Toxotes chatareus
Encyclopedia
Toxotes chatareus, sometimes known by the common name
s seven-spot archerfish or largescale archerfish, is a species of perciform fish in the archerfish genus Toxotes
. They are usually no larger than 20 centimetres (7.9 in) but may grow up to 40 centimetres (15.7 in). Unlike most archerfish, T. chatareus are sooty rather than silvery in colour. They are omnivorous, feeding on insects, fish, and vegetative matter at the surface of the water. Breeding occurs in the wet season, and 20,000 to 150,000 eggs may be laid at one time.
T. chatareus are distributed throughout southeast Asia and the Indo-Pacific and Australia. They may live in brackish or fresh
water, inhabiting mangrove swamps and estuaries as well as further upstream in slow-moving rivers. While occasionally caught and eaten, T. chatareus are more commonly kept in the aquarium. They may be sold with other Toxotidae under the collective label "archerfish". Caring for T. chatareus in aquaria is somewhat difficult as they need live food given at the surface, rather than flake food.
T. chatareus have five or six dorsal spines, the fourth of which is the longest, and twelve or thirteen dorsal soft rays. The dorsal spines are generally shorter in specimens collected from freshwater than those from brackish water. T. chatareus also have three anal spines and fifteen to seventeen anal soft rays. T. chatareus have 33 or 34 lateral line
scales. The caudal (tail) fin in almost square. The anal fin is undivided and the third anal spine is longest.
Overall, the body is sooty but sometimes silvery or gold. The dorsal side is "greenish brown". The pectoral fins are clear or "dusky" in colour. Pelvic fins may be darker and heavily pigmented. T. chatareus are white and usually has six or seven dark blotches, alternating long and short, along the dorsal side. A dark blotch is also found at the base of the caudal fin. The colour of these blotches may become darker or lighter due to time of day, environment, and stress. The blotches of young fish are darker than those of older fish. Startled or stressed fish are darker than unstressed fish; fish found in cloudy water may be completely white. It is unknown whether sexual dimorphism
occurs.
have four. The markings on their flanks are also alternating long and short spots rather than bands. T. chatareus also have six or seven markings on its sides, whilst banded archerfish have four to five. T. chatareus has 29–30 lateral line scales, compared to 33–35 in T. jaculatrix. T. chatareus are also less common upstream than T. microlepis
.
s and other fishes, as well as zooplankton
, rotifer
s, cladocerans, and insects (terrestrial and aquatic). T. chatareus has been called a "specialised insectivore
" because it does not prey upon certain insects, particularly those that feed upon C4 plants
. Diet appears to be ontogenetic (varying with age); small fish do not consume any vegetative matter, whilst it comprises one-fourth of the diet of larger fish. Diet also varies with location; when upstream, T. chatareus feed on insects, but when in the estuary, they feed on crustaceans.
ing. Spawning in T. chatareus are homochronal (females only spawn once per season) and iteroparous (spawning occurs more than once in a fish's lifespan). Breeding in Toxotes chatareus occurs in the wet season
. T. chatareus breed both in brackish and in fresh water. Spawning occurs in shallow, muddy lagoons. Females lay about 20,000 to 150,000 buoyant eggs, each 0.4 millimetres in diameter. Females become mature at about 19 centimetres (7.5 in), and males become mature at about 18 centimetres (7.1 in). T. chatareus become reproductively active at 24 months. When they first hatch, larvae may be less than 4 mm in length; when they first feed, they are 5 mm and their mouthparts have become well-developed. There is no parental care in this species. Breeding in this species does not involve travelling downstream
; nonetheless, populations may be affected by the construction of obstacles along rivers they inhabit. T. chatareus has not been bred in captivity.
, and northern Australia. They are generally found in temperature ranges of 25 to 30 °C (77 to 86 °F), though they have been recorded at temperatures as high as 36 °C (96.8 °F) in the Alligator Rivers
region and as low as 20.5 °C (68.9 °F) in the Burdekin river
region; these are believed to be the upper and lower limits of their tolerance, respectively. Brackish mangrove swamps form its main habitat, but T. chatareus are also found in freshwater rivers and streams. It occurs in rivers of the Kimberley region of Western Australia, the Kakadu
area of the Northern Territory
and Arnhem Land
in Australia. On the Mekong river, it may be found as far north as Thailand
and Laos
. They are also found in the upper parts of the Burdekin river
, somehow having overcome the Burdekin Falls. T. chatareus are distributed more "patchily" in eastern Australia, and are less abundant.
