Abstract
Passive acoustics is a tool to monitor behavior, distributions, and biomass of marine invertebrates, fish, and mammals. Typically, fixed passive acoustic monitoring platforms are deployed, using a priori knowledge of the location of the target vocal species. Here, we demonstrate the ability to conduct coastal surveys of fish choruses, spatially mapping their distributions with an autonomous surface vehicle. For this study, we used an autonomous Liquid Robotics Wave Glider SV3 equipped with a Remora-ST underwater acoustic recorder and hydrophone. The exploratory 15-day deployment transited through three marine reserves, resulting in approx. 200 hours of passive acoustic recordings, and revealed five distinct fish choruses from La Jolla to Capistrano Beach, CA (approx. 80 km separation), each with unique acoustic signatures. Choruses occurred in the evening hours, typically in the 40 to 1000 Hz band. There was a lack of both temporal and frequency partitioning amongst the choruses, but some choruses exhibited distinct spatial niches by latitude and water temperature. These results suggest that the mobility of the Wave Glider allows for persistent surveys and studies that otherwise may be too challenging or costly for stationary or ship-based sensors; a critical consideration for documenting biological activity over large spatiotemporal scales, or sampling of nearshore marine reserves.
Highlights
Sound production plays an important role in the life history of many marine animals including invertebrates, fish and mammals (Tyack, 1998)
Knowledge of the location of fish choruses and their associated spawning aggregations is vital to the implementation of fisheries protection measures
Five distinct fish choruses were recorded by our Wave Glider equipped with a passive acoustic recorder transiting from La Jolla to Capistrano Beach, CA, confirming that the Wave Glider is a potential tool for future fisheries passive acoustic work in this region
Summary
Sound production plays an important role in the life history of many marine animals including invertebrates, fish and mammals (Tyack, 1998). Fish in some spawning aggregations are known to vocalize during certain time periods over a few hours (Cato, 1978). This “chorus” results in a significant increase in ambient sound pressure levels due to the large number of fishes producing sound at the same time. Passive acoustics can be used to record sound production. It enables monitoring of soniferous animal presence and behavior over large temporal (i.e., on the order of years) and spatial (i.e., on the order of 10s km) scales because of the ocean’s transparency to sound (Jensen et al, 2011). While passive acoustic monitoring can generate long temporal records at a single location, the spatial
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