Thursday, September 12, 2013

Answer: What kind of fish?

Short answers:  

1. Fish?  Stoplight Parrotfish (Sparisoma viride). 

2.  Geology?  Parrotfish bite into the coral, scraping off a bit with each bite.  They digest the algae they get in that bite, then the coral bits are excreted into the water, making up a large amount of sand.  In essence, much of the white sand of Caribbean island beaches is made up of fish poop!  (Okay, the excreted, indigestable bits of pulverized coral.)  

Stoplight parrotfish (Sparisoma viride)

My solution:  As you can see from the comments, there are many paths to solving this.  I solved it by searching for: 

     [ Caribbean fish guide ] 

And finding which has a very high quality guide to the reef fishes of the world.  From their home page I chose "Caribbean, Bahamas, Florida" and then did a quick scan of the fish families.  It wasn't a "small oval" fish, or any of the other's I clicked, until I found the parrotfish category.  Once you see the parrotfish page, it's pretty clearly that kind of beast.'s parrotfish categorization page

To find the geological effects of this fish... My first search (like many of you) was for 

     [ stoplight parrotfish geology ] 

but the results were too diffuse to be useful.  (Search question:  Why didn't I include the double quotes a la "stoplight parrotfish"?  Because I figured that bigram--stoplight then parrotfish would be pretty common only as a fish reference.  So I didn't bother.)  

So I modified my query to be:  

     [ parrotfish geology ] 

and quickly found many articles about the effect of parrotfish (in general, not just the Stoplight parrotfish) on sand creation in the Caribbean.  

Just to triangulate what I was reading, I did the same search on Scholar to see a few scholarly papers on the topic.  

One paper,  "Rate of bioerosion by Parrotfish in Barbados marine environments" (1) points out that "[stoplight parrotfish] were observed to spend 80% of their time feeding on surfaces covered with filamentous algae and 20% on sand. Only Sparisoma viride consistently leaves well-defined scars on live coral."

But there's a debate among different sources about how MUCH sand a parrotfish produces each year.  If you look at the comments, some say it's 1 ton (2,000 pounds) / year / fish, while others say it's 200 pounds / year / fish.  Since that's SUCH a variance, I'm going to let the crowd work on the rate of sand production / fish for a bit longer.  The mystery remains!  
3.  How MUCH sand does a single parrotfish create in a year?  

As noted in the comments, some male parrot fish keep harems of females nearby. When the dominant male dies, one of the females will change gender and color and become the alpha male for the harem.

There's also a striking difference in appearance between the adults and the juveniles. Here's a photo I took yesterday of a juvenile Stoplight parrotfish. 

Stoplight parrotfish,  juvenile (Sparisoma viride)
Tomorrow I'll comment more on the "sand production" question, but give it a shot. It's a genuine difference of data question.  Since they vary by a factor of 10, one estimate should be clearly very wrong!  

Back to vacation!  Nice job everyone.  

And... just for Remmij, who asked for a picture of the Hilma Hooker, here's one shot of one our buddies entering the wreck through a hatch opening (it was on the top, but the wreck is laid over on its side, so this is now on the side of the wreck...)   
Entering the Hilma Hooker wreck at 80 feet.

(1) Frydl, Paul, and Colin W. Stearn. "Rate of bioerosion by parrotfish in Barbados reef environments." Journal of Sedimentary Research 48.4 (1978): 1149-1157.


  1. Ichthylogy Florida Museum of Natural History -

    Parrotfish may produce as much as one ton of coral sand per acre of reef each year. 

    Other research/scholar papers provided a level of information that makes quick retrieval & deciphering quite difficult. I would like tips on how to zero in (besides Control F) when scanning very detailed journals.

  2. bedankt voor de duik uitzicht!… and the seabed/ground truth on the Lionfish population. The HH looks like an interesting visit with very good water conditions - even if there is a diver traffic jam.
    includes a couple images of HH on the surface, in the final seconds
    and until Sergey invents GoogleGills, dive safely:
    5, maybe 6, rules
    and you may want to skip the stoplight tacos…anything that snoozes in its own mucous sack shouldn't be high on the ingestion menu, jmo.
    besides, they are such fine looking creatures, why munch them on a whim?
    not a stoplight

  3. I was rushed in my previous comments. I gave only one reference but I did look up scholar journals/papers as well.

    I switched to using 'sparisoma viride' rather than 'stoplight parrotfish' and found it gave more credible results. Other websites likely gleaned from credible results but not accurately. But I did find scholar results so specialized that to find "how much sand" was not so easy. As said before we aren't writing a paper on the topic.

    I found the study of fish was ichthylogy and that gave better results when I included that term. It eliminates those sites that may not be credible.

    I switched to looking at the bioerosion of coral reefs & not focusing on the parrotfish. Good results and again I found it was quite indepth. No simple statement like Stoplight Parrotfish are known to produce.I did find results that took live SP fish weighing them & again 24 hours later (assuming digestion was complete) and then examining internal organs but I think this is way beyond our type of searching.

    If we were to define our searches would it be "the results of information that is gathered efficiently from a credible source and reported concisely". What is our type of searching?

  4. regarding the sand production: I was in the 200lb camp, but that seems to be incorrect - am going with the Shedd Aquarium and the 2000lbs number. Maybe a zero got dropped somewhere and then the 200lb number was erroneously picked up and spread?
    parrotfish poo production
    also ran across this short video of a parrotfish in a sack atop a sand pile:
    mucous & poo in AU
    found the video in the crowd comments here, some interesting bits:
    guess I would rather pay to stand on a fish poop beach than ruminate on the terra-bipedal poop interpretations…
    Complex Pile
    it should be filled with methane.
    hopefully, if Android gets to a "P" codename, it will be peppermint of perogi and not p…
    A codenames