Inconspicuous, recovering, or northward shift: status and management of the white shark (Carcharodon carcharias) in Atlantic Canada

Abstract

<jats:p> Although white sharks (Carcharodon carcharias) are considered rare in Atlantic Canada waters, recent sighting records indicate a potentially increasing presence. We combine sighting data with satellite telemetry tracks of large juvenile/adult white sharks tagged in U.S. (n = 9) and Atlantic Canada waters (n = 17) to show seasonal white shark presence and distribution in Atlantic Canada, returns by individuals over multiple years, and high site fidelity to the region. Telemetry data indicate that white sharks are a more common and consistent occurrence in Canadian waters than previously thought, presenting two potential scenarios: 1) tagging technology is revealing white shark presence that was historically cryptic, and/or 2) a northward range expansion of white sharks in the Northwest Atlantic, potentially due to climate change, population recovery, and/or increasing pinniped prey. Given combined sighting and telemetry data indicate a current need for proactive management of white sharks in Atlantic Canada waters, we propose the basis for a management action plan, addressing conservation priorities, management goals and research incentives while considering the potential for human-shark interactions. </jats:p>

First Application of 360-Degree Camera Technology to Marine Predator Bio-Logging

“…The remote monitoring of marine megafauna is made difficult by the logistical challenges of working in the marine environment, as well as the operational limits of the most recent electronic tag technologies. The proliferation of satellite-based telemetry and its application to studying the behavior and physiology of marine megafauna have greatly expanded our ability to describe basic, yet poorly understood elements of these species' biology (Hart and Hyrenbach, 2009;Hussey et al, 2015;Sequeira et al, 2018), and are now being used to better understand the risks they face (e.g., Queiroz et al, 2019) and to gauge how they will respond to a warming ocean (e.g., Bastien et al, 2020). Satellite-based telemetry is, however, limited in its ability to store and transmit substantial volumes of data, and therefore it cannot fully resolve the relationship between an individual animal's state and the external environment.…”

An illicit artisanal fishery for North Pacific white sharks indicates frequent occurrence and high mortality in the Gulf of California

“…More recent abundance could be driven by an increasing ENP population, which has been suggested (Lyons et al, 2013;Tinker et al, 2016) though estimates of population size vary widely (Burgess et al, 2014;Chapple et al, 2011). This has been observed in the North Atlantic, where increasing population size and/or prey recovery has been linked to increased regional abundance, which was cryptic and underestimated prior to satellite tracking (Bastien et al, 2020;Skomal et al, 2017). While studies combining PSATs and acoustic tags have revealed crucial new information for ENP white sharks (Boustany et al, 2002;Chapple et al, 2016;Del Raye et al, 2013;Domeier & Nasby-Lucas, 2008;Jorgensen et al, 2010Jorgensen et al, , 2012aJorgensen et al, , 2012bWeng et al, 2007;White et al, 2019b), only sharks tagged with SLRT (e.g., SPOT) tags have provided continuous movement information over multiple years (Nasby-Lucas & Domeier, 2019), including movements into the Gulf (Domeier, 2012;Domeier & Nasby-Lucas, 2013).…”

“…for measurement and biological sampling; however, no collection of white shark data was observed. Finally, satellite tracking studies in other ocean basins have shown that white shark presence can be underestimated by observational methods (Bastien et al, 2020). Any of these dynamics may have limited regional white shark observations in the Gulf.…”

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“…Behaviors were classified as transient when scores were ≤1.25 and resident when ≥1.75. As SPOT tag transmissions can be irregular in time, complete tracks for individuals were segmented for any time gaps >20 days (Bastien et al, 2020) prior to model fitting. Resulting segments of less than 10 locations or shorter than 5 days were not included in subsequent analyses.…”