Marine Animal Sounds

Jacques Cousteau, the pioneering ocean explorer and documentary filmmaker, called the ocean “The Silent World.”  In fact, that was the title of his first major film.  Well, we hate to break this news to you, but Jacques lied.  Maybe, it was more like a fib or half-truth, but it was definitely misleading.  The sea is an incredibly noisy place.  But back when Cousteau started making his documentaries, underwater movie cameras weren’t equipped with hydrophones (underwater microphones).  So he was making silent movies for the same reason that Charlie Chaplin made silent movies in the 1920s: the technology didn’t yet exist to make “talking” films.  Rather than say, “Sorry we can’t convey to you the symphony of sounds we’re hearing down here,” Cousteau instead chose to say “Don’t worry about not having any audio; you’re not missing much anyway.”  Of course, he didn't actually say this, but that was the message.

This false impression that the sea is silent has persisted for decades.  A wide variety of crustaceans, fishes, and marine mammals produce sound.  Nerdy acousticians estimate that about twenty percent of all ray-finned fishes (class Actinopterygii, which accounts for the majority of all vertebrate species) are soniferous.  About 6,800 out of the roughly 34,000 known species of ray-finned fishes produce sound.  Two-thirds of all ray-finned fish families contain species capable of producing sound.  Sound production has evolved independently many times among fishes, demonstrated by the wide variety of mechanisms used to make sound.  Some fish make sound by vibrating their swim bladder, some grind specialized teeth together, and some rub bones together.  The loudest biological sounds on the planet are made by marine animals (blue whales and finback whales), and these sounds can travel thousands of kilometers, across entire ocean basins. 

So what’s all this sound about?  Marine animals use sound to communicate, navigate, and feed.  For example,  male oyster toadfish use sound to attract mates, damselfishes use sound signals to facilitate courtship, and members of  the drum family of fish (Sciaenidae) use sound to signal danger.  Sperm whales produce low-frequency click sounds that are thought to function like a depth sounder, allowing the whale to sense how far it is from the seafloor or from the surface.  Bowhead whales migrate under vast expanses of Arctic sea ice and they may use their low-frequency sounds to sense the thickness of the ice and/or to find openings in the ice through which they can breathe.  Many toothed whales, such as bottlenose dolphins and killer whales, possess very sensitive echolocation that can be used to detect prey.  But use of echolocation can come at a cost; the clicking sounds of an echolocating predator may tip off the prey that they are being hunted.  So, bottlenose dolphins and killer whales also hunt by silently eavesdropping on the calls made by their prey.

Atlantic croaker, Micropogonias undulatus, a noisy fish featured prominently on the bottlenose dolphin's menu (photo by Don Flescher, NOAA/NEFSC).  Check out some of our nerdy science articles on this topic.

Perhaps the most ubiquitous sound in the sea is that of small decapod crustaceans, called snapping shrimp or pistol shrimp (family Alpheidae).  With a name like “pistol shrimp,” you know they must have a fascinating story.  Pistol shrimp are found in coastal waters of the tropical and temperate zones, usually inhabiting reefs and rocky bottom.  Similar to fiddler crabs, pistol shrimp have one large claw and one small one.  Their large claw is like a high-powered water gun that shoots a tiny stream of “water bullets.”  The claw compresses the water and shoots it out under such great force that the stream of water is momentarily super-heated to a temperature approaching that of the sun’s surface.  (This is all true, we promise!).  The super-heated water boils, making tiny bubbles.  The hot stream of “water bullets” is cooled rapidly by the surrounding water, causing the bubbles to collapse.  The snapping sound that we hear is the sound of those bubbles collapsing.  All these bursting bubbles create shock waves that the pistol shrimp uses to stun prey (small fish), defend against predators, and defend their territory from other pistol shrimp.  Pistol shrimp even have tiny helmets that protect them from the effects of the shock waves produced by their water gun.  (Again, we’re not making any of this up!) 

 

Pistol (snapping) shrimp, Alpheus cedrici (photo by A. Anker & S. Grave).  This gun slinger is a southpaw. 

Sound Recording Library

Here are some examples of sounds recorded off the coasts of North Carolina, Georgia, and Florida.  Periodically, we'll add more recordings of other species to this collection, so check back again. 

1. Oyster toadfish "boat whistle" calls and pistol shrimp.

This handsome fellow is a male oyster toadfish, Opsanus tau.  To attract females that are ready to spawn, male toadfish call from the entrance of their burrows, making a sound that is often compared to ship's horn or boat whistle.  If he is a sufficiently good singer, the female will lay her clutch of eggs inside his burrow, and he will be the sole provider of parental care until they hatch out.  This recording was made in Post Office Creek at Long Tabby on Sapelo Island, Georgia.  Several male oyster toadfish are making their "boat whistle" call.  Pistol shrimp can also be heard in the recording. This recording was made at 8:55 PM on March 5, 2018.

2. Silver perch spawning chorus and pistol shrimp.

Silver perch, Bairdiella chrysoura, belong to the family Scianeidae, commonly known as the drumfishes.  Mature males of this family produce sound during their spawning season by vibrating their swim bladders.  Species in this family form loud spawning choruses.  This recording was made at 7:15 PM on March 7, 2017 at Marsh Landing on Sapelo Island, GA.  (Image from NOAA/SEFSC Pascagoula Laboratory) 

3. Atlantic croaker, Micropogonias undulatus, knock call.

Frequency spectrogram of doublet "knock" calls made by juvenile Atlantic croaker.  In this graph, time (seconds) is shown on the horizontal axis and acoustic frequency ("pitch," in Hertz) is on the vertical axis.  Color indicates the amplitude or loudness of the sound (hot colors are louder).  The function of the croaker's knock call is unknown, but we do know that it isn't related to reproduction.  The call can be heard outside of the spawning season, far away from where croaker are known to spawn.  Both males and females make this sound, juveniles become capable of making this call at quite a young age.  This recording was made in September 2000 of juvenile croaker in an aquaculture research pond at the University of North Carolina's Institute of Marine Sciences, in Morehead City, NC. The croaker were caught in the Neuse River Estuary and temporarily stocked in the artificial pond. Check out some of our nerdy science articles on this topic.

4. Atlantic croaker disturbance call (also referred to as an alarm call). 

Spectrograms of a single knock call (top) and an alarm or disturbance call (bottom) made by juvenile Atlantic croaker.  Croaker is one of the most common fish caught by anglers in the coastal waters of the Mid-Atlantic, Southeast, and Gulf of Mexico regions.  Croaker make this sound when they are in danger, such as when dangling from a fish hook, and it is why they were given their common name.  This recording was made of a juvenile croaker (~100 mm, standard length), briefly held in the air. 

For Further Information

Now that we’ve convinced you that marine bioacoustics is the coolest thing ever, you’ll want to know where to go to learn more.  Here are a few suggestions:

DOSITS: Discovery of Sound in the Sea    

NC State University CMAST Soundscapes Gallery 

URI Graduate School of Oceanography (Fish & Mowbray archives) 

Ocean Conservation Research-Sound Library  

NOAA Fisheries: passive acoustic monitoring  

Macaulay Library of Sound     

 

If you want to be one of the cool kids and make your own recordings of marine animal sounds, here is what you need:  HTI 96 Marine Mammal Hydrophone

The business end of the HTI 96 hydrophone.  It's quite compact, just a couple of inches in length, but attached to a long cable.

This is a good-quality, simple hydrophone that can be plugged into a just about any phone or recording device that has an audio jack.  (Sorry, iPhone users).  It will run you a few hundred dollars.  It’s expensive, but for an oceanographic instrument, it’s considered to be pretty cheap.