Giant Freshwater Stingray
The giant freshwater stingray (Himantura chaophraya) is a species of stingray in the family Dasyatidae, native to large rivers and estuaries of Southeast Asia. It is one of the largest freshwater fishes in the world, with reports from the Chao Phraya and Mekong Rivers of individuals weighing 500–600 kg (1,100–1,300 lbs). Its numbers are dwindling due to overfishing and habitat loss, and some local populations are in danger of going extinct. The smaller freshwater whipray of New Guinea and northern Australia was once considered to be conspecific with the giant freshwater stingray but is now recognized as a separate species.
Originally described from Thailand (where it occurs in the Chao Phraya, Nan, Mekong, Bongpakong, Tachin and Tapi Rivers), the giant freshwater stingray is also found in Indonesia (the Mahakam River Basin in Kalimantan) and Malaysia (the Kinabatangan River in Sabah). The rays across these different regions are likely to be isolated from each other, and it is yet unclear whether they represent populations of the same species or a species complex. It prefers a sandy habitat.
The giant freshwater stingray has a relatively thin, more or less oval-shaped pectoral fin disk and minute eyes. The snout is very broad with a projecting triangular tip. The mouth is small, with 4–7 papillae (2–4 large central and 1–4 small lateral) on the floor. The whip-like tail measures 1.8–2.5 times the length of the disk and lacks fin folds. The serrated spine on the tail is the largest of any stingray, reaching 38 cm (15 in) long. It is covered with a sheath of toxic mucus and is capable of piercing bone.
The upper surface of the body and tail are covered with small, rough tubercles, becoming sharp on the tail beyond the spine. The back is uniform brown to gray in color, sometimes becoming lighter towards the margins. The underside is white, with a distinctive broad, black band edged with small spots around the margins of the pectoral and pelvic fins. The tail is black past the spine. This species reaches at least 4.6 meters (15 ft) long and 1.9 meters (6.2 ft) across.
Wels Catfish
The wels catfish (pronounced /ˈwɛls/ or /ˈvɛls/; Silurus glanis), also called sheatfish, is a large catfish found in wide areas of central, southern, and eastern Europe, and near the Baltic and Caspian Seas. It is a scaleless fresh and brackish water fish recognizable by its broad, flat head and wide mouth. Wels catfish can live for at least thirty years and have very good hearing.
The wels catfish lives on annelid worms, gastropods, insects, crustaceans, and fish; the larger ones also eat frogs, mice, rats and aquatic birds such as ducks.
The wels catfish lives in large, warm lakes and deep, slow-flowing rivers. It prefers to remain in sheltered locations such as holes in the riverbed, sunken trees, etc. It consumes its food in the open water or on the bottom, where it can be recognized by its large mouth. Wels catfish are kept in fish ponds as food fish.
Wels catfish's mouth contains lines of numerous small teeth, two long barbels on the upper jaw and four shorter barbels on the lower jaw. It has a long anal fin that extends to the caudal fin, and a small sharp dorsal fin positioned relatively far forward. It uses its sharp pectoral fins to capture prey. With these fins, it creates an eddy to disorient its victim, which it then simply engulfs in its enormous throat. It has very slippery green-brown skin. Its belly is pale yellow or white. Colour varies with environment. Clear water will give the fish a black coloration while muddy water will often tend to produce brownish specimens. Weight and length are not correlated linearly, and also depend on the season.
Nile Perch
The Nile perch (Lates niloticus) is a species of freshwater fish in family Latidae of order Perciformes. It is widespread throughout much of the Afrotropic ecozone, being native to the Congo, Nile, Senegal, Niger, and Lake Chad, Volta, Lake Turkana and other river basins. It also occurs in the brackish waters of Lake MaryutEgypt. Originally described as in
Labrus niloticus, among the marine wrasses, the species has also been referred to as Centropomus niloticus. Common names include African snook, Capitaine, Victoria perch (a misleading trade name, as the species is not native to Lake Victoria), and a large number of local names in various African languages, such as the Luo name Mbuta.
