Fish sex so loud that it could deafen dolphins

A species of Mexican fish amasses in reproductive orgies so loud they can deafen other sea animals, awed scientists said earlier this week, calling for preservation of the “spectacle” threatened by overfishing. An individual spawning Gulf corvina, said the research team, utters a mating call resembling “a really loud machine gun,” with multiple, rapid sound pulses.

And when hundreds of thousands of fish get together to spawn once a year, “the collective chorus sounds like a crowd cheering at a stadium or perhaps a really loud beehive,” study co-author Timothy Rowell from the University of San Diego said.

“The sound levels generated by chorusing is loud enough to cause at least temporary if not permanent hearing loss in marine mammals that were observed preying on the fish,” he said.

Rowell and colleague Brad Erisman of the University of Texas used specialized underwater sound gear to eavesdrop on spawning Gulf corvina, a popular eating fish. Each spring, all adults of the species migrate to a single site — the Colorado River Delta in the northernmost part of Mexico’s Gulf of California — for what scientists call a “spawning aggregation” that can number into the low millions.

The frenzy sees all the world’s adult corvinas gathered in less than 1 percent of their usual home range for a few weeks. During this time, male corvinas emit calls that reverberate through the hulls of fishing boats, and can be heard even above water — drawing in the fishers.

Earlier this year, Rowell and Erisman, with other experts, reported in the journal Scientific Reports that listening to the love calls of corvinas can help scientists keep track of their numbers for conservation purposes.

Pursuing their research, Erisman and Rowell recorded the fish and said they were “a bit surprised by how loud the aggregation is.”

They took measurements in March and April 2014, when an estimated 1.5 million corvinas gathered to procreate.

“These spawning events are among the loudest wildlife events found on planet Earth,” Rowell said by email. It is, furthermore, “the loudest sound ever recorded for a fish species.”

The frequencies of sound produced by the corvina fell within a range that could harm the hearing of seals, sea lions and dolphins, or even deafen them, the duo concluded.