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Interesting Facts about Humphead Parrotfish
[Phylum: Chordata] [Class: Actinopterygii] [Order: Labriformes] [Family: Labridae (Tribe Scarini)]
There are about 100 species of parrotfishes, but the green humphead parrotfish (Bolbometopon muricatum) is the giant that can grow up to 150 centimetres long.
This page contains some fascinating facts about the largest living parrotfish, including where they are found, what they eat, and how they reproduce.
Where Do Green Bumphead Parrotfish Live?
Most of the parrotfish species thrive in tropical and subtropical ocean waters, largely at depth ranges between one and 30 metres deep.
Hence, the best places to find the green humphead parrotfish are the outer reef slopes and wide-ranging coral formations in:
- Southeast Asia (e.g. the Philippines, Indonesia, Malaysia)
- Western and Central Pacific Islands (Fiji, Palua, Samoa)
- The Red Sea and East African Coast (e.g. Kenya, Mozambique)
- Northern Australia (including GBR and Papua New Guinea)
The feeding behaviour of parrotfish (sometimes called "ecosystem engineers") helps to maintain healthy reefs by increasing reef turnover, enhancing sand production, and preventing excessive algae growth.
Unlike other types of parrotfish, the bumphead has several distinctive characteristics in terms of their appearance, behavioural patterns, and ecological importance.
Pro Tip: This erosive action and the distribution of coral sands in marine biomes is only possible because of some unique adaptations in their dentition (arrangement and structure of teeth).
Characteristics of the Green Humphead Parrotfish
Even though we included the green humphead in our list of funniest fish names, genus Bolbometopon has several other common names too, including:
- buffalo parrotfish
- bumphead parrotfish
- double-headed parrotfish
- giant parrotfish
The body shape of most parrotfish is elongated and laterally compressed. The head is quite bulbous (rounded) and they have large fish scales.
As you might expect, the body colour of green humphead parrotfish is mostly a subtle mix of pale greens and blue (e.g. primarily bluish-green skin colouration like the queen parrotfish).
By comparison, the juveniles tend to have more of a mottled appearance and they're often associated with similar small reef fishes, such as damselfishes.
But wait - there's more:
The key feature has to be the large pink or pale green bulbous hump on top of the scaleless forehead. This vertical head profile tends to be more pronounced in male adults.
The hump is made of dense bone tissue (not cartilage) and they use it in head-butting sessions, especially during social interactions.
The body is mostly covered in large scales and they have fused teeth that form the familiar "parrot-like" beak. The teeth are exposed from the lips because they use them for crushing hard corals and for scraping coral reef polyps to gain access to embedded algae growth.
Fun Fact: Green humphead parrotfish tend to be most active with Acropora coral. Typical species include elkhorn coral, staghorn coral, and table coral. Studies suggest a single adult will ingest up to five (5) tons of reef carbonate on an annual basis.
Green Humphead Parrotfish Size and Weight
The smallest of the species is the bluelip parrotfish (Cryptotomus roseus). It rarely grows more than thirteen (13) centimetres long (5 inches).
Yet, the gigantic green humphead parrotfish (Bolbometopon muricatum) is the biggest, growing in excess of one metre long (4 feet). At full maturity, the biggest specimens can weigh around forty six (46) kilograms (more than 100 pounds).
What Do Parrot Fish Eat?
Apart from being diurnal feeders, parrotfishes are also gregarious in nature and often gather in large aggregations during the day to feed or spawn.
Moving together in groups of fifty (50) or more improves their foraging efficiency. It also provides some defence against their main predators (large sharks and moray eels).
They are typical corallivores that use their strong jaws and muscles to feed on:
- Epilithic algae (growing on rocks or corals)
- Living coral (especially the reef-building corals)
- Other types of detritus
- cyanobacteria
- microscopic invertebrates (e.g. mixed in with algal films and reef rubble)
- Sea sponges
- Tunicate sea squirts
Fun Fact: Parrotfishes are noisy when they eat, and scuba divers often hear them as they crunch and grind their way through broken pieces of coral. Even so, this feeding habit helps to create fine white sand and it contributes to beach formations.
How Do Parrotfish Reproduce?
The relatively complex reproductive system of parrotfish involves various social structures, including the process known as hermaphroditism.
The two mating systems are known as harem spawning (where a dominant male guards a group of females) and group spawning.
But, even though most labriformes are "protogynous hermaphrodites", green humphead parrotfishes are actually "gonochoristic".
Hence, they are born as either a male or a female and they do not change sex upon reaching adulthood - which typically occurs between the ages of five (5) and eight (8).
Here's the thing:
Because the mating strategy takes place through external fertilisation, males and females will release eggs and sperm at suitable spawning sites above the reef.
It's a ritual that often involves multiple males and females releasing their gametes at the same time and usually coinciding with specific lunar cycles (e.g. full moon or new moon).
It can take several days for larvae to hatch, settle on the reef, and begin a new life as juvenile green humphead parrotfish.
Threats and Predators
The average lifespan for green humphead parrotfish is up to forty (40) years in the wild. However, they are slow-growing, mature late, and they have low replenishment rates.
As a result, the populations are declining in many areas, mostly due to coral habitat degradation, overfishing, and spearfishers hunting them during the night (mainly due to their predictable spawning patterns).
Despite being large and heavily armoured with thick scales, some of the most pressing human-induced threats to their survival include:
- Climate change (resulting in varying degrees of coral bleaching).
- Illegal fishing practices (e.g. spearfishing) and overfishing.
- Underwater garbage pollution.
- Habitat degradation and destruction (including habitat loss from dynamite fishing).
Pro Tip: According to the IUCN Red List of Threatened Species assessment in March 2007, the conservation status of green humphead parrotfish (Bolbometopon muricatum) is "Vulnerable" (VU) and the current population trend is "Decreasing".