The importance of parrotfish poo

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Humans usually have one gender. Fish are much more interesting gender wise. Some species grow up as male, others as female and change sex later in life. Some fish are born without a gender and develop one when needed. Did you know that the cute little anemonefish family you see in an anemone is not a family at all? The biggest fish is the female, the smaller one the male and the cute little kids are not their kids and they are genderless. When something happens to mom, dad turns into mom and one of the kids turn into dad. Other fish species are slightly less bizarre. They just start their live as female and turn into male when necessary, like the parrotfish. But not only the change in sex makes a parrotfish interesting.

Parrotfish have a useful diet. They scrape the algae from the rubble, and sometimes from the reef as well and thus preventing algae overgrowth. Because of their scraping behavior they digest a lot of extra material they do not eat. And that extra material is the most important for us beach lovers: they grind rock and reef into really fine sand, which they excrete. If you stay close to a parrotfish for a while, you will notice that they poo quite a lot. You regularly see clouds of sands trailing behind a parrotfish. These clouds eventually end up on land and the crystal clear white sand you see there is the evidence of parrotfish on the reef; their poo is all over the place. It even turns out that some islands are almost entirely made up of their poo. Want to know more? Have a look here.
The species which produces the most poo is the Bumphead parrotfish. Much overfished, because they are so large and eat in schools, their jaws are so big that they eat a lot of live hard coral besides the algae and can do quite some damage to a coral reef. The BBC made some interesting footage about their destructive behavior.


MCP is interested in which fish species occur where on our different dive locations for our baseline study. If we know this, we can set up a long term monitoring program and look for any disturbances (natural or human). Currently we are trying to find out which parrotfish we have, besides some other families. Anybody who ever paid a little attention to parrotfish will acknowledge that identifying different species is not easy, as our volunteers will readily agree on. At first glance they all look more or less the same, but fortunately if you look closely (especially on pictures, where you have better time) you will start to see some differences. But even now, after more than a dozen dives looking for them we discover more species every week. Bumphead parrotfish we do not see (any more), but with 21 other species the variety of parrotfish is quite big.


We welcome all volunteers, but if you just happen to be an ichthyologist (that’s a fish expert, if your Greek needs a little brushing up) specializing in parrotfish, now would be a really, really nice time to come.

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