The European tracking network through time: united efforts to advance aquatic conservation in Europe.

Biotelemetry networks have transformed our capacity to study the movements and ecology of aquatic animals, yet their development has been geographically uneven over time. While North America and Australia (among others) already hosted mature, well-coordinated infrastructures in the early 2000s, Europe has long lacked a formal framework for collaboration. The European Tracking Network (ETN) emerged in 2017 as a grassroots response to this gap. Since then, ETN has grown tremendously and has become a sustainable network with a central data system and research infrastructure installed all across Europe, enabling collaborative research on a multitude of species and environments while maintaining a strong track record in capacity building. ETN operates through a decentralised model in which national and regional partners lead infrastructure deployment while contributing data to a shared data platform that adheres to FAIR principles and supports collaborative tools, interactive dashboards and a dedicated R-package. ETN has successfully enabled a growing body of transnational research on species movements, habitat connectivity and behavioural ecology, as well as meta-analyses that maximise data reuse and help reduce animal use. At the same time, ETN faces challenges common to large-scale telemetry initiatives, including the need for stable funding, potential equipment incompatibility, the risk of false-positive detections, a potential lack of community buy-in, and ongoing discussions around data ownership and proper attribution. By working proactively with the community and stakeholders, ETN could address most of these potential challenges through the development of open transmission protocols, by aligning data policies with community needs, and by enhancing stakeholder engagement. Looking ahead, ETN is positioning itself at the interface of digital twins, machine learning, multisensor integration and responsible stewardship. Together, these efforts are transforming ETN into a key component of a global aquatic animal observatory, supporting evidence-based management and conservation across European aquatic ecosystems and beyond. Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s40317-026-00475-z.