SPECIES OF REEF FISH
The male squaresport anthias produces a light blue patch on its side when it is trying to attract females. The patch is hard to see in natural light at 25 meters but is highly visible in ultraviolet light at that depth. It is not clear whether the fish can see in ultraviolet light. Sea moths have a proboscis-like snout and clawlike fins. The hop along the ocean bottom and probe with their snout for food.
Coral Trout are one of the most popular catches of reef fisherman due to the high prices paid for them as well as their taste. Coral Trout are one the top members of the reef’s food chain, eating many kinds of smaller fish, with damselfish being one of the mainstays of their diet. One of visually stunning characteristics of the coral trout is the male’s ability to instantly change its colour when putting on courtship displays for females. Depending on species, coral trout typically grow anywhere from 70 to 120 centimeters in size. [Source: Great Barrier Reef.com]
The eight-centimeter (three-inch) -long yellowhead jawfish lives in a 30-centimeters (12-inch) burrow that its digs for itself. When a predator comes around it dives into the burrow tail first. The fish lines its burrows with pebble walls and often get into fights with other jawfish over possession of pebbles. Female jawfish place newly hatched young in their mouth to keep them protected for predators while allowing water to circulate and provide them with oxygen. When feeding the jawfish hides her young in a reef hole. Males also incubate eggs in their mouth. Some fasten an upside-down jellyfish to their back for camouflage and defense.
Websites and Resources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Fishbase fishbase.se ; Encyclopedia of Life eol.org ; Smithsonian Oceans Portal ocean.si.edu/ocean-life-ecosystems ; Woods Hole Oceanographic Institute whoi.edu ; Cousteau Society cousteau.org ; Monterey Bay Aquarium montereybayaquarium.org ; MarineBio marinebio.org/oceans/creatures ; Websites and Resources on Coral Reefs: Coral Reef Information System (NOAA) coris.noaa.gov ; International Coral Reef Initiative icriforum.org ; Wikipedia article Wikipedia ; Coral Reef Alliance coral.org ; Global Coral reef Alliance globalcoral.org ;Global Coral Reef Monitoring Network gcrmn.net
Strange Coral Reef Fish
Stephanie Pappas wrote in Live Science: The animal-built habitat of a reef, in turn, shelters other strange creatures. Take the rose-veiled fairy wrasse (Cirrhilabrus finifenmaa), which lives in deep, poorly lit reefs called "twilight reefs." These fish look like something a 6-year-old with access to the 64-crayon Crayola box might dream up: Their bodies are a rainbow of pink, orange, purple and blue. Research published in the journal Proceedings of the Royal Society B in 2020 found that coral reefs provide the perfect environment for the evolution of gaudy colors. The clear water allows males and females to see each other well, and they may evolve colorful bodies to attract mates; the structural refuge offered by hard corals means that animals face less costs for their showiness than animals in more open waters, because they can more easily escape predators despite being quite visible..[Source: Stephanie Pappas, Live Science, April 20, 2022]
Another common coral reef denizen is the bullethead parrotfish (Chlorurus sordidus), which has some of the strongest teeth on Earth, according to the Smithsonian National Museum of Natural History — all the better to chew up the hard exoskeletons of coral to get to the tasty polyps inside. As if this diet weren't odd enough, parrotfish also sleep in cocoons of their own mucus to protect themselves from blood-sucking parasites.
Gardens of eels resembling 70-centimeter (two-foot) -high sea grass can be found in some parts of the world, with the most well-known ones in the Red Sea. These eels bury their tails in the sand in holes that are tightly sealed with mucous. Colonies of garden can have thousands of members and the eel's mucus lined holes are sometimes only a few inches apart. Anchored to their holes the eels sway in the current eating sea squirts, fish eggs and tiny crustaceans that float by. Because they disappear quickly whenever a threatening object like a big fish, boat or a diver appears they were not discovered until the 1960s.