T. chatareus are known to occur in shaded areas with vegetation overhead, usually at the top layer of the water column. They are found only where there is an intact riparian area, as this is a major source of their food. T. chatareus are usually not found in fast-flowing streams.
. They are sometimes caught by angler
s and are described as "reasonable eating". T. chatareus are caught and sold in markets, where they are often grouped with the banded archerfish
and simply sold as "archerfish".
T. chatareus are sometimes kept in the aquarium
. In aquaria, they can reach about 20 centimetres (7.9 in) in length, compared to 40 centimetres (15.7 in) in the wild. They are one of only three archerfish
species to be commonly traded (the others being T. jaculatrix
and T. microlepis
). They require an aquarium 100 centimetres (39.4 in) deep with a volume of 170 to 209 l (359.3 to 441.7 ). T. chatareus prefer brackish water and need a tall aquarium. T. chatareus have the ability to "jump" out of the water, which in the wild is used to capture prey on low-hanging branches; they are capable of jumping out of an aquarium that is too short or uncovered. They are compatible with others of their species of similar size, but larger individuals may harass smaller individuals. T. chatareus must be fed live food at the surface, though it does occasionally take flake food; because of this, caring for them is difficult in most home aquaria.
T. chatareus are fairly common and not considered endangered. However, the destruction of their mangrove swamp habitat and increased fishing pressure may pose a risk in the future. The construction of weir
s and tidal barrage
s within its habitat may affect populations in rivers. The growing population in Southeast Asia is also causing pollution to its habitat.
A study found increased (greater than 0.5 μg/g) levels of mercury
in four out of ten specimens sampled at Lake Murray
in Papua New Guinea
. This may have contributed to increased mercury levels in locals who consumed several species of fish from the lake, T. chatareus included. Compared to the other fishes tested, T. chatareus displayed a high level of mercury. Sediments from the nearby Porgera mine are the source of this mercury; the cause of the high level at which the mercury was accumulated
is not known.
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s seven-spot archerfish or largescale archerfish, is a species of perciform fish in the archerfish genus Toxotes
Archerfish
The archerfish are a family of fish known for their habit of preying on land based insects and other small animals by literally shooting them down with water droplets from their specialized mouths...
. They are usually no larger than 20 centimetres (7.9 in) but may grow up to 40 centimetres (15.7 in). Unlike most archerfish, T. chatareus are sooty rather than silvery in colour. They are omnivorous, feeding on insects, fish, and vegetative matter at the surface of the water. Breeding occurs in the wet season, and 20,000 to 150,000 eggs may be laid at one time.
T. chatareus are distributed throughout southeast Asia and the Indo-Pacific and Australia. They may live in brackish or fresh
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
water, inhabiting mangrove swamps and estuaries as well as further upstream in slow-moving rivers. While occasionally caught and eaten, T. chatareus are more commonly kept in the aquarium. They may be sold with other Toxotidae under the collective label "archerfish". Caring for T. chatareus in aquaria is somewhat difficult as they need live food given at the surface, rather than flake food.
Description
Toxotes chatareus are of moderate size, usually between 15 and 20 cm (5.9 and 7.9 ). Rarely, they may reach up to 40 centimetres (15.7 in) in length. T. chatareus weigh up to 700 grams (24.7 oz). T. chatareus are believed to have a lifespan of three to five years.T. chatareus have five or six dorsal spines, the fourth of which is the longest, and twelve or thirteen dorsal soft rays. The dorsal spines are generally shorter in specimens collected from freshwater than those from brackish water. T. chatareus also have three anal spines and fifteen to seventeen anal soft rays. T. chatareus have 33 or 34 lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
scales. The caudal (tail) fin in almost square. The anal fin is undivided and the third anal spine is longest.
Overall, the body is sooty but sometimes silvery or gold. The dorsal side is "greenish brown". The pectoral fins are clear or "dusky" in colour. Pelvic fins may be darker and heavily pigmented. T. chatareus are white and usually has six or seven dark blotches, alternating long and short, along the dorsal side. A dark blotch is also found at the base of the caudal fin. The colour of these blotches may become darker or lighter due to time of day, environment, and stress. The blotches of young fish are darker than those of older fish. Startled or stressed fish are darker than unstressed fish; fish found in cloudy water may be completely white. It is unknown whether sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
occurs.
