The shifting pelagic ecosystem: monitoring and synthesis
The small Polar cod (Boreogadus saida) is by far the dominant forage fish in Arctic seas where it typically represents 95% of all offshore fishes. It is responsible for up to 75% of the transfer of energy (in the form of lipids) from zooplankton to other fishes, seabirds, and marine mammals. Hence, many of the services provided to local communities by the pelagic ecosystem are rooted in this single pivotal fish. The main zooplankton prey of the larval, juvenile and adult stages of Polar cod are copepods of the genera Pseudocalanus and Calanus. As the extreme conditions of Arctic seas relax under climate warming, the replacement of Polar cod by boreal species such as the sand lance (Ammodytes pacificus), capelin (Mallotus villosus) and ice lanternfish (Benthosema glaciale) will signal a shift of the Arctic ecosystem to more productive North-Atlantic and North-Pacific boreal ecosystems. When will this shift occur? What are the expected impacts of this shift on traditional and emerging ecosystem services? Will significant stocks of commercial species such as Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) develop in the Canadian Arctic as seen recently around Svalbard? Our previous studies of how ongoing shifts in sea-ice regime and the production of microalgae (the food of copepods) cascade on copepods and Polar cod have provided powerful insights into these questions. In particular during ArcticNet’s Cycle II, we (1) described how the development of an autumn phytoplankton bloom disrupts the overwintering cycle of Calanus copepods; (2) documented the establishment and reproduction of the Pacific sand lance in the Beaufort Sea and Canadian Archipelago and the ice lanternfish in Baffin Bay; and (3) discovered a surprisingly strong statistical relationship between ice break-up date in the spring-summer and the ensuing biomass of Polar cod juveniles in the fall. Overall, 49 publications with international teams and contributing to three IRISes describe the pelagic ecosystems of arctic/subarctic seas, focusing on how the existing assemblages of ice algae, phytoplankton, zooplankton and fish will benefit initially from the regression of the ice cover and the warming of the surface ocean, before being replaced progressively over the century by Atlantic and Pacific assemblages.
In continuity with these advances, this project will determine how fisheries resources in Baffin Bay could be impacted by the replacement of Polar cod by Atlantic forage fishes. Precisely, the lipid profiles and contaminant loads of Polar cod, sand lance, capelin and ice lanternfish will be compared in Baffin Bay. Samples will be obtained thanks to a close collaboration with local fishers through project 14 (Geoffroy), as well as from the annual ArcticNet expedition on the CCGS Amundsen. State-of-the-art analyses of lipids and contaminants will be conducted in collaboration with project 59 (Stern). We will also collaborate with the above projects to train Inuit experts in the sampling and study of pelagic fisheries resources in Baffin Bay. An indigenous graduate student has been recruited (Yoan Awashish Soucy, MSc to be turned into PhD). Two undergraduates (Tommy Pontbriand and Pascale Caissy) will assist this summer and will later recruit as graduate students on the project. This proposal is directly leveraged by my NSERC and CRC grants; the upgrading of the EK60 fish/zooplankton sonar of the Amundsen to the cutting-edge EK80 frequency-profiling sonar that can differentiate pelagic fish thanks to their acoustic signatures (CFI-MSI); and an increased CFI-MSI contribution to the operation of the CCGS Amundsen to Amundsen Science.