How parrotfish play a vital role in ensuring reef health?
Colourful, tropical creatures with big beaks rather like their feathered namesake – the parrot – parrotfish are known best for two things – eating most of time and pooping. Now, this may seem disgusting, but once you know more about these fish, you will realise that they are saviours of coral reefs. That’s because they spend around 90% of the day eating algae that damage the reefs. This continuous eating cleans the reefs and this ensures the health of the corals.
How does it go about doing this? Each parrotfish has around 1,000 teeth, line up in 15 rows and cemented together to form the beak structure, which they use for biting into the coral. When the teeth wear out, they fall to the ocean floor. But, this does not perturb the parrotfish, because it has so many rows of teeth. These powerful teeth break down bits of coral which are later excreted into nothing but fine white sand that lines the beaches of the South Pacific. This process is known as bioerosion and it helps keep algae under check which provides the right environment for young corals to grow.
You may scoff at the idea that some of the most beautiful beaches in this region are the creation of parrotfish or rather its poop! But, scientists estimate that a single Chlorurus gibbus parrotfish can excrete more than 2,000 pounds of sand each year!
There are about 80-90 species of parrotfish regarded as a family (Scaridae) that live in reefs all around the world, but they all generally live about 5-7 years and grow to 1-4 feet in length. The largest of the family is the bumphead parrotfish found in the Indo-Pacific waters, measuring more than 4 feet and reaching a weight of 100 pounds. Species vary in size from the five-inch Bluelip Parrotfish to the 4 foot Rainbow Parrotfish. Coloring ranges from reds to greens, blues and yellows, as well as grays, browns, and blacks. The parrotfish swims by rowing itself along with its pectoral (side) fins.
They eat and eat all through the day. At night, they sleep in the safety of a cocoon they make out of the mucous they secrete and by finding a suitable hiding place in the coral. It’s nature’s way of keeping them safe from predators.
Like most fish, male parrotfish contains harems of females. This means that in the event of there being no dominant male in a school which may comprise around 30-40 fishes, the largest female changes gender and colour to become the dominant. Once the transformation is complete, they can mate with the other females in the school. Parrotfish release many tiny eggs into the water, which become part of the plankton. The eggs float freely, settling into the coral until hatching.
Unfortunately, humans are their main predators as these fish are considered a delicacy in countries of the South Pacific where they are overfished. And when their numbers are depleted, algae levels shoot up affecting the health of the coral reefs. According to a recent study, reefs where parrotfish were abundant in the 1980s are the ones that are healthy today.
Picture Credit : Google