Getting a Bigger Picture: Combining Acoustic and Satellite Telemetry to Document Migration and Habitat Use of Immature Female Blue Sharks (Prionace glauca)

We initiated a program to track and document the habitat use of female juvenile blue sharks (Prionace glauca) off the coast of Nova Scotia. Forty sharks (20 per year) were angled, acoustically tagged and released in summer of 2013 and 2014, and 39 of them were detected post-release showing that they had survived catch-and-release angling. In summer and autumn, the animals mostly occupied the continental shelf off Nova Scotia at distances of about 20-40 km offshore, but moved away to unknown  areas to overwinter. Acoustically tagged animals tagged in 2013 (60%) and 2014 (32%) were detected off Halifax in the summer of the year after their initial tagging, showing certain individuals exhibited site fidelity to precise portions of the region. However, other tagged sharks were detected in the Gulf of Maine, Gulf of St. Lawrence and off Sable Island and no animal was detected for more than two years near Halifax. Limited satellite tag data suggests that the observed site fidelity may be “broader” than suggested by the acoustic tags, that the fish that return to the Halifax region in years after tagging may overwinter close by, and that those that don’t return show a different migration path.