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 spines, much like those paper folding fan 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.
Here are some examples of freshwater ray-finned fishes that can be seen in Singapore.
A) ORDER CYPRINIFORMES
Cypriniform fishes can be recognised by their lack of teeth on their jaws. Instead, they have a pair of gills that are modified into a bone with a series of pharyngeal teeth. Most species only have one dorsal fin.
Family Cyprinidae
Most species from this family have only one soft dorsal fin, and a number of species have short barbels around their mouths.
The Harlequin Rasbora (Trignostigma heteromorpha) is a native freshwater fish that lives in clear, acidic shaded forest streams. This species is gregarious, and can be identified by a black triangular blotch marking the posterior half of the sides of its body. It feeds mainly on small insects and other invertebrates. Being an attractive fish, it is very popular in the aquarium trade. This small fish gets to about 5cm long.
The Einthoven's Rasbora (Rasbora einthovenii) is a native fish that lives mainly in shallow forest streams, though it can sometimes be found in streams in open habitats as well. It is gregarious, and can be identified by a thin, dark lateral line on the sides of its body in the middle, from the tip of its mouth to its tail. It feeds mainly on small invertebrates, growing to about 8cm long.
The Two-spot Rasbora (Rasbora elegans) is a native fish that inhibits forest streams, often in shoals and sometimes with other species. It is usually fast-moving, feeding mostly on small invertebrates. This species can be identified by a dark blotch in the middle of the body, and another smaller one nearer to the tail, though the blotches may be quite faint in some specimens. It grows to about 13cm long.
The Saddle Barb (Systomus banksi) is a native species that is usually found in forest streams, and sometimes in streams in less shady areas. It is gregarious, and can be recognised by a large dark blotch just below the dorsal fin. Sometimes, smaller dark patches can be seen towards the tail. This is an omnivorous species, feeding on water plants as well as small invertebrates. In the earlier days, this fish was sometimes reared in village wells, acting as an indicator that the water was safe for drinking without contamination. It gets to about 10cm long.
The Spanner Barb (Systomus lateristriga) or T-barb is a native species that is usually found in forest streams. It can be identified by having two vertical bands on the anterior half of its body, and a horizontal band on the posterior half. It is omnivorous, feeding on both small invertebrates and plant matter. This is a relatively large barb, growing to about 18cm long.
Family Cobitidae
Members of this family are usually small, elongated, bottom-dwelling fishes with short barbels around the mouth. Their bodies are covered tiny scales. They can be differentiated from similar-looking fishes of the same order by having a spine below the eye.
The Spotted Eel-loach (Pangio muraeniformis), also known as the Spotted Coolie Loach, is a native fish that lives in slow-flowing, shaded forest streams and pools. This eel-like fish is seldom seen, as it usually hides among the leaf litter at the bottom. It can be identified by the long and slender body with irregular dark blotches, the three bands on its head, and three pairs of short barbels around the mouth. This small fish grows to about 8cm long, and feeds on bottom-dwelling invertebrates.
B) ORDER SYNBRANCHIFORMES
Members of this order are usually eel-like with elongated and slender bodies. However, unlike the true eels, they have poorly developed gills, and many are air-breathing.
Family Mastacembelidae
Members of this family are usually called spiny eels for the series of short spines along their backs. They have rayed fins and a long, proboscis-like snout used for probing in the substrate for small bottom-dwelling invertebrates. They have very tiny scales.
The Buff-backed Spiny Eel (Macrognathus maculatus) is a native species which usually lives in forest streams. It is nocturnal, and hides among the vegetation or under the leaf litter in the day. This is the only spiny eel species known to exist for certain in Singapore, and can be recognised by its dark brown body, light brown back, and proboscis-like snout. It can grow to almost 20cm long, and feeds on small, bottom-dwelling invertebrates.
Family Synbranchidae
Members of this family are commonly called swamp eels. They have long, cylindrical bodies lacking pectoral fins, while the caudal and dorsal fins are very reduced. They are air-breathers, and hence will drown if they cannot get to the water surface. Most species hide in burrows in the day, and only emerge at night to hunt for small animals.
