Portal:Fish

The Murray cod (Maccullochella peelii) is a large Australian predatory freshwater fish of the genus Maccullochella in the family Percichthyidae. Although the species is called a cod in the vernacular, it is not related to the Northern Hemisphere marine cod (Gadus) species. The Murray cod is an important part of Australia's vertebrate wildlife—as an apex predator in the Murray-Darling River system—and also significant in Australia's human culture. The Murray cod is the largest exclusively freshwater fish in Australia, and one of the largest in the world. Other common names for Murray cod include cod, greenfish, goodoo, Mary River cod, Murray perch, ponde, pondi and Queensland freshwater cod.

The scientific name of Murray cod derives from an early Australian fish researcher Allan Riverstone McCulloch and the river from which the explorer Major Mitchell first scientifically described the species, the Peel River. This was for a number of years changed to M. peelii peelii to differentiate Murray cod from Mary River cod, which were designated as a subspecies of Murray cod. However, as of 2010, Mary River cod have been raised to full species status (M. mariensis), thus Murray cod have reverted simply to M. peelii. (Full article...)

Alopias palatasi, commonly referred to as the serrated giant thresher, is an extinct species of giant thresher shark that lived approximately 20.44 to 13.7 million years ago during the Miocene epoch, and is known for its uniquely serrated teeth. It is only known from such isolated teeth, which are large and can measure up to an excess of 4 centimetres (2 in), equating to a size rivaling the great white shark, but are rare and found in deposits in the East Coast of the United States and Malta. Teeth of A. palatasi are strikingly similar to those of the giant thresher Alopias grandis, and the former has been considered as a variant of the latter in the past. Scientists hypothesized that A. palatasi may have had attained lengths comparable with the great white shark and a body outline similar to it. (Full article...)

The American paddlefish (Polyodon spathula), also known as a Mississippi paddlefish, spoon-billed cat, or spoonbill, is a species of ray-finned fish. It is the last living species of paddlefish (Polyodontidae). This family is most closely related to the sturgeons; together they make up the order Acipenseriformes, which are one of the most primitive living groups of ray-finned fish. Fossil records of other paddlefish species date back 125 million years to the Early Cretaceous, with records of Polyodon extending back 65 million years to the early Paleocene. The American paddlefish is a smooth-skinned freshwater fish with an almost entirely cartilaginous skeleton and a paddle-shaped rostrum (snout), which extends nearly one-third its body length. It has been referred to as a freshwater shark because of its heterocercal tail or caudal fin resembling that of sharks, though it is not closely related. The American paddlefish is a highly derived fish because it has evolved specialised adaptations such as filter feeding. Its rostrum and cranium are covered with tens of thousands of sensory receptors for locating swarms of zooplankton, its primary food source. The only other species of paddlefish that survived to modern times was the Chinese paddlefish (Psephurus gladius), last sighted in 2003 in the Yangtze River in China and considered to have gone extinct no later than 2010.

The American paddlefish is native to the Mississippi River basin and once moved freely under the relatively unaltered conditions that existed prior to the early 1900s. It commonly inhabited large, free-flowing rivers, braided channels, backwaters, and oxbow lakes throughout the Mississippi River drainage basin, and adjacent Gulf Coast drainages. Its peripheral range extended into the Great Lakes, with occurrences in Lake Huron and Lake Helen in Canada until about 1917. American paddlefish populations have declined dramatically primarily because of overfishing, habitat destruction, and pollution. Poaching has also been a contributing factor to its decline and is liable to continue to be so as long as the demand for caviar remains strong. Naturally occurring American paddlefish populations have been extirpated from most of their peripheral range, as well as from New York, Maryland, Virginia, and Pennsylvania. They have been reintroduced in the Allegheny, Monongahela and Ohio river systems in western Pennsylvania. However, their current range has been reduced to the Mississippi and Missouri River tributaries and Mobile Bay drainage basin. American paddlefish are currently found in twenty-two states in the U.S., and are protected under state, federal and international laws. (Full article...)

The roughtail stingray (Bathytoshia centroura) is a species of stingray in the family Dasyatidae, with separate populations in coastal waters of the northwestern and southwestern Atlantic Ocean. This bottom-dwelling species typically inhabits sandy or muddy areas with patches of invertebrate cover, at a depth of 15–50 m (49–164 ft). It is seasonally migratory, overwintering in offshore waters and moving into coastal habitats for summer. The largest whip-tail stingray in the Atlantic, the roughtail stingray grows up to 2.6 m (8.5 ft) across and 360 kg (800 lb) in weight. It is plain in color, with an angular, diamond-shaped pectoral fin disc and a long, whip-like tail bearing a subtle fin fold underneath. The many thorns on its back and tail serve to distinguish it from other stingrays that share its range.

