Parrotfish poop for healthy reefs!

Consider what makes healthy reefs in this, the 3rd International Year of the Reef (IYOR). Dr. Farahnaz Solomon, Marine Biologist and IYORTT team member, provides some insight into the characteristics of one of the more colourful and important coral reef inhabitants – parrotfishes. She highlights the vital role they play and why their protection is necessary to ensure the persistence of reefs in Tobago and the Caribbean.

As a lover of bright vivid colors, my admiration was won instantly by the delightfully garish parrotfishes, inhabitants of coral reefs. These thick scaled reef inhabitants possess a very fickle sense of fashion – not only does every species have a different color scheme, but they also change “outfits” as they move from babies, to juveniles, to adults. As my interest in reef fish deepened, I quickly learnt that there were more fascinating, albeit unusual, characteristics of these beauties than colour. Their diet, sleeping behaviour, and sexual orientation are all features worthy of mention.

Queen Parrotfish with teeth fused into beak-like structure
                 Photo Credit: http://underwater-fish.blogspot.com/2011/10/queen-parrotfish-or-scarus-vetula.html

Parrotfish feed mainly on algae extracted from pieces of coral bitten off from the reef. They can bite off pieces of coral because their teeth have been fused into powerful beaks, much like a parrot’s beak, hence their name. Some individuals may spend up to 90% of their days nibbling away at the reef. If you listen carefully, you can hear them taking a bite off the reef! The rock and coral skeleton ingested are ground by their beaks and by molar-like teeth in their throats. The indigestible material is then pooped out as smooth white sand.  A large parrotfish can poop up to 200 pounds of sand per year. While the contribution of parrotfish poo to beaches will vary from place to place, as much as 85 percent of the sand produced on a beach can be pooped out by these fishes (Perry et al., 2015). So, if your beach is near a healthy population of coral-eating parrotfish, that silky white sand you dig your toes into might just be some parrotfish poop!

Parrotfish perform a far more important function in their grazing – they are the reef’s gracious and indispensable gardeners. These algal eating fishes, like other herbivorous fish, remove the algae that compete with corals. The transformation of many Caribbean reefs to algal dominated habitats in recent decades has been linked to the loss of herbivorous fish due to pollution and overfishing. Results of a recent study showed that there is indeed a strong correlation between parrotfish abundance and coral reef growth historically – coral reefs grew faster and healthier when parrotfish was abundant (Cramer et al., 2017).

Coral overgrown with algae in Jamaica
                 Photo Credit: Bob Steneck

All this daytime nibbling and crunching requires a good night’s rest, and here again parrotfish are unusual. Some parrotfish like the Queen parrotfish (Scarus vetula) wrap themselves up for the night in a mucous sleeping bag which is extruded from the mouth. This foul-smelling wrapping presumably protects them from predators and blood sucking pests.

Parrotfish surrounded by mucus sleeping bag.                  Photo Credit: https://pbs.twimg.com/media/DPoHHkUXcAAdvc7.jpg

 Then there is coloration – the feature for which they are most valued by divers and snorkelers. Parrotfishes exhibit different color patterns according to their age and sex. Early on, more than 300 species were named based on the many color forms—now this number has been reduced to just about 80.  Individual parrotfish undergo three separate stages – the juvenile, the initial (IP) and the terminal (TP) phases. Looking at the different colour patterns of the stoplight parrotfish (Sparisoma viridi), commonly found on Tobago’s reefs, one can certainly see how the different stages could be mistaken for different species.

Different colour stages of the stoplight parrotfish
                Photo Credit: https://reefguide.org/carib/stoplightparrotfish.html

Even more intriguing, parrotfishes can change sex during their lives. In the stoplight parrotfish, individuals are born as either males (primary) or females. Primary males remain as males throughout their lives. They spawn in groups with one or more females. As a female matures, she might change her sex to male, becoming a terminal male or “supermale” which is brightly and beautifully colored. This usually happens when the density of primary males is low. “Supermales” keep a harem of female parrotfish in a school. If the “supermale” dies, the largest female in the group changes sex to become male, assuming the bright colors of the “supermale.”

   

Here in the Caribbean, we don’t have the jumbo-size species like the humphead parrotfish which can exceed four feet in length and weigh over 100 pounds, but we do have at least a dozen dazzling species. Over the years, the major cause of their decline regionally has been overfishing. To  reverse or prevent this decline, some Caribbean countries such a Belize, Bonaire and Turks and Caicos have taken the bold step in banning the fishing of parrotfish. While Tobago does not have a “reef fishery”, parrotfish is harvested by both scuba divers and free divers. The level of exploitation is unknown.

Given the critical role of parrotfish in maintaining coral-dominated reef habitat, we need to ensure that these fish are properly protected. This would include the implementation of management systems such as fish sanctuaries, no fishing zones and size and gear regulations. It also means protecting the nursery habitat for these species -  many parrotfishes utilize mangroves and seagrass beds as nursery areas. Let us learn from our Caribbean neighbors and be proactive rather than reactive. With their bright colors, mucus sleeping bags, toothed beaks, sand poop and undersea green thumb, parrotfishes are certainly stars of the reef realm.

REFERENCES

Florent Charpin 2013 “Stoplight parrotfish” (On-line Image). Florent’s Guide to the Florida, Bahamas and Caribbean Reefs. Accessed May 30th, 2018 at http://reefguide.org/carib/stoplightparrotfish.html

Cramer, K. L. et al. 2017. Prehistorical and historical declines in Caribbean coral reef accretion rates driven by loss of parrotfish. Nature Communications 8, 14160 doi: 10.1038/ncomms14160.

C.T. Perry, P.S. Kench, M.J. O’Leary, K.M. Morgan and F. Januchowski-Hartley. 2015. Linking reef ecology to island building: Parrotfish identified as major producers of island-building sediment in the Maldives. Geology ; 43 (6): 503–506. doi: https://doi.org/10.1130/G36623.1

Johnson, A.Y. 2018 “Parrotfish: The fish that can save coral reefs” Accessed June 1st 2018 at https://www.virgin.com/virgin-unite/leadership-and-advocacy/parrotfish-the-fish-that-can-save-coral-reefs

Simon, M. 2014. “Absurd Creature of the week: This goofy fish poops out white-sand beaches”. Accessed June 1st, 2018 at https://www.wired.com/2014/08/absurd-creature-of-the-week-parrotfish/