Bolbometopon Research Articles

Productivity susceptibility analysis in extremely data-poor scenarios: The case of Peruvian coastal groundfish

Coastal small-scale fisheries remain largely unassessed and unregulated worldwide, which leads to a high risk of overfishing. Availability and quality of data are major barriers to performing model-based assessments, particularly in low and middle-income countries. In that context, alternative assessment methods are key to defining priorities, as well as prompting and guiding management actions. In this study, we assessed the vulnerability to overfishing of 10 extremely data-poor species of coastal groundfish in Peru, by applying an adapted Productivity Susceptibility Analysis (PSA). We classified fisheries-related Susceptibility attributes and streamlined a process to assess and integrate multiple fisheries and gears into a single score for each attribute. The data quality scores regarding productivity and susceptibility were between “limited” and “no data”, across all stocks. Therefore, expert knowledge was key for completing the assessment. Stocks of four species presented extremely high Vulnerability to overfishing: broomtail grouper (V=2.57), grape-eye seabass (V=2.50), pacific goliath grouper (V=2.28) and galapagos sheephead wrasse (V=2.24). Three showed high Vulnerability to overfishing: black snook (V=2.13), harlequin wrasse (V=2.05) and chino (V=2.01). Two showed medium Vulnerability to overfishing: mulata (V=1.89) and pacific beakfish (V=1.89). Only the stock of bumphead parrotfish showed low Vulnerability to overfishing (V=1.73). We contrasted the resulting Vulnerability scores with the limited available information on the statuses of these stocks, to evaluate the accurateness of the overfishing probability thresholds proposed in PSA literature. We found that Vulnerability scores were mostly consistent with contrasted information and that the thresholds remain useful to inform fisheries management in extremely data-poor contexts. Our results shed light on the need for the implementation of fishing regulations and the generation of biological and fishery-related data on coastal groundfish in Peru.

Assessing and managing charismatic marine megafauna in Palau: Bumphead parrotfish (Bolbometopon muricatum) and Napoleon wrasse (Cheilinus undulatus)

Abstract Bumphead parrotfish (Bolbometopon muricatum) and Napoleon wrasse (Cheilinus undulatus) are large, charismatic species with high economic and cultural value in Palau and are important for ecosystem function. As a result of intense fishing pressure, landings in Palau for both species declined dramatically in the 1990s and, in response, national legislation was enacted in 2006 that imposed a total ban on the extraction, possession, and sale of both species. In 2013 and 2021, fisheries‐independent stock assessments were conducted and found that the spawning potential ratios (SPRs) for bumphead parrotfish increased slightly from 30% to 34%. Conversely, the SPRs for Napoleon wrasse declined from 12% in 2013 to 4% in 2021. Despite the fishery being closed since 2006, these data suggest the likelihood of significant poaching, resulting in low SPR values, particularly for Napoleon wrasse. Prior to the COVID‐19 pandemic, marine tourism played a central role in the economic and social life of Palau. A willingness‐to‐pay survey found that divers would pay $1.27 million (2020 USD) more for strictly managed catches of both species, and nearly $3.00 million more if the fishery remained closed. The total market value for bumphead parrotfish peaked in 1995 at $112,190. The peak total market value for Napoleon wrasse was $66,434 in 2002. The welfare gain/loss for diver tourism is an order of magnitude greater than the fishery market gain/loss, and healthy marine ecosystems are essential for the post‐COVID‐19 economic recovery of Palau. However, because of the cultural importance of these species, there is a desire to manage this fishery for customary use. Opening a general subsistence harvest season is not recommended ecologically; however, the results suggest that if the SPR of bumphead parrotfish can recover to 40%, a limited quota of individuals with a total length of >95 cm could be sustained, which could be allocated via lottery. However, the fishery for Napoleon wrasse should remain closed given the extremely low SPR values and limited number of large adults in the population.

