Multi‐Platform Deployments of Low‐Cost Devices for Cetacean Passive Acoustic Monitoring

ABSTRACT Effective monitoring of cetacean occurrence is essential, as their populations face multiple anthropogenic threats, including shipping strikes, noise pollution, fisheries bycatch and habitat degradation. Passive acoustic monitoring (PAM) is a reliable non‐invasive method for detecting cetaceans underwater, yet its wider adoption has been constrained by the availability and cost of equipment. Recent advances in cost‐effective, user‐friendly devices offer new opportunities for expanding acoustic data collection. In this study, low‐cost acoustic recorders and underwater cameras were deployed across a range of fixed and mobile platforms in the Western Mediterranean, including fishing gear (drifting pelagic longlines and trammel nets), anchored Fish Aggregating Devices (aFADs) and boat‐based observational surveys. These deployments demonstrate the practical potential for opportunistic cetacean presence data collection through collaboration with non‐academic stakeholders, including the fishing sector and non‐profit organisations. We report visually confirmed acoustic encounters of the sperm whale ( Physeter macrocephalus ) and four dolphin species (family Delphinidae ), demonstrating that affordable PAM recorders can be used to capture cetacean vocalisations such as echolocation clicks and whistles. Despite certain limitations, these instruments can enhance the accessibility of PAM to a wide range of users, facilitating cetacean presence data collection and providing insights into interactions with human pressures, particularly fisheries. Moreover, low‐cost devices demonstrate strong potential for integration into citizen science initiatives, offering a scalable solution to reduce operational costs and allow underwater soundscape data collection across large spatial scales. As PAM gains increasing recognition within ocean observing frameworks, our study underscores the value of low‐cost PAM technologies in supporting efforts to document cetacean occurrence while fostering more inclusive approaches to marine biodiversity monitoring.