The Oriental Swamp Eel (Monopterus albus) is commonly found in streams, ponds, swamps and even some canals. It has a snake-like appearance, with its dorsal and tail fins being very reduced, and the tail tapers to a point.
The body is brown, often with dark speckles. Oriental Swamp Eels can grow to about 1m long, and are often collected for consumption in the region.
C) ORDER CYPRINODONTIFORMES
Members of this order are general small and slender fishes. They have teeth in their mouths, and possess prominent scales and a small dorsal fin.
Family Aplocheilidae
Members of this family are usually surface-dwellers and lays eggs. Some species are very colourful.
The Whitespot (Aplocheilus panchax) is a native species which can be found in a variety of habitats, such as forest streams and pools, drains, reservoirs and brackish environments. It can be recognised by a white spot on top of its head, and the lack of bands on its posterior end. This fish feeds primarily on aquatic insects and larvae, and is hence useful in controlling the population of mosquito larvae - it was sometimes introduced into mosquito-prone areas. This gregarious species can grow to about 9cm.
The Striped Panchax (Aplocheilus lineatus) is an introduced species that is occasionally seen in streams and ponds. It can be recognised by the white spot on the top of its head, a generally reddish body, and its posterior end is usually marked with several bands, either complete or disjointed. It can grow to almost 10cm long, though most are shorter. It feeds on aquatic insects and larvae, and sometimes, terrestrial insects that fall into the water and small juvenile fish.
D) ORDER BELONIFORMES
Members of this order generally have elongated bodies and long slender jaws.
Family Hemiramphidae
Members of this family are usually called halfbeaks, as their lower jaws are much longer than their upper jaws. They are usually found just under the surface of the water, and feed on fallen insects.
The Malayan Pygmy Halfbeak (Dermogenys collettei) is a native species that can be found in a variety of habitats, such as acidic forests streams, reservoirs and brackish environments. This surface-dweller can be recognised by its greyish body, shorter upper jaw compare to the much longer lower jaw, and its dorsal fin which begins behind the anal fin. It feeds on fallen insects, and grows to about 6cm long.
The Malayan Forest Halfbeak (Hemirhamphodon pogonognathus) is a native halfbeak that lives in forest streams. It can be differentiated from the previous species by its relatively longer and thinner jaws, the dorsal fin which begins before the anal fin, and the presence of a pair of pale dorsal stripes on the back of many adults. Like other halfbeaks, it lives near the water surface and feeds on fallen insects. It grows to about 10cm long.
E) 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 Clariidae
Clariid catfishes have long scaleless bodies with long-based dorsal and anal fins. The heads appear flattish, while the tail fins range from roundish to squarish. They are air-breathers, and hence are able to survive in waters low in oxygen levels. Some are even able to leave the water to move across land to other water bodies, thus earning them the common name of walking catfishes.
The Common Walking Catfish (Clarias batrachus) is a very adaptable native species that is able to live in a variety of habitats, such as ponds, canals, rural streams, reservoirs and streams in open country. During the rainy season, it can move overland from one water body to another. This species can be recognised by the greyish or brownish body, marked with narrow bands of pale spots. It has a narrow gap between the leading edge of its long dorsal fin and the edge of the bony plates on top of its roundish head, unlike most other similar species which have wider gaps. The adult can grow to about 50cm long. This nocturnal animal uses its four pairs of barbels as sensory organs to find smaller fishes and invertebrates to feed on. In the day, it hides in the soft bottom or among the leaf litter.
The African Sharptooth Catfish (Clarias gariepinus) is an introduced species that is sometimes seen in canals and rivers. It has a large, depressed head with small eyes. The body is greyish or brownish with darker mottles, and lacks the pale spots seen in the previous species. It has four pairs of barbels, and there is a wide gap between the leading edge of its long dorsal fin and the edge of the bony plates on top of its head. This huge fish can grow to about 150cm long. It feeds on small aquatic animals.
F) ORDER PERCIFORMES
This huge order of fishes 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.
Family Eleotridae
Members of this family, commonly called gudgeons, typically have cylindrical bodies with two separate dorsal fins. The pelvic fins are always separated, and most species are bottom dwellers.