Climate change disturbances contextualize the outcomes of coral-reef fisheries management across Micronesia

Climate change is increasing disturbance events on coral reefs with poorly understood consequences for fish population dynamics and fisheries management. Given growing concerns over food security for the tropical Pacific, we assessed fisheries management policies across a suite of Micronesian islands since 2014 as climate disturbance events have intensified. Disturbances associated with the 2015–2017 ENSO led to significant mortality of corals and calcifying substrates and replacement with algae and detritus, followed by a doubling of biomass across all fish guilds that was proportional to their starting points for all islands. Increased fish biomass was equally attributed to growth of individuals evidenced by increased size structures, and recruitment/survival evidenced by larger population densities. However, the pulsed increase of fish biomass lasted 1–2 years for islands with limited and isolated MPA but remained high for islands with effective MPA networks for 4 years until the study ended. Meanwhile, policies to protect grouper spawning seasons resulted in increased occurrences that were magnified by disturbances and MPA. Grouper increases were largest where both spawning season bans and MPA networks existed, helping to tease apart the management-from-disturbance responses. Smaller rates of increases over longer time were observed for species with commercial fishing bans (bumphead parrotfish, Napoleon wrasse, and sharks). Yet, occurrences remain low in comparison to remote-island baselines, and MPA only provided benefits for juveniles in inner lagoons. Recent trends for these species were less influenced by climate disturbances compared to groupers. The results cautioned how short-term responses of fish assemblages following climate disturbances can provide false signs of success for some management policies without contextual reference baselines that may not exist. Positively, improvements were noted for both MPA and species policies in our region that are expected to benefit reef resilience.

Hidden Giants: The Story of Bolbometopon muricatum at Ningaloo Reef

Bolbometopon muricatum (bumphead parrotfish, Valenciennes, 1839) is a conspicuous, iconic and ecologically important coral reef fish species. B. muricatum plays an important role in the bioerosion of the reef framework and as a result has been described as both an ecosystem engineer and keystone species. Despite the complete absence of B. muricatum from 32 years of scientific surveys across the Ningaloo Reef World Heritage Area, we recorded a total of 155 individuals of B. muricatum across 63.2 ha of reef crest surveys, equating to mean density of 2.38 ind/ha. Our observations represent the first record of this iconic species in scientific surveys at Ningaloo and in combination with qualitative observations of B. muricatum by expert witnesses, indicate B. muricatum is likely to have been present in ecologically relevant densities since 2006. The densities of B. muricatum observed at northern Ningaloo in 2021 suggest this species is removing an estimated 13.42 tonnes/ha or 1.34 kg/m2 of calcium carbonate per year, which is broadly comparable with estimates of total parrotfish bioerosion across many reefs in the central Indian and Pacific Oceans. Although not currently afforded elevated conservation status within management plans, B. muricatum possess many life-history characteristics that make them vulnerable to overfishing and may justify consideration for increased protection within the world heritage listed Ningaloo Reef Marine Park.

Night on Earth

Night on Earth

Larval dispersal and fishing pressure influence recruitment in a coral reef fishery

Abstract Understanding larval connectivity patterns in exploited fishes is a fundamental prerequisite for developing effective management strategies and assessing the vulnerability of a fishery to recruitment overfishing and localised extinction. To date, however, researchers have not considered how regional variations in fishing pressure also influence recruitment. We used genetic parentage analyses and modelling to infer the dispersal patterns of bumphead parrotfish Bolbometopon muricatum larvae in the Kia fishing grounds, Isabel Province, Solomon Islands. We then extrapolated our Kia dispersal model to a regional scale by mapping the available nursery and adult habitat for B. muricatum in six regions in the western Solomon Islands, and estimated the relative abundance of adult B. muricatum populations in each of these regions based on available adult habitat and historical and current fishing pressure. Parentage analysis identified 67 juveniles that were the offspring of parents sampled in the Kia fishing grounds. A fitted larval dispersal kernel predicted that 50% of larvae settled within 30 km of their parents, and 95% settled within 85 km of their parents. After accounting for unsampled adults, our model 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. Other islands in the archipelago provided few recruits to the Kia fishing grounds, reflecting the greater distances to these islands and lower adult abundances in some regions. Synthesis and applications. This study shows how recruitment into a coral reef fishery is influenced by larval dispersal patterns and regional variations in historical fishing pressure. The scales of larval connectivity observed for bumphead parrotfish indicate that recruitment overfishing is unlikely if there are lightly exploited reefs up to 85 km away from a heavily fished region, and that small (<1 km2) marine‐protected areas (MPAs) are insufficient to protect this species. We recommend greater efforts to understand the interactions between larval dispersal and gradients of fishing pressure, as this will enable the development of tailored fisheries management strategies.

