Methods for tagging whale sharks: insights into performance and best practices with a focus on clamp attachments

Biologging and telemetry have transformed our understanding of marine megafauna movement ecology. Yet, methodological constraints continue to limit data quality and deployment duration. Devices recording whale shark (Rhincodon typus) behaviours and movements have been used for decades, but they remain challenging to deploy and vary in success. Recently, spring-loaded clamp-based systems have emerged as one of the most widely used approaches to attach electronic tags to the fins of this globally endangered species. Currently, however, no consensus guidelines exist as to how to optimise this approach, potentially leading to continued underperforming deployments limiting analysis potential. Here, we synthesise experiences with clamp-based tagging worldwide through a targeted survey of whale shark researchers. We explore performance and challenges with a view to propose current best practices in the field.

Whale shark researcher responses to the survey highlighted clamp-based systems as a practical and more widely applicable approach than drill-based methods, which are often used to secure tags to other large sharks. They also noted that clamps have greater retention potential and are suitable for a wider range of tags compared to dart-based methods, but are still constrained by design, placement, and deployment conditions. Researchers used a variety of materials and designs to build their own clamps, often facilitated by direct collaboration with each other or key manufacturers. Clamps produced highly variable outcomes, ranging from successful long-term satellite transmissions over 200 days and short-term biologging for 48 h at 20 Hz, to premature detachment and cases of fin damage. For long-term clamps, changes in position on the fin allowed for more stable satellite transmissions over time. Some clamp designs achieved data quantity and quality close to that of drilled deployments, demonstrating their potential to rival traditional methods while offering a less invasive approach. Results emphasised the ongoing need for technological refinement and rigorous evaluation of clamp performance and associated impacts.

Based on collective insights, we present a unified approach to clamp design and positioning, and identify key priorities for advancing this attachment technology, such as aiming for positions b-2 and c-2 on the fin and ensuring the clamp bridge distance (always between 30 and 50 mm) and tension are matched to shark size. Optimising clamp systems could substantially improve our ability to generate high-quality, long-duration movement data while minimising tagging impacts on the animal where possible. This could enhance ecological and conservation research outcomes for endangered whale sharks, with broader implications for tagging other large-bodied marine megafauna.

The online version contains supplementary material available at 10.1186/s40317-026-00462-4.