The Marbled Gudgeon (Oxyeleotris marmorata), commonly referred to as Soon Hock in the region, can be found in freshwater swamps, reservoirs and mangroves in Singapore. This nocturnal fish can grow to about 60cm long, and is a popular food fish in Southeast Asia. It is brown with black blotches or bars, allowing it to blend into the surrounding leaf litter and hunt small fishes by ambush.
Family Nandidae
Members of this family are small and laterally compressed. They have large eyes, and usually have colours similar to the leaf litter. Even their body movements mimic dead leaves. These allow them to blend in nicely to the surrounding, allowing them to avoid predation and hunt small aquatic animals by ambush.
The Sunda Leaf Fish (Nandus nebulosus) is a native fish found in slow flowing forest streams. It is brown with dark blotches, appearing just like a dead leaf. This species grows to about 13cm long, and hunt small fish and crustaceans by ambush.
Family Osphronemidae
Members of this family are air-breathing and possess thread-like pelvic fins which can be used for sensory purposes. Many species practice parental care for their young.
The Forest Betta (Betta pugnax) is a native fighting fish that lives in clear, shallow forest streams. It can be recognised by its broad-based anal fin which has a pointed tip. The eyes usually have a yellowish ring.
The colour of the Forest Betta may vary, depending on its mood, ranging from light brown with greenish-blue spots to brown with dark stripes. The male is quite territorial, but not as aggressive as the Siamese Fighting Fish. This species is gregarious and often found in small shoals among the leaf litter or under the vegetation. It feeds primary on small invertebrates. The male brood the eggs in its mouth. This species grows to about 10cm long.
The Croaking Gourami (Trichopsis vittata) is sometimes mistaken with the previous species, but can be distinguished by its eyes which have a distinctive blue ring. The snout is generally more pointed, and a few dark horizontal stripes mark the sides of its body. It got its common name from its habit of producing a soft croaking sound during breeding activities. The maximum length of this species is about 6cm, and it is usually found in ponds and streams in rural areas or scrublands.
The Three-spot Gouramy (Trichogaster trichopterus), also spelled "gourami", is a native fish that lives in a variety of habitats, such as slow forest streams, open rural streams, swamps, and ponds with dense vegetation. It can be recognised by the three spots on its body - one being the eye, another near the middle of the body, and the third near the tail. It has a pair of long and thread-like pelvic fins used as tactile organs. This air-breather is omnivorous, feeding on plankton and small invertebrates. It is very popular in the aquarium trade, with many varieties being reared. The adult reaches lengths of about 15cm.
The Snakeskin Gourami (Trichopodus pectoralis) is an introduced species that is native to Thailand has established itself in some rural streams and ponds. It can be recognised by the dark horizontal band running across the middle of its body. This relatively large gourami can grow to about 26cm long, and is sometimes made into dried salted fish for consumption.
Family Anabantidae
Members of this family have a robust body and long-based dorsal and anal fins. They also have obvious spines on their gill covers. They are air breathing, and are well-known for their ability to wriggle over land from one water body to another.
The Asian Climbing Perch (Anabas testudineus) is a native fish that is found in streams and ponds in forests and rural areas, often seen resting on the bottom. It can be recognised by the thickset body, a black spot on its gill cover, and another at the base of the tail. It is able to survive for some time out of water by taking in air and retaining them in a labyrinth organ - a specialised structure in the head for absorbing atmospheric oxygen. When the habitat is damp, e.g. in swampy areas, or after heavy rains, it can "walk" across land by opening the gill plates for support, and pushing itself forward with its strong pectoral, pelvic and tail fins. This species feeds on both plant matter and small aquatic animals. It can grow to about 23cm long.
Family Channidae
Members of this family are commonly called snakeheads, due to their cylindrical body and snake-like heads. They are air-breathing and predatory, but interestingly provide parental care of their young.
The Forest Snakehead (Channa lucius) is a native snakehead which is usually found in shaded forest streams and swamps. It can be recognised by a series of dark blotches along the sides of its body, and an oblique black strip behind the eye. This predatory species feeds on smaller fish, amphibians and aquatic invertebrates. It reaches lengths of about 40cm.
