Surgeonfish Species

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palette surgeonfish (Paracanthurus hepatus)

The palette surgeonfish (Scientific name: Paracanthurus hepatus) is also known as the flagtail surgeonfish, doctorfish, blue tang, blue hippo tang, regal tang and common surgeonfish. Palette surgeonfish can live more than 30 years in the wild. In aquariums, where they more readily acquire diseases, palette surgeonfish generally do not live more than 20 years. Their average lifespan in captivity is 12 to 14 years. Dory, voiced by Ellen DeGeneres, in “Finding Nemo” was a palette surgeonfishfish.[Source: Anna Thurston, Animal Diversity Web (ADW) /=]

Palette surgeonfish are native to the Pacific Ocean and Indian Ocean. They live in tropical, marine environments and are usually found in reefs at depths of two to 40 meters (6.5 to 131 feet) in waters with a strong current. They may move seasonally, occurring at higher latitudes when water temperatures allow. Generally, palette surgeonfish range between 30° north and south latitude and 32° east to 170° west longitude. Palette surgeonfish favor coastal regions with water temperatures are between 24 and 26 °C (75 and 79 °F). They congregate near Pocillopora eydouxi, a type of coral with branching extensions, which serve as a protective hiding place when threatened. Reefs provide plant material, such as algae, necessary as food.

Humans utilize palette surgeonfish for the pet trade and have been harvested for many years. After the release of "Finding Nemo", the popularity of the fish spiked, when people paid US$30 for individuals and over US$100 for breeding pairs. The venomous caudal spine of palette surgeonfish can inflict painful but minor wounds on humans. Although overfishing has affected wild populations, palette surgeonfish are not considered threatened and have not been evaluated by the International Union for Conservation of Nature (IUCN), the US Fish and Wildlife Service, or Convention on International Trade in Endangered Species (CITES).

Palette Surgeonfish Physical Characteristics

Palette surgeonfish have an average weight of 600 grams (21.15 ounces). They range in length from 12 to 38 centimeters (4.7 to 15 inches), with their average length being 25 to 31 centimeters (inches). Sexual Dimorphism (differences between males and females) occurs: Males are larger than females.[Source: Anna Thurston, Animal Diversity Web (ADW) /=]

According to Animal Diversity Web: Palette surgeonfish are characterized by the vibrant sky blue coloration of their oval-shaped bodies. Structures called iridophores on the exterior of the fish contribute to this coloration. Adults have dark narrow lines of dark blue on the dorsal half of their body. This color extends from the eye on the anterior end and continues to the posterior end. This coloration is darker near the posterior end and is black near the tail. A circular patch of sky blue coloration is located directly behind the pectoral fin. The pectoral and caudal fins are are bright yellow. The yellow extends in a "V" shape from the caudal fin to a point just beyond the caudal spine. /=\

palette surgeonfish in a home aquarium

Coloration of palette surgeonfish changes as they mature; juveniles are bright yellow with blue spots near their eyes, and their dorsal and anal fins are tipped in light blue. Their body becomes blue as they mature. /=\

Palette surgeonfish have nine hard, sharp spines in their dorsal fin followed by 19 to 20 soft rays. Their anal fins have three spines and 18 to 19 rays. Their pectoral fins consist of 16 rays, and their pelvic fins have one spine and three rays. They have a razor-sharp caudal spine located at the base of their caudal fin. This spine contains toxins that can cause a debilitating pain to small predators and uncomfortable irritation and pain in humans. The caudal spine rests in a groove below the surface of the skin and can be extended from the body. Its base is attached to the vertebrae of the fish by a ligament directly connecting the two. The outer point of the spine is free to move with contraction of specific muscles. When threatened, a palette surgeonfish extends its caudal spine and attempts to puncture the exterior of a predator./=\

Palette Surgeonfish Behavior

According to Animal Diversity Web: Although palette surgeonfish are occasionally observed individually, most are found in pairs or small groups. In the reef, they school for protection. A group of fish, each possessing a sharp and venomous caudal spine is potentially problematic to predators; very few predators swim into the middle of a school of surgeonfish to feed off the members of the group. Palette surgeonfish aggregate with other genera of surgeonfish, including Acanthurus, Ctenochaetus, Naso, Zebrasoma, and Prionurus. The home range of palette surgeonfish is often only defined during breeding and depends on the dominance status of the fish as well as the method of breeding — paired or group broadcast spawning. [Source: Anna Thurston, Animal Diversity Web (ADW) /=]