Lates niloticus is silver in colour with a blue tinge. It has a distinctive dark black eye, with a bright yellow outer ring. One of the largest freshwater fish, it reaches a maximum length of nearly two metres (more than six feet), weighing up to 200 kg (440 lb). Mature fish average 121–137 cm (48–54 in), although many fish are caught before they can grow this large.
Adult Nile perch occupy all habitats of a lake with sufficient oxygen concentrations, while juveniles are restricted to shallow or nearshore environments. A fierce predator that dominates its surroundings, the Nile perch feeds on fish (including its own species), crustaceans, and insects; the juveniles also feed on zooplankton.
Nile perch have been introduced to many other lakes in Africa, including Lake Victoria (see below) and the artificial Lake Nasser. The IUCN's (World Conservation Union) Invasive Species Specialist Group considers Lates niloticus one of the world's 100 worst invasive species. The state of Queensland in Australia levies heavy fines on anyone found in possession of a living Nile perch, since it competes directly with the native Barramundi, which is similar but does not reach the same size as the Nile perch.
Kaluga
The Kaluga (Huso dauricus) is a large predatory sturgeon found in the Amur River basin. Also known as the River Beluga, they are claimed to be the largest freshwater fish in the world, with a maximum size of at least 1,000 kg (2,205 lb) and 5.6 m (18.6 ft). Like the slightly larger Beluga, it spends part of its life in saltwater.The Kaluga is one of the biggest of the sturgeon family.
Kaluga caviar comes from the Kaluga "River Beluga" sturgeon.
Giant Barb
The giant barb or Siamese giant carp, Catlocarpio siamensis (Thai: กระโห้ or กะมัน), is the largest species of carp in the world. These migratory fish are found only in the Mae Klong, Mekong and Chao Phraya river basins. This fish is a desirable food fish, which may have caused a serious decline in its numbers.
They are usually seen in the big pools along the edges of large rivers, but will seasonally enter smaller canals, floodplains and flooded forests. Young barbs are usually found in smaller tributaries and swamps, but can acclimatize to living in ponds, canals and swamps. The fish generally live in pairs.
These are migratory fish, swimming to favorable areas for feeding and breeding in different parts of the year.
These slow-moving fish subsist on algae, phytoplankton and fruits of inundated terrestrial plants, rarely (if ever) feeding on active animals. In the lower Mekong basin, young giant barbs have been reported as occurring primarily in October.
Mekong Giant Catfish
The Mekong giant catfish, Pangasianodon gigas, is a species of catfish (order Siluriformes) in the shark catfish family (family Pangasiidae), native to the Mekong basin in Southeast Asia.
The Mekong giant catfish is perhaps the most interesting and most threatened species in the Mekong river. For this reason conservationists have chosen it as a sort of “flagship” species to promote conservation on the Mekong (Hogan et al. 2004, MGCCG, 2005). With recorded sizes of up to 10.5 ft (3.2 m) and 660 lb (300 kg), the Mekong’s giant catfish currently holds the Guinness Book of World Record’s position for the world’s largest freshwater fish (Mydans et al. 2005, Hogan et al. 2004, Hogan et al. 2007). Although research projects are currently on going, relatively little is known about this species.
Historically the fish has a natural range that reaches from the lower Mekong in Vietnam (above the tidally influenced brackish water of the river’s delta) all the way to the northern reaches of the river in the Yunnan province of China, spanning almost the entire 4,800 km length of the river (Lopez et al. 2007, Hogan et al. 2007). Due to threats which will be discussed below, this species no longer inhabits the majority of its original habitat, now believed to only exist are small, isolated populations in the middle Mekong region (Hogan et al. 2004). Fish congregate during the beginning of the rainy season and migrate up-stream to spawn (Hogan et al. 2004). They live primarily in the main channel of the river where the water depth is over 10 m (Mattson et al. 2002) while researchers, fishermen and officials have found this species in the Tonle Sap river and lake in Cambodia (also a UNESCO Biosphere reserve). In the past fishermen have reported the fish in a number of the Mekong’s tributaries, however today essentially no sightings are reported outside of the main Mekong river channel and the Tonle Sap region.
