogenetic shifts in isotope-inferred trophic ecology of Atlantic bluefin tuna Thunnus thynnus in Atlantic Canada

Jacob Burbank1,*, Brianne Kelly2, Alex Hanke3, Hugues P. Benoît4, Michael Power5

1Gulf Fisheries Centre, Fisheries and Oceans Canada, 343 Université Avenue, Moncton, New Brunswick E1C 9B6, Canada
2World Wildlife Fund Canada, 410 Adelaide St. West, Toronto, Ontario M5V 1S8, Canada
3St. Andrews Biological Station, Fisheries and Oceans Canada, 125 Marine Science Drive, St. Andrews, New Brunswick E5B 0E4, Canada
4Maurice Lamontagne Institute, Fisheries and Oceans Canada, 850 Route de la Mer, Mont Joli, Quebec G5H 3Z4, Canada
5Department of Biology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
*Corresponding author:

ABSTRACT: Upper trophic level predators can greatly influence the dynamics and productivity of forage fish species. Quantifying this influence requires information on prey consumption; however, establishing feeding habits of highly mobile predators is particularly challenging. Stable isotopes of carbon and nitrogen (δ13C and δ15N) have been applied to characterize the trophic ecology of Atlantic bluefin tuna Thunnus thynnus (ABFT) in several important regions; however, applications in Canada are lacking. Here, we used δ13C and δ15N values of ABFT muscle tissue collected in 2014-2018 on 2 important foraging grounds along the coast of Atlantic Canada to evaluate the temporally integrated trophic ecology of this ecologically and commercially important species. Populations of some small pelagic fish species in these areas have been depleted, and predation by ABFT is considered a potentially important contributor. Isotopic diet reconstructions found that Atlantic mackerel were the dominant prey in the southern Gulf of St. Lawrence, and a combination of Atlantic herring and sandlance were the most dominant prey consumed on the Scotian Shelf. Diet reconstructions identified an ontogenetic shift in prey consumption, with more sandlance consumed by smaller ABFT and a shift to higher consumption of Atlantic mackerel and Atlantic herring as fish increased in size. Isotopic niche overlap indicated relatively high overlap for adults among years, suggesting that ABFT did not show substantial inter-annual variation in their trophic ecology. Overall, the study provides insight into the trophic ecology of ABFT along the Atlantic Coast of Canada that can be integrated into investigations of predator impacts on depleted mackerel and herring populations.


KEY WORDS: Trophic ecology · Diet · Commercial fish · Predator · Ecosystem-based fisheries management · δ13C · δ15N


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Cite this article as: Burbank J, Kelly B, Hanke A, Benoît HP, Power M (2024) Ontogenetic shifts in isotope-inferred trophic ecology of Atlantic bluefin tuna Thunnus thynnus in Atlantic Canada. Mar Ecol Prog Ser 744:147-160. https://doi.org/10.3354/meps14669

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