Acanthuroidei

(Surgeonfishes and relatives)

Class Actinopterygii

Order Perciformes

Suborder Acanthuroidei

Number of families 6

Evolution and systematics

The suborder Acanthuroidei comprises six families and 128 species. The families are Ephippidae (spadefishes, or batfishes, with eight genera and 15 species), Scatophagidae (scats, with two genera and four species), Siganidae (rabbitfishes, or spinefoots, with one genus, two subgenera, and 27 species), Luvaridae (louvar, with one genus and one species), Zanclidae (Moorish idol, with one genus and one species), and Acanthuridae (surgeonfishes and tangs, with six genera and 80 species). Some researchers also place the Chaetodontidae (butterflyfishes), Pomacanthidae (angelfishes), and Drepaneidae (sicklefishes) in this suborder on the basis that these fishes are sister taxa to the acanthuroid fishes. This view is not accepted universally, and so these three families are treated elsewhere in this volume.

The Ephippidae and Scatophagidae date from the Lower Eocene, while the Siganidae, Zanclidae, and Acanthuridae are from the Middle Eocene. The origin of the Luvaridae is uncertain. The suborder is considered to be monophyletic, with or without the inclusion of the Chaetodontidae, Pomacanthidae, and Drepaneidae. One feature common to half the members of this suborder is the presence of sharp, venomous spines (Scatophagidae and Siganidae) or sharp peduncular spines or keels (Acanthuridae), which also may be venomous.

Physical characteristics

All but one species in this suborder have small to medium-size bodies that are compressed and may be deep, disc-like, ovate, or slightly elongated. The spadefishes, or batfishes (Ephippidae), have deep and highly compressed bodies, continuous dorsal fins, and highly elevated dorsal, anal, and pelvic fins. Their scales are small and ctenoid, and their mouths are small and terminal. The scats (Scatophagidae) have deep, compressed bodies, a pronounced forehead, a mouth that is nonprotrusible, and a deeply notched dorsal fin. Fin spines are sharp and reportedly venomous. The rabbitfishes, or spinefoots (Siganidae), have compressed, somewhat elongated bodies; some in the subgenus Lo have a pronounced snout. Siganids are distinguished by the presence of venomous fin spines. Color patterns vary, and some species are quite distinctive. The monotypic louvar (Luvaridae) has a large (up to 78.7 in, or 200 cm, in length) fusiform body that is slightly compressed and quite streamlined. The head is blunt, with a projecting forehead; the mouth is small and somewhat protrusible; and the opercular spines are flattened. There is a groove positioned just above the eye. There are no pelvic fins, and the caudal peduncle has a large keel and small accessory keels. The scales are dentroid and quite small. Maximum body sizes range from 6–36 in (15–91 cm) for spadefishes and batfishes, 3.5–16 in (9–40 cm) for scats, 8.5–21 in (22–53 cm) for rabbitfishes and spinefoots, and 6.3–39.5 in (16–100 cm) for surgeonfishes. Moorish idols reach about 9 in (23 cm), and louvars reach about 79 in (200 cm) in length.

The Moorish idol (Zanclidae) is also monotypic within its family. This distinctive species has a disc-like body that is strongly compressed and dorsal spines that form an elongated whiplike streamer or filament. The color pattern is a striking arrangement of yellow, black, and white. Surgeonfishes (Acanthuridae) have compressed and disc-like bodies and possess one or more scalpel-like caudal spines or keeled peduncular plates located on each side of the caudal peduncle, which vary in size with species, may be venomous, and are capable of inflicting a painful, if not serious, wound. The caudal fin is strongly lunate, emarginate, or truncate. Many species are quite colorful, whereas others are seemingly drab until close inspection reveals often minute but exquisite details.

Distribution

Five of the six families are distributed in continental and insular inshore habitats of tropical, subtropical, and warm temperate seas. The exception is the louvar, a species that is pelagic throughout its rather wide range. Spadefishes, or batfishes, and surgeonfishes occur in the Atlantic, Indian, and Pacific Oceans. Scats are limited to the Indo-West Pacific, whereas the Moorish idol is found there and in the eastern Pacific. Rabbitfishes occur in the Indo-West Pacific but also have colonized the eastern Mediterranean, via the Suez Canal.

