Dear MARMAM community, My co-authors and I are pleased to share our new open-access publication in Ecological Indicators. Benoit, V., Authier, M., Gilles, A. (2026). Developing a quantitative indicator to monitor cetacean distributional change. Ecological Indicators 187, 114897. https://doi.org/10.1016/j.ecolind.2026.114897 We used a workflow that combined simulations and modelling in a “virtual ecology” approach to understand the impact of error or uncertainty on candidate metrics for a quantitative indicator for cetacean distribution. The workflow will be tested during the upcoming OSPAR Intermediate Assessment 2029. ABSTRACT Monitoring the distribution of cetaceans is a priority in marine conservation. However, current ecosystem-wide assessments lack indicators on distribution: cetacean distribution maps fall short of quantitative reporting purposes. The need for a quantitative distribution indicator has been emphasised in the EU’s Marine Strategy Framework Directive and by different expert groups. We tested candidate metrics, including Measures of Centre and of centralisation, to summarise distribution maps into numbers whose interpretation is straightforward for policy-makers. We emulated Distance Sampling and Density Surface Modelling methodologies to estimate cetacean distributions from dedicated surveys to assess the impact of observation noise and estimation uncertainty on these candidate metrics. To understand the impact of error or uncertainty, we used a workflow that combined simulations and modelling in a “virtual ecology” approach. The Geometric Median, a Measure of Centre, and a metric of centralisation, retained the most important pieces of information from distribution maps, while also having limited sensitivity to estimation error. Our results reflect how a trade-off between the informativeness of a metric and its robustness against estimation error is unavoidable for an indicator to be policy relevant, and that appropriate thresholds need to be calibrated for its interpretation. In the context of large scale surveys, the “virtual ecologist” approach provided a practical workflow to test the accuracy of our proposed indicators, to estimate type-I error rates and calibrate threshold values. Our results, including the workflow, are a step towards having a fully operational indicator on cetacean distribution in the Northeast Atlantic. Please do not hesitate to contact us if you have any questions. Best, Anita -- Dr. Anita Gilles University of Veterinary Medicine Hannover, Foundation Institute for Terrestrial and Aquatic Wildlife Research (ITAW) Werftstr. 6 | 25761 Büsum Germany Phone: +49 (0)511-8568177 Fax: +49 (0)511-8568181 anita.gilles@tiho-hannover.de https://www.tiho-hannover.de/en/itaw/beschaeftigte/beschaeftigte-buesum/anit...