Mapping the spatial distribution of chorusing oyster toadfish (Opsanus tau) with distributed acoustic sensing.

Passive acoustic surveys of soniferous marine communities can provide useful metrics for characterizing behavior, abundance, and ecological influences; however, they typically offer limited information about the spatial distribution of biological sources. Recent advances in distributed acoustic sensing (DAS) offer the potential to conduct wide-area surveys of bioacoustic activity that would be logistically infeasible with traditional hydrophone measurements. Here, a 2.2 km DAS cable deployed in Narragansett Bay, RI, was used to map the spatial distribution of oyster toadfish chorusing over a 24-h period during their spawning season in June 2025. A localization technique was developed where nearfield beamforming was performed along a rolling subaperture across the entire array, in order to account for the lack of coherence across widely spaced channels. This method allowed for the localization of biological hotspots, which were concentrated along a breakwater at the east side of Narragansett Bay. Long-term, single-hydrophone recordings also reveal seasonal and diel patterns for the same toadfish chorus, demonstrating how temporal data from traditional acoustic sensors can complement spatial DAS measurements.