Convict Surgeonfish

There have been reports of humans suffering from ciguatera poisoning after consuming convict tangs, although the species is generally considered safe to eat.

Negative Impacts: injures humans (poisonous )

Convict tangs have been observed exhibiting tonic immobility, which may be a response to the presence of a predator. As with other surgeonfishes, they have sharp blades on either side of the tail; however, these blades are poorly developed in convict tangs and not typically used for defense. Instead, this species relies on traveling in large schools, as well as its disruptive color pattern, for protection. Although undoubtedly not a complete list of predators, convict tangs are known to be preyed upon by argus grouper, ash-colored conger eel, honeycomb grouper, cornet fish, and black-tail snapper. Eagle rays are also known to feed on convict tang gametes during spawning.

Known Predators:

• Argus grouper (Cephalopholis argus)
• Ash-colored conger eel (Conger cinereus)
• Honeycomb grouper (Epinephelus quoyanus)
• Cornet fish (Fistularia commersonii)
• Black-tail snapper (Lutjanus fulvus)
• Eagle ray (Myliobatidae sp.)

Anti-predator Adaptations: cryptic

Convict tangs have a pale body color varying from white/greenish-white to gray or even yellow. This background is overlaid with distinct, vertical black stripes, including one going through each eye. They are highly laterally compressed and have small scales, gill rakers, dorsal spines and anal spines. Their average length is 17.0 cm, with a maximum length of 27.0 cm.

Range length: 27.0 (high) cm.

Average length: 17.0 cm.

Other Physical Features: ectothermic ; bilateral symmetry

Convict tangs have a typical lifespan of 5-7 years in captivity. Their average lifespan in the wild is currently unknown.

Range lifespan
Status: captivity: 5 to 7 years.

Typical lifespan
Status: captivity: 5 to 7 years.

Convict tangs are surgeonfish that prefer to occupy coral reefs, but are also found in tidepools and other nearshore habitats such as shallow, low current beach communities. They are tropical reef fish whose latitudinal range is 26ºN to 36ºS with a longitudinal range from 25ºE to 85ºW. Convict tangs are mainly found in temperatures ranging from 24-26ºC and at depths of 0-90 m.

Range depth: 90 to 0 m.

Habitat Regions: tropical ; saltwater or marine

Aquatic Biomes: pelagic ; benthic ; reef ; coastal

Convict tangs are found throughout the Indo-Pacific region, as well as the eastern Pacific Ocean from the lower Gulf of California to Panama. They are also known as convict surgeonfish or Manini.

Biogeographic Regions: indian ocean (Native ); pacific ocean (Native )

Convict tangs are herbivores, grazing on algae found on rocks and corals. Adaptations to their algivorous diet include mouths that are slightly downwardly-directed and flexible, comb-like teeth.

Plant Foods: algae

Primary Diet: herbivore (Algivore)

The grazing of convict tangs on algae helps keep algal populations in check. Convict tangs also host symbiotic unicellular organisms in their gut, including one of the largest known bacterial species (Epulopiscium fishelsoni). Convict tangs are host to endoparasitic nematodes and trematodes, as well as at least one ectoparasitic copepod species.

Mutualist Species:

• Epulopiscium fishelsoni (Class Clostridia, Kingdom Bacteria)

Commensal/Parasitic Species:

• Spirocamallanus colei (Class Secernentea, Phylum Nematoda)
• Hysterolecitha acanthuri (Class Trematoda, Phylum Platyhelminthes)
• Caligus flexispina (Subclass Copepoda, Subphylum Crustacea)

Convict tangs are part of the human diet in tropical regions. They are also sold in the aquarium trade.

Positive Impacts: pet trade ; food

Convict tang eggs hatch into clear pelagic larvae. In Hawaiian populations it takes about 2.5 months for these planktonic larvae to develop into juveniles in a reef or tidepool; larvae typically adapt to their benthic surroundings within 24 hours. Initially, juveniles lack the vertical bars present in adults.

Development - Life Cycle: indeterminate growth

Convict tangs currently have no special conservation status.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

Convict tangs are able to perceive their environments through a number of sensory pathways, including sight, olfaction, sound and vibrations (detected by their lateral lines). Information regarding which of these senses are important in intra- and interspecific communication is currently unavailable.

Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical

Genetic studies on Polynesian populations of convict tangs indicate that, despite the pelagic larval stage, most populations exhibit limited recruitment through dispersal.

The large bacterium Epulopiscium fishelsoni was first isolated from the gut of brown surgeonfish (A. nigrofuscus); similar morphotypes, collectively called "euplos", have since been found in other surgeonfish species, including convict tangs. Euplo morphotypes found in convict tangs are 20 times longer than they are wide, which is much longer and thinner than those found in other species of surgeonfish.

Convict tangs spawn in resident spawning aggregations. Spawning groups can be as large as tens of thousands of fish with subgroups of 10-20 fish, although pair spawning has also been observed. Research in Hawaii showed that individuals may migrate up to 2 km to reach spawning sites on the seaward side of a reef or in channels connecting lagoons to open ocean.

