Bolbometopon muricatum 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Perciformes Labridae

Scientific Name: Bolbometopon muricatum (Valenciennes, 1840)
Common Name(s):
English Green Humphead Parrotfish, Bumphead Parrotfish, Double-headed Parrotfish, Humphead Parrotfish
French Filambase, Perroquet À Bosse, Perroquet Bossu Vert
Spanish Loro Cototo Verde
Bolbometopon muricatus (Valenciennes, 1840) [orth. error]
Callyodon muricatus (Valenciennes, 1840)
Scarus muricatus (Valenciennes, 1840)

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2d ver 3.1
Year Published: 2012
Date Assessed: 2007-03-02
Needs updating
Assessor(s): Chan, T., Sadovy, Y. & Donaldson, T.J.
Reviewer(s): Choat, J.H., Dulvy, N. & Hamilton, R.
Contributor(s): Raynal, M.
Donaldson and Dulvy (2004) stated that B. muricatum was common or abundant throughout much of its range historically. This species is now considered rare globally, with local densities negatively correlated with fishing pressure across six Indo-Pacific locations, and with suspected local extinctions at some localities (Dulvy and Polunin 2004). Underwater surveys across its range in suitable habitats, even at remote localities, have either failed to detect this species or have detected only rare individuals (Dulvy and Polunin 2004, T.J. Donaldson unpublished data of timed "long-swim"/gps transects). Otherwise, it is abundant only on the Great Barrier Reef and at Rowley Shoals in northwestern Australia; juvenile B. muricatum appear to be very rare in the Great Barrier Reef, Australia (Bellwood and Choat 1989) but adults achieve their highest abundance on the Great Barrier Reef (mean = 31 fish per hectare) over the recorded range of this species (J.H. Choat pers. comm.). Based on rapid visual census from a series of transects of 50x5 m at depth of 12 m on individual reefs at Coringa-Herald National Nature Reserve (located east of Cairns, Australia), the abundance of B. muricatum was estimated to range from 1 to 25 fish in northeast and southwest Herald (Oxley et al. 2003).

Elsewhere, it is relatively abundant in the Solomon Islands, Papua New Guinea, and a few other oceanic islands, and is common locally at Samoa, Sipidan Island (Malaysia), Wake Island, the Red Sea and New Caledonia. Choat and Randall (1986) described B. muricatum as widely distributed in West Indian and Pacific Oceans, and was most commonly observed on reef fronts, reef crests and flats. At other locations, it is now uncommon or rare, and is virtually extinct in Guam, Marshall Islands, parts of Fiji and East Africa, and is declining rapidly in Palau (Myers 1991, Donaldson and Dulvy 2004, Dulvy and Polunin 2004, Donaldson unpubl. data). This species is naturally rare in some parts of its range (e.g., Christmas Island, Amirantes and Farqhuar Atoll, Seychelles, and elsewhere in the Indian Ocean), a fact which cannot be attributed to over-fishing.(J.H. Choat pers. comm.). B. muricatum was rare around most the US Pacific Islands and was seen typically only at 1 or 2 islands of a region (e.g., US Line Islands, US Phoenix Islands, Marianas Archipelago, or American Samoan Islands) (R.H. Schroeder, Coral Reef Ecosystem Division of the NOAA, pers. comms. on 14th Aug 2006; 23rd and 29th Dec 2006).

See the Supplementary Material for the fishery-independent data. No fishery-dependent data are available either regionally or by country.

Donaldson and Dulvy (2004) showed that the large-sized, long-lived B. muricatum, but with low replacement rates and high vulnerability to fishing pressure, appears to be of considerable functional importance (as a major bioeroder on coral reefs and maintain ecosystem resilience) which should be protected.

Hamilton (2003) pointed out that the introduction of simple but new technologies coupled with small scale economic restructuring (from the mid 1970s till the end of 1980s, there were no cash markets for B. muricatum; greater financial development in late 1980s ended up in the development of fisheries projects; by the mid 1990s, fillets of B. muricatum were bought at a higher price than any other fish - commercialization) of the B. muricatum fishery in Solomon Islands has overexploited its stock which is in need of management.

As parrotfish are the only fish group capable of consuming reef carbonate, Bellwood et al. (2003) indicated that B. muricatum plays a crucial role in reef ecosystem processes, and its absence highlights the potential for marked changes in ecosystem function (shifting from steady-state reef calcification to carbonate accumulation).

Dulvy and Polunin (2004) revealed that informal methods of inferring whether a species is naturally rare or has declined or disappeared as a result of human activity could aid efforts to provide a more accurate estimate of the contemporary marine extinction rate in such data-poor situations.

