Ray-finned fishes (phylum Chordata, subphylum Vertebrata, superclass Osteichthyes, class Actinopterygii) are vertebrates (animals with a backbone and a hollow tube of nervous tissue called a spinal cord) characterised by their fins being supported by rays of bony/horny structures, much like those paper folding fans supported by rays of sticks.
Like other members of the superclass Osteichthyes, they have bony skeletons (instead of cartilaginous ones), and have limited physiological means to maintain the body temperature within a narrow range (i.e. they are ectothermic animals). Most species have a layer of scales covering their bodies, while some may have very reduced scales or no scales at all.
Depending on the species, these fishes may lay eggs (oviparous), bear live young (viviparous), or bear live young from eggs brood within the body (ovoviviparous).
Here are some examples of marine ray-finned fishes that can be seen in Singapore.
A) ORDER ANGUILLIFORMES
Members of this order, commonly called eels, are typically snake-like with elongate bodies. The scales are usually reduced or absent altogether. In most species, the dorsal, anal and tail fins are connected, forming a continuous structure.
Family Muraenidae
Muraenid fish, more commonly called moray eels, usually have an elongate, firm and muscular body. Many species have tubular nostrils with a very keen sense of smell, which aid them in their hunting. They have strong jaws and sharp teeth, and give painful bites if disturbed.
The
Brown-spotted Moray (Gymnothorax reevesii) has dark brown to purple blotches on its pale body. It can reach lengths of over 60cm, and hunts small fishes and invertebrates. It is usually found in coral reefs and rocky shores, and can tolerate silty conditions.
The
Estuarine Moray (Gymnothorax tile) has a purplish to reddish-brown body, marked with numerous pale speckles which may be less obvious in adults. It can grow to about 60cm long, and is found in estuaries and coastal reefs. This solitary carnivore hunts small fishes and invertebrates to feed on.
Family Ophichthidae
Members of this family generally have cylindrical and elongate bodies, giving them snake-like or worm-like appearances. The tip of the tail is often hard and pointed. They have sharp snouts and muscular bodies that are well-adapted for burrowing, and many species hide in the bottom sediment in the day, and only come out to forage at night. The larvae are pelagic though.
The
Green Worm-eel (Muraenichthys sp.) has a greenish back and a pale and somewhat translucent body. The fins are much reduced, and hence it is sometimes mistaken for a worm or a small snake. It burrows very well, and is usually found in coral reefs or reef flats. This small eel reaches a maximum length of about 20cm.
The
Collared Snake Eel (Ophichthus evermanni) has pale and dark brown blotches on its long body. This eel grows to about 80cm long, and usually hunts alone in estuaries and coastal areas at night.
B) ORDER SILURIFORMES
Members of this order are very varied in their shapes and sizes, but most have up to four pairs of barbels around their mouths and lack scales. They are usually called catfishes due to the barbels.
Family Ariidae
Catfishes from this family lack scales, but bony plates are usually present on the head and near the dorsal fin. The head is large and rounded to depressed, and the mouth is surrounded by two or three pairs of barbels. The tail fin is forked. The males usually carry the eggs in its mouth until they hatch.
The above is an unidentified ariid catfish seen in local water.
Family Plotosidae
Catfishes from this family lack scales or bony plates. The head is broad and slightly depressed, and the mouth is surrounded by four pairs of barbels. They have an eel-like, unforked tail. The spines on the fins give painful, venomous sting, and hence they should not be handled. Most species are consumed by locals.
The
Striped Eeltail Catfish (Plotosus lineatus) has an eel-like tail, and two white stripes can be seen on the sides, though they may be faint in adults. It is usually found in coastal areas, foraging for small animals near the bottom. It has venomous spines which give painful stings, and hence should be be handled with bare hands. The adult grows to about 30cm long, and is usually solitary or in small shoals.
The juveniles gather in dense schools of up to several hundred individuals.
C) ORDER BATRACHOIDIFORMES
Members of this order have broad and flattened heads, often with barbels and/or fleshy flaps around the large mouth. The gill covers usually have venomous spines, and can inflict painful stings when handled.
Family Bactrachoididae
This is the only family in the order Batrachoidiformes. Members are usually called toadfishes as many species produce a croaking sound when they are threatened or caught. Most species are bottom-dwellers, and hide in the soft substrates or cracks and crevices among rocks and corals.