Male palette surgeonfishfish may have violent encounters with one another, circling each other and displaying their caudal spine. The hue of their blue coloration changes as the encounter becomes more intense. Males attempt to injure one another with their venomous spines, each one swimming closer to the other until its caudal fin can be manipulated to slash the other. This caudal spine may have an impact on the social standing of palette surgeonfish with the other marine fish in the area. A fish of this species achieves its dominant status over previously dominant fish by flashing their venomous caudal spine. The most dominant individuals often have the largest breeding territory.

palette surgeonfish

When frightened, some palette surgeonfish, particularly juveniles, hide behind live rocks or within branching corals. An alarmed fish secures its position within the head of the coral by extending its caudal spine into the coral. This prevents a predator from pulling the fish out of its hiding place, if found. If spotted by a predator, palette surgeonfish "play dead", lying on their side, without any movement. They are often mistaken for dead and passed over by predators. In the aquarium trade, new enthusiasts worry that palette surgeonfish have died when they play dead. However, within a few days of introduction to an aquarium, palette surgeonfish become more comfortable with their environment and also often acquire dominant status.

Palette surgeonfish communicate with vision and sense using vision, touch and chemicals usually detected with smell. They can communicate by changing their coloration. This color change depends on the conditions and how they perceive their environment. Under stress, for example, their blue coloration deepens. The black marks along the body may become bleached slightly and the markings less visible. The iridiphores causing the bright blue coloration appear smaller and less iridescent, hence the darker shade of blue. Other fish in the community can detect this color change and infer potential problems. Color change also occurs during stimulation such as male dominance interactions or breeding. The coloration around the caudal spine serves as a warning to other species. In palette surgeonfish, the yellow triangular coloration extends just beyond the caudal spine. In other species of surgeonfish, the location of the caudal spine may even be emphasized by a color that is not otherwise present on the body of the fish. /=\

Palette Surgeonfish Feeding Behavior, Predators and Ecosystem Roles

Palette surgeonfish are herbivorous. Unlike many marine fish, palette surgeonfish rely only slightly on plankton. Instead, they graze on algae, using their small teeth to pull algae from rocks and coral. Fish of this species also feed on microalgae, other marine plants, and zooplankton. [Source: Anna Thurston, Animal Diversity Web (ADW) /=]

Due to the small shape of their mouth, surgeonfish can easily pick and remove algae from uneven surfaces. Aggregations of palette surgeonfish eat the fast growing algae from sponges in their habitat. This benefits the sponges and indirectly preserves habitat for species dependent on the steady growth of sponges.

Common predators of palette surgeonfish include tuna, bar jacks, and tiger groupers. /=\ Palette surgeonfish possess multiple anti-predator adaptations. Their razor-sharp caudal spine is venomous and can cause debilitating pain to small predators. The effectiveness of this defense mechanism is enhanced by the tendency of this species to congregate. If a predator were to attack a group of palette surgeonfish, it would become surrounded by surgeonfish that were thrashing their tails and slashing with their protrusible caudal spines. Palette surgeonfish also display bright aposematic coloration, warning predators of their poisonous skin and venomous spine. Other species take advantage of these defense mechanisms. Midnight parrotfish, for example, display a similar blue coloration and join groups of palette surgeonfish for protection. /=\

Palette Surgeonfish Mating and Reproduction

powder blue surgeonfish (Acanthurus leucosternon)

They are oviparous (young are hatched from eggs) and can be monogamous (having one mate at a time or polygynandrous (promiscuous), with both males and females having multiple partners. They engage in external reproduction in which sperm from the male fertilizes the female’s egg outside her body and employ broadcast (group) spawning, the main mode of reproduction in the sea. It involves the release of both eggs and sperm into the water and contact between sperm and egg and fertilization occur externally. [Source: Anna Thurston, Animal Diversity Web (ADW) /=]

Palette surgeonfish engage in seasonal breeding and year-round breeding. They are believed to breed monthly, more frequently during cooler months, from winter to early spring, but varies with location and water temperature. In the Pacific, breeding activity is most intense from December to June. In locations where water temperature does not vary considerably with season, breeding can take place throughout the year. Breeding is assumed to peak during the summer in these locations. The average number of offspring being 40,000 eggs per spawning session The time to hatching ranges from 25 to 28 hours. High quantities of eggs and sperm give water a cloudy appearance.

