Effects of hunting, fishing and climate change on the Hudson Bay marine ecosystem: I. Re-creating past changes 1970–2009

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.

► A Past model of the Hudson Bay marine ecosystem was driven with climate and harvest changes.
► Climate drivers show influence lower trophic levels.
► Harvest is more influential on predators than climate changes.
► Changes in bentho-pelagic coupling are observed in the model.
► Some marine mammal stocks cannot withstand current harvest levels.