In infancy, this species feeds on zooplankton in the river and is known to be cannibalistic (Pholprasith, 1983 as cited in Mattson et al. 2002). After approximately one year, the fish becomes herbivorous, feeding on filamentous algae probably ingesting larvae and periphyton accidentally (Pookaswan, 1989 and Jensen, 1997 as cited in Mattson et al. 2002). The fish likely obtain their food from algae growing on submerged rocky surfaces, as they do not have any sort of dentition (Pholprasith, 1983 as cited in Mattson et al. 2002).
Megalodon
The megalodon, Carcharodon or Carcharocles megalodon (pronounced /ˈmɛɡələdɒn/MEG-ə-lə-don, "big tooth" in Greek, from μέγας and ὀδούς) is an extinct megatoothed shark that existed in prehistoric times, from the Oligocene to Pleistocene epochs, approximately 25 to 1.5 million years ago.
C. megalodon may have been the largest and most powerful macro-predatory fish that ever lived. Fossil remains of C. megalodon indicate that it possibly approached a maximum of around 20.3 metres (67 ft) in length. C. megalodon has been assigned to the order Lamniformes but its phylogeny is disputed. Scientists suggest that C. megalodon looked like a stockier version of the great white shark, Carcharodon carcharias, in life. Fossil evidence confirms that C. megalodon had a cosmopolitan distribution. C. megalodon was a super-predator, and bite marks on fossil bones of its victims indicate that it preyed upon large marine animals.
According to Renaissance accounts, huge, triangular fossil teeth often found embedded in rocky formations were once believed to be petrified tongues, or glossopetrae, of the dragons and snakes. This interpretation was corrected in 1667 by a Danish naturalist, Nicolaus Steno, who recognized them as ancient shark teeth (and famously produced a depiction of a shark's head bearing such teeth). He mentioned his findings in a book, The Head of a Shark Dissected, which also contained an illustration of a C. megalodon tooth, previously considered to be a tongue stone.
A Swiss naturalist, Louis Agassiz, gave this shark its scientific name, Carcharodon megalodon, in 1835, in his research work Recherches sur les poissons fossiles (Research on fossil fish), which he completed in 1843. The teeth of the C. megalodon are morphologically similar to the teeth of the great white shark. On the basis of this observation, Agassiz assigned the genus Carcharodon to the megalodon. While the scientific name is C. megalodon, it is often informally dubbed the megatooth shark or giant white shark or even monster shark.
Giant Sea Bass
The giant sea bass (Stereolepis gigas) is a fish native to the northern Pacific Ocean. Considering its conspicuous size and its curious nature, it is surprising that relatively little is known about its biology or behavior.
There are published reports of giant sea bass reaching a size of 2.5 m (8.2 feet) and a weight of up to 255 kg (562 lbs). However in Charles F. Holder's book The Channels Islands published in 1910, the author claims specimens taken from the Gulf of California attained 800 pounds (360 kg). In the eastern Pacific its range is from Humboldt Bay, California to the Gulf of California, Mexico, most common from Point Conception southward. In the western Pacific it is found in the sea around Japan. It usually stays in relatively shallow water, near kelp forests, drop offs or rocky bottoms.