Isolated reefs support stable fish communities with high abundances of regionally fished species.

Anthropogenic impacts at isolated and inaccessible reefs are often minimal, offering rare opportunities to observe fish assemblages in a relatively undisturbed state. The remote Rowley Shoals are regarded as one of the healthiest reef systems in the Indian Ocean with demonstrated resilience to natural disturbance, no permanent human population nearby, low visitation rates, and large protected areas where fishing prohibitions are enforced. We used baited remote underwater video systems (BRUVS) to quantify fish assemblages and the relative abundance of regionally fished species within the lagoon, on the slope and in the mesophotic habitat at the Rowley Shoals at three times spanning 14 years and compared abundances of regionally fished species and the length distributions of predatory species to other isolated reefs in the northeast Indian Ocean. Fish assemblage composition and the relative abundance of regionally fished species were remarkably stable through time. We recorded high abundances of regionally fished species relative to other isolated reefs, including globally threatened humphead Maori wrasse (Cheilinus undulatus) and bumphead parrotfish (Bolbometopon muricatum). Length distributions of fish differed among habitats at the Rowley Shoals, suggesting differences in ontogenetic shifts among species. The Cocos (Keeling) Islands typically had larger‐bodied predatory species than at the Rowley Shoals. Differences in geomorphology, lagoonal habitats, and fishing history likely contribute to the differences among remote reefs. Rowley Shoals is a rare example of a reef system demonstrating ecological stability in reef fish assemblages during a time of unprecedented degradation of coral reefs.

Stock Assessment of Parrotfishes “Molmol” (Sub-Family Scarinae, Family Labridae) in the Major Fishing Grounds of Bohol, Central Visayas