The
Three-spined Toadfish (Batrachomoeus trispinosus) can be recognised by its large and flattish head, the three spines on its front dorsal fin, and the dark brown bars on its tail and body. This fish can be found from the estuarine areas to coral reefs, feeding on small animals living on the seabed. It grows to about 30cm long.
D) ORDER LOPHIIFORMES
Members of this order are commonly referred to as anglerfishes, as their first dorsal-fin spine has been modified into a luring apparatus. Their pectoral fins mostly leg-like, allowing them to crawl slowly over the substrate.
Family Antennariidae
Members of this family are usually referred to as frogfishes due to their leg-like pectoral fins and that they are usually seen "squatting", much like frogs. The first dorsal-fin spine has a well-developed bait at the tip. The mouth is large, and they hunt by camouflaging well with the environment and ambushing small fishes passing by, sometimes luring them by wriggling the bait.
The
Spotted-tail Frogfish (Lophiocharon trisignatus) has very variable body colours, ranging from greenish to olive to brown and
sometimes even black. The ones with pale colours can usually be identified by the translucent spots on the tail fin, but these spots may not be obvious on darker specimens. It can be found in seagrass meadows, coral reefs, among coral rubble. This species grows to about 18cm long.
E) ORDER MUGILIFORMES
Members of this order, usually referred to as mullets, typically have pectoral fins that are located fairly high up towards their back compared to other fishes. They are usually toothless or have small teeth, feeding on algae and detritus.
Family Mugilidae
This is the sole family in this order, comprising fishes with broad heads, small mouth, and pectoral fins that are inserted high on the body towards the back. The pectoral fins are especially obvious when viewed from the top. They usually live in shoals. Most species are found in coastal waters, with many species being able to tolerate brackish. They are important food fishes in the region.
The
Squaretail Mullet (Ellochelon vaigiensis) can usually be recognised by its squarish tail fin. This species is commonly found in coastal areas, such as coral reefs, estuaries and tidal rivers, either solitary or in shoals. It is consumed in the regions, and grows to about 55cm long.
F) ORDER ATHERINIFORMES
Members of this order usually have two dorsal fins, and the one in front has flexible spine. The anal fin is usually preceded by a spine.
Family Atherinidae
Atherinid fishes are typically small, elongate, silvery fishes with two widely separated dorsal fins. They usually appear translucent, and most have an obvious horizontal band running along the middle of the sides. Most species live close to the shore and near the surface. Some species are consumed, many of them in the form of dried fishes, while others are used as baits or made into cat food.
The
Tropical Silverside (Atherinomorus duodecimalis) is a small torpedo-shaped fish that can be recognised by the silvery appearance, greyish back, and a horizontal stripe on the sides. It is usually found in open coastal waters, mostly in schools near the surface. This small fish gets to about 10cm long.
G) ORDER BELONIFORMES
Members of this order typically have a fixed or non-protrusible upper jaw. Many species have elongate bodies and long slender jaws.
Family Belonidae
Belonid fishes, also referred to as needlefishes, can be recognised by their elongate bodies, and jaws that are extended into long beaks with sharp teeth. They are carnivorous, feeding mostly on small fishes which they catch sideways in their beaks. Many species are consumed.
The
Spottail Needlefish (Strongylura strongylura) has a long, greenish body that is rounded in cross-section. There is a prominent black spot on its rounded tail fin. This predatory species hunts small fishes to feed on, and grows to about 46cm long.
Family Hemiramphidae
Members of this family are commonly called halfbeaks as their lower jaws are usually much longer than their upper jaws. Most species are omnivorous, feeding on both plant matter floating near the water surface and small animals. Many species are popular food fishes in the region.
The
Black-barred Halfbeak (Hemiramphus far) can be recognised by the short black bars on the sides of its body. This species is often seen in schools near the water surface in coastal areas. It can get to about 44cm long, and feeds on plant matter and phytoplankton.
The
Quoy's Halfbeak (Hyporhamphus quoyi) has a forked tail and a relatively shorter lower jaw with a reddish tip. It is usually seen in coastal areas near the surface. This species grows to about 35cm.
The
Striped-nose Halfbeak (Zenarchopterus buffonis) is commonly seen in shoals in tidal rivers, mangroves and other coastal areas. The tail is roundish to squarish. The longer lower jaw has a black stripe along the middle, and an obvious white spot at the tip. It grows to about 23cm long.