Habitat

All but the louvar, which is pelagic, inhabit shallow coral and rocky reefs, although some species inhabit estuaries or even freshwater habitats. Spadefishes and batfishes favor marine coral and rocky reefs as well as brackish water habitats that include mangroves, sea grasses, or sand and rubble flats. The scats have the greatest flexibility, moving from coral and rocky reefs into brackish water estuaries and freshwater streams. Rabbitfishes also are found on coral (some exclusively) or rocky reefs, on algal or sea grass beds, or around mangroves, but some enter brackish waters. Louvars move up and down in the pelagic water column. The Moorish idol is found on coral or rocky reefs, as are the surgeonfishes, although the latter also may occur on sea grass and algae beds and around mangroves.

Behavior

All members of this suborder except one may be found singly, in small groups, or in aggregations, schools, or mixed-species schools. The exception is the louvar, a solitary fish that probably aggregates only to breed. Many of these fishes, including some rabbitfishes and surgeonfishes, are territorial. Others, such as some rabbitfishes, patrol home ranges in pairs. Numerous species of rabbitfishes also have post-larvae that often form large schools when they settle onto reefs as post-larvae and recruit into (join) the population as juveniles. Batfishes tend to hover singly or in small groups near structures but can form large schools in deeper water as well. Their juveniles mimic fallen leaves. Scats also move about

near shelter but form larger aggregations in estuaries, bays, or open water.

Feeding ecology and diet

Spadefishes, or batfishes, are omnivorous and feed on benthic algae and invertebrates. Some species are capable of crushing bivalve or gastropod shells and crustaceans. Although scats have markedly herivorous tendencies, they are also known to be omnivorous; they even feed on detrital materials and have been observed to feed on feces discharged by ships or sewage systems. Aquatic macrophytes consitute the bulk of the stomach contents of both S. argus and S. tetracanthus in freshwater habitats. Rabbitfishes are herbivorous or omnivorous, and schools of juveniles are efficient, if not rapid, grazers. The louvar feeds on gelatinous mesoplankton in the water column. The Moorish idol feeds primarily on sponges but also plucks other benthic invertebrates. Surgeonfishes are largely herbivorous and browse or graze on benthic algae. Some species are adapted to feeding on plankton in the water column.

Reproductive biology

Almost all members of this suborder spawn pelagic eggs. The exceptions appear to be the scats, which spawn demersal eggs and engage in parental care, and some of the rabbitfishes, which spawn eggs that sink to the bottom. Mating strategies vary within and between families. Courtship and spawning are accomplished in pairs, in pairs within spawning aggregations, or in groups of varying sizes at spawning aggregation sites. Thus, spadefishes, or batfishes, spawn in pairs and possibly in aggregations. Scats spawn demersal eggs, and at least one species practices parental care. Rabbitfishes of the subgenus Lo form relatively long-term monogamous pairs. Others in the family, however, spawn in aggregations, in either short-term pairs or groups. Rabbitfishes have been spawned in captivity, and some species are now important in mariculture. Louvars probably spawn in aggregations in the open sea. Moorish idols spawn in pairs or in pairs within aggregations. Surgeonfishes spawn in pairs, as pairs within aggregations, and in groups. The larvae of many of these fishes are well adapted to a prolonged existence in the open sea.

Conservation status

No species is listed by the IUCN, but some species collected for the aquarium trade, including certain surgeonfishes and batfishes, may be at risk locally because of overfishing.

Significance to humans

Rabbitfishes and surgeonfishes are important in subsistence and artisanal fisheries. The louvar is taken as a minor commercial food fish, as are some of the spadefishes, or batfishes. Scats are grown for the live reef food fish trade or taken in subsistence fisheries. Fishes important to the aquarium trade include scats, batfishes, and certain rabbitfishes and surgeonfishes. The Moorish idol also is collected for aquaria, but they do not do well in captivity.

Species accounts

List of Species

Lined surgeonfish

Acanthurus lineatus

family

Acanthuridae

taxonomy

Acanthurus lineatus Linnaeus, 1758, "Indies." No type specimens are known.

other common names

French: Chirurgien zébré; German: Blaustreifen-Doktosfisch; Japanese: Nijihagi.