Mating System: polygynandrous (promiscuous)

Convict tang populations near the equator can spawn at any time during the year, while populations elsewhere may only spawn seasonally (in Hawaii spawning occurs around full moons in February and March).

Breeding interval: Convict tangs breed annually.

Breeding season: Spawning can occur year round in equatorial habitats and seasonally in other parts of the range.

Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); broadcast (group) spawning; oviparous

Convict tangs are broadcast spawners and provide no parental investment to offspring.

Parental Investment: no parental involvement

Form spawning aggregations (Ref. 27825).

Body olivaceous gray, with 4 vertical stripes (1 stripe on head across the yellow eye; 1 on caudal peduncle); shading to white ventrally, often with a sharp line of demarcation. Sharp, forward-pointing, erectile spine on each side of caudal peduncle which folds down into a groove. Scales minute. Teeth with denticulations on sides and top. Gill rakers 18-22 in anterior row, 19-24 in posterior row.Description: Characterized further by having small caudal spine; greatest depth of body 1.8-1.9 in SL (Ref. 90102).

Hysterolecitha Infestation. Parasitic infestations (protozoa, worms, etc.)

Dorsal spines (total): 9; Dorsal soft rays (total): 22 - 26; Analspines: 3; Analsoft rays: 19 - 22

Occur in lagoon and seaward reefs with hard substrate; young abundant in tide pools (Ref. 3145, 48637). Often feeding near freshwater run-offs where certain algae grow on rocks that are grazed (Ref. 48637). Feed on filamentous algae in large aggregations. Roving herbivore (Ref. 57615). Diurnal species (Ref. 113699:31), spawning takes place between midday and dusk (Ref. 717, 38697). Also Ref. 58534, 58652.

Adults occur in lagoon and seaward reefs with hard substrate; young abundant in tide pools (Ref. 3145, 48637). Benthopelagic (Ref. 58302). Often feeding near freshwater run-offs where certain algae grow on rocks that are grazed (Ref. 48637). Occasionally form schools; feed on filamentous algae in large aggregations. During spawning, clouds of eggs and sperm are preyed upon by eagle rays which are often present during spawning. Form spawning aggregations (Ref. 27825). Size of metamorphosis from post-larva stage to juvenile is 3.2 cm (Ref. 9267). Utilized as a food fish (Ref. 7364). Minimum depth reported taken from Ref. 27115.

fisheries: commercial; aquarium: commercial

分布於印度-泛太平洋區，西自東非洲，東至巴拿馬，北起日本南，南迄羅得豪島、帕拉島及杜夕島；包含密克羅尼西亞。台灣產於北部、東北部、南部、小琉球、綠島及蘭嶼等。

一般以流刺網、延繩釣或潛水鏢魚法等捕獲。觀賞及食用兼具。剝皮後，煮薑絲湯，肉質鮮美。尾柄上骨質盾板非常銳利，易傷人，處理時需小心。因食物鰱之關係，可能具熱帶海魚毒。

體呈橢圓形而側扁。頭小，頭背部眼前稍凸。口小，端位，上下頜各具一列扁平齒，齒固定不可動，齒緣具缺刻。背鰭及臀鰭硬棘尖銳，分別具XI棘及III棘，各鰭條皆不延長；胸鰭近三角形；尾鰭略內凹或近截形。體一致為具光澤之灰綠色至黃綠色，腹面白色，體側與腹面顏色相交處另具1條波狀黑色縱紋，隨著成長而明顯；頭部及體側共約有5條黑色橫色，第一條橫帶貫穿眼部而成1條眼帶，最後一條則位於尾柄前方；尾鰭前方之尾柄背側另具1條黑色鞍狀斑，腹側則有1個黑點；頭背側由眼間隔至吻端的正中央另具1條黑色窄帶；各鰭淡色至黃綠色。

棲息於潟湖和礁區海域，棲息深度在0-90公尺左右，幼魚則常出現於潮池。平時不太聚集成群，但覓食時會聚集成群以抵抗其它具有領域性的草食魚類攻擊。主要以絲狀藻為食。當產卵時亦有群集成群的習性。

Acanthurus triostegus, also known as the convict tang, convict surgeonfish, or manini, is a small surgeonfish in family Acanthuridae of the order Perciformes. It is typically about 17 cm (7 in) long, but some individuals may reach 27 cm. These tangs are widespread. They are found in the Indo-Pacific except for seas around the Arabian Peninsula, in the Pacific at the Hawaiian Islands, and in the Eastern Pacific they are found in the lower Gulf of California and down to Panama, including the Revillagigedo Islands, Clipperton Island, Cocos Island, and Galápagos Islands with some reports throughout the Mediterranean and Adriatic Sea most likely entering through the Suez Canal.

Occurs in lagoon and seaward reefs with hard substrate to a depth of at least 90 m and feeds on a wide variety of filamentous algae. Occasionally forms schools; feeds in large aggregations, thus overwhelming territorial herbivores. During spawning, clouds of eggs and sperm of this species are preyed upon by eagle rays which are often present during spawning. Size of metamorphosis from postlarva stage to juvenile is 3.2 cm (Ref. 9267). Commonly ciguatoxic in Tuvalu (Ref. 9513).