According to Animal Diversity Web: Palette surgeonfish congregate in breeding groups, composed of both males and females. These groups spontaneously form. Groups dissolve and reform several times prior to spawning. A group begins to swim upward and, at the crest of this upward movement, they release their gametes. Palette surgeonfish are broadcast spawners; eggs and sperm are released directly into the water, and fertilization takes place externally. The quickened pace of their swimming during breeding is believed to allow for dispersal and mixing of the sperm and eggs. Eggs are then carried away by currents. On occasion, palette surgeonfish have been observed breeding with individual mates rather than in groups. In this case, a male's coloration may change. The male and female then circle around one another, showing off their coloration before breeding. There is pre-fertilization provisioning but no parental involvement in parenting. As broadcast spawners, males and females disperse after releasing their gametes into the water.

Palette Surgeonfish Development

Eggs of palette surgeonfish hatch in 25 to 28 hours (average 26 hours), with the time to independence ranging from four to seven days, with independence occurring on average at five days. Freshly-hatched larvae are severely underdeveloped and lack a heart beat at hatching. Larvae are nourished by yolk from the egg. Newly hatched larvae are buoyant but remain in a resting state until the heart begins to beat, up to five hours after hatching. [Source: Anna Thurston, Animal Diversity Web (ADW) /=]

Larvae develop quickly and feed in great numbers off shore. Two days after hatching, fins and pigment in the eyes begin to develop, and larvae begin to make short swimming movements. Development continues with jaws and the gut, and by the seventh day scales and intestines begin to form. Speed of development is related to light intensity. Larvae mature after about 37 days. /=\

Sexual maturity is not measured by age but rather by size. Males generally reach sexual maturity around 11 centimeters in length. Females, however, do not reach sexual maturity until about 13 centimeters in length. Juvenile palette surgeonfish resemble adults, however, they differ in coloration. Juveniles also have a more rounded caudal fin than adults. Additionally, the ventral and poster tips the caudal fin in adults extend beyond the middle section of the fin.

Lined Surgeonfish

Lined surgeonfish (striped surgeonfish, Acanthurus lineatus)

Lined surgeonfish (Scientific name: Acanthurus lineatus) are also known as striped surgeons. A very long-lived fish, they have a lifespan of 30 to 45 years. The members of the species living near the Great Barrier Reef live to an average age of 32 years. The lined surgeonfish that live in American Samoa have an average lifespan of 11 years.[Source: Madison Krablin, Animal Diversity Web (ADW) /=]

Lined surgeonfish are native Indian Ocean and Pacific Ocean from southern Japan in the north to Australia in the south. They are prevalent in the Great Barrier Reef, the Indian Ocean, in reefs around the American Samoa, the coasts of eastern Africa and Madagascar, the southeastern coast of India, the coasts of the Philippines and Indonesia, and the northeast and northwest coasts of Australia.

The lined surgeonfish lives in shallower water compared to other surgeonfish. They surgeonfish are typically found at depths of one to 10 meters (3.28 to 32.81 feet) in waters between 26° to 30°C (79° to 86°F) live along the edges of coral reefs and on flat algal mats near coral reefs. Juvenile lined surgeonfish tend to live near the surface in the pelagic zone in the open ocean. As they mature they migrate to deeper water around reefs. (Craig, 1996; Randall, 2001; Sale, 1991) /=\

Humans utilize lined surgeonfish as food and in the pet trade. They are popular spearfishing catches and food source in American Samoa. In French Polynesia, lined surgeonfish are harvested for the marine aquarium trade. Lined surgeonfish have venom in their caudal spines

Lined surgeonfish are listed as a species of "least concern" on the International Union for Conservation of Nature (IUCN) Red List. It is not listed in the United States Endangered Species Act or the Convention on International Trade in Endangered Species (CITES) Appendices. An executive order in 2001, banned night spearfishing and SCUBA fishing in America Samoa to help prevent overfishing. To help sustain this species, Australia has put a catch limit into effect. Only five lined surgeonfish that are longer than 25 centimeters can be kept per day.

