Beaches Made of Fish Poo

Beaches Made of Fish Poo

Posted: September 10, 2015

If you’ve ever bathed in the sun on a tropical white sand beach, you were probably lying in mounds of fish poo. I’m Anna Rothschild, and this is Gross Science.

Parrotfish live in tropical waters near coral reefs around the world. They eat the algae that clings to the coral, scraping it off with their bird-like beaks. They’ll often break off whole chunks of coral, which they grind up with these teeth they have not in their mouths, but in their throats called “pharyngeal teeth.” The coral passes right through them, and comes out the other end as a fine, white sand. The amount varies by species, but it’s estimated that a single giant humphead parrotfish can poop out over 11,000 lbs of sand a year! In fact, a huge portion of the sand found in Caribbean and Hawaiian beaches was actually created this way.

But, that’s not the only thing that makes these guys a little gross. When juvenile parrotfish sleep, they swaddle themselves in mucus. Scientists aren’t entirely sure why they do this, but they think the mucus cocoon might be a way to block the fish’s scent from either predators or parasites that try to feast on them while they sleep.

Finally, one more noteworthy characteristic is that some parrotfish change their sex during their lifetime. This can happen in a variety of ways, but in many species, all the babies are born female and then some will become male once they mature. Way to go, parrotfish—be who you wanna be!

As you can tell, these creatures have a ton of truly excellent qualities, including how they taste. In many places, parrotfish meat is considered a delicacy. But research is indicating that these guys are a really important part of reef communities. By eating algae, they help keep reefs clean and healthy. So, we need to be careful to protect these sand-pooping, mucus-wrapped, weed-wackers of the sea.

Ew.

PRODUCTION CREDITS:

Host, Writer, Editor, Animator

Anna Rothschild

DP, Sound

Elizabeth Gillis

Many thanks to Dr. David Bellwood.

Home Comforts

Music Provided by APM

IMAGES

Humphead parrotfish

Flickr/Tchami

Plage Feuillere

Wikimedia Commons/Smiley

Protective Cocoon envelops Sleeping Parrotfish

Getty Images/Reinhard Dirscheri

aiga toilet women bg

openclipart/jean_victor_balin

aiga toilet men bg

openclipart/jean_victor_balin

GRILLED PARROT FISH

Flickr/whologwhy

SFX

Cockroaches

Freesound/StateAardvark­
(used with permission from author)

Squeak Pack/squeak_10

Freesound/Corsica_S

Swishes

Freesound/pogotron

Produced by WGBH for PBS Digital Studios

POSTER IMAGE

Parrotfish

©WGBH Educational Foundation 2015

Want more info?

Absurd Creature of The Week post from Wired on parrotfish:
http://www.wired.com/2014/08/absurd-creature-of-the-week-parrotfish/
(If you like Gross Science, you should be following this series by Matt Simon. It’s awesome.)

The Bellwood Lab:
http://www.bellwoodlab.com/