Colorful Reef Fish
Napoleons are impressive-looking and colorful medium-size fish that get their name from the bump on their forehead which reminded some of a French-style tri-corner hat. Other colorful and unusual-looking reef fish include chromis, lizardfish, batfish and hogfish.
Sweetlips are a fish found in the Pacific and Indian oceans that have thick "lips" and pucker their mouths like it will kiss. They are a schooling fish with yellow fins and spots arranged in a zebra-style patterns on its back. Other colorful schooling fish include unicornfish, surgeonfish and some species of angelfish and damselfish.
The fairy basset, a pinkish and yellow fish, spends most of its life swimming upsidedown. Related to sea horses, trumpetfish fool predators and prey by imitating plants by hovering just above the reef while they search for food. They spends most of their live swaying in soft coral gardens with their nose in the sand and tail overhead, waiting for meals to pass their way.╆
Gobies are a huge family of fish that are small in size and have short lifespans. One of their main function within reef ecosystems is serving as prey for a large number of predators within the same habitat. Gobies mainly reside at the bottom levels of the reef and typically travel either alone or in small groups so as to avoid detection from predators. [Source: Great Barrier Reef.com]
Coral gobies Gobies are often found around coral reefs or in tidal pools. They make up the largest marine fish family. Some inch-long translucent gobies live and feed in the mantles of giant clams. Another kind leaps from tidal pool to tidal pool as the tide retreats. Somehow they know exactly where all the pools are and never miss. Apparently they make a mental map while tide is high and remember it when the tide is low.
One of most renowned experts on gobies is the former Emperor Akihito of Japan. Much of his works has been devoted to distinguishing between the difficult-to-distinguish goby species through comparisons of minute details of the fish’s shoulder blades. Akihito spent a great deal of time looking at specimens under a microscope in his palace laboratory. Peter Miller, an emeritus professor at the University of Bristol, told the Times of London, “He has made a very useful contribution, and I’m not saying that because he’s the Emperor. I have referenced his papers myself. I doubt there are more than a dozen scientists in the world who can match his expertise.”
There are more than 2,000 different species worldwide. Among them is the crabeye goby which has fin markings called double eyespots that mimic huge eyes and are spaced at the same distance as the eyes of gobies that feed on fish that feed on gobies.
The orange-colored goby, fish found off the shores of Japan, changes sex. When a group of females are placed together the largest one turns into male, fertilizes the eggs and guards them. When a large male is placed with a small male the small male becomes a female.
The Exyrias akihito is a species of goby named after Emperor Akihito . A bottom feeder, it is 10 centimeters long a and has big bug eyes and orange speckles on its translucent body. Another species of gobies found near Japan live in burrows built by bulldozer shrimp. The two sea creatures have a symbiotic relationship. The gobies alert the nearly blind shrimps to approaching dangers. The shrimps, in return build the burrows used by the gobies and keep them clean by bulldozing the sand in search of food.
Cardinal Fish are small, elusive species that have large eyes and mouths and are notable for having a dorsal fin separated from a single protrusion into twin fins — something that is among reef-dwelling fishes. Cardinal Fish are nocturnal and typically bury themselves within gaps in coral or caves during the daylight hours before emerging at night to feed mostly on shrimp and crab. Appearance-wise, cardinal fish are often relatively drab in color and inconspicuous which helps them evade predators. Many are red or pinkish, the source of their name, and some are brightly colored,. [Source: Great Barrier Reef.com]
The Banggai cardinalfish(Scientific name: Pterapogon kauderni) is endemic to the Banggai Archipelago in Indonesia but has been introduced outside of its natural range through the ornamental live reef trade. The main threats to the Banggai cardinalfish are harvest for the ornamental live reef trade and habitat destruction. In 2016, NOAA Fisheries listed the species as threatened under the Endangered Species Act. [Source: NOAA]
The Banggai cardinalfish is a small fish. It weighs up to 11 grams (less than half an ounce and reaches lengths of eight centimeters (3.4 inches) and lives up to 5 years with an average life span of 2.5 to 3 years. The species is differentiated from all other cardinalfish by its tasseled first dorsal fin, elongated anal and second dorsal fin rays, and deeply forked caudal fin. It is brilliantly colored with contrasting black and light bars with whitish spots over a silvery body. The dot pattern is unique to individual fish and can be used to identify specimens. Generally, males and females look similar; however, on average, males have a larger mouth gape relative to their total body length and can be distinguished during brooding when their oral cavity becomes enlarged.