In the Solomon Islands, Aswani and Hamilton (2004) stated that protection of the highly fecund large females would enhance the sustainability of the Roviana fishery.

Donaldson and Dulvy (2004) recommended (1) implementing a moratorium on commercial fishing and export; (2) educating stakeholders and the general public on the importance of conserving B. muricatum; (3) creating and enforcing larger marine reserves that incorporate key habitat; and (4) carrying further research on its population ecology and behaviour.

D. Fenner (pers. comm., 22nd Oct 2006) suggested that it is important to protect and monitor B. muricatum, a coral predator, because its removal might have effects on coral reef ecosystem with unknown consequences.

Gillett and Moy (2006) suggested that B. muricatum (a species that is inherently not very resilient to fishing pressure) should be a conceptual issue for consideration on the control of the fishing gear selectivity (especially selectivity of spearfishing).

Russ and Alcala (1998) suggested that the small size of most marine protected areas in heavily fished regions would show little positive effects on reef-bioeroding parrotfish abundances.

G.R. Allen (pers. comm. 16 January 2007) recommended blanket protection of this species, offering the "chance for the numerous immature fish to grow and form the nucleus of the globally exceptional concentration" of this giant reef fish.

For this historically abundant species, more information on its present abundance, biology, age-and-growth and management practices is recommended before it disappears due to unsustainable exploitation.

Given all the above information it seems reasonable to infer at least a 30% population reduction of the Humphead Parrotfish in the last three generations (the last 30 years) due to over-exploitation in parts of its range.
For further information about this species, see 63571_Bolbometopon_muricatum.pdf.
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Previously published Red List assessments:

Geographic Range [top]

Range Description:Recorded from the Red Sea east to the Line Islands and Tuamotu Archipelago (French Polynesia), north to Taiwan, the Yaeyama Islands (Japan), and Wake Island (United States Minor Outlying Islands), south to northwest Australia, the Great Barrier Reef and New Caledonia (Randall et al. 1990, Myers 1999).
Countries occurrence:
American Samoa; Australia; Christmas Island; Cocos (Keeling) Islands; Egypt; French Polynesia (Society Is., Tuamotu); Guam; Indonesia; Japan (Nansei-shoto); Kenya; Kiribati; Madagascar; Malaysia; Maldives; Mauritius; Micronesia, Federated States of ; Mozambique; Myanmar; New Caledonia; Niue; Northern Mariana Islands; Palau; Papua New Guinea; Philippines; Samoa; Seychelles; Solomon Islands; Somalia; Taiwan, Province of China; Tanzania, United Republic of; Tonga; United States Minor Outlying Islands (Wake Is.); Vanuatu; Yemen (Socotra)
FAO Marine Fishing Areas:
Indian Ocean – western; Indian Ocean – eastern; Pacific – western central; Pacific – northwest; Pacific – eastern central
Additional data:
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:B. muricatum are locally patchily distributed, adults always found in small shoals (<= 40 individuals) (Donaldson and Dulvy 2004).

Choat and Randall (1986) stated B. muricatum does not display sex-associated patterns of colour change, maintaining a uniform body colouration in adult females and males. Juvenile shows a distinct colour pattern.

Hamilton (2003) described B. muricatum is the largest of all parrotfish, reaching over 50 kg and living to an age of at least 40 years.

Gladstone (1986) revealed that B. muricatum individuals usually occur as part of schools containing 20 to almost 100 fish which often move into shallow waters during feeding around Lizard Island in Great Barrier Reef.

Based on a histological analysis of gonad collected from 169 females in Solomon Islands in 2000-2001, the size of maturity was found to be 620 mm FL, in which some specimens as small as 610 mm FL showed significant gonad development (Hamilton 2003).

Hamilton and Adams (unpubl. data) showed that 100% female maturity occurs at 650 mm SL.

FishBase 2006 ( estimates that the minimum population doubling time ranges from 4.5 to 14 years; this estimate is derived from a formula that utilizes length and infinity (Linf), length at maximum yield (Lopt), time at length "0" (t0) and K (= 0.10), and may need to be recalculated given the maximum age of this species (J.H. Choat, pers. comm., 18 September 2006). FishBase (2006) calculates that the decline threshold equals 0.85; this species is vulnerable to extinction if this threshold value is exceeded over the longer of 10 years or three generations.

