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

Abstract

Assessing progress for the endangered white shark (Carcharodon carcharias) relative to Canadian conservation objectives requires understanding distribution patterns. From the largest tagging dataset 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 vs elsewhere in their range. The component of the population detected in Canadian waters annually was highly variable, yet proportionately small. Juveniles and sub-adults were 4.7 and 3.4 times more likely, respectively, to move northward than adults. From June to November, all PSAT-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.

Direct measurement of cruising and burst swimming speeds of the shortfin mako shark (Isurus oxyrinchus) with estimates of field metabolic rate

“…Knowledge of the physiological ecology of large pelagic fishes is particularly important for revealing mechanisms that underpin habitat suitability, species distributions and ecological functioning (Bernal et al ., 2010 ), information which can inform the conservation of threatened populations (McKenzie et al ., 2016 ; Vedor et al ., 2021 ). For example, behaviours and activity levels occurring at fine spatio‐temporal scales are likely to be key drivers of trophic interactions, which will affect habitat selection and thereby distributions (Andrzejaczek et al ., 2019 ; Bowlby et al ., 2022 ), ultimately driving spatial overlap with anthropogenic activities such as fishing (Queiroz et al ., 2016 ; Queiroz et al ., 2019 ; Queiroz et al ., 2021 ). Nonetheless, due to the inherent difficulties in studying large animals in open‐ocean environments, data on the fine‐scale behaviours and energetics of apex predators such as sharks are often lacking (Lawson et al ., 2019 ; McKenzie et al ., 2016 ; Payne et al ., 2015 ; Sims, 2003 ).…”