Fish Yell When It’s Too Noisy

How fish deal with all the noise in their environment

April 25, 2019 

The ocean is noisy too

We are constantly exposed to noise, whether it’s walking by a construction site or the sound of a siren or a neighbor using a lawn mower. It’s getting harder and harder to find a quiet spot. That’s even true for fish. It turns out there are a lot of things that make noise underwater, including boat traffic, waves and even marine life.

All of that sound, both natural and man-made, makes it difficult for fish to detect predators and prey, communicate, and generally make sense of the watery world around them.

Fish shout to be heard

To better understand the effects of noise on fish, researchers studied the oyster toadfish in two environments. The first was at Newport River; a noisy site with more than 100 boats per day passing by. The second was Jarrett Bay; a much quieter site with roughly 25 boats per day passing through. Both sites are in Carteret County near Morehead City and Beaufort. The study also included playing recordings of dolphin sounds (dolphins are natural predators) as well as other marine creatures and boat sounds near the habitats where the fish live.

The findings? North Carolina Sea Grant reports the study found that fish compensated for the noisy underwater environment by amplifying their vocalizations. Yes, you could say the fish were shouting.

Researchers report toadfish increased their vocalization volume by 8.5 decibels. The problem is the ambient noise level for boats passing by was 14.6 decibels. The toadfish may still not be heard. Researchers also found toadfish reduced their calling rates-and even stopped calling altogether when dolphin sounds were mixed in with the boat sounds.

One other finding: toadfish living near the noisy boat channel had lower reproductive rates. It seems a little peace and quiet is good for people and fish.

—Frank Graff

 Frank Graff is a producer/reporter with UNC-TV, focusing on Sci NC, a broadcast and online science series.