physical characteristics

The body is compressed and disc-like and possesses a large, venomous, scalpel-like caudal spine on each side of the caudal peduncle. The caudal fin is strongly lunate. There are nine spines and 27–30 soft rays in the dorsal fin, three spines and 25–28 soft rays in the anal fin, and 16 soft rays in the pectoral fin. Body coloration is striking and consists of a yellowish green background, bright blue stripes (narrow and oblique on the head) edged with black on the flank but lacking the black edge on the head, and lavender blue to bluish white on the belly. The pelvic fins are bright orange. The caudal fin has two vertical lines of dark blue set against a background of purplish gray, replaced by yellow at the base of the fin. The remaining fins are purplish gray yielding to greenish yellow at the base. Larvae are acronurus, in that they are orbicular in shape; transparent, with a silvery sheen over the head, chest, and abdomen; and scaleless and have narrow, vertically oriented ridges along the body. (Acronurus refers to the last, well-developed but seemingly different, post-larval stage of surgeonfishes in the genera Acanthurus, Ctenochaetus, and Zebrasoma. Originally this stage was proposed to be a separate genus of surgeonfishes until closer examination revealed otherwise.) The second anal, second dorsal, and pelvic spines are elongated and venomous. Larvae are well adapted to the pelagic realm and may remain there for more than 39 days. Adults may grow to 15 in (38 cm) in length and can live for as long as 30–45 years.

distribution

Indo-West Pacific, from East Africa east to the Marquesas and the Tuamotu Archipelago, north to southern Japan, and south to New South Wales, Australia; strays rarely to the Hawaiian Islands. Replaced by the very similar species A. sohal in the vicinity of the Arabian Peninsula (Red Sea and Persian Gulf).

habitat

Usually found on exposed reef fronts at depths of 3.3–9.8 ft (1–3 m).

behavior

Highly territorial. Patrols territories along the reef front and aggressively attacks conspecifics, other surgeonfishes, and other herbivores. Temporarily assumes a darker coloration of the head during territorial displays and encounters. Wields its caudal spines as effective weapons against attack.

feeding ecology and diet

Herbivorous. Browses on filamentous and fleshy algae using specialized teeth.

reproductive biology

Migrates to and spawns in aggregations at specific sites, although it sometimes spawns in pairs. Reported to spawn in early morning during the first 1–3 hours of a falling tide just before the full moon. Has been observed spawning at sunset as well. Tidal state, rather than time of day, more likely accounts for the temporal pattern of spawning. Spawning occurs year-round at lower latitudes but may be seasonal at higher latitudes. Eggs and larvae are pelagic.

conservation status

Not listed by the IUCN.

significance to humans

An important species in subsistence and artisanal food fisheries. Also collected for larger aquaria.

Orangespine unicornfish

Naso lituratus

family

Acanthuridae

taxonomy

Naso lituratus Forster in Bloch and Schneider, 1801, probably Tahiti, French Polynesia.

other common names

French: Nason a éperon orange; German: Gelbklingen-Nasendoktor; Japanese: Miyako-tenguhagi.

physical characteristics

The body is compressed and disc-like, although it elongates with growth. The snout is pronounced, and the forehead slants at a 45-degree angle from just forward of the dorsal fin. The caudal peduncle consists of two peduncular plates, each featuring a large keel facing forward. The caudal fin is emarginate and sexually dimorphic; the males have filaments that trail from each corner of the fin. There are six spines and 28–31 soft rays in the dorsal fin, two spines and 29–31 soft rays in the anal fin, 17–18 soft rays in the pectoral fin, and one spine and three soft rays in the pelvic fin. The body is dark grayish brown with a yellowish patch on the nape, a yellow margin along either side of the snout from the eye to just behind the mouth, a black snout, and an orange mouth. The peduncular plates and keels are bright orange. The dorsal fin is black with a thin blue margin at the base and a broader blue margin along the outer edge. The caudal fin is also black, with a yellow submarginal band on the edge. The anal fin is yellow at the base, followed by an orange band, a narrow submargin of light blue, and a narrow outer margin of black. The pelvic fin is yellow, and the pectoral fin is a faint black. Grows to about 18 in (46 cm) in length.

distribution

Western Pacific, from Surugu Bay, Honshu, Japan, south to the Great Barrier Reef and New Caledonia, and east to the Hawaiian and Pitcairn Islands; recently reported from Clipperton Island in the Eastern Pacific. Also found in the eastern Indian Ocean from the coast of Western Australia south to Ningaloo Reef. Replaced by N. elegans in the western Indian Ocean, including southern Indonesia, and the Red Sea.

habitat

Coral and rocky reefs in tropical and subtropical waters, generally above 98 ft (30 m) but occasionally as deep as 295 ft (90 m).

behavior

Occurs singly or in small groups.

feeding ecology and diet

Herbivorous. Browses on benthic algae but favors tough or leafy species from the genera Sargassum, Dictyota, and Pocockiella.

reproductive biology

Reported to spawn in pairs but also may spawn in aggregations. Eggs and larvae are pelagic. Larval life is lengthy, in excess of 69 days.

conservation status

Not listed by the IUCN.

significance to humans

Taken in subsistence and artisanal fisheries and a popular target of spearfishers. Juveniles and subadults also are collected for the aquarium trade.