The Banggai cardinalfish feeds primarily on copepods, but it also eats planktonic organisms when they are abundant in the area. It lives in shallow, calm waters among coral reefs and seagrass beds. Like many cardinalfishes, sex roles are reversed, and males provide parental care, brooding and hatching eggs in their mouths. Males release fully formed juveniles.
The main threats to the Banggai cardinalfish are commercial harvesting for the ornamental live reef trade, due to its colorful traits, and habitat destruction. The fish's coral reef habitat is destroyed by the use of fish bombs (typically made with fertilizer and phosphorus) and cyanide to catch fish for the live reef fish trade. Runoff from agriculture and human population growth, increase waste and nitrates in the marine environment, promoting algal blooms, which the light and oxygen available for corals.
Pearlfish are long, slim, scaleless fish that live mostly among clefts in the sea floor. Their homes are often so narrow they have to enter them tail first. One type of pearlfish that feeds in the open water shelters itself in the cavity of pearl oyster shell. The fish gets its name because sometimes it dies in the shells and gets covered in mother-of-pearl. Pearlfish are interesting because they often live inside sea cucumber hosts, often entering and exiting them on a daily basis head first or tail first through the host’s anus. During the day the pearlfish rest inside a hollow cavity in their hosts and at night they slip out to forage among the reef. See Sea Cucumbers.
Atlantic pearlfish(Scientific name: Carapus bermudensis) are native to the western Atlantic Ocean from Bermuda to Brazil, including southern Florida, the Gulf of Mexico and the West Indies. [Source: Stephanie Chong and Derek Sheldon, Animal Diversity Web (ADW) /=]
Atlantic pearlfish are found in tropical and subtropical waters in reefs, coastal areas and on or near the sea bottom, in coral-dominated communities or shallow sea grass beds, at depths of one to 235 meters (3.28 to 771 feet) and most common at depths of one to 34 meters (3.28 to 12 feet) . Their average lifespan in the wild is three years. They are commonly being found living inside the bodies of sea cucumbers (Holothuroidea) or occasionally other marine intervebrates./=\
Pearlfish are well protected from predation by their hosts, sometimes even feeding while still halfway inside them. They are able to take advantage of their hosts' anti-predator adaptations, such as their poisonous Cuverian tubules; these are not activated when an Atlantic pearlfish enters. Pearlfish also have a higher tolerance to sea cucumber toxins than other reef fish do. Potential predators include other fishes, including other pearlfish. The main species used as hosts are the West Indian sea cucumber (Actinopyga agassizi), furry sea cucumber or the fissured sea cucumber (Astichopus multifidus), chocolate chip sea cucumber or cookie dough sea cucumber (Isostitchopus badionotus), donkey dung sea cucumber (Holothuria mexicana) and brown rock sea cucumber (Holothuria glaberrima).
Atlantic pearlfish are nocturnal (active at night) carnivores that capture most of their prey while outside of their hosts. Caridean shrimps are their main source of food. They also occasionally feed on other small decapods, isopods, annelids, copepods, and fish remains and even smaller pearlfish. Little is known of the reproductive behavior of Atlantic pearlfish. While many carapids pair sexually, this speices is thought to be an open-water broadcast spawner, with females scattering eggs over substrate and males releasing sperm over them.
