Parrotfish are brightly colored, large scaled fish that obtain their name from the fused teeth that create a ‘beak’ that they use to rasp algae from coral surfaces. Relatively common on coral reefs in the Caribbean; parrotfish are really quite remarkable in their coloration, life history and their importance to coral reef ecosystems.
Parrotfish are largely herbivorous eating primarily filamentous algae, sea grass and occasional crustaceans that grow on coral. In the process of scraping algae from the coral, parrotfish inadvertently consume huge quantities of coral skeleton or calcium carbonate. Their specialized alimentary tracts extract the non organic material and researchers believe that 75% of the gut contents of parrotfish is inorganic sediment or sand, so we can thank parrot fish for some of the white sand on our favorite beaches. If you watch a parrotfish for a while you will see they expel long trails of sandy excrement. A study in Bermuda estimated that parrotfish create a ton of sand per acre of coral reef per year.
Identification of parrotfish is tricky because they go through three primary phases: juvenile, initial and terminal and some parrotfish species have intermediate phases between the primary phases. To further complicate identification most parrotfish are hermaphroditic; they change sexes to get to the terminal phase. All terminal phase parrotfish are male. In certain species some are born male with some females changing as they mature; in other species all terminal phase fish have changed sex.
Unlike many fish that have to guard a territory for a sparse food resource, parrotfish feed on easily found and renewed foods, so they are not usually territorial about the food resource and allow several species of parrotfish to share feeding groups. Large terminal phase males will vigorously defend a harem of females.
Parrotfish are pelagic spawners; the females release tiny buoyant eggs into the water, the eggs are fertilized by the males and then attach to plankton and stay on the plankton until they hatch. There are 78 species of parrotfish worldwide and 14 species occur in the Caribbean.
How do Parrotfish Sleep?
Have you ever seen a fish wearing pajamas? Some parrotfish create a mucous sack for sleeping. The mucous secreted from an organ on their head. Scientists think the cocoon masks their scent, making them harder for nocturnal predators, like moray eels, to find. Other sleeping strategies include hiding under coral, camouflage and burying themselves in the sand.
What Role do Parrotfish Play on a Healthy Reef?
The ecology of coral reefs is complex and parrotfish play an important role. They are one of the most important grazers on reef seaweed and algae, and their grazing is critical to the balance of algae growth on coral. If there are no fish grazing upon the algae, the coral will be smothered by algal growth. The importance of algae grazers upon the coral reef ecosystem was illustrated in the mid 1980s when there was a die-off of an herbivorous urchin (Diadema antillarum). As this urchin disappeared the coral became overgrown with foliose macroalgae, which smothers coral. Recent studies done in Discovery Bay, Jamaica, and other locations appear to show a massive comeback of Diadema, and noticable regeneration of the reefs.
In January 2012 the Center for Biological Diversity filed a lawsuit in United States Federal court seeking greater protection for threatened coral reefs, specifically elkhorn and staghorn corals in the Caribbean, both protected under the Endangered Species Act in the Caribbean. The lawsuit asserted that the National Marine Fisheries Service – a branch of the National Oceanic and Atmospheric Administration – ignored science showing that parrotfish play and important role in maintaining the health of coral reefs when setting catch limits for parrotfish in the US Virgin Islands. The lawsuit explained that excessive algal growth threatens the health of Caribbean reefs, choking out corals and degrading the habitat of other reef creatures, such as fish, sea turtles and lobsters.
Can you Eat Parrotfish?
Parrotfish and other reef fish are taken in the Caribbean for mostly local use. They are not sought out for overseas shipping, but in some locations the pressure on reef fish is great. A few years ago we were anchored in the south end of Barbuda and some local fisherman came by and asked to trade fish for rum. They were offering parrotfish and a queen triggerfish. Look around almost any fish market on an Eastern Caribbean Island and you will see reef fish for sale. Clearly there is a delicate balance between human needs and intact ecosystems.
Next time you are snorkeling or diving and see a parrotfish expel a load of sand, you can thank it for the valuable job it does maintaining coral reefs and building beaches.
Devi Sharp is a retired wildlife biologist and exploring the Caribbean with her husband, Hunter on their sailboat Arctic Tern.