Scientists have recorded the sounds of millions of spawning North American perch, some of the loudest ever seen in marine animals.
Fish of the gorbyl family are close relatives of the perches we know. They are found throughout the warm belt of North America, from California to Florida, and are highly sought after by fishermen and food lovers. Interestingly, contrary to popular belief, these fish are "talking": their compartmentalized swim bladder is controlled by muscles and can produce sounds that slabs use for communication.
The croaker Cynoscion othonopterus lives off the coast of California. Each spring, more than a million of them climb up the Colorado River to spawn. During this period, the delta is literally teeming with these fish, which attract potential partners with loud "cries", as do crickets or frogs. In 2014, this process was observed by ichthyologists Brad Erisman from the University of Texas at Austin and Timothy Rowell from the Scripps Institute. Their article is published in the journal Biology Letters.
For several days, biologists recorded what was happening in the river using sonars and underwater microphones, finding that the volume of the spawning "fish choir" of C. othonopterus can reach an incredible 150 dB. Scientists estimate that this is the loudest sound ever recorded for fish, and one of the loudest among aquatic animals in general.
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Indeed, such a loudness level is already considered directly hazardous to health: for comparison, a fire siren emits a sound with an intensity of 100 dB, and an artillery shell - 120 dB. Rowell and Erisman also believe that the "songs" of spawning perch can be harmful to other aquatic animals, damaging their hearing. Fortunately, they "sing" only once a year, and their spring "concerts" can well wait out at a safe distance.