Portal:Fish

Hypnos monopterygius, also known as the coffin ray or Australian numbfish, is a species of electric ray endemic to Australia, where it is common in inshore waters shallower than 80 m (260 ft). It is the sole member of its genus Hypnos, and family Hypnidae. This small species typically reaches 40 cm (16 in) in length. Greatly enlarged pectoral fins and an extremely short tail, coupled with diminutive dorsal and caudal fins all concentrated towards the rear, give the coffin ray a distinctive pear-like shape. It is a varying shade of brown in colour above, and has tiny eyes and a large, highly distensible mouth.

The sluggish and nocturnal coffin ray frequents sandy or muddy habitats, where it can bury itself during daytime. Able to produce a powerful electric shock reaching 200 volts for attack and defense, it can deliver a severe – albeit non-fatal – shock to a human. This species is a voracious predator that feeds mainly on benthic bony fishes, often tackling fish approaching or exceeding itself in size. On occasion, it may also consume invertebrates and even small penguins and rats. Reproduction is aplacental viviparous, in which the developing embryos are nourished by yolk and maternally produced histotroph ("uterine milk"). The female gives birth to 4–8 pups during summer. Not valued commercially, it is very hardy and can usually survive being captured and discarded. The International Union for Conservation of Nature (IUCN) has listed this species under Least Concern, as its population does not seem threatened by human activity. (Full article...)

The copper shark (Carcharhinus brachyurus), bronze whaler, or narrowtooth shark is a species of requiem shark found mostly in temperate latitudes. It is distributed in a number of separate populations in the northeastern and southwestern Atlantic, off southern Africa, in the northwestern and eastern Pacific, and around Australia and New Zealand, with scattered reports from equatorial regions. The species can be found from brackish rivers and estuaries to shallow bays and harbors, to offshore waters 100 m (330 ft) deep or more. Females are found apart from males for most of the year, and conduct seasonal migrations. A large species reaching 3.3 m (11 ft) long, the copper shark is difficult to distinguish from other large requiem sharks. It is characterized by its narrow, hook-shaped upper teeth, lack of a prominent ridge between the dorsal fins, and plain bronze coloration.

Feeding mainly on cephalopods, bony fishes, and other cartilaginous fishes, the copper shark is a fast-swimming predator that has been known to hunt in large groups, using their numbers to their advantage; however for most of the time they remain solitary. Off South Africa, this species associates closely with the annual sardine run, involving millions of southern African pilchard (Sardinops sagax). Like other requiem sharks, it is viviparous, with the developing embryos mainly nourished through a placental connection formed from the depleted yolk sac. Females bear litters of 7 to 24 pups every other year in coastal nursery areas, after a gestation period of 12 or perhaps as long as 21 months. It is extremely slow-growing, with males and females not reaching maturity until 13–19 and 19–20 years of age respectively. (Full article...)

The Atlantic blue marlin (Makaira nigricans) is a species of marlin endemic to the Atlantic Ocean. It is closely related to, and usually considered conspecific with, the Indo-Pacific blue marlin, then simply called blue marlin. Some authorities consider both species distinct.

The Atlantic blue marlin (hereafter, blue marlin) feeds on a wide variety of organisms near the surface. It uses its bill to stun, injure, or kill while knifing through a school of fish or other prey, then returns to eat the injured or stunned fish. Marlin is a popular game fish. The relatively high fat content of its meat makes it commercially valuable in certain markets. It is the national fish of the Commonwealth of The Bahamas and is featured on its coat of arms. (Full article...)

The sicklefin lemon shark (Negaprion acutidens) or sharptooth lemon shark is a species of requiem shark belonging to the family Carcharhinidae, widely distributed in the tropical waters of the Indo-Pacific. It is closely related to the better-known lemon shark (N. brevirostris) of the Americas; the two species are almost identical in appearance, both being stout-bodied sharks with broad heads, two dorsal fins of nearly equal size, and a plain yellow-tinged coloration. As its common name suggests, the sicklefin lemon shark differs from its American counterpart in having more falcate (sickle-shaped) fins. This large species grows up to 3.8 m (12 ft) long. It generally inhabits water less than 92 m (302 ft) deep in a variety of habitats, from mangrove estuaries to coral reefs.