H) ORDER GASTEROSTEIFORMES
Members of this order usually have their bodies encased in bony plates (i.e. dermal plates). The mouth is usually small.
Family Pegasidae
Members of this family are usually referred to as seamoths for their fan-like pectoral fins, which flattens out when they are at rest, hence resembling the wings of moths (with some imagination). They are typically small fishes with depressed bodies that are completely covered with a layer of dermal plates. They can "walk" over the substrate with their tentacle-like pelvic fins.
The
Slender Seamoth (Pegasus volitans) can be recognised by its flattened head with a long snout, slender and tapering body, and fan-like pectoral fins. The body is usually marked with numerous small spots. The colour is rather variable, and the animal can be olive,
brownish or black. It can get to about 16cm long.
I) ORDER SYNGNATHIFORMES
Members of this order usually have elongate bodies that are encased in a series of bony plates. The mouth is usually very small and for most species, located at the end of a tube-like snout.
Family Syngnathidae
This family comprises the seahorses and true pipefishes. Their body is typically slender and elongate, and is encased in a series of bony rings. They may or may not have a prehensile tail. Their snouts are long and tube-like, and the toothless mouth is located at the tip. Most species feed on tiny benthic and planktonic organisms. Interestingly, the females deposit their eggs on the belly or base of the tails of the males, either in a pouch or a special surface full of blood vessels. The males will fertilise the eggs and carry them until they hatch. Many species are dried and sold in the curio trade, or used in traditional medicine in Asia.
The
Tigertail Seahorse (Hippocampus comes) is usually seen in the reef, often holding on to branching sponges or seaweed with its prehensile tail. It got its common name from the dark stripes on its tail, which resemble tiger stripes with some imagination. The body colour can vary from yellow with darker patches, or black with lighter patches. It can be recognised by its small and low coronet with five distinct knobs or spines. The snout is long and slender. This species can grow to about 18cm long. Like other seahorses, the females have a tube-like ovipositor which will be inserted into the males' brood pouches to deposit the eggs.
The
Spotted Seahorse (Hippocampus kuda) is usually seen in seagrass meadows, and is known to be able to tolerate brackish water. It can be
yellow, orange, brown or black in colour. The tail is prehensile. It can be differentiated from the previous species by the more obvious coronet which is usually overhanging at the back. The body is usually covered in tiny darker spots. It can grow to about 17cm long. Like other seahorses, the females have a tube-like ovipositor which will be inserted into the males' brood pouches to deposit the eggs. In some places, they are also called the
yellow seahorse as many of them are yellowish in colour.
The
Alligator Pipefish (Syngnathoides biaculeatus) is usually found in sheltered coastal areas among seagrasses, seaweed or floating weeds. It got its common name from its shape, which bears some resemblance to the alligator, with the long snout, tapering body and a long tail without a tail fin. The colour can be green, brown or grey, depending on the habitat. The males carry the eggs on its belly. It has a prehensile tail, which it uses to hold on to the surrounding seagrass or seaweed. This species can get to about 29cm long.
The
Short-bodied Pipefish (Choeroichthys brachysoma) is usually found in tide pool, seagrass meadows and coral reefs. It is brown in colour, with two series of small black spots along each side of body, and some may have several white speckles. The snout is long, the body tapering, and the tail terminates with a small fan-like fin. The male carries the eggs on the belly. This species gets to about 7cm long.
The
Hippichthys Pipefishes (Hippichthys spp.) are usually found among seagrass or seaweed. They have a long and slender body, and obvious bands can usually be seen. Some species may be spotted. The colour can be quite variable within the same species, ranging from bright colours to green and yellowish, to
dark colours like brown or black.
Family Centriscidae
Members of this family are commonly called razorfishes for their extremely compressed, razor-like bodies. They have a layer of thin bony plates covering their body, and a very long and sharp first dorsal spine. They usually swim vertically with the mouth facing downwards.
The
Longspine Razorfish (Aeoliscus strigatus), like other razorfishes, has a highly compressed body covered in thin bony plates. It has a long, tube-like snout, and a long, moveable spine in its dorsal fin. This spine points upwards while the fish swims vertically with the snout oriented downwards. This species is often seen in schools in coral reefs or seagrass meadows, feeding mainly on zooplankton. It can grow to lengths of about 15cm.