The Common Snakehead (Channa striata), or Aruan, is the commonest native snakehead in Singapore, and occurs in a variety of habitats including slow-moving forest and rural streams, canals, reservoirs, and rural ponds. The body of this fish is brownish above with irregular dark bars, while the underside is white. It is a predatory species, feeding on small fishes, amphibians and invertebrates. It can grow to about 90cm long, and is reared in the region as a food fish. Eating it is believed to aid in the healing of wounds. The adults raise the juvenile fish in a well-protected, underwater nest constructed of vegetation.
Family Cichlidae
Fishes from this family are native to India, the Middle East, Africa and Latin America, and hence all the ones seen in Singapore are introduced. They are characterised by a laterally compressed body with a continuous dorsal fin. The males are territorial and aggressive towards each other, even though they are generally gregarious in nature. Cichlids are omnivorous, feeding on plant matter and small aquatic animals.
The Mozambique Tilapia (Oreochromis mossambicus) is introduced from Africa to Singapore as a food fish, and has established well in various ponds, canals, reservoirs and tidal rivers. It can be recognised by its thick lips, grey to olive body with a few darker bands/blotches on the sides. Sexually active males are black, and will dig and defend a round burrow to entice the females to breed with it. The female carry the eggs and protects the young in its mouth. This species is omnivorous, feeding on algae, water plants and small aquatic animals. It reaches a maximum length of 40cm.
The Green Chromide (Etroplus suratensis) is an introduced species that is native to India and Sri Lanka. It is a popular aquarium fish, though in the region it is also consumed. It can be recognised by the broad vertical bars on the sides of its body, which are darker below and fade off towards the top. It also has a dark spot at the base of the pectoral fin, and many of the scales have a pearly spot. This fish grows to about 30cm long.
The Mayan Cichlid (Cichlasoma urophthalmus) is an introduced aquarium fish native to Central America. It can be seen in some canals and ponds. This species can be recognised by the black bands on the sides of its body, and a black blotch at the base of the tail. It can grow to about 30cm long.
The Midas Cichlid (Amphilophus citrinellus) is another introduced aquarium fish that is native to South America. It can be recognised by its brownish, orange or reddish coloration and a bump on its fore head. This species grows to about 30cm long.
The Threadfin Acara (Acarichthys heckelii) is another introduced aquarium fish that is native to South Amerrica. It can grow to about 20cm long. It usually has a few long filaments extending from the dorsal fins, and the body is marked with light and dark blotches or bands.
G) ORDER LEPISOSTEIFORMES
Members of this order, commonly called gars, are native to North and South America, but occasionally individuals released by irresponsible pet owners are found in our waterways.
Family Lepisosteidae
There is only one family in this order, and the members have elongated bodies with thick scales. The jaws are elongated with long and sharp teeth.
The Spotted Gar (Lepisosteus oculatus) is sometimes seen in canals and ponds, released by irresponsible pet owners. They can be recognised by the dark spots densely covering the body, head and fins. This huge fish can attain lengths of about 150cm. It is predatory, feeding on various kinds of small animals.
The Alligator Gar (Atractosteus spatula) is occasionally seen in canals and ponds, released by irresponsible pet owners. This fish can be recognised by its olive brown body that is marked with numerous small dark blotches. This very huge fish can grow to more than 300m long, and feeds on waterfowl, reptiles, amphibians, fishes and crustaceans.
References
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.
Here are some examples of freshwater ray-finned fishes that can be seen in Singapore.
A) ORDER CYPRINIFORMES
Cypriniform fishes can be recognised by their lack of teeth on their jaws. Instead, they have a pair of gills that are modified into a bone with a series of pharyngeal teeth. Most species only have one dorsal fin.
Family Cyprinidae
Most species from this family have only one soft dorsal fin, and a number of species have short barbels around their mouths.
The Harlequin Rasbora (Trignostigma heteromorpha) is a native freshwater fish that lives in clear, acidic shaded forest streams. This species is gregarious, and can be identified by a black triangular blotch marking the posterior half of the sides of its body. It feeds mainly on small insects and other invertebrates. Being an attractive fish, it is very popular in the aquarium trade. This small fish gets to about 5cm long.