The issue on the overfishing of parrotfishes, locally known as “molmol” (subfamily Scarinae under family Labridae), in the coastal waters of Bohol province in Central Visayas has been raised by the Provincial Agricultural and Fishery Council (PAFC) of Bohol through Resolution No. 1 series of 2018 that pushes for the implementation of “open and closed fishing season” of all parrotfishes in the entire province. In any management intervention, baseline assessment of the stocks in question should be done as a significant basis for appropriate measures to be taken, thus this study. In Bohol, apart from the economic value, they carry essential functions in maintaining the ecological balance in the reef ecosystem. Parrotfishes are considered economically important as preferred fish among locals and tourists. The stock assessment of parrotfishes in Danajon Bank in the Bohol Sea and Cebu Strait was conducted by the National Stock Assessment Program (NSAP) Region 7 from 2015 to 2018 in 16 coastal municipalities of Bohol. It recorded 24 Scarine species across six genera. The green humphead parrotfish (Bolbometopon muricatum), categorized as vulnerable under the International Union for Conservation of Nature (IUCN) red list, was noted in Cebu Strait in 2015. Scarus ghobban, comprising 82.25%, dominated the catch in Danajon Bank; Scarus forsteni (30.07%) in Bohol Sea; and Chlorurus sordidus (58.45%) in Cebu Strait. Among the Scarines, S. ghobban dominated across fishing grounds from 2015 to 2018 with an aggregate of 10,267.69 kg (or 63.94%) monitored catch equivalent to 0.26% relative to all other species surveyed in the same period. The assessment also indicated that among the 22 fishing gear types being observed as used in catching parrotfishes, speargun is the most prevalent or frequently used. Moreover, the same assessment showed that the catch seasonality of S. ghobban determined from spear gun appears to be abundant during the first quarter in a year; in June, August, and December when higher monthly mean Catch per Unit Effort (CPUE) were also noted. However, the annual mean CPUE of speargun has decreased from 11.93 kg/day in 2017 to 9.22 kg/day in 2018. Population parameters of S. ghobban as the top one species were estimated using the FAO-ICLARM Stock Assessment Tools (FISAT) software and Froese Indicator Tool. Biological indicators for S. ghobban show signs of overfishing as reflected on its high fishing mortality (F/M), decreasing average length below maturity length, decreasing catch per unit effort in the current year, low percentage of mature in the catch, and increasing exploitation ratio (E). All of which already breached the limit reference points. In 2017 and 2018, the mature size composition of the catch was only 1.9 percent and 0.3 percent, respectively, far off from the 90-100% target and below the 50% limit. The values indicate that majority of the samples were small sizes; however, it cannot be determined if they were juveniles since this study excludes reproductive sampling. Optimum length (Lopt) was estimated at 29 cm (Total Length); lengths within ± 10% Lopt range at 26.1 to 31.9 cm and megaspawner at 31.9 cm up. Based on the results, suggested recommendations are indicated herein for possible consideration of the policymakers.

On the use of the bumphead parrotfish (<i>Bolbometopon muricatum</i>) as a mobile shelter by a bluefin trevally (<i>Caranx melampygus</i>) in an oceanic reef system in the Philippines

On the use of the bumphead parrotfish (<i>Bolbometopon muricatum</i>) as a mobile shelter by a bluefin trevally (<i>Caranx melampygus</i>) in an oceanic reef system in the Philippines

Biodiversity of Natuna as a Potential Ramsar Site of Wetlands with International Importance in Indonesia

Ramsar site designation is an acknowledgment of a wetland’s importance. In this study, we conducted a biodiversity survey around Natuna to examine its eligibility as the next Ramsar site in Indonesia. This biodiversity survey was conducted through sampling for biological resources, using either transect, trapping, or visual observation. We surveyed 32 sampling stations for endangered and vulnerable fish, water birds, and wetland-dependent species. Samples were identified in meristic and morphometric form. We identified numerous endemic species and critically endangered, threatened, and vulnerable species. The most prominent native species are the endemic Presbytis natunae. Notable wood species are Eusideroxylon zwageri and Dipterocarpus sp., both critically endangered species. Sea grass species found in the coastal regions are Halodule pinifolia, Halophila ovalis, Enhalus acoroides, and Thalassia hemprichii. There are 52 species of fish found in the Natuna Sea, notably Bolbometopon muricatum, Oxymonacanthus longirostris, Plectropomus areolatus, and the endemic Cheilinus undulates. Numerous migrating birds and water birds are also found in the wetland and coastal region. The study concluded that Natuna fulfilled as a Ramsar site criteria based on its biodiversity characteristics and the support it provided to vulnerable species. We call for concentrated effort from the government for a successful nomination of Natuna as a Ramsar site..

Inventory of commercially important coral reef fishes in Tawi-Tawi Islands, Southern Philippines: The Heart of the Coral Triangle

