[BlueTrend Mini Classroom] The Chameleon of the Sea? Coral's Best Ally – The parrotfish That Changes Sex Over a Lifetime

The Editor says: Have you ever heard a "click-click-click" sound while diving? Did you know that's actually the sound of parrotfish feeding? Their teeth fuse into a beak-like dental plate that efficiently scrapes algae off rocky reefs and coral reefs, allowing coral to grow healthily — making them one of the ocean's most important "cleaners." Follow BlueTrend and get to know them!

Introduction to the Parrotfish Family

Parrotfish primarily inhabit rocky reef coastlines, especially tropical waters rich in coral reefs.

Parrotfish primarily inhabit rocky reef coastlines, especially tropical waters rich in coral reefs. Most parrotfish undergo a "female-first, then male" sex change during their growth, and their coloration shifts with each phase. There's also an interesting behavior: juvenile parrotfish swimming together in schools display a uniform coloration, as if they're all wearing the same uniform.

Females typically display duller colors such as reddish-brown or dark gray, which has earned them the nickname "oyster fish" in local parlance.

Female parrotfish tend to have more subdued coloration, often reddish-brown or dark gray, which is why females are sometimes nicknamed "oyster fish." As they mature, some females undergo a sex change and become males, at which point their coloration gradually shifts to vivid blue-green patterns — which is why male parrotfish are also commonly called "greenbacks" or "greenies."

Because the same species of parrotfish can cycle through several color phases during its lifetime, and because males and females look so different, even ichthyologists often find them difficult to tell apart.

Guardians of the Coral Reef – Parrotfish

coral plays many different roles in the ocean and is one of the keys to maintaining marine ecological balance. Out in the vast sea, coral not only has to find a suitable place to grow but also has to worry about being "invaded" by fast-reproducing algae. That's where their "allied friend — the parrotfish" becomes so important. Let's take a look at these three types of parrotfish!

Bioeroders (Large excavators)

These are primarily large parrotfish, such as the Steephead parrotfish and the Bumphead parrotfish. As the name implies, they possess strong, hard beaks that allow them to chisel open rock walls and crunch through reef rock. While their feeding activity can damage parts of the coral, it also opens up new substrate and aids in substrate turnover.

Scrapers (Small excavators)

These are primarily small-to-medium parrotfish, such as the Bluebarred parrotfish and Swarth's parrotfish. Using their sharper beaks, they scrape the reef surface and clear encrusting algae from the substrate, giving juvenile coral more clean space to grow. When they feed, they often leave paired bite marks on the coral surface.

Browsers

The Carolines parrotfish (Calotomus carolinus) and the Spiny parrotfish are prime examples of browser-type parrotfish. Their uniquely hard teeth, combined with an outstanding digestive system, allow them to easily bite through large, leafy algae — tough Sargassum and toxic Galaxaura are all on their menu. With their hearty appetites, they effectively consume overgrown algae and are considered saviors of the coral reef.

A Protected Icon – The Bumphead Parrotfish

Among all parrotfish, the massive Bumphead parrotfish is the largest species in the family.

The Bumphead parrotfish is deep gray in color, with a distinctive vertical hump rising from the top of its head to its snout. Its imposing body is paired with small eyes and a mouth full of hard, protruding teeth. They can reach a maximum length of 1.3 m and weigh over 50 kg — and they can live for more than 40 years, making them a remarkably long-lived species!

Their primary diet consists of algae and coral, which they excavate and grind up using their hard teeth.

Bumphead parrotfish are gregarious. At night, they typically shelter in large, shadowy caves, and sometimes even inside shipwrecks. Each morning they begin to stir, and once the sun rises they head out to forage in coral-rich areas. Notably, they are smart enough to vary their feeding routes periodically, giving benthic organisms time to regrow.

Bumphead parrotfish were once distributed across coral reefs throughout Taiwan, but due to overfishing their numbers have become extremely scarce. On July 2, 2014, the Council of Agriculture listed them as Category II protected wildlife.

Xiaoliuqiu Wanted – Parrotfish Family

Got a photo? Beep beep beep! Wanted!

How to Participate:

• Activity period: August 15, 2023 – September 30, 2023 (112/9/30)

• Activity details: Upload photos or complete classifications during the period to earn raffle entries (winner drawn and announced on October 2)

• How to enter:

  1. Upload a Xiaoliuqiu wildlife photo to earn one raffle entry

  2. Upload a photo of one of the designated wanted species listed above and complete the photo classification to earn one additional raffle entry

Raffle Prizes:

• Wetsuit * 1 (valued at $11,600 / piece, available in men's and women's sizes)

• Fins * 2 (valued at $4,300 / pair, size selectable)

• Booties * 3 (valued at $1,080 / pair, size selectable)

Further Reading

• 2023 Xiaoliuqiu Marine Citizen Science Biological Database

• Parrotfish Biological Database

• Bumphead parrotfish photos provided by: Giam