The physical act of reproduction can be a noisy affair for many animals, but for the Gulf corvina (Cynoscion othonopterus), it’s downright deafening. Every spring, millions of the snowboard-size gray fish migrate to the Colorado River delta and sync their spawning to the tides and the phases of the moon. The aggregation can span tens of kilometers, and scientists believe male corvinas—like crickets or frogs—make a throaty croaking noise to communicate with potential mates. Over the course of 4 days in the spring of 2014, researchers used sonar and underwater microphones to record where the fish were and the sounds they were making. At the loudest, the instruments recorded the chorusing fish at more than 150 decibels, the team reports today in Biology Letters. That makes the sound the loudest ever recorded for a fish, and one of the loudest sounds ever captured underwater. The collective clicking is so noisy, in fact, that the researchers say it could harm the hearing of other marine animals like seals and whales. Fortunately, it only happens once a year.