Often found lying on the bottom buried in sediment, the roughtail stingray is a generalist predator that feeds on a variety of benthic invertebrates and bony fishes. It is aplacental viviparous, with the embryos receiving nourishment initially from yolk, and later from histotroph ("uterine milk") produced by the mother. The venomous tail spine of the roughtail stingray is potentially dangerous to humans. The International Union for Conservation of Nature (IUCN) has listed this species as vulnerable overall. (Full article...)

Otodus megalodon (/ˈmɛɡələdɒn/ MEG-əl-ə-don; meaning "big tooth"), commonly known as megalodon, is an extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Early Pliocene epochs. O. megalodon was formerly thought to be a member of the family Lamnidae and a close relative of the great white shark (Carcharodon carcharias), but has been reclassified into the extinct family Otodontidae, which diverged from the great white shark during the Early Cretaceous.

While regarded as one of the largest and most powerful predators to have ever lived, megalodon is only known from fragmentary remains, and its appearance and maximum size are uncertain. Scientists differ on whether it would have more closely resembled a stockier version of the great white shark (Carcharodon carcharias), the basking shark (Cetorhinus maximus) or the sand tiger shark (Carcharias taurus). The most recent estimate with the least error range suggests a maximum length estimate up to 20.3 meters (67 ft), although the modal lengths are estimated at 10.5 meters (34 ft). Their teeth were thick and robust, built for grabbing prey and breaking bone, and their large jaws could exert a bite force of up to 108,500 to 182,200 newtons (24,390 to 40,960 lbf). (Full article...)

The Pondicherry shark (Carcharhinus hemiodon) is an extremely rare species of requiem shark, in the family Carcharhinidae. A small and stocky gray shark, it grows not much longer than 1 m (3.3 ft) and has a fairly long, pointed snout. This species can be identified by the shape of its upper teeth, which are strongly serrated near the base and smooth-edged near the tip, and by its first dorsal fin, which is large with a long free rear tip. Furthermore, this shark has prominent black tips on its pectoral fins, second dorsal fin, and caudal fin lower lobe.

The Pondicherry shark is critically endangered. It was once found throughout Indo-Pacific coastal waters from the Gulf of Oman to New Guinea, and is known to enter fresh water. Fewer than 20 specimens are available for study, and most aspects of its natural history are unknown. It probably feeds on bony fishes, cephalopods, and crustaceans, and gives birth to live young with the embryos forming a placental connection to their mother. While the International Union for Conservation of Nature (IUCN) has listed the Pondicherry shark as Critically endangered, it had been thought to be extinct since the 1970s. It is probably threatened by intense and escalating fishing pressure throughout its range. The shark is among the 25 "most wanted lost" species that are the focus of Global Wildlife Conservation's "Search for Lost Species" initiative. The Pondicherry has been spotted in rivers in India in the late 2010s. A Pondicherry shark was caught in the Menik Ganga (river) in SE Sri Lanka in 2011. It was photographed and released alive. (Full article...)

The Japanese angelshark (Squatina japonica) is a species of angelshark, family Squatinidae, found in the northwestern Pacific Ocean off China, Japan, and Korea. It is a bottom-dwelling shark found in sandy habitats down to 300 m (980 ft) deep. This species has the flattened shape with wing-like pectoral and pelvic fins typical of its family, and grows to 1.5 m (4.9 ft) or more in length. Its two dorsal fins are placed behind the pelvic fins, and a row of large thorns occurs along its dorsal midline. Its upper surface is cryptically patterned, with numerous squarish dark spots on a brown background.

Feeding on fishes, cephalopods, and crustaceans, the Japanese angelshark is a nocturnal ambush predator that spends most of the day lying still on the sea floor. This species gives birth to live young, which are sustained during gestation by yolk. The litter size varies from two to 10. The Japanese angelshark is not dangerous to humans unless provoked. It is fished in large numbers and used for meat and shagreen, a type of leather. (Full article...)

