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Threadfin
Threadfins are silvery grey perciform fish of the family Polynemidae. Found in tropical to subtropical waters throughout the world, the threadfin family contains eight genera and about 40 species. An unrelated species sometimes known by the name threadfin, ''Alectis indicus'', is properly the Indian threadfish (family Carangidae). Ranging in length from in the dwarf threadfin (''Parapolynemus verekeri'') to in fourfinger threadfin (''Eleutheronema tetradactylum'') and giant African threadfin (''Polydactylus quadrifilis''), threadfins are both important to commercial fisheries as a food fish, and popular among anglers. Their habit of forming large schools makes the threadfins a reliable and economic catch. Description Their bodies are elongated and fusiform, with spinous and soft dorsal fins widely separated. Their tail fins are large and deeply forked, indicating speed and agility. The mouth is large and inferior; a blunt snout projects far ahead. The jaws and palate pos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dwarf Threadfin
The dwarf paradise fish (''Parapolynemus verekeri''), also known as the streamer threadfin or streamered tasselfish, is a species of ray-finned fish from a family Polynemidae, the threadfins. It is the only species in the genus ''Parapolynemus'' and it is found in Australia and New Guinea. Description The dwarf paradise fish is the smallest species of threadfin which has an elongated body with a large oblique and turned down mouth. It has two separate dorsal fins, the first of which has 8 spines and the second which has a single spine and 11-14 soft rayswhile the anal fin has 3 spines and 10 -12 soft rays. The base of the anal fin is shorter than that of the second dorsal fin. The caudal fin has long lobes with the lower usually being the longest; normally it is longer than the distance from the snout to the start of the second dorsal fin. The pectoral fins have 12 to 14 simple raysand are located near the midline of the body and may extend beyond the rear end of the anal fin's ba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indian Threadfish
The Indian threadfish (''Alectis indica''), also known as the Indian threadfin, diamond trevally, mirror fish or plumed trevally, is a large species of coastal marine fish of the jack family, Carangidae. The species is widespread in the waters of the tropical Indo-West Pacific Ocean, ranging from east Africa to India, Asia, Indonesia and Australia. Adult fish tend to inhabit coastal waters over reefs down to 100 m in depth, while juveniles inhabit a variety of environments including estuaries and seagrass beds. The Indian threadfish is similar to the other two species in the genus ''Alectis'', with a slight concavity in the profile of the head the most obvious distinguishing feature. It is a large species, growing to 165 cm and 25 kg in weight. The species is carnivorous, consuming fishes, cephalopods and crustaceans. The Indian threadfish is of minor commercial importance, and has been the subject of aquaculture in Singapore. Taxonomy and naming The Indian threa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giant African Threadfin
The giant African threadfin (''Polydactylus quadrifilis'') is a species of ray-finned fish from the threadfin family Polynemidae. It is found in the eastern Atlantic Ocean off the west coast of Africa. Description The giant African threadfin is, as its common name indicates, a large species of threadfin attaining a maximum total length of , although the more common size is . It has a pointed snout and analmost straight dorsal profile on the head. It has two separate dorsal fins, the first dorsal fin has 8 spines with the second of these being thicker than the rest, and the second dorsal fin contains a single spine and 13 soft rays. The anal fin has 3 spines and 11 soft rays, its base approximately equal in length to the base of the second dorsal fin. The pectoral fin has 12 or 13 unbranched rays and it measures 20 to 24% of the standard length of the fish, its tip not extended as far as the tip of pelvic fin. There are 4 pectoral filaments with the first being the shortest, the fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fourfinger Threadfin
''Eleutheronema tetradactylum'', the fourfinger threadfin, is a species of marine ray-finned fish, a threadfin from the family Polynemidae which occurs in the Indian and western Pacific Ocean. Description ''Eleutheronema tetradactylum'' has two dorsal fins; the first has 9 spines and the second has 13–15 soft rays, with 13 being the mean. The anal fin has 3 spines and 14–19 soft rays. The pectoral fins have 16–18 rays, and there are 4 pectoral filaments. The upper sides of the head and body have a slight darkish silver tinge, lighting in the lower flanks. Both dorsal fins show a blackish anterior margin, with the remaining parts of the fins translucent and slightly dusky. The membranes of the pectoral fins are vivid yellow in smaller individuals, but in larger fish this becomes duskier. The pectoral filaments are white. The pelvic fins are white with a yellow front edge, while the caudal fin is blackish with a yellowish base. This species can attain a maximum total length of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentanemus Quinquarius
