Giant fish orgy produces one of the loudest sounds in the ocean

A diagram shows the frequencies of the corvinas' mating chorus. Photo by Brad E. Erisman and Timothy J. Rowell/Biology Letters

Dec. 21 (UPI) -- Every spring, millions of fish in the Gulf migrate to the Colorado River Delta to mate. The frenzy of horny corvinas produces a chorus of machine gun-like noise.

Scientists have for the first time recorded and analyzed orgy's sonic signature. According to their latest paper on the subject, published this week in the journal Biology Letters, the chorus is one of the loudest natural sound found beneath the ocean waves.

"We show that calls by male corvina represent the loudest sounds recorded in a marine fish, and the spatio-temporal magnitude of their collective choruses are among the loudest animal sounds recorded in aquatic environments," Brad Erisman, a fisheries ecologist at the University of Texas at Austin, and Timothy Rowell, a Ph.D. candidate at the University of California, San Diego, Scripps Institution of Oceanography, wrote in their newly published paper.

The researchers suggest the chorus is loud enough to harm the hearing of the mammals that prey on corvina, including dolphins, seals and sea lions.

Erisman and Rowell used special equipment to record the underwater sounds generated by the mating corvinas. They were surprised by the result.

"At first, we thought our equipment was broken," Erisman told Scientific American. "No one anticipated fish would be this loud."

Each fish produces a short sonic pulse during mating. When millions make the sound, it yields a deafening chorus. The noise is loud enough to be heard above the water. And as one might expect, the phenomenon attracts visitors.

The corvina, sometimes called drum or croaker, is a popular eating fish. A single fishing boat can net thousands of corvina in a matter of minutes. A fleet of several hundred boats can net millions -- at least they could. There are signs that corvina fishing isn't quite as easy as it once was, a sign of overfishing and evidence the population is in decline.

In their latest study, scientists suggest conservationists track the corvinas' mating chorus to gauge the population's health. Scientists argue more needs to be done to ensure one of the sea's loudest sounds doesn't go quiet.

"While this wildlife spectacle is at great risk of disappearing due to overfishing, regional conservation efforts are focused on other endangered marine animals," researchers wrote. "A precautionary approach should be adopted by fisheries managers to ensure that this wildlife spectacle does not disappear."