The Einthoven's Rasbora (Rasbora einthovenii) is a native fish that lives mainly in shallow forest streams, though it can sometimes be found in streams in open habitats as well. It is gregarious, and can be identified by a thin, dark lateral line on the sides of its body in the middle, from the tip of its mouth to its tail. It feeds mainly on small invertebrates, growing to about 8cm long.
The Two-spot Rasbora (Rasbora elegans) is a native fish that inhibits forest streams, often in shoals and sometimes with other species. It is usually fast-moving, feeding mostly on small invertebrates. This species can be identified by a dark blotch in the middle of the body, and another smaller one nearer to the tail, though the blotches may be quite faint in some specimens. It grows to about 13cm long.
The Saddle Barb (Systomus banksi) is a native species that is usually found in forest streams, and sometimes in streams in less shady areas. It is gregarious, and can be recognised by a large dark blotch just below the dorsal fin. Sometimes, smaller dark patches can be seen towards the tail. This is an omnivorous species, feeding on water plants as well as small invertebrates. In the earlier days, this fish was sometimes reared in village wells, acting as an indicator that the water was safe for drinking without contamination. It gets to about 10cm long.
The Spanner Barb (Systomus lateristriga) or T-barb is a native species that is usually found in forest streams. It can be identified by having two vertical bands on the anterior half of its body, and a horizontal band on the posterior half. It is omnivorous, feeding on both small invertebrates and plant matter. This is a relatively large barb, growing to about 18cm long.
Family Cobitidae
Members of this family are usually small, elongated, bottom-dwelling fishes with short barbels around the mouth. Their bodies are covered tiny scales. They can be differentiated from similar-looking fishes of the same order by having a spine below the eye.
The Spotted Eel-loach (Pangio muraeniformis), also known as the Spotted Coolie Loach, is a native fish that lives in slow-flowing, shaded forest streams and pools. This eel-like fish is seldom seen, as it usually hides among the leaf litter at the bottom. It can be identified by the long and slender body with irregular dark blotches, the three bands on its head, and three pairs of short barbels around the mouth. This small fish grows to about 8cm long, and feeds on bottom-dwelling invertebrates.
B) ORDER SYNBRANCHIFORMES
Members of this order are usually eel-like with elongated and slender bodies. However, unlike the true eels, they have poorly developed gills, and many are air-breathing.
Family Mastacembelidae
Members of this family are usually called spiny eels for the series of short spines along their backs. They have rayed fins and a long, proboscis-like snout used for probing in the substrate for small bottom-dwelling invertebrates. They have very tiny scales.
The Buff-backed Spiny Eel (Macrognathus maculatus) is a native species which usually lives in forest streams. It is nocturnal, and hides among the vegetation or under the leaf litter in the day. This is the only spiny eel species known to exist for certain in Singapore, and can be recognised by its dark brown body, light brown back, and proboscis-like snout. It can grow to almost 20cm long, and feeds on small, bottom-dwelling invertebrates.
Family Synbranchidae
Members of this family are commonly called swamp eels. They have long, cylindrical bodies lacking pectoral fins, while the caudal and dorsal fins are very reduced. They are air-breathers, and hence will drown if they cannot get to the water surface. Most species hide in burrows in the day, and only emerge at night to hunt for small animals.
The Oriental Swamp Eel (Monopterus albus) is commonly found in streams, ponds, swamps and even some canals. It has a snake-like appearance, with its dorsal and tail fins being very reduced, and the tail tapers to a point.
The body is brown, often with dark speckles. Oriental Swamp Eels can grow to about 1m long, and are often collected for consumption in the region.
C) ORDER CYPRINODONTIFORMES
Members of this order are general small and slender fishes. They have teeth in their mouths, and possess prominent scales and a small dorsal fin.
Family Aplocheilidae
Members of this family are usually surface-dwellers and lays eggs. Some species are very colourful.
