MEPS 497:285-301 (2014)  -  DOI: https://doi.org/10.3354/meps10578

Trophic niche partitioning among sympatric baleen whale species following the collapse of groundfish stocks in the Northwest Atlantic

Katherine Gavrilchuk1,2,6,*, Véronique Lesage3,6, Christian Ramp2, Richard Sears2, Martine Bérubé4, Stuart Bearhop5, Gwénaël Beauplet1,6 

1Department of Biology, Université Laval, 1045 ave de la Médecine, Québec, Québec G1V 0A6, Canada
2Mingan Island Cetacean Study, 284 Green St., Saint Lambert, Québec J4P 1T3, Canada
3Maurice Lamontagne Institute, Fisheries and Oceans Canada, 850 route de la Mer, Mont-Joli, Québec G5H 3Z4, Canada
4Marine Evolution and Conservation, Centre of Evolutionary and Ecological Studies, University of Groningen, Broerstraat 5,
9712 CP Groningen, The Netherlands
5Centre for Ecology and Conservation, University of Exeter, Cornwall Campus, Treliever Rd, Penryn, Cornwall TR10 9EZ, UK
6Present address: Québec-Océan, Université Laval, 1045 ave de la Médecine, Québec, Québec G1V 0A6, Canada
*Corresponding author:

ABSTRACT: Ecologically similar species may coexist when resource partitioning over time and space reduces interspecific competition. Understanding resource use within these species assemblages may help predict how species relative abundance might influence ecosystem functioning. In the Gulf of St. Lawrence, Canada, 4 species of rorqual whales (blue Balaenoptera musculus, fin B. physalus, minke B. acutorostrata and humpback Megaptera novaeangliae) coexist during the summer feeding period. They can be observed within hundreds of meters of one another, suggesting an overlap in ecological niches; yet fine-scale habitat use analyses suggest some resource partitioning. While major ecological changes have been observed in marine ecosystems, including the Gulf of St. Lawrence, we have little understanding of how the removal of predatory fish might cascade through ecosystems. Here, we take advantage of a 19 yr tissue collection subsequent to a fishery collapse (which occurred in 1992) to investigate trophic niche partitioning within a guild of rorqual whales following the loss of a key ecosystem component, groundfish. We analyzed stable isotope ratios for 626 rorqual individuals sampled between 1992 and 2010. Using Bayesian isotopic mixing models, we demonstrated that the 4 rorqual species segregated trophically by consuming different proportions of shared prey. An overall increase in δ15N values over the study period (post groundfish collapse), particularly for fin and humpback whales, suggested a progressive use of higher-trophic level prey, such as small pelagic fish, whereas the stability of blue whale diet over time confirmed their specialized feeding behaviour. This study provides the first long-term assessment of trophic ecology among rorqual populations on this Northwest Atlantic feeding ground, and evidence for differential resource use among large marine predators following ecosystem change.


KEY WORDS: Trophic niche · Interspecific · Stable isotopes · δ13C · δ15N · Rorqual · Ecosystem change


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Cite this article as: Gavrilchuk K, Lesage V, Ramp C, Sears R, Bérubé M, Bearhop S, Beauplet G (2014) Trophic niche partitioning among sympatric baleen whale species following the collapse of groundfish stocks in the Northwest Atlantic. Mar Ecol Prog Ser 497:285-301. https://doi.org/10.3354/meps10578

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