Palette tang

Paracanthurus hepatus

family

Acanthuridae

taxonomy

Paracanthurus hepatus Linnaeus, 1766, Ambon and Molucca islands, Indonesia. Western Atlantic localities are in error.

other common names

English: Blue tang, hippo; German: Paletten-Doktorfisch.

physical characteristics

The body is compressed and somewhat disc-like; it elongates with growth. The caudal fin is truncated in adults, but slightly rounded in juveniles. There are nine spines and 19–20 soft rays in the dorsal fin, three spines and 18–19 soft rays in the anal fin, 16 soft rays in the pectoral fin, and one spine and three soft rays in the pelvic fin. The caudal peduncle has a single folding spine on each side. The body is a vivid bright blue, and the belly is a paler shade of blue or, in Indian Ocean specimens, yellowish blue. A black band curves backward from the eye to the caudal peduncle. A second black band runs back along the middle of the body from just behind the pectoral fin and joins the upper band just before the caudal peduncle. The caudal fin is mainly yellow, the yellow arising just ahead of the caudal spine, with black margins that arise at the caudal peduncle. Grows to 10.2 in (26 cm) in length.

distribution

Tropical and subtropical waters of the Indo-West Pacific, from East Africa east to Micronesia, the Line Islands, and the Samoa Islands, north to Kochi Prefecture in Japan, and south to northern New South Wales, Australia. Observations of this species in Hawaiian Islands are attributed to releases of aquarium stock.

habitat

Outer coral and rocky reefs and channels in clear water areas with strong or moderate current. Juveniles and subadults prefer

to shelter in shrublike corals. Not common and patchy in distribution wherever it occurs. Depth range of 6.6–131 ft (2–40 m).

behavior

Occurs in small aggregations that hover 3.3–6.6 ft (1–2 m) above the substrate.

feeding ecology and diet

Omnivorous. Feeds on zooplankton and benthic algae.

reproductive biology

Reproductive biology is not well known. Courtship probably is paired or paired within a spawning aggregation. Eggs and larvae are pelagic, with a larval life in excess of 37 days.

conservation status

Not listed by the IUCN. Localized populations are vulnerable to overfishing of juveniles for the aquarium trade.

significance to humans

Collected for the aquarium trade, in which it is highly prized. Juveniles and subadults that shelter in corals are relatively easy to collect.

Striped bristletooth

Ctenochaetus striatus

family

Acanthuridae

taxonomy

Ctenochaetus striatus Quoy and Gaimard, 1825, Guam, Mariana Islands.

other common names

German: Brauner Borstenzahndoktor; Japanese: Sazanamihagi.

physical characteristics

The body is compressed and disc-like, with a venomous, scalpel-like caudal spine on each side of the caudal peduncle. The caudal fin is lunate. There are eight spines and 27–31 soft rays in the dorsal fin, three spines and 24–28 soft rays in the anal fin, and 17 (sometimes 16) soft rays in the pectoral fin. Adult coloration varies from dark gray to orangish brown. Can change color temporarily from dark brown to light tan. Melanistic, albinistic, and xanthic color patterns have been reported as well. There are several fine pale blue lines along the flank. Fine orange spots appear on the upper head and back to the anterior base of the dorsal fin. Both the dorsal and anal fins have narrow dark brown and pale blue bands, running longitudinally in alternation. Juveniles and subadults are especially colorful, with a small black spot located at the posterior base of the dorsal fin. Grows to 10.2 in (26 cm) in length.

distribution

Indo-West Pacific, from the Red Sea south to East Africa, east to Pitcairn Island and French Polynesia (absent from the Marquesas Islands), north to southern Japan, and south to the Great Barrier Reef and New Caledonia.

habitat

Found on coral, rock, pavement, and rubble of exposed reefs, reef flats, and lagoons in tropical waters. Depth range from 3.3 to 98 ft (1–30 m).

behavior

Found singly but also in small and very large aggregations. Also participates in mixed-species aggregations with other surgeonfishes and parrotfishes, among others.

