The 18-inch-long palenose parrot-fish is the most-common parrotfish species we have here in Hawai‘i, and also the smallest. Several of the other species grow up to three feet long, and they are all collectively known as uhu. The Hawaiian name uhu means “loose bowels,” as every time you see one of these fish zoom by they are always pooping. This is because they eat sick or dying coral with their sharp, beak-like teeth, and then they poop out the bits of dead coral which helps make our beautiful white sandy beaches here. This fish is super important to the health of the coral reef, as it eats the sick coral, making room for new healthy coral growth.
What is amazing about the pale-nose parrot-fish males are their extremely beautiful purple, blue, green and yellow colors. The uhu babies are a solid gry or brown, and the adult females are drab and blend into the colors of the lava reef. Once the females become adults, several of them will change into males, as they carry both male and female genetics. It takes about a full year for a gray-colored female to turn into this brightly-colored male. The male then will go into different colonies of females for breeding, to spread the genetics around, keeping the entire species evolving and healthy. If the reef where a colony of uhu is living is stable with lots of food and good habitat, then very few males will be produced by the colony of females. If the reef where they live is losing its live coral and becomes unstable, then the females produce more males that venture out into new reef systems for breeding to help the entire colony to evolve with the changes to the reef.
It is really important if you like to fish to NOT remove the adult male breeder parrot-fish, as they can breed with over 10 females and produce many millions of eggs. If a male is removed off of the reef then those 10 females won’t have the ability to reproduce for an entire year until a new male has converted. This ruins a whole year of reproduction and can reduce the parrotfish colony for many years to come, which can negatively affect the entire coral reef ecosystem.
What is really special to observe is the pale-nose parrot-fish sleeping behavior. During the day they dart around on the reef so fast they just look like a blue burr, but at night they come up into three-feet-deep water and sleep in caves or cracks in the reef. They even turn brighter colors, and when I am out night diving they show up in my bright dive lights like a well lit Christmas tree. You can go right up to them and just observe their colors up close because they think they are protected. When they go to sleep they emit a jelly-like, clear substance that they sleep in, like a cocoon. This external mucus layer is toxic to most predators like the giant moray eel and white-tipped reef shark, and acts to keep them safe while they sleep.
You can see the pale-nose parrot-fish in action day and night in the movie “The World’s Guide To Hawaiian Reef Fish” on the underwater educational web page, and soon all of the movies will be up on the Vimeo pay-to-view site so you can watch them online versus having to purchase a DVD. Great education for the kids when they are learning from home.
Terry Lilley is a marine biologist living in Hanalei Kauai and a co-founder of Reef Guardians Hawaii a non-profit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians please visit their web at www.reefguardianshawaii.org.