Bumphead Parrotfish is a heavily exploited and conservation dependent species. Major extrinsic threats include unregulated or under-regulated fishing and habitat loss, particularly for juvenile habitat (coral lagoons). Intrinsic threats include aggregatory behaviour, particularly during spawning and nocturnal resting periods, which can result in increased susceptibility to rapid depletion and a hyperstable fishery. The species is also long-lived which reduces its ability to recover from heavy fishing effort. While there are few time series data available, it is clear that this species is far less common across much of its range than it once was, with several countries documenting declines exceeding 80%. While there are signs of population increases in areas where the species is effectively restricted from harvest, it is suspected that the global population has declined by at least 30% (possibly more) over the past three generations (69 years, or ~1955–2024) and that the causes of this decline have not ceased and will continue into the future. It is therefore listed as Vulnerable A2bcd with a recommendation to improve fishing regulation, protect coral habitat, and monitor abundance trends.

This is a patchily-distributed species that has been recorded from tropical and sub-tropical waters of the western Indian Ocean (including the Red Sea) to French Polynesia, however, it does not appear to occur in the Persian Gulf, the Arabian Sea, or the Bay of Bengal (Randall et al. 1990, Myers 1999). The depth range for this fish is 1–40 m.

This species was once considered common throughout much of its range (Donaldson and Dulvy 2004), however it is now considered uncommon to rare in some regions, with local densities negatively correlated with fishing pressure, and with suspected local extirpation at various localities, including sites in the western Indian Ocean, Guam, the Marshall Islands, parts of Fiji, eastern Africa (Kenya, Mozambique, Madagascar) and the Gulf of Aden (Dulvy and Polunin 2004, Lindfield et al. 2014, Samoilys et al. in review 2025).  

Time series data on abundance/biomass are largely unavailable, however, it is readily apparent from historical accounts that this species is less abundant across the majority of its range now than in the past, particularly in regions where it is exploited. In an effort to estimate global population abundance trends, Kobayashi et al. (2011) used a bootstrap-based modelling approach to estimate the total abundance across its entire range as well as a “virgin” abundance estimate. There are many caveats and assumptions associated with this approach, however, Kobayashi et al. (2011) postulated that the estimated contemporary abundance at the time of writing was 35–50% less than the estimated “virgin” abundance. Kobayashi et al. (2011) also used a generalized additive model to estimate annual density from 1997–2009 (12 years) at 14 countries across the species’ range. In some countries, there was a clear decline (e.g., Indonesia), whereas in others, there was a clear increase (e.g., French Polynesia) or a fluctuating pattern (e.g., Japan).

Marked decline was noted from the Solomon Islands over a 10-year period due to exploitation (Hamilton et al. 2019). Underwater visual census surveys conducted in 2000 and again in 2018 in Roviana Lagoon, western Solomon Islands showed that abundances of all size classes of the species declined by 62% while adult only abundances declined by 78% over the 18-year time period. Using a joint model of abundance and its reported maximum catch, it was estimated that in 2018, the population was 8% of its 1980s abundance (92% decline over 38 years; Hamilton et al. 2019). In parts of Micronesia, the species is largely caught below its mean size of sexual maturation (Houk et al. 2012).

Thomson et al. (2021) reported on the presence of this species at Ningaloo Reef (Australia) despite its absence there in scientific surveys for 32 years (1987–2019). These authors estimated that it had been present on Ningaloo Reef in ecologically relevant numbers since 2006 and that their numbers have increased between 2005–2020 at this location. The authors attributed the lack of sightings in scientific surveys to methodological differences (e.g., previous surveys did not survey the reef area where the species resides). This could also affect the absence of this species in other surveys throughout the species range.

Friedlander et al. (2023) calculated spawning potential ratio in Palau from fisheries independent data and it showed a slight increase from 30% to 34% for the years 2013 and 2021. Visual census survey data in Palau by the same authors showed a mean density of 2.75 individuals per hectare in 2013 and 2.72 in 2021 (non-significant difference). 

There are some landings data available, however these must be used with caution if attempting to correlate them with abundance. In addition to the usual caveats that must be considered, this species exhibits hyperstability (Hamilton et al. 2016). In a hyperstable scenario, catch-per-unit-effort (CPUE) remains constant despite population declines, thus creating the illusion that catch rates (and by inference populations) are sustainable. In many cases, species which aggregate at predictable times or locations show a pattern consistent with hyperstability as fishers concentrate efforts on these aggregations. In the case of this species, night-time spearfishing on aggregated fish during nocturnal resting periods is a major source of landings which contributes to this hyperstable scenario. Because of this hyperstability, when CPUE begins to decline, abundance may already be at a critically low level.

FAO landings data are available for Saudi Arabia. Landings from 2000–2022 ranged from 254–6.9 mt with a generally declining trend but there is no estimate of effort available. 

Region-specific population information is included in the Supplementary Information. 

Overall, it is suspected that the global population has declined by at least 30% over the past three generations (69 years or from ~1955–2024).

This species is the largest of all parrotfish, reaching over 75 kg in weight and a total length of at least 150 cm (Gladstone 1986, Muñoz et al. 2012). It is gregarious and adults occur primarily on seaward reef crests and fronts, but may also occur on outer lagoon reefs at depths of 1 to 40 m; it also enters outer reef flats at low tide to forage. Adults are inactive nocturnally (a labrid trait) sleeping in schools in shallow water. Juveniles are largely restricted to lagoons.
 