The black dogfish (Centroscyllium fabricii) is a species of dogfish shark in the family Etmopteridae. It is common over the outer continental shelf and continental slope at depths of 180–2,250 m (590–7,380 ft). Females generally inhabit deeper water than males, and depending on the region, smaller sharks may occur at different depths than larger ones. This species is distributed widely in the Atlantic Ocean, from Greenland and Iceland to Virginia and West Africa in the north, and off southwestern Africa and Argentina in the south. The largest member of its family, the black dogfish, typically measures 60–75 cm (24–30 in) long. It has a stocky, dark brown body that is darker below than above, and bears scattered, minute bioluminescent organs. Its two dorsal fins are preceded by stout spines, and the anal fin is absent.

Active and schooling, the black dogfish is an opportunistic predator and scavenger that mainly consumes bony fishes, crustaceans, and cephalopods. It is aplacental viviparous, with females producing litters of four to 40 pups that are sustained to term by a yolk sac. There is no well-defined breeding season, and mating and birthing take place year-round. The black dogfish contributes significantly to the bycatch of deep-sea commercial fisheries operating in the North Atlantic; it is of little commercial value and is usually discarded. As large portions of its range see little deepwater fishing activity and its northwestern Atlantic population seems to be stable, the International Union for Conservation of Nature has listed this species under Least Concern overall. It has been assessed as Near Threatened in the northeastern Atlantic, where its numbers may have declined from heavy fishing pressure. (Full article...)

Kuhl's maskray (Neotrygon kuhlii), also known as the blue-spotted stingray, blue-spotted maskray, or Kuhl's stingray, is a species of stingray of the family Dasyatidae. It was recently changed from Dasyatis kuhlii in 2008 after morphological and molecular analyses showed that it is part of a distinct genus, Neotrygon. The body is rhomboidal and colored green with blue spots. Maximum disk width is estimated 46.5 cm (18.3 in). It is popular in aquaria, but usually not distinguished from the blue-spotted ribbontail ray. The ribbontail has a rounded body, is a brighter green with brighter blue and more vivid spots, but Kuhl's maskray is larger. The stingray's lifespan is estimated at 13 years for females and 10 years for males. The blue-spotted stingray preys on many fish and small mollusks. It is also generally found from Indonesia to Japan, and most of Australia. Kuhl's maskray also is targeted by many parasites, such as tapeworms, flatworms, and flukes. (Full article...)

The great white shark (Carcharodon carcharias), also known as the white shark, white pointer, or simply great white, is a species of large mackerel shark which can be found in the coastal surface waters of all the major oceans. It is the only known surviving species of its genus Carcharodon. The great white shark is notable for its size, with the largest preserved female specimen measuring 5.83 m (19.1 ft) in length and around 2,000 kg (4,400 lb) in weight at maturity. However, most are smaller; males measure 3.4 to 4.0 m (11 to 13 ft), and females measure 4.6 to 4.9 m (15 to 16 ft) on average. According to a 2014 study, the lifespan of great white sharks is estimated to be as long as 70 years or more, well above previous estimates, making it one of the longest lived cartilaginous fishes currently known. According to the same study, male great white sharks take 26 years to reach sexual maturity, while the females take 33 years to be ready to produce offspring. Great white sharks can swim at speeds of 25 km/h (16 mph) for short bursts and to depths of 1,200 m (3,900 ft).

The great white shark is arguably the world's largest-known extant macropredatory fish, and is one of the primary predators of marine mammals, such as pinnipeds and dolphins. The great white shark is also known to prey upon a variety of other animals, including fish, other sharks, and seabirds. It has only one recorded natural predator, the orca. (Full article...)

The nursehound (Scyliorhinus stellaris), also known as the large-spotted dogfish, greater spotted dogfish or bull huss, is a species of catshark, belonging to the family Scyliorhinidae, found in the northeastern Atlantic Ocean. It is generally found among rocks or algae at a depth of 20–60 m (66–197 ft). Growing up to 1.6 m (5.2 ft) long, the nursehound has a robust body with a broad, rounded head and two dorsal fins placed far back. It shares its range with the more common and closely related small-spotted catshark (S. canicula), which it resembles in appearance but can be distinguished from, in having larger spots and nasal skin flaps that do not extend to the mouth.

