Researchers hoping to better understand fish distributions by recording the sounds they make have picked up something unusual: barely-audible, cricket-like noises they think could be nighttime fish farts. The team programmed a torpedo-shaped robot called a glider to head out to sea from Tampa Bay and back, running up and down the water column in a saw-tooth pattern, sampling ocean sounds for 25 seconds every 5 minutes. The glider also recorded location data and measured seawater temperature, salinity, and depth over the course of 1 week. By comparing the grunts and whistles on their recordings to known fish calls, University of South Florida researchers found red grouper (shown, Epinephelus morio) and toadfishes (Opsanus spp.) were the most frequent fish sounds recorded, the team reports this month in Marine Ecology Progress Series. These fish produced sounds throughout the day and night, mostly deeper than 40 meters. The probable farts were recorded shallower than 40 meters, and were most likely a group of fish, including menhaden and herring, releasing gas from an internal buoyancy organ called a swim bladder. By mapping these sounds, the researchers hope to get a better picture of species distributions and likely spawning areas—important information for management and conservation efforts.
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