A slow-moving predator feeding mainly on bony fishes, the sicklefin lemon shark seldom travels long distances and many individuals can be found year-round at certain locations. Like other members of its family, this species is viviparous, with females giving birth to no more than 13 pups every other year, following a gestation period of 10–11 months. Although they are potentially dangerous to humans and known to respond vigorously to any provocation, under normal circumstances, sicklefin lemon sharks are cautious and tend to retreat if approached. The IUCN has assessed this species as Endangered; its low reproductive productivity and rate of movement limits the capacity of depleted stocks to recover. Off India and Southeast Asia, this species has been severely depleted or extirpated by unregulated exploitation for its meat, fins, and liver oil. (Full article...)

The smalleye hammerhead (Sphyrna tudes), also called the golden hammerhead or curry shark, is a small species of hammerhead shark in the family Sphyrnidae. This species was historically common in the shallow coastal waters of the western Atlantic Ocean, from Venezuela to Uruguay. It favors muddy habitats with poor visibility, reflected by its relatively small eyes. Adult males and juveniles are schooling and generally found apart from the solitary adult females. Typically reaching 1.2–1.3 m (3.9–4.3 ft) in length, this shark has a unique, bright golden color on its head, sides, and fins, which was only scientifically documented in the 1980s. As in all hammerheads, its head is flattened and laterally expanded into a hammer-shaped structure called the cephalofoil, which in this species is wide and long with an arched front margin bearing central and lateral indentations.

The yellow-orange pigments of the smalleye hammerhead seem to have been acquired from the penaeid shrimp Xiphopenaeus kroyeri, the main food of juvenile sharks, and from sea catfish and their eggs, the main food of adults. The golden color may serve to conceal it from predators such as larger sharks. This species is viviparous, with the developing embryos sustained by a placental connection formed from the depleted yolk sac. Females bear litters of five to 19 pups every year following a gestation period of 10 months. Reproductive seasonality, litter size, and size at maturity vary between geographical regions. Because of its abundance, the smalleye hammerhead is an economically important bycatch of artisanal gillnet fisheries throughout its range, and is used as food. In recent years, overfishing has caused marked declines in its numbers off Trinidad, northern Brazil, and probably elsewhere. Coupled with the smalleye hammerhead's low reproductive rate, this led the International Union for Conservation of Nature to list the smalleye hammerhead as critically endangered in 2020. (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 (4,410 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 Christmas darter (Etheostoma hopkinsi) is a species of ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae which includes the perches, ruffes and pike-perches. It is found in the Savannah, Ogeechee and Altamaha catchment areas in South Carolina and Georgia. It is a small but colorful fish, typically less than 5 cm (2 in) in total length, with blackish, red and green streaks on its flanks. Green and red are associated with Christmas, hence the common name Christmas darter. Like other darters, it lives on or close to the stream-bed, in riffles and vegetation-laden stretches of small rivers, creeks and spring-fed streams. It feeds on aquatic insects and probably breeds in the spring, but its biology and behavior are poorly known.

The Christmas darter is closely related to the Savannah darter and the Christmas Eve or Hannukah darter, the latter of which is sometimes considered a subspecies of the Christmas darter rather than a species in its own right. The Christmas darter may hybridize with other darter species, though hybridization is hampered by behavioral and biological barriers. The Christmas darter is a common species in suitable habitat and the International Union for Conservation of Nature (IUCN) has assessed it as being of least concern for conservation purposes. In South Carolina, it is considered a conservation priority species, as it may be threatened in future by impoundment of rivers, siltation and deforestation. (Full article...)

The cutthroat trout (Oncorhynchus clarkii) is a fish species of the family Salmonidae native to cold-water tributaries of the Pacific Ocean, Rocky Mountains, and Great Basin in North America. As a member of the genus Oncorhynchus, it is one of the Pacific trout, a group that includes the widely distributed rainbow trout. Cutthroat trout are popular gamefish, especially among anglers who enjoy fly fishing. The common name "cutthroat" refers to the distinctive red coloration on the underside of the lower jaw. The specific name clarkii was given to honor explorer William Clark, coleader of the Lewis and Clark Expedition.

