Conservation implications of white shark ( Carcharodon carcharias) behaviour at the northern extent of their range in the Northwest Atlantic

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Bowlby, Heather D., Joyce, Warren N., Winton, Megan V., Coates, Peterson J., Skomal, Gregory B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2022
• Subjects: Northwest Atlantic
• Online Access: http://dx.doi.org/10.1139/cjfas-2021-0313; https://cdnsciencepub.com/doi/full-xml/10.1139/cjfas-2021-0313; https://cdnsciencepub.com/doi/pdf/10.1139/cjfas-2021-0313

Assessing progress for the endangered white shark ( Carcharodon carcharias) relative to Canadian conservation objectives requires understanding distribution patterns. From the largest tagging data set in the Northwest Atlantic (2010–2020; 272 deployments), we determined the proportion of the population detected in Canadian waters, characterized patterns in occupancy, and explored the behavioural characteristics of animals while in Canadian waters versus elsewhere in their range. The component of the population detected in Canadian waters annually was highly variable, yet proportionately small. Juveniles and subadults were 4.7 and 3.4 times more likely, respectively, to move northward than adults. From June to November, all pop-up satellite archival tagged white sharks remained primarily in coastal locations within the 200 m bathymetric contour and exhibited shallow diving behaviour within the top 100 m of the water column. However, individuals in Canadian waters experienced a more restricted temperature range and used proportionately less of the water column. Accounting for behavioural effects on distribution when predicting habitat use from environmental associations will become critical to evaluate the population-level impact of recovery actions implemented under Canadian legislation.