feeding ecology and diet

Herbivorous. Feeds upon benthic algae, blue-green algae, and diatoms. Reported to cause ciguatera poisoning because of their diet. Ciguatera poisoning is caused by the cumulative deposition of a class of polyether toxins within the tissues of fishes. The toxins are produced by certain microscopic dinoflagellate organisms of the genus Gambierdiscus, which are transmitted by the food chain, increasing in intensity by a factor of ten in each successive level within the chain. The striped bristletooth ingests these organisms while feeding upon algae. If a contaminated fish is consumed by man, the concentrated poison contained within its tissues causes neurological damage that can be fatal.

reproductive biology

Migrates to outer channels or exposed reefs to spawn in aggregations on an outgoing tide. Eggs and larvae are pelagic.

conservation status

Not listed by the IUCN.

significance to humans

Taken for subsistence and artisanal food fisheries but may cause ciguatera poisoning at some localities. Also collected infrequently for the aquarium trade but often they do not do very well in captivity; juveniles are more highly prized than adults.

Yellowspotted sawtail

Prionurus maculatus

family

Acanthuridae

taxonomy

Prionurus maculatus Ogilby, 1887, Port Jackson, New South Wales, Australia.

other common names

German: Gelbfleken-Sägedoktor; Japanese: Nizadai.

physical characteristics

Body is compressed and slightly elongated, with a protruding mouth and a snout with a dorsal profile that is slightly concave. there are nine spines and 24–26 soft rays in the dorsal fin, three spines and 23–25 soft rays in the anal fin, 17–18 soft rays in the pectoral fin, and one spine and five rays in the pelvic fin. the caudal fin is slightly emarginate to truncate in shape. as with other members of this genus, this species is distinguished by the presence of three peduncular plates, each having a lateral keel on either side of the caudal peduncle. the body coloration is bluish gray with several small yellow spots. the peduncular plates are black, and the keels are blue, usually with a white mark on the last plate. the caudal fin is gray with yellow spots and has a deep blue margin, as does the anal fin. juveniles have a series of narrow yellow bars that eventually, with age, become vertical rows of yellow spots. grows to about 17.3 in (44 cm) in length.

distribution

Western Pacific and restricted to the Southern Hemisphere, from southern Queensland on the Great Barrier Reef south to New South Wales and east to Lord Howe Island, Norfolk Island, and the Kermadec Islands. Waifs recruit seasonally to New Zealand during warmer summer months but probably do not reproduce successfully.

habitat

Tropical and warm temperate waters in protected areas of coral reefs, rocky reefs, and bays but also on outer coral and rocky reefs. Depth range is 6.6–98 ft (2–30 m).

behavior

This species usually is found in aggregations.

feeding ecology and diet

Herbivorous. Feeds on benthic algae that grows mainly on rocks or coral substrates.

reproductive biology

Probably pair-spawns but also may form spawning aggregations in which pair spawning occurs. Males probably change color pattern to attract a female from the aggregation, and the two touch their ventral surfaces together before the release of gametes, without an upward dash into the water column. Eggs and larvae are pelagic.

conservation status

Not listed by the IUCN.

significance to humans

May be taken incidentally as a food fish.

Yellow tang

Zebrasoma flavescens

family

Acanthuridae

taxonomy

Zebrasoma flavescens Bennett, 1828, Hawaiian Islands.

other common names

German: Gelber Segelflosser; Japanese: Kiirohagi.

physical characteristics

Body is compressed and disc-like, with a concave head, a pronounced snout, and a protruding mouth. The dorsal fin is highly elevated and has four to five spines and 23–26 soft rays. The anal fin has three spines and 19–22 soft rays, and the pectoral fin has 14–16 soft rays. The body is a bright yellow, but the caudal spine sheath is white. Known to hybridize with Z. scopas. Grows to more than 7.9 in (20 cm) in length.

distribution

Tropical waters of the northern Pacific Ocean, from Minamitori-shima (Marcus Island) east to Wake Island, the Marshall Islands (uncommon), the Hawaiian Islands, and Johnston Island. Also in the Ogasawara, Ryukyu, and Mariana Islands. A waif was reported from Hong Kong, and other records, both in Polynesia and in the Indian Ocean, are probably xanthic morphs of Z. scopas.

habitat

Coral and rocky reefs, either exposed reef slopes to 265 ft (81m) or in bays and lagoons as shallow as 3.3 ft (1 m).

behavior

May be found in small groups or singly. Groups often move from point to point to browse on algae. Sometimes observed in mixed-species schools.

feeding ecology and diet

Herbivorous. Browses on filamentous algae on coral reefs.

reproductive biology

This species has two mating systems. Single males may defend territories, court passing females, and engage in pair spawning in the water column. Alternatively, group spawning at spawning aggregation sites occurs. The spawning season is limited by the effects of seasonally cooler water temperatures at higher latitudes. Eggs and larvae are pelagic.

conservation status

Not listed by the IUCN but subject to overfishing, particularly in parts of the Hawaiian Islands, for the aquarium trade.

significance to humans

An important species in the aquarium trade and the number one exported species from the Hawaiian Islands.

