A new reproducible, minimally invasive fin-clamp enabling biologging and animal-borne video studies of juvenile sharks

Abstract Background Fine-scale studies of juvenile shark ecology remain limited because existing tags are often too large or invasive to be deployed on sharks <2 m length. Consequently, high-resolution behavioral and physiological data from early life stages are scarce, despite their ecological relevance for understanding juvenile shark ecology and vulnerability–information needed to inform conservation status and management of shark populations. Here, we provide a proof-of-concept for a reproducible, minimally invasive fin-clamp attachment to address this knowledge gap. We assess tag stability, the quality of collected data, and the impact on post-tagging recovery and added hydrodynamic drag. Results We tested two iterations of fin-clamps (prototype and miniaturized) on eight juvenile smooth hammerhead sharks (0.97 to 1.45 m total length) using a tri-axial acceleration, depth, temperature, and video logger, achieving retention from 16 h to 19 days. The miniaturized fin-clamp (reduced size, weight, and improved release mechanism) enabled easier attachments in under 10 s and resulted in more consistent retention times with a more stable tag position. Corrected accelerometry-derived tailbeat frequency closely matched video-based estimates, validating the quality of acceleration data across both iterations. Asymptotic models of tailbeat dynamics indicated post-release recovery within 1.6–2.7 h. We applied the “ jiggle method ” to shark accelerometry data to estimate swimming speed, which was then used to parameterize computational fluid dynamics simulations. Results revealed a non-linear decrease in tag-induced penalties relative to shark size: high drag penalties for sharks ≤1 m total length but markedly lower drag penalties for individuals ≥1.2 m, providing empirical guidance on practical size thresholds for future tagging. Conclusions The fin-clamp is a reproducible, minimally invasive system for high-resolution biologging of 1.2–2 m sharks, collecting unprecedented combined behavioral and video data for sharks of this life stage. By quantifying tag-induced hydrodynamic penalties and recovery periods, this study establishes empirical and ethical guidelines for its responsible application. The fin-clamp thus provides a tool to address current knowledge gaps constraining conservation and management of coastal shark populations, including identification of critical juvenile habitats, assessment of anthropogenic stressors, and characterization of movement patterns relevant to species recovery plans, with broader applicability to welfare-conscious biologging of other elasmobranch species.