Sturgeon in the context of Benthos

Louisiana (French: Louisiane [lwizjan]; Spanish: Luisiana [lwiˈsjana]; Louisiana Creole: Lwizyàn) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25th in population, with roughly 4.6 million residents. Reflecting its French heritage, Louisiana is the only U.S. state with political subdivisions termed parishes, which are equivalent to counties, making it one of only two U.S. states not subdivided into counties (the other being Alaska and its boroughs). Baton Rouge is the state's capital, and New Orleans, a French Louisiana region, is its most populous city with a population of about 363,000 people. Louisiana has a coastline with the Gulf of Mexico to the south; a large part of its eastern boundary is demarcated by the Mississippi River and the mouth of the Mississippi or delta defines much of its lower topography.

Much of Louisiana's lands were formed from sediment washed down the Mississippi River, leaving enormous deltas and vast areas of coastal marsh and swamp. These contain a rich southern biota, including birds such as ibises and egrets, many species of tree frogs—such as the state-recognized American green tree frog—and fish such as sturgeon and paddlefish. More elevated areas, particularly in the north, contain a wide variety of ecosystems such as tallgrass prairie, longleaf pine forest and wet savannas; these support an exceptionally large number of plant species, including many species of terrestrial orchids and carnivorous plants. Over half the state is forested.

The Amur River (Russian: река Амур) or Heilong River (simplified Chinese: 黑龙江; traditional Chinese: 黑龍江) is a perennial river in Northeast Asia, forming the natural border between the Russian Far East and Northeast China (historically the Outer and Inner Manchuria). The Amur proper is 2,824 km (1,755 mi) long, and has a drainage basin of 1,855,000 km (716,000 sq mi). If including its main stem tributary, the Argun, the Amur is 4,444 km (2,761 mi) long, making it the world's tenth longest river.

The Amur is an important river for the aquatic fauna of Northeast Asia. The river basin is home to a variety of large predatory fish such as northern snakehead, Amur pike, taimen, Amur catfish, predatory carp and yellowcheek, as well as several species of trout and anadromous salmonids. The largest fish species in the Amur is the kaluga, a sturgeon that is one of the largest freshwater fish in the world, attaining a length as great as 5.6 m (18 ft). The Amur is also home to the northernmost populations of the Amur softshell turtle and Indian lotus.

Roe, (/roʊ/ ROH) or hard roe, is the fully ripe internal egg masses in the ovaries, or the released external egg masses, of fish and certain marine animals such as shrimp, scallop, sea urchins and squid. As a seafood, roe is used both as a cooked ingredient in many dishes, and as a raw ingredient for delicacies such as caviar.

The roe of marine animals, such as the roe of lumpsucker, hake, mullet, salmon, Atlantic bonito, mackerel, squid, and cuttlefish are especially rich sources of omega-3 fatty acids, but omega-3s are present in all fish roe. Also, a significant amount of vitamin B₁₂ is among the nutrients present in fish roes.

Caviar or caviare is a food consisting of salt-cured roe of the family Acipenseridae. Caviar is considered a delicacy and is eaten as a garnish or spread. Traditionally, the term caviar refers only to roe from wild sturgeon in the Caspian Sea and Black Sea (beluga, ossetra and sevruga caviars). The term caviar can also describe the roe of other species of sturgeon or other fish such as paddlefish, salmon, steelhead, trout, lumpfish, whitefish, or carp.

The roe can be fresh (non-pasteurized) or pasteurized, which reduces its culinary and economic value.

In fish anatomy and turtle anatomy, a barbel is a slender, whisker-like sensory organ near the mouth (sometimes called whiskers or tendrils). Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some species of shark such as the sawshark. Barbels house the taste buds of such fish and are used to search for food in murky water.

The word barbel comes from Latin barbula 'little beard'. Barbels are sometimes erroneously referred to as barbs, which are found in bird feathers for flight.

A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages. The term scale derives from the Old French escale, meaning a shell pod or husk.

Scales vary enormously in size, shape, structure, and extent, ranging from strong and rigid armour plates in fishes such as shrimpfishes and boxfishes, to microscopic or absent in fishes such as eels and anglerfishes. The morphology of a scale can be used to identify the species of fish it came from. Scales originated within the jawless ostracoderms, ancestors to all jawed fishes today.Most bony fishes are covered with the cycloid scales of salmon and carp, or the ctenoid scales of perch, or the ganoid scales of sturgeons and gars. Cartilaginous fishes (sharks and rays) are covered with placoid scales. Some species are covered instead by scutes, and others have no outer covering on part or all of the skin.