Tawi-Tawi, Southern Philippines, which has over 300 islands and huge reef systems, is geographically located at the heart of the Coral Triangle, the global center of coral reef biodiversity. In this study, we conducted an inventory survey of market fishes in Tawi-Tawi from October 2015 to December 2018. We considered 11 major commercially important coral reef fishes, namely, surgeonfish (family Acanthuridae), parrotfish (subfamily Scarinae, family Labridae), snapper (family Lutjanidae), grouper (subfamily Epinephelinae, family Serranidae), sweetlips (family Haemulidae), goatfish (family Mullidae), emperor (family Lethrinidae), triggerfish (family Balistidae), coral bream (family Nemipteridae except genus Nemipterus), fusilier (family Caesionidae) and rabbitfish (family Siganidae). We further compared the results with published reports from Palawan and Panay Island which are also located along the Sulu Sea, the region with the highest coral reef fish diversity in the Philippines. Overall, we recorded a total of 266 species of reef fish in Tawi-Tawi with Epinephelinae (48 species), Lutjanidae (40 species) and Acanthuridae (33 species) as the most speciose groups. Further investigation showed that the average relative abundance of the three most abundant species in each family/subfamily is about 64.5% (range, 51.6% for Acanthuridae to 87.6% for Balistidae) of their respective groups. Based on the status assessment of the International Union for Conservation of Nature, one species (Scarus hypselopterus) was considered as Near Threatened (NT), four species (Bolbometopon muricatum, Epinephelus fuscoguttatus, Epinephelus polyphekadion and Plectropomus areolatus) as Vulnerable (VU) while the majority were considered as Least Concern (LC). The number of species recorded in Tawi-Tawi was much higher than in Palawan and Panay Island which had a total of only 159 species and 139 species, respectively. Moreover, Tawi-Tawi had about five times more unique species than either of the two other areas. Our study indicates the importance of the reefs of Tawi-Tawi and the Sulu Archipelago in general as the richest in the Philippines in terms of commercially important coral reef fish species diversity. Various factors that explain the high diversity of reef fishes on the reefs of Tawi-Tawi and the importance of conserving these valuable ecosystems are discussed.

Interspecific variation of prevalence by Scaphanocephalus (Platyhelminthes: Trematoda: Heterophyidae) metacercariae in parrotfishes (Labridae: Scarini) from an Okinawan coral reef.

Metacercarial cysts of the parasite Scaphanocephalus (Platyhelminthes: Trematoda: Heterophyidae) are frequently found on the pectoral fins and skin of parrotfishes (Labridae: Scarini) inhabiting Okinawan coral reefs in southern Japan. The prevalence of metacercarial cysts in 30 parrotfish species was investigated and compared through a market survey. Although parasite prevalence differed between parrotfishes, all species examined are considered to be suitable hosts. Prevalence was high in Scarus chameleon (38.5%, n = 13), S. rubroviolaceus (33.4%, 2797), S. ghobban (26.6%, 6441), and several other species that share, in part, common feeding habits. Conversely, prevalence was low in S. prasiognathos (0.4%, 1842), Bolbometopon muricatum (0.4%, 270), and Hipposcarus longiceps (0.1%, 8512) which have different feeding habits. Despite a few exceptions, feeding ecology and other indirect behaviors are considered to affect the prevalence of metacercarial cysts in parrotfishes. Taxonomic affiliation and nocturnal mucous cocoon usage are not considered to affect parasite prevalence.

An updated checklist of the marine fish fauna of Redang Islands, Malaysia.

