Movement, depth and temperature preferences of an important bycatch species, Arctic skate Amblyraja hyperborea, in Cumberland Sound, Canadian Arctic

Abstract

Climate change and increasing exploitation of resources are threats to Arctic marine species. Knowledge of vertical and horizontal movements of species is critical to understand their spatial ecology to inform effective ecosystem-based management. Recently, Arctic skate Am bly - raja hyperborea, a largely unstudied, cold water, deep-dwelling species has become a common bycatch species in groundfish fisheries throughout the Arctic. To investigate Arctic skate move- ment, depth and temperature preferences, 9 adults were tagged with pop-off archival transmitting tags in Cumberland Sound, Canadian Arctic, in August 2010 and August 2011 for 40 to 100 d. Of the 9 individuals tagged, 5 transmitted reliable data to satellites. Arctic skate occupied waters between 1.2 and 2.9°C (2.5 ± 0.1°C; mean ± SD) and 317 and 1355 m (944 ± 154 m). Tags popped off within a 37 km straight-line distance from the tagging location, indicating limited horizontal dispersal during the pre-ice formation period of late summer and early winter. Although mixed- effect models indicated that occupied depth varied with the diel cycle, the relationship was weak and depth variation was small, suggesting diel vertical migration does not appear to be a common strategy. Activity levels, estimated from detailed time series depth profiles, indicated multiple behaviours from resting to large depth changes (>150 m per 0.5 h). Given the levels of bycatch of this species in developing Arctic fisheries, overlap in habitat with the commercially valuable Greenland halibut Reinhardtius hippoglossoides and historical declines of skate populations, it is recommended that the IUCN Red List designation of 'Least Concern' for the Arctic skate be re-evaluated.