The Whitespot (Aplocheilus panchax) is a native species which can be found in a variety of habitats, such as forest streams and pools, drains, reservoirs and brackish environments. It can be recognised by a white spot on top of its head, and the lack of bands on its posterior end. This fish feeds primarily on aquatic insects and larvae, and is hence useful in controlling the population of mosquito larvae - it was sometimes introduced into mosquito-prone areas. This gregarious species can grow to about 9cm.
The Striped Panchax (Aplocheilus lineatus) is an introduced species that is occasionally seen in streams and ponds. It can be recognised by the white spot on the top of its head, a generally reddish body, and its posterior end is usually marked with several bands, either complete or disjointed. It can grow to almost 10cm long, though most are shorter. It feeds on aquatic insects and larvae, and sometimes, terrestrial insects that fall into the water and small juvenile fish.
D) ORDER BELONIFORMES
Members of this order generally have elongated bodies and long slender jaws.
Family Hemiramphidae
Members of this family are usually called halfbeaks, as their lower jaws are much longer than their upper jaws. They are usually found just under the surface of the water, and feed on fallen insects.
The Malayan Pygmy Halfbeak (Dermogenys collettei) is a native species that can be found in a variety of habitats, such as acidic forests streams, reservoirs and brackish environments. This surface-dweller can be recognised by its greyish body, shorter upper jaw compare to the much longer lower jaw, and its dorsal fin which begins behind the anal fin. It feeds on fallen insects, and grows to about 6cm long.
The Malayan Forest Halfbeak (Hemirhamphodon pogonognathus) is a native halfbeak that lives in forest streams. It can be differentiated from the previous species by its relatively longer and thinner jaws, the dorsal fin which begins before the anal fin, and the presence of a pair of pale dorsal stripes on the back of many adults. Like other halfbeaks, it lives near the water surface and feeds on fallen insects. It grows to about 10cm long.
E) 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 Clariidae
Clariid catfishes have long scaleless bodies with long-based dorsal and anal fins. The heads appear flattish, while the tail fins range from roundish to squarish. They are air-breathers, and hence are able to survive in waters low in oxygen levels. Some are even able to leave the water to move across land to other water bodies, thus earning them the common name of walking catfishes.
The Common Walking Catfish (Clarias batrachus) is a very adaptable native species that is able to live in a variety of habitats, such as ponds, canals, rural streams, reservoirs and streams in open country. During the rainy season, it can move overland from one water body to another. This species can be recognised by the greyish or brownish body, marked with narrow bands of pale spots. It has a narrow gap between the leading edge of its long dorsal fin and the edge of the bony plates on top of its roundish head, unlike most other similar species which have wider gaps. The adult can grow to about 50cm long. This nocturnal animal uses its four pairs of barbels as sensory organs to find smaller fishes and invertebrates to feed on. In the day, it hides in the soft bottom or among the leaf litter.
The African Sharptooth Catfish (Clarias gariepinus) is an introduced species that is sometimes seen in canals and rivers. It has a large, depressed head with small eyes. The body is greyish or brownish with darker mottles, and lacks the pale spots seen in the previous species. It has four pairs of barbels, and there is a wide gap between the leading edge of its long dorsal fin and the edge of the bony plates on top of its head. This huge fish can grow to about 150cm long. It feeds on small aquatic animals.
F) ORDER PERCIFORMES
This huge order of fishes 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.
Family Eleotridae
Members of this family, commonly called gudgeons, typically have cylindrical bodies with two separate dorsal fins. The pelvic fins are always separated, and most species are bottom dwellers.
The Marbled Gudgeon (Oxyeleotris marmorata), commonly referred to as Soon Hock in the region, can be found in freshwater swamps, reservoirs and mangroves in Singapore. This nocturnal fish can grow to about 60cm long, and is a popular food fish in Southeast Asia. It is brown with black blotches or bars, allowing it to blend into the surrounding leaf litter and hunt small fishes by ambush.
Family Nandidae
Members of this family are small and laterally compressed. They have large eyes, and usually have colours similar to the leaf litter. Even their body movements mimic dead leaves. These allow them to blend in nicely to the surrounding, allowing them to avoid predation and hunt small aquatic animals by ambush.