BackgroundRedang Islands Marine Park consists of nine islands in the state of Terengganu, Malaysia. Redang Island is one of the largest off the east coast of Peninsular Malaysia, which is famous for its crystal-clear waters and white sandy beaches. The ichthyofauna of the Redang archipelago was surveyed by underwater visual observations between August 2016 and May 2018. Census data were compiled with existing records into the checklist of the marine fish of the Redang archipelago presented herein. A total of 314 species belonging to 51 families were recorded. The most speciose families (Pomacentridae, Labridae, Scaridae, Serranidae, Apogonidae, Carangidae, Gobiidae, Chaetodontidae, Lutjanidae, Nemipteridae and Siganidae) were also amongst the most speciose at the neighbouring Tioman archipelago (except Chaetodontidae). The coral fish diversity index value for the six families of coral reef fishes (Chaetodontidae, Pomacanthidae, Pomacentridae, Labridae, Scaridae and Acanthuridae) of the study sites was 132. We estimated that there were 427 coral reef fish species in the Redang archipelago. According to the IUCN Red List, eight species are Near Threatened (Carcharhinus melanopterus, Chaetodon trifascialis, Choerodon schoenleinii, Epinephelus fuscoguttatus, E. polyphekadion, Plectropomus leopardus, Taeniura lymma and Triaenodon obesus), eleven are Vulnerable (Bolbometopon muricatum, Chaetodon trifasciatus, Chlorurus sordidus, Dascyllus trimaculatus, Epinephelus fuscoguttatus, E. polyphekadion, Halichoeres marginatus, Heniochus acuminatus, Nebrius ferrugineus, Neopomacentrus cyanomos and Plectropomus areolatus) and three are Endangered (Amphiprion clarkia, Cheilinus undulatus and Scarus ghobban) in the Redang archipelago.New informationFive species are new records for Malaysia (Ctenogobiops mitodes, Epibulus brevis, Halichoeres erdmanni, H. richmondi and Scarus caudofasciatus) and 25 species are newly recorded in the Redang archipelago.

Reef development on a remote coral atoll before and after coral bleaching: A geospatial assessment

Coral reefs are consolidated calcium carbonate (CaCO3) platforms built over hundreds of thousands of years by calcifying organisms including corals, encrusting algae and invertebrates. The geomorphic integrity of coral reefs depends on the carbonate budget, which quantifies the net gain or loss of calcium carbonate, given additive and removal processes. Here, we construct three carbonate budgets for Cocos (Keeling) atoll in the East Indian Ocean from seafloor records of carbonate producers before, during and after a coral bleaching event (2015–2017). A satellite image is used to upscale 367 in-situ observations across the complete atoll (are 225 km2). Growth of calcifying encrusters is monitored on settlement plates from 2015 to 2016, while bioerosion is quantified from parrotfish surveys and macroborer analysis of rubble. The highest rates of production were on the outer atoll forereef and in the northern lagoon (1.5 and 1.61 kg m−2 yr−1 respectively). The forereef produced an order of magnitude more calcium carbonate (approximately 13,114 t per year in 2015) than the other zones due to a high coverage of live branching coral (ca 50%) combined with a large forereef area (123 km2). The greatest rates of removal occurred on the shallow forereef (−1.67 kg m−2 yr−1) driven largely by Bolbometopon muricatum parrotfish bioerosion, resulting in a net loss of carbonate in 2017 (−0.15 kg m−2 yr−1). Accounting for parrotfish bioerosion, the net atoll budget was estimated to be 5976 t of calcium carbonate in 2015, which reduced by 46% over the coral bleaching period to 3200 t in 2017. Compared to other Indian Ocean reefs, this is a relatively minor impact of coral bleaching on the carbonate budget at Cocos (Keeling) atoll.

Community-based management fails to halt declines of bumphead parrotfish and humphead wrasse in Roviana Lagoon, Solomon Islands

Community-based fisheries management that integrates local knowledge and existing user rights is often seen as a solution to the failures of top-down fisheries management in the Pacific. In Roviana Lagoon, Western Solomon Islands, a network of community-based marine protected areas (MPAs) was established in the early 2000s to conserve declining populations of bumphead parrotfish (Bolbometopon muricatum) and other locally valuable fish species such as humphead wrasse (Cheilinus undulatus). We aimed to evaluate the success of these protected areas at preventing declines of B. muricatum and C. undulatus. We conducted 27 underwater visual census (UVC) surveys at permanent passage and outer reef monitoring sites in Roviana Lagoon in 2018 and compared our findings with results from 72 UVC surveys that we had conducted at the same sites 18 yrs earlier. We also interviewed Roviana spearfishers about their maximum nightly B. muricatum catches from 2018, the early 2000s and the 1980s. Abundances of all B. muricatum and C. undulatus sighted on UVC surveys declined by 62% and 57%, respectively, between 2000 and 2018, and abundances of adult B. muricatum and C. undulatus declined by 78% and 72%, respectively, over the same period. Using a joint model of B. muricatum abundance and its reported maximum catch, we estimated that in 2018 the population of B. muricatum was 8% of its 1980’s abundance. By modelling projected rates of decline over three generations, we show that populations of B. muricatum and C. undulatus in Roviana Lagoon meet the IUCN Red List thresholds for Critically Endangered (CR). The probable causes of these declines are sustained fishing pressure, poor enforcement of community-based management measures and loss of fish nursery habitats due to logging. Our findings suggest urgent co-management of the ridge-to-reef system is needed to prevent further fish population declines in Roviana Lagoon.