Paddlefish are members of the ray-finned fish family Polyodontidae, which belong to the basal order Acipenseriformes, one of two living groups within this order alongside sturgeons (Acipenseridae). Their most distinctive feature is an elongated rostrum that enhances electroreception, allowing them to detect prey in murky water. Both recent and fossil paddlefish occur exclusively in North America and Eastern Asia.

Eight species are known, six of which are prehistoric and only known from fossils—five from North America and one from China. Of the two species to have survived until modern times, the American paddlefish (Polyodon spathula) inhabits the Mississippi River basin in the United States, while the now extinct Chinese paddlefish (Psephurus gladius, also known as the "Chinese swordfish") inhabited the Yangtze and Yellow River basins in China. The earliest known paddlefish fossil, Protopsephurus, dates to approximately 120 million years ago during the Early Cretaceous epoch in China.

Electroreception and electrogenesis are the closely related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes, such as the electric eel, to stun prey. The capabilities are found almost exclusively in aquatic or amphibious animals, since water is a much better conductor of electricity than air. In passive electrolocation, objects such as prey are detected by sensing the electric fields they create. In active electrolocation, fish generate a weak electric field and sense the different distortions of that field created by objects that conduct or resist electricity. Active electrolocation is practised by two groups of weakly electric fish, the order Gymnotiformes (knifefishes) and family Mormyridae (elephantfishes), and by the monotypic genus Gymnarchus (African knifefish). An electric fish generates an electric field using an electric organ, modified from muscles in its tail. The field is called weak if it is only enough to detect prey, and strong if it is powerful enough to stun or kill. The field may be in brief pulses, as in the elephantfishes, or a continuous wave, as in the knifefishes. Some strongly electric fish, such as the electric eel, locate prey by generating a weak electric field, and then discharge their electric organs strongly to stun the prey; other strongly electric fish, such as the electric ray, electrolocate passively. The stargazers are unique in being strongly electric but not using electrolocation.

The electroreceptive ampullae of Lorenzini evolved early in the history of the vertebrates; they are found in both cartilaginous fishes such as sharks, and in bony fishes such as coelacanths and sturgeons, and must therefore be ancient. Most bony fishes have secondarily lost their ampullae of Lorenzini, but other non-homologous electroreceptors have repeatedly evolved, including in two groups of mammals, the monotremes (platypus and echidnas) and the cetaceans (Guiana dolphin).

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 basal 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.

Polypodium hydriforme is a species of cnidarian that parasitizes in the eggs of sturgeon and similar fishes (Acipenseridae and Polyodontidae). It is one of few animals that lives inside the cells of other animals. P. hydriforme is the only species in the class Polypodiozoa.

The kaluga (Sinosturio dauricus), also known as the river beluga, is a large predatory sturgeon found in the Amur River basin from Russia to China and near Hokkaido in Japan. With a maximum size of at least 1,000 kg (2,205 lb) and 5.6 m (18 ft), the kaluga is one of the biggest of the sturgeon family. Unike the slightly larger beluga, this fish has five major rows of dermal scutes and feeds on salmon and other fish in the Amur with nail-like teeth in its jaws. They have grey-green to black backs with a yellowish green-white underbelly. Akin to the beluga, it spends part of its life in salt water, being semi-anadromous.

The kaluga has been hunted to near extinction for its valuable roe. Despite constant anti-poaching patrols, poachers still continue to catch the fish. In Russia, illegally fishing for kaluga anywhere on the Amur River is a felony punishable by law. However, kalugas are known to have an aggressive nature, and instances of them toppling fishing boats and drowning fishermen have been reported, although no concrete evidence exists of them assaulting or hunting people.

Isinglass (/ˈaɪzɪŋɡlæs, -ɡlɑːs/ EYE-zing-gla(h)ss) is a form of collagen obtained from the dried swim bladders of fish. The English word origin is from the obsolete Dutch huizenblaas – huizen is a kind of sturgeon, and blaas is a bladder, or German Hausenblase, meaning essentially the same. The bladders, once removed from the fish, processed, and dried, are formed into various shapes for use.

It is used mainly for the clarification or fining of some beer and wine. It can also be cooked into a paste for specialised gluing purposes.