Pearlfish Characteristics, Development and Behavior
Pearlfish range in length from 15 to 24 centimeters (5.91 to 9.45 inches). Both sexes are roughly equal in size and look similar. According to Animal Diversity Web: Atlantic pearlfish are characterized by a short predorsal region and a dorsal fin which is longer than the anal fin, extending along the body and meeting at the ends of the tail. The anus is located anteriorly, close to the throat. The body is scaleless and eel-like in appearance, being long and laterally compressed. There are no enlarged dentary or premaxillary fangs, spaces between their teeth. Pectoral and pelvic fins are also absent. These fish have constricted, two-chambered swim bladders, as well as visceral cradles and elaborate pre-dorsal bones. They have small conical teeth all along their jaws, as well as cardiform teeth on the frontal, external regions of the premaxillary bones. Coloration is typically silver and white, with red markings.
Although its complete life history and development have yet to be described, it is assumed that eggs of this species follow a similar pattern to a closely related species, Carapus actus. Eggs are laid in a gelatinous flat that floats freely in open waters. After hatching from elliptical, planktonic eggs, larvae undergo two separate growth phases. In the first phase, the larvae develop into vexillifers, which are characterized by a branched dorsal filament called the vexillum. As the vexillifers continue to grow, they lose their vexilla and enter the tenuis stage. Atlantic pearlfish larvae in this stage are very long (7-8 centimeters) and thin, transparent, and develop a long caudal filament. At this stage, these fish become demersal and may enter a host or remain free-swimming. The larval period is estimated to last for three months.
Atlantic pearlfish sense and communicate with vision, touch, sound, chemicals usually detected by smelling as well as vibrations. They are able to produce sounds, which are structured in regular pulse emissions and are heard over long distances from within their hosts. These sounds signal their sex to other pearlfish. In sexual encounters, sounds are reduced to a single pulse emission. Sound emissions can be divided into two groups: stridulatory (non-harmonic sounds created by rubbing body parts against each other, such as teeth and pectoral fins) and swim bladder vibrations (sounds from vibration of the swim bladder against a deformation of its wall). These vibrations are detected by other Atlantic pearlfish through their lateral line systems. These fish locate potential hosts primarily using chemical cues as well as through vision, olfaction and rheotaxis (sensation of water).
Pearlfish That Live Inside Sea Cucumbers
Transparent eight-inch-long pearlfish that live inside some species of a sea cucumber usually enter their host tail-first or by nudging open the sea cucumber's anus with its nose. Inside it is protected from its enemies. For food it eats the sea cucumber's internal organs, which the sea cucumber regrows almost as fast as they are eaten.
Young pearlfish can enter the anus easily. After they have have entered a host for the first time they transform into their definitive forms, shrinking to about one third of their length, beginning to grow again after transformation is complete.When they are older they have insert their sharp-pointed tail into the anus and twist their body and enters the sea cucumber like a corkscrew.
Atlantic pearlfish have both commensal and parasitic symbiotic relationships with sea cucumbers. The preferred host appears to be Actinopyga agassizi, though they are found in body cavities of other sea cucumber species as well. These fish search for hosts by swimming with their heads towards the bottom, searching for water currents exhaled from a potential host. Entrance is typically through a host's anus, after which a fish may remain in the gut or bite through to the alimentary canal or respiratory tree. Atlantic pearlfish typically enter their hosts tail-first, though they are known to enter head first as well. Unlike other families in this order, carapids are not known to be parasitic, using their hosts for shelter only. Although uncommon, it is possible for more than one fish to live in one host. Atlantic pearlfish leave their hosts at dusk to feed, and re-enter hosts by daylight. These fish do not have a well defined home range; they may return to the same host each night after feeding, but it is not necessary.
Clownfish and Anemonefish
Clownfish and anemonefish are small colorfully-striped fish often found hanging among the tentacles of sea anemones. Also known as anemonefish, most are bright orange with with white or back markings and have big eyes and a cute expression. They are members of the colorful damselfish family (Pomacentridae). Amphiprion is a genus of ray-finned fish which comprises all but one of the clownfish or anemonefish species with the the subfamily Amphiprioninae of the family Pomacentridae.