Lined Surgeonfish Characteristics

Lined surgeonfish range in length from 18.3 to 38 centimeters (7.20 to 15 inches). Their average weight is 285 grams (10.04 ounces). They range in size from 2.7 to 3.2 centimeters as juveniles. Both sexes are roughly equal in size and look similar. The fish has distinct markings — a bright yellow background with blue stripes lined by black stripes running lengthwise across its bodies. The stripes curve around the fish’s facial features. [Source: Madison Krablin, Animal Diversity Web (ADW) /=]

stamp from 1971

According to Animal Diversity Web: Lined surgeonfish have dorsal fins consisting of nine spines and 27 to 29 soft rays, and anal fins consisting of three spines and 25 to 28 soft rays. Both of these sets of fins are yellow with blue stripes. These fish have 16 transparent yellow pectoral fins, and 14 to 16 gill-rakers. Lined surgeonfish also have yellow-black pelvic fins, black caudal fins, and a violet-silver underside. The caudal spine of this species is highly venomous.. /=\

Lined surgeonfish have closely-placed, rounded teeth with denticulate edges (tooth-like projections), that allow for easy grazing of algae. This species also has a thick-walled stomach that acts as a gizzard when sand is ingested and helps grind its food for better digestion.

The colors of lined surgeonfish change in certain situations. When they get excited or aggressive their colors intensify and their caudal fins turn from black to white. At night, the fish become lighter in color in order to be more visible in the water column./=\

Lined Surgeonfish Behavior and Feeding

Lined surgeonfish live solitary, sedentary lives but sometimes gather in schools. They establish their territories individually around coral reefs, although they spend nights in deep-water fissures. They are very loyal to their territory, returning to it 99.9 percent of the time. One of the few times they leave it is to spawn. [Source: Madison Krablin, Animal Diversity Web (ADW) /=]

Lined surgeonfish are very territorial and defend the algae found in their territory from other grazing fish. The size of their range territory is four to 12.5 square meters. They become very aggressive to the fish that enter their territory and have been observed circling, parallel swimming, chasing, and changing their body colors to warn the intruders. The lined surgeonfish become more aggressive to others during high tide. With low tide, these fish are forced to move into deeper waters. The fish are also affected by high water turbulence. It causes them to feed less, leave their territory, and become less aggressive.

whitecheek surgeonfish (Acanthurus nigricans)

Lined surgeonfish communicate with vision and sense using touch, vibrations and chemicals usually detected by smell. All fish, including lined surgeonfish, have a lateral line system. This system allows organisms to detect movement and vibrations in the water surrounding them. Lateral lines provide lined surgeonfish with a sense of space so that they have awareness of what is near them. Epithelial cells detect the vibrations and send electrical impulses to alert the organism. The fish change color to show that they are agitated or excited; their colors become brighter and their caudal fins change from black to white. /=\

Lined surgeonfish spend about 80 percent of their day feeding, mostly in shallow water, and have been spotted taking food from neighboring territories. They are herbivores and mostly algivores (eats algae). They graze on the salts and filaments of rhodophytes (red algae), chlorophytes (green algae), and turf algae on rocks and corals. Because of their diet, this species has high levels of short-chained fatty acids and low levels of protein amino acids, meaning they do not rely heavily on fermentation to gain energy. Humans are their main predators, mainly by way of intentional fishing. Groupers and other predaceous fish are the only reported natural predators of this species. [Source: Madison Krablin, Animal Diversity Web (ADW) /=]

Lined Surgeonfish Mating, Reproduction and Offspring

Lined surgeonfish are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). Polygynandrous (promiscuous), with both males and females having multiple partners, they employ sexual fertilization in which sperm from the male parent fertilizes an egg from the female parent and employ broadcast (group) spawning, the main mode of reproduction in the sea. It involves the release of both eggs and sperm into the water and contact between sperm and egg and fertilization occur externally. /=\