Giant sea bass were once a relatively common inhabitant of Southern California waters, yet in the 1980s it was facing the threat of local extinction off the California coast. Beginning in the late 1800s, the species supported both a commercial fishery taking hundreds of thousands of pounds annually, and a sport fishery that also landed hundreds of fish each year. Spear fishermen also exploited the giant sea bass, first as free divers, and then after the mid 1950s using scuba gear. Often the divers would target the species when they moved into shallow water during the summer months to spawn. By the late 1970s, biologists with the California State Department of Fish and Game, recognized that the local population of giant sea bass was in serious trouble. Actions were taken, resulting in protection from commercial and sport fishing that went into effect in 1982. Yet for almost two decades encounters with giant sea bass were scarce. The giant sea bass reproduces slowly with a population doubling time of more than 14 years and is still listed as critically endangered.
Due to its size and carnivorous nature it can pose some threat to humans.
Whale Shark
The whale shark, Rhincodon typus, is a slow-moving filter feeding shark, the largest living fish species. The largest confirmed individual was 12.65 metres (41.50 ft) in length. The heaviest weighed more than 36 tonnes (79,000 lb), but unconfirmed claims report considerably larger whale sharks. This distinctively-marked fish is the only member of its genus Rhincodon and its family, Rhincodontidae (called Rhinodontes before 1984), which belongs to the subclass Elasmobranchii in the class Chondrichthyes. The shark is found in tropical and warm oceans, lives in the open sea with a lifespan of about 70 years. The species originated about 60 million years ago. Although whale sharks have very large mouths, they feed mainly, though not exclusively, on plankton, microscopic plants and animals, although the BBC program Planet Earth filmed a whale shark feeding on a school of small fish.
The species was distinguished in April 1828, following the harpooning of a 4.6-metre (15.1 ft) specimen in Table Bay, South Africa. Andrew Smith, a military doctor associated with British troops stationed in Cape Town described it the following year. He published a more detailed description in 1849. The name "whale shark" comes from the fish's physiology; as large as a whale, it too is a filter feeder.
As a filter feeder it has a capacious mouth which can be up to 1.5 metres (4.9 ft) wide and can contain between 300 and 350 rows of tiny teeth. It has five large pairs of gills. Two small eyes are located towards the front of the shark's wide, flat head. The body is mostly grey with a white belly; three prominent ridges run along each side of the animal and the skin is marked with a "checkerboard" of pale yellow spots and stripes. These spots are unique to each individual and are useful for counting populations. Its skin can be up to 10 centimetres (3.9 in) thick. The shark has a pair each of dorsal fins and pectoral fins. Juveniles' tails have a larger upper than lower fin while the adult tail becomes semi-lunate (crescent-shaped). Spiracles are just behind the eyes.
Sturgeon
Sturgeon is the common name used for some 26 species of fish in the family Acipenseridae, including the genera Acipenser, Huso, Scaphirhynchus and Pseudoscaphirhynchus. The term includes over 20 species commonly referred to as sturgeon and several closely related species that have distinct common names, notably sterlet, kaluga and beluga. Collectively, the family is also known as the True Sturgeons. Sturgeon is sometimes used more exclusively to refer to the species in the two best-known genera; Acipenser and Huso.
One of the oldest families of bony fish in existence, sturgeon are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia and North America. They are distinctive for their elongated bodies, lack of scales, and occasional great size: Sturgeons ranging from 7–12 feet (2-3½ m) in length are common, and some species grow up to 18 feet (5.5 m). Most sturgeons are anadromous bottom-feeders, spawning upstream and feeding in river deltas and estuaries. While some are entirely freshwater, very few venture into the open ocean beyond near coastal areas.
Several species of sturgeons are harvested for their roe, which is made into caviar—a luxury good which makes some sturgeons pound for pound the most valuable of all harvested fish. Because they are slow-growing and mature very late in life, they are particularly vulnerable to exploitation and to other threats, including pollution and habitat fragmentation. Most species of sturgeons are currently considered vulnerable, endangered or critically endangered.
Sturgeon and related paddlefish appeared in the fossil record approximately 200 million years ago, making them among the most ancient of actinopterygian fishes. In that time they have undergone remarkably little morphological change, indicating that their evolution has been exceptionally slow and earning them informal status as living fossils. This is explained in part by the long inter-generation time, tolerance for wide ranges of temperature and salinity, lack of predators due to size, and the abundance of prey items in the benthic environment.