The royal threadfin (''Pentanemus quinquarius'') is a species of ray-finned fish, a threadfin from the family Polynemidae, the threadfins. It is found in the eastern Atlantic Ocean along the western coast of Africa. Description The royal threadfin is a medium-sized threadfin species reaching a maximum total length of , although a more normal length is . It has two separate dorsal fins, the first dorsal fin has 8 spines and the second dorsal fin has a single spine and 14 or 15 soft rays. The anal fin contains 3 spines and 24 to 30 soft rays, with a base which is longer than that of the second dorsal-fin. The pectoral fin has 14 to 16 unbranched rays and is 30% to 42% of the fish's standard length with its tip extending to or just short of the centre of the base of the anal fin. The pectoral fin is situated far below the midline of body. There are 5 pectoral filaments, the first being the shortest and this filament just reaches to or extends beyond the start of the anal fin. The rem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlantic Threadfin
The Atlantic threadfin (''Polydactylus octonemus'') is a species of ray-finned fish a threadfin from the family Polynemidae which is native to subtropical and temperate waters of the western Atlantic Ocean and the Gulf of Mexico. Description The Atlantic threadfin is a medium-sized species of threadfin which grows to a maximum total length of , although most fish have a total length of around . It has a pointed snout and an almost straight dorsal profile on its head. There are two separate dorsal fins, the first dorsal fin contains 8 spines in which the bases of each spine is a similar thickness to the others, and the second dorsal fin has a single spine and 11 to 13 soft rays. The anal fin has 3 spines and 12 to 14 soft rays, The base of the anal fin is longer than that of the second dorsal fin. The pectoral fin has 14 to 16 unbranched rays and has a length equivalent to 24%-29% of the standard length and its tip does not reach the tip of pelvic fin. There are 8 pectoral filament ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euryhaline
Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the molly (''Poecilia sphenops'') which can live in fresh water, brackish water, or salt water. The green crab (''Carcinus maenas'') is an example of a euryhaline invertebrate that can live in salt and brackish water. Euryhaline organisms are commonly found in habitats such as estuaries and tide pools where the salinity changes regularly. However, some organisms are euryhaline because their life cycle involves migration between freshwater and marine environments, as is the case with salmon and eels. The opposite of euryhaline organisms are stenohaline ones, which can only survive within a narrow range of salinities. Most freshwater organisms are stenohaline, and will die in seawater, and similarly most marine organisms are stenohaline, and cannot live in fresh water. Osmoregulation Osmoregulation is the active process by which an organism maintains its level of water cont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salinity
Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to ‰). Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it, and is a thermodynamic state variable that, along with temperature and pressure, governs physical characteristics like the density and heat capacity of the water. A contour line of constant salinity is called an ''isohaline'', or sometimes ''isohale''. Definitions Salinity in rivers, lakes, and the ocean is conceptually simple, but technically challenging to define and measure precisely. Conceptually the salinity is the quantity of dissolved salt content of the water. Salts are compounds like sodium chloride, magnesium sulfate, potassium nitrate, and sodium bicarbonate which dissolve into ions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone (sedimentary rocks) through lithification. Sediments are most often transported by water (fluvial processes), but also wind (aeolian processes) and glaciers. Beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of aeolian transport and deposition. Glacial moraine deposits and till are ice-transported sediments. Classification Sediment can be classified based on its grain size, grain shape, and c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Estuary
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world. Most existing estuaries formed during the Holocene epoch with the flooding of river-eroded or glacially scoured valleys when the sea level began to rise about 10,000–12,000 years ago. Estuaries are typically classified according to their geomorphological features or to water-circulation patterns. They can have many different names, such as bays, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as Stream#Creek, creek, Stream#Brook, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to Geographical feature, geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "Burn (landform), burn" in Scotland and northeast England, and "beck" in northern England. Sometimes a river is defined as being larger than a creek, but not always: the language is vague. Rivers are part of the water cycle. Water generally collects in a river from Precipitation (meteorology), precipitation through a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crustacea
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can be treated as a subphylum under the clade Mandibulata. It is now well accepted that the hexapods emerged deep in the Crustacean group, with the completed group referred to as Pancrustacea. Some crustaceans (Remipedia, Cephalocarida, Branchiopoda) are more closely related to insects and the other hexapods than they are to certain other crustaceans. The 67,000 described species range in size from '' Stygotantulus stocki'' at , to the Japanese spider crab with a leg span of up to and a mass of . Like other arthropods, crustaceans have an exoskeleton, which they moult to grow. They are distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous (two-parted) limbs, and by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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