J) ORDER TETRAODONTIFORMES
Members of this order generally lack spines in their anal fins and possess much reduced pelvic fins. The mouth is relatively small, though they may have massive and powerful jaws with enlarged teeth.
Family Monacanthidae
The members of this family are usually called filefishes or leatherjackets, as most species have tiny spines on their scales, giving their skin a rough texture. They have a small mouth with pointed teeth. Members also have two dorsal fins, with the first one having a prominent spine that can be locked in an upright position by another much smaller spine. All species are able to change their colours to blend into the surrounding. Several species are consumed in the region.
The
Seagrass Filefish (Acreichthys tomentosus) is commonly seen among seagrass and seaweed. It can be recognised by the triangular back profile, a triangular skin flap on the belly, and a fan-shaped tail fin without any filament. The body is usually marked with olive or brownish mottles. This species grows to about 7cm long, feeding on invertebrates on the substrate.
The
Fan-bellied Filefish (Monacanthus chinensis) is found in seagrass meadows and coral reefs. This species is much larger than the previous one, growing to about 38cm long. Apart from the size, it can also be differentiated by the filaments it has at the tips of the fan-shaped tail fin. The sides of the body are usually marked with broad oblique brown bars.
The
Prickly Leatherjacket (Chaetodermis penicilligerus) is found in seagrass meadows and among seaweeds in coral reefs. It is easily recognised by its hairy appearance with the numerous hair-like structures on its body. This species grows to a maximum length of about 32 cm.
Family Triacanthidae
Members of this family are commonly known as tripodfishes, due to their slender and pointed pelvic fins, which resemble the legs of a tripod with some imagination. The body is slightly compressed and covered by moderately thick skin with numerous tiny scales. Most species are bottom dwellers, feeding on small invertebrates.
The
Longtail Tripodfish (Tripodichthys blochii) can be recognised by its slender and pointed pelvic fins, relatively long snout and spiny dorsal fin with pale membranes. It is usually seen in coastal areas and feeds on bottom-dwelling invertebrates. This species can get to about 15m long.
Family Tetraodontidae
Members of this family are commonly referred to as puffers or blowfish, due to their ability to
inflate themselves with water or air to deter predators. They generally have large heads, with the eyes located high up. The jaws are modified into a beak with four heavy and powerful teeth. They often have numerous tiny spines on their bodies, which become more visible when they are inflated. Most species are poisonous, and many are known to excrete poison from their skin to deter predators. Every year, many people die from eating puffers due to unprofessional methods of preparation, as these fishes need to be carefully prepared before they can be consumed.
The
Yelloweye Puffer (Arothron immaculatus) is found in sandy areas, seagrass meadows and coral reefs. It can be recognised by its greyish-brown to brown body, sometimes marked with darker blotches. The tail fin is yellow with a black border. This species grows to a maximum length of about 30cm.
The
Oblong Blowfish (Takifugu oblongus) is usually found in shallow coastal areas, including areas with brackish water. It can be recognised by the olive to brownish body that is marked with numerous pale spots on the back, and pale vertical bars by the sides. Sometimes, two or more dark bands can be seen on the back. This species can grow to about 40cm long.
Family Diodontidae
Members of this family are commonly called porcupinefishes due to the numerous big spines covering their bodies. Like the puffers, they are able to inflate their body with air or water as well. They have a large and broad head with a relatively large mouth, with the teeth fused to form a powerful beak for crushing their prey, which are usually hard-shelled, bottom-dwelling invertebrates. Some species are poisonous, though several are eaten by locals in the region without special methods of preparation.
The
Masked Porcupinefish (Diodon liturosus) is usually found in coral reefs and coral rubble areas. It can be recognised by the dark blotches with pale borders on the yellowish brown body, covered in numerous spines. This species feeds on crustaceans and molluscs. The above photo was taken in Malaysia.
K) ORDER PLEURONECTIFORMES
Members of this order are commonly called flatfishes due to their highly compressed bodies. The juveniles are bilaterally symmetrical, but one eye will slowly migrate to the other side of the body as they mature. Hence, the adults are not bilaterally symmetrical, with both eyes on the same side of the body. They usually lie on the substrate, sometimes concealed under the sand except for the pair of protruding eyes which allow them to look out for prey and predators.
Family Soleidae
Members of this family, commonly called soles, are highly compressed flatfishes with both eyes on the right side of their bodies. They are usually oval-shaped, and lack spines in their fins.