The Sunda Leaf Fish (Nandus nebulosus) is a native fish found in slow flowing forest streams. It is brown with dark blotches, appearing just like a dead leaf. This species grows to about 13cm long, and hunt small fish and crustaceans by ambush.
Family Osphronemidae
Members of this family are air-breathing and possess thread-like pelvic fins which can be used for sensory purposes. Many species practice parental care for their young.
The Forest Betta (Betta pugnax) is a native fighting fish that lives in clear, shallow forest streams. It can be recognised by its broad-based anal fin which has a pointed tip. The eyes usually have a yellowish ring.
The colour of the Forest Betta may vary, depending on its mood, ranging from light brown with greenish-blue spots to brown with dark stripes. The male is quite territorial, but not as aggressive as the Siamese Fighting Fish. This species is gregarious and often found in small shoals among the leaf litter or under the vegetation. It feeds primary on small invertebrates. The male brood the eggs in its mouth. This species grows to about 10cm long.
The Croaking Gourami (Trichopsis vittata) is sometimes mistaken with the previous species, but can be distinguished by its eyes which have a distinctive blue ring. The snout is generally more pointed, and a few dark horizontal stripes mark the sides of its body. It got its common name from its habit of producing a soft croaking sound during breeding activities. The maximum length of this species is about 6cm, and it is usually found in ponds and streams in rural areas or scrublands.
The Three-spot Gouramy (Trichogaster trichopterus), also spelled "gourami", is a native fish that lives in a variety of habitats, such as slow forest streams, open rural streams, swamps, and ponds with dense vegetation. It can be recognised by the three spots on its body - one being the eye, another near the middle of the body, and the third near the tail. It has a pair of long and thread-like pelvic fins used as tactile organs. This air-breather is omnivorous, feeding on plankton and small invertebrates. It is very popular in the aquarium trade, with many varieties being reared. The adult reaches lengths of about 15cm.
The Snakeskin Gourami (Trichopodus pectoralis) is an introduced species that is native to Thailand has established itself in some rural streams and ponds. It can be recognised by the dark horizontal band running across the middle of its body. This relatively large gourami can grow to about 26cm long, and is sometimes made into dried salted fish for consumption.
Family Anabantidae
Members of this family have a robust body and long-based dorsal and anal fins. They also have obvious spines on their gill covers. They are air breathing, and are well-known for their ability to wriggle over land from one water body to another.
The Asian Climbing Perch (Anabas testudineus) is a native fish that is found in streams and ponds in forests and rural areas, often seen resting on the bottom. It can be recognised by the thickset body, a black spot on its gill cover, and another at the base of the tail. It is able to survive for some time out of water by taking in air and retaining them in a labyrinth organ - a specialised structure in the head for absorbing atmospheric oxygen. When the habitat is damp, e.g. in swampy areas, or after heavy rains, it can "walk" across land by opening the gill plates for support, and pushing itself forward with its strong pectoral, pelvic and tail fins. This species feeds on both plant matter and small aquatic animals. It can grow to about 23cm long.
Family Channidae
Members of this family are commonly called snakeheads, due to their cylindrical body and snake-like heads. They are air-breathing and predatory, but interestingly provide parental care of their young.
The Forest Snakehead (Channa lucius) is a native snakehead which is usually found in shaded forest streams and swamps. It can be recognised by a series of dark blotches along the sides of its body, and an oblique black strip behind the eye. This predatory species feeds on smaller fish, amphibians and aquatic invertebrates. It reaches lengths of about 40cm.
The Common Snakehead (Channa striata), or Aruan, is the commonest native snakehead in Singapore, and occurs in a variety of habitats including slow-moving forest and rural streams, canals, reservoirs, and rural ponds. The body of this fish is brownish above with irregular dark bars, while the underside is white. It is a predatory species, feeding on small fishes, amphibians and invertebrates. It can grow to about 90cm long, and is reared in the region as a food fish. Eating it is believed to aid in the healing of wounds. The adults raise the juvenile fish in a well-protected, underwater nest constructed of vegetation.