Lined surgeonfish breed throughout the year. The main breeding season is October to February. The average time to hatching is 27 hours and the average time to independence is zero minutes On average males and females reach sexual or reproductive maturity at age four years when they are about 160 millimeters long.. There is no parental involvement in the raising of offspring.

sohal surgeonfish (Acanthurus sohal, sohal tang)

Lined surgeonfish spawn in large groups of 50 to 200 fish. Usually the female releases her eggs and multiple males fertilize them with their milt (seminal fluid). Spawning times vary upon location, but is usually in the early morning hours around the time of a full moon. According to Animal Diversity Web: In Palau and Guam, this species has been observed spawning early in the morning. In the Great Barrier Reef, spawning takes place in the afternoon. Because spawning requires leaving their territory, it is thought that the time of day for spawning is a strategy to minimize food loss in their territories from competitors. This species forms a spawning aggregation and form non-permanent pairs to mate.

Lined surgeonfish spawn on the outer reef channel in waters three to five meters deep. The eggs are less than one millimeter in diameter when spawned. The egg contains a drop of oil so it can float. Upon development of the yolk the egg begins to sink. Approximately 27 hours after spawning the egg hatches and after 42 hours the lined surgeonfish has a sense of awareness of its surroundings. At 4 days old, the larva is 2.7 to 3.2 centimeters and has a moving jaw and swimbladder. The larval stage lasts for 39.5 days in the pelagic (living in the open ocean, far from land) zone of the ocean, until they metamorphose to adulthood and move to coral reefs. Lined surgeonfish have indeterminate growth (they continue growing throughout their lives) but experience rapid growth for the first three to 4 years of their life, reaching close to maximum adult size within the first 10 percent of their lifespan.

Convict Tangs

The convict tang (Scientific name: Acanthurus triostegus) is a kind of surgeonfish also known as the fiveband surgeonfish, convict surgeonfish or Manini. Their lifespan in captivity is typically five to seven years. Their average lifespan in the wild is unknown. Genetic studies on Polynesian populations indicate that, despite their open ocean larval stage, most populations exhibit limited recruitment through dispersal.[Source: Rex Gamoke, Animal Diversity Web (ADW) /=]

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 mainly occupy coral reefs, but are also found in tidepools and other nearshore habitats such as shallow, low current beach communities in waters ranging from 24-26ºC (75-79ºF) at depths of zero to 90 meters (0 to 300 feet).

Convict tangs are eaten by people in tropical regions and sold a aquarium fish. They are venomous and their negative impacts on human include bites, stings and injuries. There have been reports of humans suffering from ciguatera poisoning after consuming convict tangs, although the species is generally considered safe to eat. Convict tangs currently have no special conservation status in regard to IUCN or CITES.

convict tang (Acanthurus triostegus)

Convict tangs are herbivores that graze on algae found on rocks and corals. Adaptations to their algivorous diet include mouths that are slightly downwardly-directed and flexible, comb-like teeth. The grazing of convict tangs on algae helps keep algal populations in check. Their main known predators are Argus groupers, ash-colored conger eels, honeycomb groupers, cornet fish, black-tail snapper and Eagle rays. 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.

Convict Tang Characteristics and Behavior

Convict tangs reach lengths of 27 centimeters (10.6 inches), with an average length of 17 centimeters (6.7 inches). They 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. [Source: Rex Gamoke, Animal Diversity Web (ADW) /=]

Convict tangs are often found in both large and small schools but are also seen alone. While less territorial than other tangs and surgeonfish, tank size is still an important consideration for those keeping them as pets. Convict tangs have been observed in the wild exhibiting tonic immobility (death feigning).

Convict tangs sense using vision, touch, sound, vibrations and chemicals usually detected with smelling or smelling-like senses. They are able to perceive their environments through a number of sensory pathways, including vibrations detected by their lateral lines.