Cutthroat trout usually inhabit and spawn in small to moderately large, clear, well-oxygenated, shallow rivers with gravel bottoms. They reproduce in clear, cold, moderately deep lakes. They are native to the alluvial or freestone streams that are typical tributaries of the rivers of the Pacific Basin, Great Basin and Rocky Mountains. Cutthroat trout spawn in the spring and may inadvertently but naturally hybridize with rainbow trout, producing fertile cutbows. Some populations of the coastal cutthroat trout (O. c. clarkii) are semi-anadromous. (Full article...)

The crossback stingaree or banded stingaree (Urolophus cruciatus) is a species of stingray in the family Urolophidae. It is endemic to southeastern Australia, mainly off Victoria and Tasmania but also marginally to New South Wales and South Australia. This bottom-dwelling fish generally inhabits sand and reef habitats deeper than 100 m (330 ft) off Victoria, and muddy habitats in shallow bays and estuaries off Tasmania. Befitting its name, the crossback stingaree has a distinctive dark pattern on its back, consisting of a midline stripe that is crossed by three transverse bars. It has an oval pectoral fin disc with a blunt snout and a skirt-shaped curtain of skin between the nostrils. Its tail is short with no skin fold along the sides, and a deep, leaf-shaped caudal fin. The youngest rays may have a small dorsal fin in front of the stinging tail spine. This species reaches 50 cm (20 in) in length.

During the day the crossback stingaree is usually inactive and can be found partially or completely buried in sand on the sea floor. It is a carnivore and adults forage for crustaceans, polychaete worms and other small invertebrates on the seafloor. Juveniles feed on smaller crustaceans such as isopods, amphipods and shrimps. (Full article...)

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...)

The cloudy catshark (Scyliorhinus torazame) is a common species of catshark, belonging to the family Scyliorhinidae. It is a bottom-dweller that inhabits rocky reefs in the northwestern Pacific Ocean, from the shore to a depth of 320 m (1,050 ft). Growing up to 50 cm (20 in) long, this small, slim shark has a narrow head with a short blunt snout, no grooves between the nostrils and mouth, and furrows on the lower but not the upper jaw. It is also characterized by extremely rough skin and coloration consisting of a series of dark brown saddles along its back and tail, along with various darker and lighter spots in larger individuals.

The diet of the cloudy catshark consists of molluscs, crustaceans, and bony fishes. It is oviparous, with females laying encapsulated eggs two at a time in nursery areas. The claspers of the male bear numerous hooks that likely serve to facilitate copulation. This harmless shark can be readily maintained in captivity and is used as a model organism for biological research. It is caught incidentally, and generally discarded, by commercial fisheries. These activities do not appear to have negatively affected its population, leading it to be listed under Least Concern by the International Union for Conservation of Nature (IUCN). (Full article...)

The Pacific blue-eye (Pseudomugil signifer) is a species of fish in the subfamily Pseudomugilinae native to eastern Australia. Described by Austrian naturalist Rudolf Kner in 1866, it comprises two subspecies that have been regarded as separate species in the past and may be once again with further study. It is a common fish of rivers and estuaries along the eastern seaboard from Cape York in North Queensland to southern New South Wales, the Burdekin Gap in central-north Queensland dividing the ranges of the two subspecies.

A small silvery fish averaging around 3.25 cm in total length (1+1⁄8–1+3⁄8 in), the Pacific blue-eye is recognisable by its blue eye-ring and two dorsal fins. It forms loose schools of tens to thousands of individuals. It eats water-borne insects as well as flying insects that land on the water's surface, foraging for them by sight. The Pacific blue-eye adapts readily to captivity. (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...)

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...)

An electric fish is any fish that can generate electric fields. Most electric fish are also electroreceptive, meaning that they can sense electric fields. The only exception is the stargazer family (Uranoscopidae). Electric fish, although a small minority of all fishes, include both oceanic and freshwater species, and both cartilaginous and bony fishes.

Electric fish produce their electrical fields from an electric organ. This is made up of electrocytes, modified muscle or nerve cells, specialized for producing strong electric fields, used to locate prey, for defence against predators, and for signalling, such as in courtship. Electric organ discharges are two types, pulse and wave, and vary both by species and by function. (Full article...)