Sex composition
Information not available

Length-age relationship
Information not available.
Current Population Trend:Decreasing
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:This species is gregarious and occurs in aggregations of up to several (> 75) individuals on seaward and clear outer lagoon reefs at depths of 1 to 30m; also enters outer reef flats at low tide to forage. Pelagic spawning on a lunar cycle; utilises resident spawning aggregations sites (Johannes 1981, Gladstone 1986). Eggs and larvae are pelagic. Primarily a corallivore, but also feeds upon benthic algae; this species uses its large gibbus head to ram corals and break them into pieces that are more easily ingested. Aggregations of this species are important producers of coral sand on reefs and may be important in the maintenance of ecosystem resilience (Bellwood et al. 2003). Reportedly wary on reefs near human settlement or use. This species sleeps in large groups, thus rendering them highly vulnerable to exploitation by spearfishers (mainly in the Pacific region) and netters at night (Myers 1999).

Additional notes, as follows:

Exposed reef crests are the primary habitat of B. muricatum (J.H. Choat, pers. comm. on 4th Jan 2007).

In unfished areas, B. muricatum may enter outer reef flats at depths of 1 to at least 30 m (Myers 1991).

Lieske and Myers (1994) observed that juveniles can be found in lagoons, while adults are in clear outer lagoon and seaward reefs at depths of at least 30 m.

Very small individuals are restricted to the shallow inner lagoon in Solomon Islands (Aswani and Hamilton 2004).

At Roviana Lagoon, Solomon Islands, juveniles are limited to the shallow inner lagoon environment, while larger individuals occur predominantly in passages (Hamilton 2004).

B. muricatum feeds substantially on live coral (Gladstone 1986, Myers 1991, Bellwood et al. 2003) and benthic algae (Randall et al 1990).

Gladstone (1986) described B. muricatum as generally timid and difficult to approach.

Bellwood et al (2003) reported that B. muricatum produces significant bioerosion in the Indo-Pacific. Based on 132 timed transects (20-min long, 5 m wide) at 9 reefs in the Great Barrier Reef, schools of 30 to 50 huge (up to 120 cm TL) specimens with each individual removing 2.33 m³ or 5.69 tonnes of structural reef carbonate each year.

Spawning behaviour in a tightly packed school of about 100 individuals (pair spawning activities among this mobile group) was observed from the seafloor (15 m deep) to about 2 m below the surface on the morning of January 15, 1985 in Great Barrier Reef (Gladstone 1986). None of the B. muricatum in the spawning school was smaller than about 60 cm TL (Gladstone 1986). Choat and Randall (1986) recorded a group spawning (40 to 50 fish) on the outer face of Yonge reef in Great Barrier Reef during December 1983.

Sexual Pattern
Randall and Bruce (1983) had suggested sex inversion occurs in B. muricatum. J.H. Choat, pers. comm., 18 September 2006) stated that this species does not appear to be diandric; there is an extended prereproductive period of sexual differentiation from which males are produced.

Fecundity and Recruitment
Information not available
Movement patterns:Full Migrant

Use and Trade [top]

Use and Trade: This species is consumed as food. Aswani and Hamilton (2004) reported that divers in Roviana Lagoon, Solomon Islands would selectively target the largest individuals among a school of resting B. muricatum so as to let the remaining fish to flee. By the mid 1990s, fillets of B. muricatum were bought at a higher price than any other fish in Solomon Islands (Hamilton 2003).

With not much market interest for B. muricatum in Palau now (Y. Sadovy pers. comm.; source: unpublished interviews done by the Society for the Conservation of Reef Fish Aggregations).

Lieske and Myers (1994) described B. muricatum to be vulnerable to overfishing. The habit of sleeping in large groups making B. muricatum highly vulnerable to be caught by commercial spearfishermen (Myers 1991).

Threats [top]

Major Threat(s): B. muricatum forms mixed sized schools and is extremely vulnerable to overfishing (Hamilton 2003).

Shoaling and group resting behaviour render B. muricatum highly vulnerable to spearfishing, particularly at night-time (Donaldson and Dulvy 2004) and mainly in the Pacific region (J.H. Choat pers. comm.). Spearfishing at night has reduced the numbers of B. muricatum (Gladstone 1986, D. Fenner pers. comm. on 27th July 2006).

In Roviana Lagoon (Solomon Islands), artisanal spear fishers use their sophisticated indigenous knowledge of the spawning behaviour and ecology of B. muricatum to catch as many fish as possible in a night (Hamilton 2003).

The belief that B. muricatum predominantly aggregate at night around the new moon period and that catch rates are far greater during the new moon was not supported by field survey done in 2000-2001 (Aswani and Hamilton 2004).