Convict Tang Mating, Reproduction and Offspring

Convict tangs are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). They engage in seasonal breeding and year-round breeding. They engage in external reproduction in which sperm from the male fertilizes the female’s egg outside her body and employ broadcast (group) spawning, the main mode of reproduction in the sea. It involves the release of both eggs and sperm into the water and contact between sperm and egg and fertilization occur externally. [Source: Rex Gamoke, Animal Diversity Web (ADW) /=]

Atlantic blue tang (Acanthurus coeruleus)

Convict tangs are polygynandrous (promiscuous), with both males and females having multiple partners. Spawning tends to occur year round in equatorial habitats and seasonally in other parts of the range. In Hawaii it occurs around full moons in February and March. Because they are broadcast spawners they provide no parental investment to offspring after they the eggs are fertilized.

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 two kilometers to reach

Convict tang eggs hatch into clear pelagic larvae capable of living in the open ocean, far from land.. They typically adapt to their benthic surroundings within 24 hours.Among Hawaiian populations it takes about 2.5 months for these planktonic larvae to develop into juveniles in a reef or tidepool. Initially, juveniles lack the vertical bars present in adults.

Blue Tangs

The blue tangs is (Scientific name: Acanthurus coeruleus) is a kind of surgeonfish also known as Barbero or Médico that lives up to 12 to 15 years in the wild. The fish live around shallow marine reefs throughout the western Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea. They range from New York in the north to the Amazon delta in the south. They are found as far east as Bermuda and Ascension Island but are most common in the Caribbean, coastal Florida and the Bahamas. [Source: Genna Woodruff, Animal Diversity Web (ADW) /=]

Blue tangs live primarily on hard-coral reefs at depths of two to 40 meters (6.5 to 131 feet). . They can also be found near soft corals, rubble, seagrass beds, and algal beds. Young fish prefer areas with plenty of cover. Breeding individuals congregate at flat, sandy areas between patches of reef. They shelter in coral holes and crevices.

Blue tangs are herbivorous as adults, feeding largely on filamentous algae. They avoid eating calcareous material, like corals, because they lack the gizzard-like stomach of other surgeonfishes. They feed singly, in small groups, or in large aggregations numbering over 100 fish. Large aggregations sometimes ravish damselfish gardens on reefs. Blue tangs that live in smaller populations do more foraging in the water column and will eat plankton. Predators include reef sharks, tunas, snappers, jacks, groupers, and barracudas. Juveniles may also be taken by trumpetfish. Pelagic eggs are commonly eaten by small bar jacks, yellowtail snappers, and the black durgon. Because of their flattened shape and sharp caudal spines, it is difficult for predators to swallow blue tangs. Defense from predators while grazing and spawning is also accomplished by schooling. Attacks are more often observed on solitary fish.

range of Atlantic blue tang (Acanthurus coeruleus)

Blue tangs help keep algae populations under control, which prevents the overgrowth and suffocation of corals. Increases in algal density have greatly increased blue tang population size. Most blue tangs move within single reef habitats but they may also live on wider ranges around the reef. Juveniles graze algae and pick molted skin and parasites from green turtles in cleaning stations with surgeonfish and sergeant majors.

Blue tangs are sometimes used as a bait fish and are popular aquarium fish. They are enjoyed by snorkelers and divers. Blue tangs can cause ciguaterra poisoning if eaten. Their sharp caudal spine can cause painful injuries. Their sudden movements can cause the spine to create a deep wound, posing a risk of infection. Blue tangs are not threatened. They are not on the IUCN Red list and have no special status with CITES.

Blue Tang Characteristics and Behavior

Blue tangs reach lengths of 39 centimeters (15 inches). A sexually mature fish is typically over 10 centimeters long. Both sexes are roughly equal in size and look similar. According to Animal Diversity Web: Adult coloration is deep blue and occasionally purple. Mature fish are able to temporarily change color between near-black and pale white. These color shifts can encompass the entire fish or portions of it and are different between the sexes. Similar to other fishes in the family Acanthuridae, Acanthurus coeruleus is a laterally compressed, pancake-shaped fish with high eyes, a subterminal mouth, yellow caudal spine at the base of the tail, and a dorsal fin that ends at the caudal peduncle. Juveniles are bright yellow. Older juveniles are blue or orange-brown with grey stripes. The sharp caudal spine is found in a horizontal groove on the peduncle and can be extended during aggressive interactions. Acanthurus coeruleus has nine dorsal spines, 26-28 dorsal soft rays, three anal spines, and 24-26 anal soft rays.