Family Cichlidae
Fishes from this family are native to India, the Middle East, Africa and Latin America, and hence all the ones seen in Singapore are introduced. They are characterised by a laterally compressed body with a continuous dorsal fin. The males are territorial and aggressive towards each other, even though they are generally gregarious in nature. Cichlids are omnivorous, feeding on plant matter and small aquatic animals.
The Mozambique Tilapia (Oreochromis mossambicus) is introduced from Africa to Singapore as a food fish, and has established well in various ponds, canals, reservoirs and tidal rivers. It can be recognised by its thick lips, grey to olive body with a few darker bands/blotches on the sides. Sexually active males are black, and will dig and defend a round burrow to entice the females to breed with it. The female carry the eggs and protects the young in its mouth. This species is omnivorous, feeding on algae, water plants and small aquatic animals. It reaches a maximum length of 40cm.
The Green Chromide (Etroplus suratensis) is an introduced species that is native to India and Sri Lanka. It is a popular aquarium fish, though in the region it is also consumed. It can be recognised by the broad vertical bars on the sides of its body, which are darker below and fade off towards the top. It also has a dark spot at the base of the pectoral fin, and many of the scales have a pearly spot. This fish grows to about 30cm long.
The Mayan Cichlid (Cichlasoma urophthalmus) is an introduced aquarium fish native to Central America. It can be seen in some canals and ponds. This species can be recognised by the black bands on the sides of its body, and a black blotch at the base of the tail. It can grow to about 30cm long.
The Midas Cichlid (Amphilophus citrinellus) is another introduced aquarium fish that is native to South America. It can be recognised by its brownish, orange or reddish coloration and a bump on its fore head. This species grows to about 30cm long.
The Threadfin Acara (Acarichthys heckelii) is another introduced aquarium fish that is native to South Amerrica. It can grow to about 20cm long. It usually has a few long filaments extending from the dorsal fins, and the body is marked with light and dark blotches or bands.
G) ORDER LEPISOSTEIFORMES
Members of this order, commonly called gars, are native to North and South America, but occasionally individuals released by irresponsible pet owners are found in our waterways.
Family Lepisosteidae
There is only one family in this order, and the members have elongated bodies with thick scales. The jaws are elongated with long and sharp teeth.
The Spotted Gar (Lepisosteus oculatus) is sometimes seen in canals and ponds, released by irresponsible pet owners. They can be recognised by the dark spots densely covering the body, head and fins. This huge fish can attain lengths of about 150cm. It is predatory, feeding on various kinds of small animals.
The Alligator Gar (Atractosteus spatula) is occasionally seen in canals and ponds, released by irresponsible pet owners. This fish can be recognised by its olive brown body that is marked with numerous small dark blotches. This very huge fish can grow to more than 300m long, and feeds on waterfowl, reptiles, amphibians, fishes and crustaceans.
References
- Alfred, E. R. 1966. The fresh-water fishes of Singapore. Zoologische Verhandeligen 78 : 1–68, 8 pls.
- Baker, N. 2013. Ecology Asia. Retrieved Apr 16, 2013, from http://www.ecologyasia.com.
- Baker, N. & K. Lim, (Vertebrate Study Group, Nature Society Singapore). 2008. Wild Animals Of Singapore. Draco Publishing and Distribution Pte. Ltd. 180 pp.
- Fisheries and Aquaculture Department, Food and Agriculture Organization of the United Nations. Fisheries and Aquaculture Fact Sheets. Retrieved Apr 16, 2013, from http://www.fao.org/fishery/factsheets/en.
- Froese, R. & D. Pauly. Editors. 2013. FishBase, version (02/2013). Retrieved Apr 16, 2013, from http://www.fishbase.org.
- Lim, K.K.P & P.K.L. Ng. 1990. A Guide to the Freshwater Fishes of Singapore. Singapore Science Centre, Singapore. 160 pp.
- Ng, P. K. L. & N. Sivasothi (eds.), 1999. A guide to the mangroves of Singapore II: Animal diversity. Singapore Science Centre, 168p.
- Yeo, D. C. J. & K. K. P. Lim. 2010. Aplocheilus lineatus, a non-native killifish (Actinopterygii: Cyprinodontiformes: Aplocheilidae) in Singapore. Nature in Singapore, 3: 327–332.
