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Marine Ecology Progress Series

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MEPS 511:265-284 (2014)  -  DOI: https://doi.org/10.3354/meps10897

The role of harp seals, fisheries and food availability in driving the dynamics of northern cod

Alejandro D. Buren1,3,*, Mariano Koen-Alonso2, Garry B. Stenson2

1Memorial University of Newfoundland, St. John’s, Newfoundland A1B 3X9, Canada
2Northwest Atlantic Fisheries Centre, Fisheries and Oceans Canada, PO Box 5667, St. John’s, Newfoundland A1C 5X1, Canada
3Present address: Northwest Atlantic Fisheries Centre, Fisheries and Oceans Canada, PO Box 5667, St. John’s, Newfoundland A1C 5X1, Canada
*Corresponding author:

ABSTRACT: The Atlantic cod Gadus morhua population off Newfoundland collapsed in the early 1990s due to over-exploitation, and despite marked reduction in fishing effort the stock remains depressed. Harp seal Pagophilus groenlandicus predation has been repeatedly proposed as an explanation for this lack of recovery, but other hypotheses include reduced prey availability and/or food quality (i.e. lack of capelin Mallotus villosus), as well as fisheries catches and environmental effects. Using a bioenergetics-allometric model, we gauged the relative contributions of these drivers on the lack of recovery and dynamics of the northern cod stock. Biomass dynamics were best explained by a combination of fisheries removals and capelin availability, whereas seal consumption was found not to be an important driver of the northern cod stock. Prey availability was linked to reduced somatic condition during the 1990s and 2000s. We discuss evidence that suggests that cod may be experiencing depensatory dynamics, but not related to a ‘predator pit effect’. Our study suggests that trophic control is bottom-up, and that a depressed capelin stock could be a serious impediment for cod rebuilding.


KEY WORDS: Impact · Predation · Predator-prey · Marine mammal ·Groundfish · Forage fish · Predator pit


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Cite this article as: Buren AD, Koen-Alonso M, Stenson GB (2014) The role of harp seals, fisheries and food availability in driving the dynamics of northern cod. Mar Ecol Prog Ser 511:265-284. https://doi.org/10.3354/meps10897

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