Adults may range up to 6 km from nocturnal resting sites (Hamilton 2004). School size varies from approximately 8–10 individuals up to large groups of 100–150 adults (Gladstone 1986, Dulvy and Polunin 2004, Hamilton and Choat 2012). Gladstone (1986) described this species as generally timid and difficult to approach. It is reportedly wary on reefs near human settlement or use. The presence of a protected area, live coral, and algal cover positively influences its distribution and abundance in the Andaman Islands (Krishnan et al. 2013, Patankar et al. 2012).

Pelagic spawning occurs on a lunar cycle at resident spawning aggregation sites (Johannes 1981; Gladstone 1986; Hamilton et al. 2007, 2008; Muñoz et al. 2024). Eggs and larvae are pelagic. Unlike many parrotfishes, which are functional hermaphrodites, histological evidence suggests that the sexual pattern of this species is essentially gonochoristic with high incidences of anatomical but non-functional hermaphroditism. That is, all males pass through an immature female (or bisexual) phase as demonstrated by adult testis retaining the ex-ovarian lumen and peripheral sperm sinuses in the gonad wall. Females reach sexual maturity over a broad size range starting at around 50 cm total length and 100% are mature at 70 cm and 11 years of age. Males also reach maturity over a wide size range beginning at ~47 cm total length (Hamilton 2004, Hamilton et al. 2007). 

Local recruitment may be an important part of the population dynamics of this species. Using genetic parentage analyses and modelling dispersal patterns of larvae of this species from the Kia fishing grounds in the Solomon Islands, it was predicted that 34% of recruitment to the Kia fishery was spawned locally. Extrapolating the spatial resolution of the model revealed that a high proportion of the larvae recruiting into the Kia fishing grounds came from nearby regions that had abundant adult populations and highlighted the value of localized spatial management (Hamilton et al. 2021).

This species is a specialist on microbial algae which is removed by selective biting from inert calcareous surfaces (Gladstone 1986, Randall et al. 1990, Bellwood et al. 2003). Aggregations of this species are important producers of coral sand on reefs and may be important in the maintenance of reef ecosystem resilience (Bellwood et al. 2003). This species produces bioerosion; large adults can remove at least 5 tons of carbonate reef structures per year (Bellwood et al. 2003, Comeros-Raynal et al. 2012).

This species may reach ages in excess of 40 years (Andrews et al. 2015) and reaches sexual maturity at 5–7 years (Taylor et al. 2018). Using a maximum age of 40 years and an age at maturity of 6 years and applying the mean generational turnover formula in Depczynski and Bellwood (2006), one generation length is estimated at 23 years, therefore, we estimate three generation lengths to be about 69 years. The equation applied by Depczynski and Bellwood (2006) is similar to and yields the same result as the recommended methods in the IUCN Red List Guidelines for calculating generation length (IUCN Standards and Petitions Committee 2024) of “Age of first reproduction + [z * (length of the reproductive period)], where z is a number between 0 and 1; z is usually <0.5, depending on survivorship and the relative fecundity of young vs. old individuals in the population.”.

The major extrinsic threats to this species are from uncontrolled fishing for both local and export uses and the destruction of or damage to inshore habitats and coral reef decline due to coral bleaching. Juveniles depend on healthy lagoon habitat that is vulnerable to sedimentation or other disturbances. In the Solomon Islands, for example, a 24-fold decline in juvenile abundance was noted due to habitat loss relating to logging operations (Hamilton et al. 2017).

The species is highly vulnerable to night spearfishing and the very distinctive recruitment requirements may have a role in adult distributions (which are very patchy at geographic scales) and abundance. This latter is important because the placement of marine protected areas as conservation measures would depend heavily on where these are placed and would need to include key habitat particularly inshore recruitment sites. 

Fishery based models of demographic processes, such as those applied by NOAA (Kobayashi et al. 2011) rather than direct examination of life history parameters and key life history processes may not produce meaningful stock/status assessments of this species.

Intrinsic threats include its long life span and aggregate behaviour, particularly during nocturnal resting periods. These aggregations are easily located by fishers and can be quickly depleted. This creates a hyperstable fishery in which catch-per-unit-effort (CPUE) may remain high despite large declines in abundance (Hamilton et al. 2016).

This species is primarily used as a food source and is traded on local, national, and international scales where it retains a high value; it often demands the highest prices in markets (e.g., in the Solomon Islands, Hamilton 2003). In some areas, the species has a high cultural value and is favoured for ceremonial events (e.g., in Fiji; Dulvy and Polunin 2004). It has also become a popular species among the recreational diving community.

This is a conservation-dependent species and there are various levels of conservation actions at regional scales (see Supplementary Information). In regions where this species is protected (i.e., with a prohibition on harvest), the species seems to have positively responded in terms of increases in abundances (e.g., Palau). While there are marine protected areas scattered throughout the range of the species, many are of insufficient size or are insufficiently monitored and enforced to effectively reach conservation targets for this species.

Recommended conservation actions include: (1) implementing and enforcing reasonable take limits where the species is fished; (2) educating stakeholders on the important ecological role of this species and its susceptibility to heavy fishing pressure; (3) creating and enforcing large marine reserves that incorporate key habitat; and (4) reduction in anthropogenic disturbances to habitat, particularly for juvenile habitat.

Research recommendations to inform and improve conservation actions include generation of quantitative time series data on abundance. Much of the life history of the species is not well-known and calls for more research to better understand threats and identify management approaches.

Region specific conservation measures are presented in the Supplementary Information.