Along with other members of the Chondrostei and the Acipenseriformes order, sturgeon are primarily cartilaginous, lack a vertebral centrum, and are covered with bony plates called scutes rather than scales. They also have four barbels—tactile organs that precede their toothless mouth and are dragged along often murky river bottoms. Sturgeon are distinctly and immediately recognizable for their elongated bodies, flattened rostra, distinctive scutes and barbels, and elongated upper tail lobes.
They are primarily benthic feeders. With their projecting wedgeshaped snout they stir up the soft bottom, and use the barbels to detect shells, crustaceans and small fish, on which they feed. Having no teeth, they are unable to seize prey, though larger specimens can swallow very large prey items, including whole salmon.
Leedsichthys
Leedsichthys was a giant pachycormid (an extinct group of Mesozoic bony fish) that lived in the oceans of the Middle Jurassic period. The closest living relative of the pachycormids is the bowfin, Amia calva, but this is only very distantly related.
The name Leedsichthys means "Leeds' fish", after the fossil collector Alfred Nicholson Leeds, who discovered it before 1886 near Peterborough, England. The fossils found by Leeds gave the fish the species epithet problematicus, because the remains were so fragmented that they were extremely hard to recognize and interpret.
Unfortunately, although the remains of over seventy individuals have been found, these are usually partial and fragmentary. This has made it difficult to estimate its length. Arthur Smith Woodward, who described the specimen in 1889, estimated it to be 30 feet (around 9 metres) long, by comparing the tail of Leedsichthys with another pachycormid, Hypsocormus. In 1986, Martill compared the bones of Leedsichthys to a pachycormid that he had recently discovered, but the unusual proportions of that specimen gave a wide range of possible sizes. More recent estimates, from documentation of historical finds and the excavation of the most complete specimen ever from the Star Pit near Whittlesey, Peterborough, support Smith Woodward's figures of between 30 and 33 feet (9 and 10 meters). Recent work on growth ring structures within the remains of Leedsichthys have also indicated that it would have taken 21-25 years to reach these lengths, and isolated elements from other specimens indicate that a maximum size of just over 53 feet (16 metres) is not unreasonable.
Xiphactinus
Xiphactinus (from Latin and Greek for "sword-ray") was a large, 4.5 to 5 m (15 to 20 feet) long predatory bony fish that lived in the Western Interior Sea, over what is now the middle of North America, during the Late Cretaceous. When alive, the fish would have resembled a gargantuan, fanged tarpon (to which it was, however, not related). The Portheus molossus described by Cope is a junior synonym of the species. Skeletal remains of Xiphactinus have come from Kansas, Alabama, and Georgia in the United States, as well as Europe and Australia.
Xiphactinus audax was a voracious predator fish. At least a dozen specimens have been collected with the remains of large, undigested or partially digested prey in their stomachs. In particular, one 13 feet (4.0 m) fossil specimen was collected by George F. Sternberg with another, nearly perfectly preserved 6 feet (1.8 m) long ichthyodectid Gillicus arcuatus, inside of it. The larger fish apparently died soon after eating its prey, most likely due to the smaller fish prey struggling and rupturing an organ as it was being swallowed. This fossil can be seen at the Sternberg Museum of Natural History in Hays, Kansas.
Goliath Grouper
The goliath grouper is found primarily in shallow tropical waters among coral and artificial reefs at depths of up to 165 feet (50 m). Their range includes the Florida Keys, the Bahamas, most of the Caribbean, and practically all of the Brazilian coast, where they are known as mero. On some occasions it is caught in New England off Maine and Massachusetts but it is not that common. In the eastern Atlantic Ocean, it occurs from Congo to Senegal.
Young grouper may live in brackish estuaries, canals, and mangrove swamps, unusual behavior among grouper.
