Feeding ecology of the Greenland shark under different ice conditions

• Main Authors: Fisk, Aaron, McMeans, Bailey, Fryer, Brian, Idrobo, Carlos, Berkes, Fikret, Arts, Michael, Campana, Steven, Dennard, Susan
• Format: Dataset
• Language: English
• Published: Canadian Cryospheric Information Network 2016
• Subjects: Climate change; Feeding; Fisheries; Greenland shark; Habitats; Sea ice; Traditional Knowledge; International Polar Year-Feeding ecology of the Greenland shark under different ice conditions; Arctic; Nunavut; Baffin Bay; Baffin Island; Canada; Greenland; Cumberland Sound; Baffin; International Polar Year; inuit; ringed seal; Turbot; Zooplankton; Copepods
• Online Access: https://dx.doi.org/10.5443/11452; https://www.polardata.ca/pdcsearch/?doi_id=11452

To date, five sampling trips to Cumberland Sound have been completed, three during times of open water (July-August 2007, 2008, 2009) and two during times of ice cover (April 2008, 2009). Preliminary results indicate that the Greenland shark is feeding at a high trophic position and on benthic and pelagic resources, based on chemical tracers. The Greenland shark appears to feed on seal during both open water and ice cover, and does not appear to target different resources with season based on chemical tracers. However, some consumers, like ringed seals and predatory zooplankton appear to switch to a lower trophic level during open water, likely to exploit large number of Calanus copepods. Results from several satellite tags suggest that sharks are highly mobile, with regards to depth (i.e. vertical movement) and distance (i.e. horizontal movement). Based on our hierarchical models regarding turbot, we found a strong connection between environmental fluctuations and variations in fishery catch rates between 1987 and 2003. We hope to use the environmental predictors we were able to isolate in order to guide management decisions and improve efficiency of the Inuit fishery. The traditional knowledge survey revealed how Inuit make sense of the environment by using their generative logic product of extensive interaction with the arctic environment. To approach Inuit knowledge from this perspective becomes a platform to develop resource management strategies that encompass Inuit beliefs and values. We are currently completing sample analysis for chemical tracers, and hope to soon better understand both temporal and spatial variability in the feeding behaviour of Greenland sharks and other consumers inhabiting Cumberland Sound. : Purpose: The Greenland shark is the largest fish (up to 7 m) and one of only two shark species that regularly inhabit the arctic seas. Virtually every marine organism has been found in the stomach of these large sharks, including ringed seals. This sharks can be very numerous in the Arctic (> 40,000 sharks/year have been harvested in Baffin Bay), and thus their impact on ringed seal populations could be very significant. The continued health of marine mammal populations is critical to aboriginal people of the Arctic. Unfortunately, we know little about the role of the Greenland shark in arctic ecosystems or how this might vary with changing climatic or ice conditions. The major goal of this project is to determine the feeding ecology of the Greenland shark in Cumberland Sound, Baffin Island, Nunavut, Canada under different ice conditions (open water versus full ice cover), with a particular focus on assessing the importance of marine mammal predation. Additionally, we hoped to understand the environmental mechanisms driving catch rates in the Inuit turbot fishery of Cumberland Sound. We use a combination of chemical tracers and stomach contents to investigate Greenland shark feeding ecology, and hierarchical modeling to assess catch rates of the fishery through time. Greenland sharks are also satellite tagged to better understand their movement and habitat use. Finally, this project has integrated local/traditional Inuit knowledge on the Greenland shark and its ecosystem (Cumberland Sound). : Summary: As the largest fish and most prolific eater in the Arctic seas, the Greenland shark is a very unique vertebrate in the Arctic ecosystem. Given their diet, Greenland sharks hold a position in the food web similar to that of polar bears. Little is known about how these sharks behave or how their behaviour might shift in response to changes in climate. Given their importance in the Arctic food web, this project is assessing the feeding ecology and behaviour of the Greenland shark under different ice conditions to determine how different environments affect this fish. This assessment is being completed through the use of satellite tracking, chemical tracers, stomach contents and traditional knowledge.