Chemistry of the consumption and excretion of the bumphead parrotfish (Bolbometopon muricatum), a coral reef mega-consumer

Bolbometopon muricatum are ecologically unique mega-consumers in coral reef ecosystems. They primarily divide their dietary intake between living scleractinian corals and coral rock, a substrate richly colonized by non-coral biota. Here we examine how the chemical, structural, and energetic content of these two main classes of forage material may influence B. muricatum feeding behavior and selectivity. We then also examine nutrient content, pH, and alkalinity of the carbonate-rich feces of B. muricatum as a step toward understanding how B. muricatum defecation could affect reef nutrient dynamics and localized seawater chemistry. Our results suggest that by most measures, coral rock constitutes a richer food source than living corals, exhibiting higher levels of eight biologically relevant elements, and containing approximately three times greater caloric value than living corals. Additionally, the two forage types also presented distinct mineralogy, with the coral rock resembling a Mg-enriched carbonate phase in contrast to the primarily aragonitic live corals. Despite the fact that individual B. muricatum excrete tons of macerated coral annually, the low measured concentrations of N and P in feces suggest that this excretion may have relatively minor effects of reef macronutrient budgets. We also observed negligible local-scale impacts of B. muricatum feces on seawater pH and alkalinity. The approaches applied here integrate perspectives from marine biogeochemistry, materials science, and ecology. Collectively, these results provide preliminary insight into how reef chemistry could shape foraging of this dominant and vulnerable coral reef consumer and how it, in turn, might affect the chemistry of these reefs.

Protected areas and benthic characteristics influence the distribution of the Vulnerable bumphead parrotfish Bolbometopon muricatum in the Andaman and Nicobar Islands, India

AbstractThe Vulnerable bumphead parrotfish Bolbometopon muricatum, a highly prized fishery resource worldwide, has experienced population declines throughout its geographical range. There is limited knowledge of the distribution and abundance of, and threats to, this fish in Indian waters, particularly for the Andaman and Nicobar Islands. To assess the species’ distribution and conservation status we conducted underwater surveys across 75 sites around 51 islands and interviewed 99 fishers across the Andaman and Nicobar archipelago. We recorded a total of 59 individual B. muricatum across nine sites from the northernmost island in the Andamans (Landfall Island) to the southernmost island in the Nicobars (Great Nicobar Island). Interviews revealed that most fishers (100% in Nicobar, 94% in Middle Andaman, 62% in South Andaman) had seen B. muricatum, and knowledge of the species is highest amongst spearfishers. Generalized linear models indicated that presence of marine protected areas and high live coral cover influenced the abundance and distribution of B. muricatum. The species' density seems to be naturally low in the archipelago. We discuss our findings in the light of protecting rare and threatened species, and recommend strengthening the existing marine protected areas in these islands.

