Looking for the elusive fish farts: Can we monitor Atlantic herring in the Gulf of Maine with passive acoustics?

Herring (Clupea pallasii and Clupea harengus) produce Fast Repetitive Tick (FRT) sounds by expelling air bubbles in the water through their anal duct. Theoretical and experimental studies have shown that FRT sounds from compact schools of herring have the potential to be detectable up to 1 km away from an acoustic recorder in calm conditions. While FRT sounds have been recorded in the wild in the Northeast Pacific and in the Northeast Atlantic, they have never been detected in the Northwest Atlantic where herring are also present. In this study, we investigated whether passive acoustics can be used to detect the presence of Atlantic herring FRT sounds in the Gulf of Maine to help inform fisheries management measures in the region. We examined passive acoustic data collected in the Gulf of Maine since 2014, focusing on the detection of individual FRT sounds, changes in the overall soundscape, and feeding sounds from herring predators. To manage the large dataset, we narrowed down our temporal and spatial search using data from NOAA bottom trawl surveys, long-term echosounder recordings from bottom landers, herring landings from commercial fishing vessel trip reports, visual sightings of whales, and observations of marine mammals feeding on herring.