The
Peacock Sole (Pardachirus pavoninus) is found in coastal sandy areas. It can be recognised by its oval-shaped body, the eyes on the right side of the body, and the numerous pale spots with dark margins. This species grows to about 25cm long.
Family Paralichthyidae
Members of this family, commonly called sand flounders, have ovate bodies, large head, and both eyes on the left side of the bodies for adult fishes. The eyes are separately by a bony ridge, and they have two nostrils on each side of head. There is an obvious line (i.e. the lateral line) by the side of the body, with a distinct curve just above the pectoral fins.
Several species of
Pseudorhombus Flounders (Pseudorhombus spp.) can be found in Singapore, usually in shallow waters on sandy or muddy substrates. They can be identified by the patterns on their body, but it is often hard to determine in the field.
Family Cynoglossidae
Members of this family are flatfishes with both eyes on the left side of the body of adult fishes. The highly compressed body tapers to a point at the tail end, giving the fish a tongue-like shape, and hence they are often referred to as tongue-soles.
The above is an unidentified tongue-sole found in shallow waters in a seagrass meadow.
L) ORDER SCORPAENIFORMES
Members of this order are distinguished by a ridge on the cheek, formed from the extension of one of the bones on the skeleton. They are hence sometimes called mail-cheeked fishes. Many have spines or bony plates on their heads and bodies, and a number are venomous.
Family Platycephalidae
Members of this family are commonly called flatheads for their depressed heads. The eyes are on top, allowing them to have a good view of their surrounding since they are bottom dwellers. Their bodies are often elongate, and their mouths are large. The lower jaw is slightly longer than the upper jaw.
The
Fringe-eyed Flathead (Cymbacephalus nematophthalmus) can be recognised by the 6 to 9 skin tentacles just above each eye which give it its common name. There are several bony ridges on its head with spines on them, and there are usually a few darker bars on its back and sides. This solitary species is usually found on the bottom of coastal sandy areas and coral reefs, feeding on smaller animals. It can reach lengths of about 58cm.
Family Synanceiidae
Members of this family are usually called stonefish for their rock-like appearances. They have a hypodermic-needle-like spine in their dorsal fins which is connect to venom glands near the base. Most people who were stung stepped onto them by accident, since they are generally very well-camouflaged. The pressure releases a highly poisonous neurotoxin into the wound, which can be fatal to humans.
The
Hollow-cheeked Stonefish (Synanceja horrida) is usually found in coral reefs or nearby rubble and muddy areas (where they can be partially to almost completely buried). It has a pair of small eyes on top of its head, with a deep depression below each eye. The skin is leathery and warty, usually of a dull colour which allows the fish to
blend into the surrounding. As with other stonefishes, the venomous spine is located on its back in the dorsal fin. This species ambushes small fishes that unknowingly swim near to its upward-facing mouth. It can grow to about 47cm long.
Family Scorpaenidae
Members of this family are commonly called scorpionfishes, due to the venomous spines in their fins and on their heads, giving painful stings to those who handled them. Most species are bottom dwellers, or live near the bottom. Many of the larger species are consumed in the region.
The
Painted Scorpionfish (Parascorpaena picta) can be identified by the robust body, and the second spine above the upper jaw in front of the eyes is directed forward. It is usually found in the reef, and can grow to about 17cm long. It has venomous spines.
The
Longspine Scorpionfish (Paracentropogon longispinis) has a laterally compressed body with the dorsal fin beginning right above the eyes, giving it a crested appearance. This bottom dweller with venomous spines can be seen in coral reefs and seagrass meadows. It gets to about 10cm long.
M) ORDER PERCIFORMES
This huge order comprises mostly members possessing dorsal fins with hard and spiny in the front portion, and soft-branching rays towards the rear. In some species, these two portions are split into two separate fins: the spiny dorsal fin and the soft dorsal fin.
As there are many families and species of this order recorded from Singapore, I will provide more details in a separate blog entry:
Perciformes Fishes (Phylum Chordata: Order Perciformes) of Singapore.
References
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- Weber, M. & L.F. De Beaufort,.1922. The fishes of the Indo-Australian Archipelago. IV. Heteromi, Solenichthyes, Synentognathi, Percesoces, Labyrinthici, Microcyprini. E. J. Brill, Leiden. 410 pp.