Juvenile blue tangs are solitary and occupy home ranges that increase with body size. Juveniles aggressively defend their home ranges from A. bahianus juveniles. Juveniles also avoid damselfishes (Stegastes), that overlap in range with them. Adult blue tangs have three social modes: territorial (defend an area within the home range),, wandering, and schooling. Territorial (defend an area within the home range), adults chase conspecifics. Schooling adults are not aggressive. Wanderer adults are not aggressive nor do they interact with other individuals like schooling fish do. Wanderers are mostly chased by other fish including conspecifics, ocean surgeons (A. bahianus), and damselfish (Stegastes). Occasionally large, multi-species aggregations are formed, including doctorfish (A. chirurgus) and other surgeonfish /=\

Blue tangs are active during the day, hiding in crevices on the reef at night to avoid predators. They are not migratory. Juveniles are rarely seen on reefs, because of their dependence on cover, but intermediate phases and adults are common. The size of their range territory is 0.04 to 13.3 square meters with an average territory size is 0.92 square meters. Home ranges increase relative to body size.

Blue tangs use vision to communicate and to locate food. They may also use chemical cues and touch, but little is known about communication and perception channels in these fish. /=\ They communicate with vision and touch and sense using vision, touch and chemicals usually detected with smell.

Blue Tang Mating, Reproduction and Offspring

juvenile blue tang (Acanthurus coeruleus)

Blue tang are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). They are sequential hermaphrodites in which individuals change their sex at some point in their lives and typically produces eggs and sperm at different stages their lives and typically have male organs and sperm before female organs and eggs). Reproduction is external, meaning the male’s sperm fertilizes the female’s egg outside her body. [Source: Genna Woodruff, Animal Diversity Web (ADW) /=]

Blue tang are polygynandrous (promiscuous), with both males and females having multiple partners. Breeding occurs once or twice a year. The breeding season is year-round, but more often during winter. The average time to hatching is 24 hours. On average males and females reach sexual or reproductive maturity at age one year. Pre-fertilization provisioning and protecting is done by females. There is no parental involvement in parenting. /=\

According to to Animal Diversity Web: Blue tangs generally mate in large resident aggregations over sandy patches between reefs. These fish seem to prefer locations six to 10 meters deep with reasonably strong currents to sweep the fertilized eggs to sea. Mating readiness is indicated by color changes in the adults, who change from a uniform deep blue to pale blue on the front half of the body and dark blue on the rear half of the body. Courting females and a small number of males break off from the aggregation and release gametes at the water's surface in a behavior called a "spawning rush." Often, spawning rushes are not successful and are broken off by the female. Pair spawning is limited to small populations.

Prior to a spawning aggregation, small groups of fish travel from nearby reefs before forming schools of over one-hundred individuals. Although spawning aggregations typically occur every day at a given location, they are often restricted to less than 20 individuals. The largest spawning occurs in the late afternoon three to eight days following the full moon in the winter months. However, the exact variables contributing to spawning aggregations are still unknown. It is likely that offshore currents, moon phase, predator abundance, and light levels all play a role in predicting spawning aggregations. Generally, spawning aggregation sites are also used by Acanthurus bahianus and members of the genera Scarus and Sparisoma.

Upon hatching, the pelagic larvae are less than two millimeters in length. The young, called ""acronuri"", are transparent, silvery, and diamond-shaped. They begin to develop scales and dorsal and anal fins at two to six millimeters in length. The caudal spine appears when the larvae reach 13 millimeters in length. Older acronuri drift to nearshore areas where they meta morphose into juveniles, including losing their silver color, developing a more rounded profile, and developing an elongated snout.

Image Sources: Wikimedia Commons; YouTube, Animal Diversity Web, NOAA

Text Sources: Animal Diversity Web (ADW); National Oceanic and Atmospheric Administration (NOAA); Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated March 2023

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