Nursehounds have nocturnal habits and generally hide inside small holes during the day, often associating with other members of its species. A benthic predator, it feeds on a range of bony fishes, smaller sharks, crustaceans, and cephalopods. Like other catsharks, the nursehound is oviparous in reproduction. Females deposit large, thick-walled egg cases, two at a time, from March to October, securing them to bunches of seaweed. The eggs take 7–12 months to hatch. Nursehounds are marketed as food in several European countries under various names, including "flake", "catfish", "rock eel", and "rock salmon". It was once also valued for its rough skin (called "rubskin"), which was used as an abrasive. The International Union for Conservation of Nature (IUCN) has assessed the nursehound as Vulnerable, as its population in the Mediterranean Sea seems to have declined substantially from overfishing. (Full article...)

A fish (pl.: fish or fishes) is an aquatic, anamniotic, gill-bearing vertebrate animal with swimming fins and a hard skull, but lacking limbs with digits. Fish can be grouped into the more basal jawless fish and the more common jawed fish, the latter including all living cartilaginous and bony fish, as well as the extinct placoderms and acanthodians. In a break to the long tradition of grouping all fish into a single class (Pisces), contemporary phylogenetics views fish as a paraphyletic group.

Most fish are cold-blooded, their body temperature varying with the surrounding water, though some large active swimmers like white shark and tuna can hold a higher core temperature. Many fish can communicate acoustically with each other, such as during courtship displays. The study of fish is known as ichthyology. (Full article...)

The alligator gar (Atractosteus spatula) is a euryhaline ray-finned fish in the clade Ginglymodi of the infraclass Holostei /hoʊˈlɒstiaɪ/, being most closely related to the bowfins. It is the largest species in the gar family (Lepisosteidae), and is among the largest freshwater fish in North America. The fossil record traces its group's existence back to the Early Cretaceous over 100 million years ago. Gars are often referred to as "primitive fishes" or "living fossils", because they have retained some morphological characteristics of their early ancestors, such as a spiral valve intestine, which is also common to the digestive system of sharks, and the ability to breathe in both air and water. Their common name was derived from their resemblance to the American alligator, particularly their broad snouts and long, sharp teeth. It is suggested that an alligator gar can grow up to 10 ft (3.0 m) in length.

The body of an alligator gar is torpedo-shaped, usually brown or olive colored, fading to a lighter gray or yellow ventral surface. In very rare occurrences, they can also be black, seen in gars that have a high level of melanin. Their scales are not like the scales of other fishes; rather, they are ganoid scales, which are bone-like, rhomboidal-shaped scales, often with serrated edges, and covered by an enamel-like substance. Ganoid scales are nearly impenetrable, and are excellent protection against predation. Unlike other gar species, the upper jaw of an alligator gar has a dual row of large, sharp teeth that are used to impale and hold prey. Alligator gar are stalking, ambush predators, primarily piscivores, but they also ambush and eat waterfowl and small mammals they find floating on the water's surface. (Full article...)

The African knifefish, Gymnarchus niloticus – also called the aba aba – is an electric fish, living at the bottoms of rivers and lakes. It is the only species in the genus Gymnarchus and the family Gymnarchidae, within the order Osteoglossiformes. It is a long slender fish with no pelvic or anal fins, and a tail fin shaped like a rat's tail. It swims using its elongated dorsal fin, allowing it to keep its body straight while it moves. This in turn enables it to produce a steady but weak electric field, which it uses to locate its prey. It is large for a river fish; adults can reach 1.6 m (5.2 ft) in length and 19 kg (42 lb) in weight.

In 1950, Hans Lissmann noticed that the fish could swim equally well forwards or backwards, clearly relying on a sense other than vision. He demonstrated that it could locate prey by electroreception, making it the first fish known to have this ability. (Full article...)

The onefin electric ray or Cape numbfish (Narke capensis) is a common but little-known species of electric ray in the family Narkidae, native to South Africa and Namibia. It is a benthic fish found in shallow coastal bays over sandy or muddy bottoms. This small species reaches 38 cm (15 in) in length, and has a nearly circular pectoral fin disc and a short, muscular tail that supports a large caudal fin. It can be identified by its single dorsal fin, which is located over the large pelvic fins. Its dorsal coloration is yellowish to dusky brown.

Like other members of its family, the onefin electric ray can defend itself with a strong electric shock produced from a pair of kidney-shaped electric organs beside its head. It feeds mainly on polychaete worms, and likely gives birth to live young. The International Union for Conservation of Nature (IUCN) presently lacks enough information to assess the conservation status of this species. It is often caught incidentally by bottom trawl fisheries off South Africa, and may also be impacted by pollution from coastal development. (Full article...)