Comparison to other archerfish
T. chatareus can be distinguished by their sooty colour, as opposed to the typical silver of most other archerfish. They have five dorsal spines, whereas T. jaculatrixBanded archerfish
The banded archerfish is a brackish water perciform fish of the archerfish genus Toxotes. It is silvery in colour and has a dorsal fin towards the posterior end. It has distinctive, semi-triangular markings along its sides. It is best known for its ability to spit a jet of water to "shoot down"...
have four. The markings on their flanks are also alternating long and short spots rather than bands. T. chatareus also have six or seven markings on its sides, whilst banded archerfish have four to five. T. chatareus has 29–30 lateral line scales, compared to 33–35 in T. jaculatrix. T. chatareus are also less common upstream than T. microlepis
Smallscale archerfish
The smallscale archerfish is a perciform fish of genus Toxotes. As its name suggests, the scales of the smallscale archerfish are smaller than those of other archerfish. They reach a maximum length of...
.
Diet and feeding
Like other archerfish, Toxotes chatareus are able to spit streams of water to knock prey into the water. T. chatareus can hit prey at distances of up to 150 centimetres (59.1 in). They feed during the day, consuming plant matter and insects. They are omnivorous; their diet comprises crustaceanCrustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s and other fishes, as well as zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
, rotifer
Rotifer
The rotifers make up a phylum of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John Harris in 1696, and other forms were described by Anton van Leeuwenhoek in 1703...
s, cladocerans, and insects (terrestrial and aquatic). T. chatareus has been called a "specialised insectivore
Insectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
" because it does not prey upon certain insects, particularly those that feed upon C4 plants
C4 carbon fixation
C4 carbon fixation is one of three biochemical mechanisms, along with and CAM photosynthesis, used in carbon fixation. It is named for the 4-carbon molecule present in the first product of carbon fixation in these plants, in contrast to the 3-carbon molecule products in plants. fixation is an...
. Diet appears to be ontogenetic (varying with age); small fish do not consume any vegetative matter, whilst it comprises one-fourth of the diet of larger fish. Diet also varies with location; when upstream, T. chatareus feed on insects, but when in the estuary, they feed on crustaceans.
Breeding
Toxotes chatareus reproduce by spawnSpawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
ing. Spawning in T. chatareus are homochronal (females only spawn once per season) and iteroparous (spawning occurs more than once in a fish's lifespan). Breeding in Toxotes chatareus occurs in the wet season
Wet season
The the wet season, or rainy season, is the time of year, covering one or more months, when most of the average annual rainfall in a region occurs. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the...
. T. chatareus breed both in brackish and in fresh water. Spawning occurs in shallow, muddy lagoons. Females lay about 20,000 to 150,000 buoyant eggs, each 0.4 millimetres in diameter. Females become mature at about 19 centimetres (7.5 in), and males become mature at about 18 centimetres (7.1 in). T. chatareus become reproductively active at 24 months. When they first hatch, larvae may be less than 4 mm in length; when they first feed, they are 5 mm and their mouthparts have become well-developed. There is no parental care in this species. Breeding in this species does not involve travelling downstream
Fish migration
Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres...
; nonetheless, populations may be affected by the construction of obstacles along rivers they inhabit. T. chatareus has not been bred in captivity.
Distribution
Toxotes chatareus are found in India, Burma, Indonesia and New GuineaNew Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, and northern Australia. They are generally found in temperature ranges of 25 to 30 °C (77 to 86 °F), though they have been recorded at temperatures as high as 36 °C (96.8 °F) in the Alligator Rivers
Alligator Rivers
The Alligator Rivers is the name of a region in the Arnhem Land region of the Northern Territory of Australia, containing three rivers the East, West and South Alligator River...
region and as low as 20.5 °C (68.9 °F) in the Burdekin river
Burdekin River
The Burdekin River in Queensland, Australia rises on the western slope of the Seaview Range and flows into the Pacific Ocean at Upstart Bay over 200 km to the southeast of the source. The river was first encountered by Europeans during the expedition led by Ludwig Leichhardt in 1845 and named...
region; these are believed to be the upper and lower limits of their tolerance, respectively. Brackish mangrove swamps form its main habitat, but T. chatareus are also found in freshwater rivers and streams. It occurs in rivers of the Kimberley region of Western Australia, the Kakadu
Kakadu National Park
Kakadu National Park is in the Northern Territory of Australia, 171 km southeast of Darwin.Kakadu National Park is located within the Alligator Rivers Region of the Northern Territory of Australia. It covers an area of , extending nearly 200 kilometres from north to south and over 100 kilometres...
area of the Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
and Arnhem Land
Arnhem Land
The Arnhem Land Region is one of the five regions of the Northern Territory of Australia. It is located in the north-eastern corner of the territory and is around 500 km from the territory capital Darwin. The region has an area of 97,000 km² which also covers the area of Kakadu National...
in Australia. On the Mekong river, it may be found as far north as Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
and Laos
Laos
Laos Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ Sathalanalat Paxathipatai Paxaxon Lao, officially the Lao People's Democratic Republic, is a landlocked country in Southeast Asia, bordered by Burma and China to the northwest, Vietnam to the east, Cambodia to the south and Thailand to the west...
