Hello MARMAM community, I am pleased to share our paper recently published Open Access in the Journal of the Acoustical Society of America (JASA): Gemma Veneruso, Lucille Chapuis, Gordon D. Hastie, Lewis Le Vay and Line S Cordes (2025) "Tidal flow masks acoustic detections of harbour porpoises (*Phocoena phocoena*): Implications for passive acoustic studies of cetaceans. https://doi.org/10.1121/10.0039560 ABSTRACT: Passive acoustics is widely used to detect vocalising cetaceans, yet in tidal environments, strong currents facilitate sediment transport, creating “flow noise” that may mask signals and bias detection ranges. Although detection ranges are known to vary with background noise, the magnitude and spatiotemporal scale of such variation in tidal environments remain poorly quantified. Flow noise may fluctuate within tidal cycles and across small spatial scales, with consequences for estimating cetacean occurrence. To examine this, we tested the effects of flow noise on harbour porpoise (Phocoena phocoena) echolocation click detection, from data collected from an array of moored recorders in a tidal stream environment. Flow noise overlapping with porpoise clicks varied by up to 29 dB in mean sound pressure levels within tidal cycles ( 12 h). Differences between sites<500 m apart were also significant, and modelled relationships between porpoise occurrence and tidal flow speed changed when a fixed detection threshold was applied. These findings show that flow noise in tidal habitats is heterogeneous across space and time, which may bias estimates of cetacean occurrence and distribution. Accounting for flow noise is therefore essential in ecological studies and is particularly relevant in environmental assessments of tidal energy developments. With best wishes, Gemma Veneruso