Longfin spadefish

Platax teira

family

Ephippidae

taxonomy

Platax teira Forsskal, 1775, Luhaiya, Yemen, Red Sea.

other common names

English: Teira batfish; French: Poisson lune; German: Langflossen-Fledermausfisch; Japanese: Mikazuki-tsubame-uo.

physical characteristics

Body is deep and highly compressed. The dorsal fin is continuous, and the anal, dorsal, and pelvic fins are greatly elevated. Scales are ctenoid and small. The mouth is terminal, with tricuspid teeth. Juveniles also have deep bodies and elevated anal, dorsal, and pelvic fins (the latter extremely long), with the dorsal and anal fins extending backward beyond the caudal fin. These fins are reduced in size somewhat with age (i.e. the fins do not grow with age relative to the rest of the body). Larvae have a deep or moderately deep body and a relatively compressed caudal fin; the head and trunk are combined into a broad, ball-like structure that eventually deepens with growth. There are no scales present on the body of the larvae at settlement. Settlement refers to the transformation of a pelagicdwelling larva to a Reef-dwelling post-larva or juvenile. Grows to more than 17.7 in (45 cm) in length.

distribution

Tropical and subtropical waters from the Red Sea and Indian Ocean east to Fiji, north to southern Japan, and south to Australia's Great Barrier Reef and Lord Howe Island.

habitat

Coral and rocky reefs, usually drop-offs, deep lagoons, and pinnacles along the outer reef to a depth of at least 66 ft (20m). Juveniles usually are found in protected areas of shallow reefs and bays.

behavior

Occurs singly or in small aggregations as adults and juveniles. Juveniles often mimic floating leaves in shallow waters.

feeding ecology and diet

Omnivorous, feeding on a variety of small benthic invertebrates and algae.

reproductive biology

Probably pair-spawns within aggregations or smaller groups. Eggs and larvae are pelagic.

conservation status

Not listed by the IUCN.

significance to humans

Collected for the aquarium trade.

Louvar

Luvarus imperialis

family

Luvaridae

taxonomy

Luvarus imperialis Rafinesque, 1810, Sicily, Italy.

other common names

Japanese: Amashiira.

physical characteristics

Fusiform body, which is compressed slightly and streamlined. Pelvic fins are absent. The head is blunt, with a projecting forehead, and there is a groove above the eye. Opercular spines are flattened. Scales are dentroid and minute. The caudal peduncle has small accessory keels that flank the large caudal keel. The mouth is small and slightly protrusible. Metamorphosis from larvae to adults involves considerable change. Numerous juvenile characters are absent in adults. For example, juveniles possess jaw teeth, fin spines, and a rudimentary locking mechanism. Grows to 78.7 in (200 cm) in length.

distribution

Tropical, subtropical, and temperate waters of the Atlantic (including the Mediterranean Sea), Indian, and Pacific Oceans.

habitat

Epipelagic, from the surface to relatively deeper waters.

behavior

Poorly known. This species generally is solitary in the open ocean but probably aggregates for courtship and spawning.

feeding ecology and diet

Feeds on gelatinous mesoplankton, primarily jellyfishes and ctenophores.

reproductive biology

Not well known. Spawning commences in late spring and runs throughout the summer months. Species is reportedly quite fecund; one female examined had an estimated 47.5 million eggs. Pelagic spawning with pelagic larvae.

conservation status

Not listed by the IUCN.

significance to humans

May be taken incidentally in commercial fisheries.