James Prosek wrote in National Geographic, Clownfish get their name from the bold color strokes on their body (from rich purplish browns to bright oranges and reds and yellows), often divided by stark lines of white or black, quite like the face paint on a circus clown. Seeing clownfish darting among the tentacled folds of an anemone is like watching butterflies flitting around a flowering plant in a breeze-blown meadow — mesmerizing. [Source: James Prosek, National Geographic, January 2010]
Clownfish and anemonefish are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature), heterothermic (having a body temperature that fluctuates with the surrounding environment) and have bilateral symmetry (both sides of the animal are the same). They belong to subfamily Amphiprioninae, of which members are protandrous hermaphrodites, meaning that all individuals develop first into males and then possibly into females later. [Source: Animal Diversity Web (ADW) /=]
Scientists recognize 29 species living in tropical and subtropical waters in Indian and western Pacific oceans. They live among the reefs from East Africa to French Polynesia and from Japan to eastern Australia, with the greatest concentration of diversity on the north coast of New Guinea in the Bismarck Sea (where with a little luck and a competent guide you can see seven species on one reef). See Separate Article on CLOWNFISH AND ANEMONEFISH SPECIES
In the early 2000s, clownfish became international stars due to Disney-Pixar’s film “Finding Nemo”. Clownfish are also extremely popular with the diving community. They are characterised by their recognisable markings — a bright orange colouring coupled with a glowing white or light blue band. While they are small in size, they are also popular for being one of the most accessible species of fish to snorkelers because of their inclination to inhabit shallower waters. [Source: Great Barrier Reef.com]
Rabbitfish live (Scientific name: Siganidae) near the sea bottom in shallow water around coral reefs. They are brightly yellow, black and white in color. They feed on phytoplankton or attached algae that grows at the base of dead corals and have a single row of spade-like teeth that enable them to snip off bits of its food. A relative of sharks, rabbitfish are so named because their peaceful temperament, the shape of their heads, snout mouths and teeth are sort of like that of a rabbit. Some species have poisonous dorsal fins that it extends when frightened. Males and females mate for life. Generally, smaller reef fishes such as siganids live between three and five years.
The Siganidae family is composed of one genus, Siganus, and two subgenera, Siganus with 22 species and Lo with five species. Siganids get their common name, rabbitfishes, from their ounded blunt snout, and rabbit-like appearance of the jaws. They browse individually or in schools over the reef or feed on plankton within the water column. The fossil history of the Siganidae family contains three known fossil genera. From the Eocene Period (56 million to 33.9 million years ago) there is Ruffoichthys from Italy and Siganopygaeus from Turkmenistan. From the Oligocene Period (33 million to 23.9 million years ago) there is Archaeoteuthis from Switzerland. [Source: R. Jamil Jonna, Animal Diversity Web (ADW) /=]
Rabbitfish are native to he tropical Indian Ocean and the Pacific Ocean and are now found in the eastern Mediterranean as well. Siganus rivulatus entered the Mediterranean from the Red Sea through the Suez Canal and is now locally common in the Mediterranean. Rabbitfish mainly inhabit reefs, shallow lagoons, sea grasses or mangrove areas. They can be found along reef edges with broken rock, reef flats with scattered coral heads or near grass flats, and often come into very shallow waters to feed in algae. /=\
According to Animal Diversity Web: Members of the Siganidae family first produce small adhesive egg sacs, which then become larvae. The larval stage is planktonic and develops into a distinctive post-larval stage called the acronurus, which is characteristic for members of the suborder Acanthuroidei. In the acronurus stage the body is transparent and individuals remain pelagic (living in the open ocean, far from land) for an extended period before settling into the adult habitat and rapidly changing into the juvenile form. There is considerable morphological difference between larvae and adults and current information suggests that males reach sexual maturity before females throughout the family. /=\
Rabbitfish are most threatened by predation during the planktonic, larval stage and very few larvae survive. Their poisonous spine defenses are an illustration of predation pressures they face. The sharp, strong spines are coated with a mucous mixed with venom and can inflict painful wounds. As for their place in the reef ecosystem, they fill the roles of grazer and planktivore which are important in keeping thick mats of filamentous and leafy algae from smothering the corals. They keep the mat only one to two millimeters thick and can strip vegetation from a 10 meters wide ring around the reef. Some rabbitfish use the reef mainly for shelter but “hover above it in brilliant, shifting shoals, while feeding on plankton.” These fish deposit feces in the small crevices where they hide, which is important in promoting the growth and diversity of corals
Some rabbitfish are important food fishes in many areas and colorful species are popular in the aquarium trade. The fast growth rate and shallow browsing habits of rabbitfish make them ideal for aquaculture, as evidenced by numerous studies on their growth and reproduction. Currently, there is no known conservation threat to any member of the rabbitfish family.
