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Abstract: An ecosystem model was created for the Hudson Bay region, Canada, for 1970–2009, aiming to identify ecosystem linkages while bringing together research from diverse sources. The model presented here in detail includes 40 functional groups. Using the Ecopath with Ecosim (EwE) modelling framework we are able to provide estimates for previously unknown parameters such as the biomass of fish species. In addition to providing a comprehensive overview of the trophic dynamics within the system, temporal simulations mimic the changes known to occur in the region. The model is fitted to catch data for the Hudson Bay region, along with environmental drivers (sea surface temperature and ice cover). Declines in sea ice and increases in the spring bloom facilitate a shift from benthic to pelagic pathways in lower trophic levels of the model. Polar bears, bearded seals and eastern Hudson Bay belugas demonstrate the greatest declines due to hunting mortality. Additional model scenarios testing the model sensitivity to hunting and environmental pressures indicate higher trophic level organisms (marine mammals) are more responsive to hunting pressures, while lower trophic levels (benthos, zooplankton) are primarily influenced by climate drivers. While marine mammals are the most well studied, the region lacks comprehensive assessments on fish and other mid trophic level organisms. This model captures many patterns present in the system, while identifying gaps in existing data for future research and provides the first step for future research simulating climate change and its impacts on the Hudson Bay ecosystem. [Copyright &y& Elsevier]

Abstract: Simulations testing the future impacts of harvest and climate change to the Hudson Bay marine ecosystem were created utilizing an existing Ecopath with Ecosim model (Hoover et al., 2013). Building on past simulations depicting known changes to the region, a suite of future scenarios was constructed to include a variety of climate change and harvest levels. Previously identified ecosystem shifts favoring pelagic species (zooplankton, planktivorous fish) over benthic species (benthos, benthic feeding fish), are further exaggerated under future climate scenarios. Environmental forcing was incorporated to mimic the declines in sea ice, and increases in temperature causing shifts in the food web from an ice algae–benthos–benthic fish pathway to a spring bloom–zooplankton–planktivorous fish dominated ecosystem. Future simulations indicate some stocks are unable to sustain current harvest levels until the end of the future simulations (2069), and may be extirpated (narwhal, eastern Hudson Bay beluga, polar bears, and walrus). Larger populations of marine mammals (ringed seals and western Hudson Bay beluga) are identified to increase in biomass even under extreme harvest and climate scenarios (a high future climate scenario coupled with a doubling in harvest rates). Harvest mortality is highlighted as an important stressor for some marine mammal stocks and should be investigated further when setting future harvest or conservation targets. [Copyright &y& Elsevier]