Southernmost observation of a juvenile bumphead parrotfish, Bolbometopon muricatum (Valenciennes, 1840)

The bumphead parrotfish, Bolbometopon muricatum, is an iconic and ecologically significant species that is vulnerable to extinction. Although the Great Barrier Reef provides extensive habitat for this species, the scarcity of juvenile fish in this region may suggest that these populations rely on colonisation by adults from further north, rather than local larval recruitment. Consequently, B. muricatum populations exhibit the strongest latitudinal gradient of any parrotfish on the Great Barrier Reef. Here, we review all records of B. muricatum from the southern Great Barrier Reef and report a new observation of a juvenile at Heron Reef. This is the southernmost report of a juvenile for this species. Given its size (standard length, 25–30 cm), this individual is likely to have settled as a larval recruit in the relative vicinity of Heron Reef, rather than migrating from a more northern site on the Great Barrier Reef or beyond.

Influence of the flesh quality and body size on the auction price of parrotfishes (Scaridae) at tropical island, southern Japan: Implications for fisheries management

Bid price of fish at auction is dependent on the situation of the date (season and supply) and quality of the fish (species, size, and freshness). In this study, how bid prices for parrotfishes (Scaridae spp.) determined at auction were investigated in a tropical island, southern Japan (Yaeyama fish market, Okinawa) between April 2011 and March 2015. Six factors, i.e. month, supply, size of fish, fishing gear type, bruising on the body, and endo-parasitic infection were chosen as variables, and their effects on bid prices were investigated using a generalized linear model with a log-normal error distribution in six selected species (Chlorurus microrhinos, Hipposcarus longiceps, Scarus ghobban, S. rivulatus, S. rubroviolaceus, Bolbometopon muricatum). All variables significantly affected the prices. The effects of supply were thought to remain for up to seven days from the AIC (Akaike’s Information Criterion) comparison, and the supply affected prices more than month did. For all species, the prices increased with fish size for smaller size ranges, but inversely decreased for larger size ranges. Prices of medium sized species took the highest values at 1.0–2.0 kg in size. Scarid fishes were mainly caught by spearfishing at night, but spear bruising on the body, parasitic infection, and being caught by gillnet significantly reduced prices (ca. minus 200–300 yen/kg for each case). Results obtained here are useful to increase the catch of higher quality fish by regulation (size, season, site etc.), to help reduce risk of price collapse triggered by large catch (oversupply), and to enable discussion of appropriate fisheries management practices.

Giant coral reef fishes display markedly different susceptibility to night spearfishing.

The humphead wrasse (Cheilinus undulatus) and bumphead parrotfish (Bolbometopon muricatum) are two of the largest, most iconic fishes of Indo‐Pacific coral reefs. Both species form prized components of subsistence and commercial fisheries and are vulnerable to overfishing. C. undulatus is listed as Endangered and B. muricatum as Vulnerable on the IUCN Red List of Threatened Species. We investigated how night spearfishing pressure and habitat associations affected both species in a relatively lightly exploited setting; the Kia fishing grounds, Isabel Province, Solomon Islands. We used fisheries‐independent data from underwater visual census surveys and negative binomial models to estimate abundances of adult C. undulatus and B. muricatum as a function of spearfishing pressure and reef strata. Our results showed that, in Kia, night spearfishing pressure from free divers had no measurable effect on C. undulatus abundances, but abundances of B. muricatum were 3.6 times lower in areas of high spearfishing pressure, after accounting for natural variations due to habitat preferences. It is likely the species’ different nocturnal aggregation behaviors, combined with the fishers’ use of night spearfishing by spot‐checking underpin these species’ varying susceptibility. Our study highlights that B. muricatum is extremely susceptible to night spearfishing; however, we do not intend to draw conservation attention away from C. undulatus. Our data relate only to the Kia fishing grounds, where human population density is low, the spot‐checking strategy is effective for reliably spearing large numbers of fish, particularly B. muricatum, and fisheries have only recently begun to be commercialized; such conditions are increasingly rare. Instead, we recommend that regional managers assess the state of their fisheries and the dynamics affecting the vulnerability of the fishes to fishing pressure based on local‐scale, fisheries‐independent data, where resources permit.