Dulvy and Polunin (2004) suggested that the decline of B. muricatum in the Lau Group in Fiji was mainly due its nocturnal aggregative behaviour in shallow lagoon water or in reef caves and the daytime foraging of shoals in depth accessible by spearfishermen.

B. muricatum was often captured for ceremonial events, indicating this species has a high cultural significant value in the Lau Island group, Fiji (Dulvy and Polunin 2004).

Low priority to enforcing legislation related to spearfishing in Fiji (Gillett and Moy 2006).

In 2001, the Samoa Fisheries Projected reported that SCUBA spearfishing activities at night had been increased rapidly in the past 12 months, in which B. muricatum was one of the target species (Gillett and Moy 2006).

Gillett and Moy (2006) pointed out that sleeping B. muricatum was one of the three main types of fish to be targeted by spearfishing.

Parrotfishes show varying degrees of habitat preference and utilization of coral reef habitats, with some species spending the majority of their life stages on coral reefs, while others primarily utilize seagrass beds, mangroves, algal beds, and /or rocky reefs. Although the majority of the parrotfishes occur in mixed habitat (primarily inhabiting seagrass beds, mangroves, and rocky reefs) approximately 78% of these mixed habitat species are experiencing greater than 30% loss of coral reef area and habitat quality across their distributions. Of those species that occur exclusively in coral reef habitat, more than 80% are experiencing a greater than 30% of coral reef loss and degradation across their distributions. However, more research is needed to understand the long-term effects of habitat loss and degradation on these species populations. Widespread coral reef loss and declining habitat conditions are particularly worrying for species that depend on live coral reefs for food and shelter especially as studies have shown that protection of pristine habitats facilitate the persistence of adult populations in species that have spatially separated adult and juvenile habitats. Furthermore, coral reef loss and declining habitat conditions are particularly worrying for some corallivorous excavating parrotfishes that play major roles in reef dynamics and sedimentation (Comeros-Raynal et al. 2012).

Conservation Actions [top]

Conservation Actions: Two marine protected areas (MPAs) ["no-take" zones] were established in Baraulu Village and Nusa Hope Village, Solomon Islands in 2002 to protect B. muricatum and other lagoon species (Aswani and Hamilton 2004).

There are no direct protective practices for B. muricatum.

The Fisheries (Restrictions on Use of Breathing (Apparatus) Regulations, 1997 ban the use of underwater breathing apparatus to "collect, take, or dive for fish", except for those with appointment from the Permanent Secretary or any person appointed by him in writing. And the Sixth Schedule of the Fisheries Regulation establishes minimum sizes for 21 tpes of fish, including many that are often caught by spearfishing (Gillett and Moy 2006).

Besides, traditional fisheries rules (e.g,. a ban on night diving, and a ban on the use of SCUBA for fishing) in most of the 410 traditional fishing areas in Fiji have their own local fishing rules and many of those are applicable to spearfishing (Gillett and Moy 2006).

The Fishing (Scuba Fishing) Regulations 2003 states no person shall scuba fish without a license (Gillett and Moy 2006).

Many different types of traditional rules (e.g., establishing small protected areas, minimun size limits, and restricting the use of underwater torches for spearfishing at night) governing fisheries exist in the 324 villages of Samoa (Gillett and Moy 2006).

Solomon Islands
Regulations 29 of the Fisheries Act, which enacted in January 2004, states "any person using under-water breathing apparatus for the purpose of harvesting any marine resource shall be guilty of an offence and liable to a fine not exceeding five thousand dollars or six months imprisonment or both such fine and imprisonment" (Gillett and Moy 2006).

Many villages regulate spearfishing (e.g. bans on night diving) by themselves (Gillett and Moy 2006).

Although traditional leader's ability to manage marine resource was found to be effective in some of the tribes in Solomon Islands, the existence of non-member (e.g., institutional context) and enforcement of harvest restriction rules are crucial so as to enhance management and minimize the public contest over natural resources (Aswani and Hamilton 2004).

Russ and Alcala (1998) suggested that the small size of most marine protected areas in heavily fished regions would show little positive effects on parrotfish abundances.

Aswani and Hamilton (2004) suggested that the prohibition on spearfishing within passage habitats in Roviana Lagoon, Solomon Islands, would provide a measure of protection the remaining important spawning stocks of B. muricatum in the Indo Pacific region.

Aswani and Hamilton (2004) recommended that any lunar ban on spearfishing should focus at late full moon quarter during which B. muricatum spawns.

Citation: Chan, T., Sadovy, Y. & Donaldson, T.J. 2012. Bolbometopon muricatum. The IUCN Red List of Threatened Species 2012: e.T63571A17894276. . Downloaded on 24 September 2018.
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