Seasonal residency, activity space, and use of deep-water channels by Greenland sharks (Somniosus microcephalus) in an Arctic fjord system

Abstract

As Arctic ecosystems become increasingly vulnerable to climate- and human-induced stressors, effective marine management will rely on the characterization of fish movements. Over a six-year study period, the movements of 65 Greenland sharks (Somniosus microcephalus) (41 males, 24 females; mean LT = 2.48 ± 0.50 m) were monitored using static acoustic telemetry. Shark presence in a typical deep-water fjord was restricted to the summer open-water period. Residency duration varied based on age class (juvenile, n = 17; subadult, n = 48); however, activity space size and extent were comparable. A quarter of tagged sharks (n = 16) returned to the system in subsequent years after tagging, with individuals redetected for a maximum of 4 years. Movements between coastal and offshore waters occurred primarily via a deep-water channel with sharks detected along the channel banks. These multiyear data depict how a potentially vulnerable Arctic predator utilizes a deep-water fjord in the context of the regional development of community inshore and offshore commercial fisheries.