Rabbitfish Characteristics and Behavior
Rabbitfish are venomous and polymorphic (“many forms”, individuals can be divided into easily recognized groups, based on structure, color, or other similar characteristics). Both sexes are roughly equal in size and look similar. Sometimes females are a little larger.
According to Animal Diversity Web: The rabbitfish have many strong spines with venom glands in dorsal and anal fins that contain a painful toxin. Most rabbitfish are countershaded, but some reef species, Siganus vulpinus, have coloration similar to butterflyfishes. The teeth of rabbitfish are compressed into a single row and asymmetrically bicuspid. The pelvic formula is unique (I, 3, I,) reflecting the hard spines at either end of the fin. The dorsal fin has 13 spines and 10 soft rays and the anal fin has seven spines and 10 soft rays. There are 23 vertebrate and the maximum length is approximately 50 centimeters.
Rabbitfishes are quite colorful and can be easily identified during daylight hours. However, at night or when threatened, they change drastically as color fades and dark blotches appear. Similarly, at death colors fade rapidly, making identification after preservation difficult. Although there are no significant differences between the sexes in this group, females are larger than males in some, if not all, species. (Kuiter, 1993; Thresher, 1984) /=\
Rabbitfish are diurnal (active during the daytime), hiding in reef crevices during nighttime and browsing over reefs to feed during the day. Some species school while others browse individually among corals. They communicate with vision and sense using touch, vibrations and chemicals usually detected by smell. /=\
Rabbitfish Mating, Reproduction and Offspring
Rabbitfish can be monogamous (having one mate at a time) or polygynandrous (promiscuous), with both males and females having multiple partners. They are oviparous (young are hatched from eggs) and iteroparous (offspring are produced in groups). Rabbitfish engage in year-round breeding. Reproduction is external, meaning the male’s sperm fertilizes the female’s egg outside her body. There is no parental involvement in the raising of offspring.
According to Animal Diversity Web: Rabbitfish characteristically school in small to large groups, with some species, such as Siganus rivulatus and Siganus luridus, breaking off into pairs or small units after spawning begins. Other members of the Rabbitfishae family, such as the foxface, form monogamous pairs. Individual pairs or groups behave aggressively towards one another resulting in wide spacing throughout the reef during spawning. Just before gametes are released, most rabbitfish move in a circular pattern and the males develop a marble color pattern. /=\
Before spawning, rabbitfish migrate to traditional spawning areas, with the location varying among species. Spawning peaks in spring and early summer, and, as with many other coastal species, rabbitfish show a prominent lunar rhythm. Spawning usually takes place at night or early morning and coincides with outgoing tides. Rabbitfish larvae also respond to the lunar cycle, as most appear inshore (after the initial pelagic (living in the open ocean, far from land) stage) three to five days before the new moon. /=\
Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; 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