Spotted scat

Scatophagus argus

family

Scatophagidae

taxonomy

Scatophagus argus Linnaeus, 1758, India. No type specimens are known.

other common names

Japanese: Kurohoshimanjûdai.

physical characteristics

Body is deep and compressed, with a deeply notched dorsal fin, a pronounced forehead, and a nonprotrusible mouth. There

are 10–11 spines and 16–18 soft rays in the dorsal fin, four spines and 13–15 soft rays in the anal fin, and 16 branched rays in the caudal fin. The spines are sharp and are reported to be venomous. The pelvic fins are attached by an axillary process. Body color is silvery green to orange, with numerous small dark spots on the flank and on the base of the dorsal, caudal, and anal fins. Larvae have a specialized stage similar to the tholichthys of larval butterflyfishes (Chaetodontidae). Grows to about 15 in (38 cm) in length.

distribution

Indo-West Pacific region from Kuwait east to Vanuatu and New Caledonia, south to Australia, north to southern Japan, and east to Pohnpei (Micronesia). Also reported from Samoa and the Society Islands.

habitat

Inshore marine, brackish, and freshwaters, usually in turbid estuaries, harbors, back bays, mangrove stands, and reefs.

behavior

Not well known. Occurs in small groups or aggregations.

feeding ecology and diet

Omnivorous, feeding on small invertebrates, including worms, crustaceans, and insects, and on benthic algae. Genus name was coined from observation of members of this genus feeding on feces and sewage discharged by ships into harbors and bays.

reproductive biology

Not well known, except from aquarium observations. Reported to spawn demersal eggs and engage in parental care, traits inconsistent with most other species in this suborder, though somewhat similar to the Siganidae.

conservation status

Not listed by the IUCN.

significance to humans

Collected for the aquarium trade for display in marine and freshwater aquaria. Also taken for subsistence or artisanal food fisheries and has been grown by commercial aquaculture for the live reef food fish trade.

Foxface rabbitfish

Siganus vulpinus

family

Siganidae

taxonomy

Siganus vulpinus Schlegel and Muller, 1844, Ternate Island, Moluccas Islands, Indonesia.

other common names

English: Foxface; German: Gelbes Dachsgesicht; Japanese: Hifuki-aigo.

physical characteristics

Body is compressed and elongate, with minute cycloid scales on the trunk. There is a single dorsal fin with 13 spines and 10 soft rays. The pelvic fins are positioned at the thorax. The pectoral fin usually has 16 rays. Fin spines are stout and venomous. The snout is long and tubelike. Body color is predominately yellow, with a chocolate-brown forehead and snout and white spotted with brown on the preopercle and opercle and on the flank directly behind the gills. The thorax

is chocolate brown, and this color extends down to the first two pelvic fin spines. The dorsal, anal, and caudal fins are yellow; the pectoral and pelvic fins are white. There is some variation between individuals. Grows to at least 9.8 in (25 cm) in length.

distribution

Indo-West Pacific region from Sumatra east to the Marshall Islands and south to the Great Barrier Reef and New Caledonia.

habitat

Seaward reefs and outer slopes, lagoons, and deeper reef flats to a depth of 98 ft (30 m). Prefers lush coral growth. Juveniles and subadults take refuge in staghorn corals.

behavior

Larvae, juveniles, and subadults occur in large schools. Pair formation, possibly monogamous, occurs when the species reaches 3.9 in (10 cm) in length. Pairs patrol a restricted home range and at times may defend a territory.

feeding ecology and diet

A browsing herbivore that feeds upon benthic algae found on the substrate or upon dead corals.

reproductive biology

Descriptions of reproductive biology of this and some other siganid species are based largely upon observations of captive individuals augmented by some field observations. This species spawns in pairs at dusk or dawn in relation to moon phase. Eggs are spherical and adhesive, measuring 0.02–0.025 in (0.55–0.66 mm), and are scattered on substrate (some siganid species have pelagic eggs, however). Larvae hatch out and measure about 0.08 in (2 mm) in length. They have a large yolk, an unformed mouth, a straight gut, unpigmented eyes, and a pattern of body pigmentation that is relatively stable with growth. Body shape is elongate, but this becomes deeper and laterally compressed with growth. Fin development begins before the yolk is absorbed and spines appear at about 0.11 in (3 mm) in length. Fin rays form at about 0.24 in (6 mm), but scales do not form until larval settlement. The larvae have the following specializations for pelagic life: long dorsal and pelvic fins that form early in development, fin spines that are serrate in shape, and the formation of spines upon the head.

conservation status

Not listed by the IUCN.

significance to humans

May be taken by subsistence and artisanal fisheries for food. Also collected for the aquarium trade.