. They are also found in the upper parts of the Burdekin river
Burdekin River
The Burdekin River in Queensland, Australia rises on the western slope of the Seaview Range and flows into the Pacific Ocean at Upstart Bay over 200 km to the southeast of the source. The river was first encountered by Europeans during the expedition led by Ludwig Leichhardt in 1845 and named...
, somehow having overcome the Burdekin Falls. T. chatareus are distributed more "patchily" in eastern Australia, and are less abundant.
T. chatareus are known to occur in shaded areas with vegetation overhead, usually at the top layer of the water column. They are found only where there is an intact riparian area, as this is a major source of their food. T. chatareus are usually not found in fast-flowing streams.
Relationship to humans
Toxotes chatareus have a minor part in fisheriesFishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
. They are sometimes caught by angler
Fisherman
A fisherman or fisher is someone who captures fish and other animals from a body of water, or gathers shellfish. Worldwide, there are about 38 million commercial and subsistence fishermen and fish farmers. The term can also be applied to recreational fishermen and may be used to describe both men...
s and are described as "reasonable eating". T. chatareus are caught and sold in markets, where they are often grouped with the banded archerfish
Banded archerfish
The banded archerfish is a brackish water perciform fish of the archerfish genus Toxotes. It is silvery in colour and has a dorsal fin towards the posterior end. It has distinctive, semi-triangular markings along its sides. It is best known for its ability to spit a jet of water to "shoot down"...
and simply sold as "archerfish".
T. chatareus are sometimes kept in the aquarium
Aquarium fish
In fishkeeping, species of aquarium fish vary with the water chemistry of the aquarium.For species of fish found in particular types of aquaria, see:*List of brackish aquarium fish species*List of freshwater aquarium amphibian species...
. In aquaria, they can reach about 20 centimetres (7.9 in) in length, compared to 40 centimetres (15.7 in) in the wild. They are one of only three archerfish
Archerfish
The archerfish are a family of fish known for their habit of preying on land based insects and other small animals by literally shooting them down with water droplets from their specialized mouths...
species to be commonly traded (the others being T. jaculatrix
Banded archerfish
The banded archerfish is a brackish water perciform fish of the archerfish genus Toxotes. It is silvery in colour and has a dorsal fin towards the posterior end. It has distinctive, semi-triangular markings along its sides. It is best known for its ability to spit a jet of water to "shoot down"...
and T. microlepis
Smallscale archerfish
The smallscale archerfish is a perciform fish of genus Toxotes. As its name suggests, the scales of the smallscale archerfish are smaller than those of other archerfish. They reach a maximum length of...
). They require an aquarium 100 centimetres (39.4 in) deep with a volume of 170 to 209 l (359.3 to 441.7 ). T. chatareus prefer brackish water and need a tall aquarium. T. chatareus have the ability to "jump" out of the water, which in the wild is used to capture prey on low-hanging branches; they are capable of jumping out of an aquarium that is too short or uncovered. They are compatible with others of their species of similar size, but larger individuals may harass smaller individuals. T. chatareus must be fed live food at the surface, though it does occasionally take flake food; because of this, caring for them is difficult in most home aquaria.
T. chatareus are fairly common and not considered endangered. However, the destruction of their mangrove swamp habitat and increased fishing pressure may pose a risk in the future. The construction of weir
Weir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...
s and tidal barrage
Tidal barrage
A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces....
s within its habitat may affect populations in rivers. The growing population in Southeast Asia is also causing pollution to its habitat.
A study found increased (greater than 0.5 μg/g) levels of mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
in four out of ten specimens sampled at Lake Murray
Lake Murray
Lake Murray may refer to:*Lake Murray , the largest lake in Papua New Guinea*Lake Murray , for a time the largest artificial lake in the world*Lake Murray , a lake and the oldest State Park in Oklahoma...
in Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
. This may have contributed to increased mercury levels in locals who consumed several species of fish from the lake, T. chatareus included. Compared to the other fishes tested, T. chatareus displayed a high level of mercury. Sediments from the nearby Porgera mine are the source of this mercury; the cause of the high level at which the mercury was accumulated
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
is not known.