Fine-scale residency and temperature-driven habitat selection in a migratory shark species

Abstract Many marine species exhibit complex and diverse movements that vary across spatial and temporal scales. These movements must be accounted for when designing effective management and conservation efforts. While environmental cues such as temperature and salinity have been shown to influence the movements of mobile species, it is increasingly documented that social factors can also influence space use and population behaviour. Understanding how various factors influence movement enhances our ability to predict the space use of highly dynamic ocean species. Spurdog ( Squalus acanthias ), known for their tendency to aggregate and use of both coastal and oceanic environments, are an ideal model species for studying drivers of movement. To investigate movement and habitat selection in spurdog, we conducted an acoustic telemetry study from June 2016 to July 2017, tagging 51 spurdog in a partially enclosed fjordic sea loch on the west coast of Scotland. The thermal profile of Loch Etive was recorded to complement the movement data. Our study revealed temperature as a pivotal driver of movement and habitat selection in spurdog, with the unique thermal environment of the fjord enabling year-round residency at a previously undocumented spatial scale, suggesting that such habitats may be especially important for mobile marine species. This study demonstrates the importance of understanding environmental influences on space use and movement to develop effective, climate-resilient management strategies for spurdog and other mobile marine species.