Moorish idol

Zanclus cornutus

family

Zanclidae

taxonomy

Zanclus cornutus Linnaeus, 1758, Indian seas. No type specimens are known.

other common names

French: Cocher jaune; German: Halterfisch; Japanese: Tsunodashi.

physical characteristics

Superficially, this species resembles the butterflyfishes (Chaetodontidae). The body is strongly compressed and disc-like, the snout is tubular, and the mouth is small, with many elongated, bristle-like teeth. The third dorsal spine is long and whiplike (the "streamer"). Coloring consists primarily of three vertical bands of white and yellow in alternation with two bands of black. The caudal fin is also black and fringed with white or yellowish white. A small patch of yellow and a horizontal band of white occur on the snout. Larvae are distinguished by a third spine that is elongate and more than twice the length of the larva's body, which develops into the "streamer" of adults. Also has a spine positioned prominently above the corner of the mouth. Body size is large, up to about 3 in (7.5 cm) in length, at metamorphosis from postlarvae to juveniles. Adults grow to at least 5.9 in (15 cm) in length.

distribution

Tropical and subtropical waters of the Indo-Pacific region from East Africa in the Indian Ocean east to the Hawaiian Islands, Rapa Island, and Ducie Atoll in the east-central Pacific and in southern Gulf of California south to Peru in the eastern Pacific. In the western Pacific, north to southern Japan, south to Australia and Lord Howe Island, and throughout Micronesia, Polynesia, and Melanesia.

habitat

Clear seaward coral and rocky reefs, reef flats, and turbid inner lagoons. Depth range from less than 9.8 ft (3 m) to more than 591 ft (180 m).

behavior

Found singly, in pairs, or in small groups of three or more. Occasionally, large aggregations in excess of 150 fishes are seen; such aggregations may be for spawning.

feeding ecology and diet

Feeds on benthic encrusting invertebrates, especially sponges, that it plucks from the substrate.

reproductive biology

Still poorly known. Pair-spawns at dusk on seaward reefs within small groups or, possibly, in larger aggregations. Eggs and larvae are pelagic, and larval life can be relatively long, thus potentially explaining their broad pattern of distribution as adults.

conservation status

Not listed by the IUCN. Aquarium trade is restricted in Germany.

significance to humans

Collected for the aquarium trade but does not do well in most aquaria. Also taken in subsistence food fisheries.

Resources

Eschmeyer, W. N., ed. Catalog of Fishes. 3 vols. San Francisco: California Academy of Sciences, 1998.

Helfman, Gene S., Bruce B. Collette, and Doug E. Facey. The Diversity of Fishes. Malden, MA: Blackwell Science, 1997.

Leis, J. M., and B. M. Carson-Ewart, eds. The Larvae of Indo-Pacific Coastal Fishes: An Identification Guide to Marine Fish Larvae. Boston: Brill, 2000.

Masuda, H., K. Amaoka, C. Araga, T. Uyeno, and T. Yoshino, eds. The Fishes of the Japanese Archipelago. Tokyo: Tokai University Press, 1984.

Myers, R. F. Micronesian Reef Fishes: A Field Guide for Divers and Aquarists. 3rd edition. Barrigada, Guam: Coral Graphics, 1999.

Nelson, J. S. Fishes of the World. 3rd edition. New York: John Wiley and Sons, 1994.

Randall, John E. Surgeonfishes of the World. Honolulu: Bishop Museum Press/Mutual Publishing, 2001.

Randall, John E., Gerald R. Allen, and Roger C. Steene. Fishes of the Great Barrier Reef and Coral Sea. Honolulu: Bishop Museum Press, 1996.

Smith, M. M., and P. C. Heemstra, eds. Smiths' Sea Fishes. Berlin: Springer-Verlag, 1986.

Thresher, R. E. Reproduction in Reef Fishes. Neptune City, NJ: T. F. H. Publications, 1984.

Periodicals

Craig, P. C., J. H. Choat, L. M. Axe, and S. Saucerman. "Population Biology and Harvest of the Coral Reef Surgeonfish Acanthurus lineatus in American Samoa." Fishery Bulletin 95 (1997): 680–693.

Johnson, G. D. "Percomorph Phylogeny: Progress and Problems." Bulletin of Marine Science 52, no. 1 (1993): 3–28.

Woodland, D. J. "Revision of the Fish Family Siganidae with Descriptions of Two New Species and Comments on Distribution and Biology." Indo-Pacific Fishes 19 (1990): 1–136.

Organizations

IUCN/SSC Coral Reef Fishes Specialist Group. International Marinelife Alliance-University of Guam Marine Laboratory, UOG Station, Mangilao, Guam 96913 USA. Phone: (671) 735-2187. Fax: (671) 734-6767. E-mail: [email protected] Web site: <http://www.iucn.org/themes/ssc/sgs/sgs.htm>

Terry J. Donaldson, PhD