Sturgeon Fish

Sturgeon, any from about 29 species of fish belonging to the family Acipenseridae (subclass Chondrostei) that are native to temperate waters of the Northern Hemisphere. The majority of species live in the ocean and migrate to rivers to breed in the spring or summer (perhaps once every few years); a few others are only found in freshwater. Eggs from a variety of species are used to make caviar. The majority of species are classified as critically endangered.

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In the Acipenseriformes order, sturgeons are connected to paddlefish (family Polyodontidae). Sturgeon fossils first emerged in strata from the Middle Jurassic period (about 174 million to 163.5 million years ago). Sturgeons are assumed to have evolved from the palaeonisciformes, a group of fish that first appeared towards the end of the Silurian Period (about 419 million years ago). Sturgeons can be found in the genera Acipenser, Huso, Scaphirhynchus, and Pseudoscaphirhynchus.

Scientific Classification of Sturgeon 

Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Acipenseriformes

Family: Acipenseridae

Physical Characteristics 

Among the bony fishes, sturgeons maintain a number of primitive characteristics. They are uncommon among bony fishes, along with other members of the subfamily Chondrostei, because their skeletons are almost completely cartilaginous. The cartilaginous skeleton, on the other hand, is a derived characteristic; sturgeon predecessors had bony skeletons. They also lack vertebral centra and are largely coated with five rows of scutes instead of scales on the sides. They also have four barbels, which are sensory organs that come before their toothless, broad mouths. They navigate their riverine surroundings by dragging their barbels around gravel or muddy substrate slightly off the bottom. Lengthened bodies, flattened rostra, unique scutes and barbels, and elongated upper tail lobes distinguish sturgeon. Although the ray-like elements in the webbing of the fins can be seen externally, the skeletal support for the paired fins of ray-finned fish lies inside the body wall.

Sturgeons are among the largest fish; some beluga (Huso huso) in the Caspian Sea have been reported to reach lengths of over 5.5 metres (18 feet) and weights of over 2000 kilogram (4400 pounds), while Kaluga (H. dauricus) in the Amur River have reached similar lengths and weights of over 1,000 kilogrammes (2,200 pounds). They are also among the fish with the longest lifespans, with some lasting well over 100 years and reaching sexual maturity at the age of 20 or more. Sturgeon are particularly vulnerable to overfishing due to their slow development and reproductive rates, as well as the high value placed on mature, egg-bearing females. Sturgeons are polyploid, with four, eight, or sixteen sets of chromosomes in some species.

The Life Cycle of Sturgeon 

Sturgeons are late-maturing, long-lived fish. Their usual lifespan is 50 to 60 years, and they do not have their first spawn until they are 15 to 20 years old. Because they require special conditions, sturgeons are broadcast spawners and do not spawn every year. Due to variable environmental conditions, such as the right photoperiod in spring, clear water with shallow rock or gravel bottom where the eggs can adhere, and proper water temperature and flow for oxygenation of the eggs, those needs may or may not be reached every year. Although a single female can produce 100,000 to 3 million eggs, not all of them will be fertilised. When the fertilised eggs come into touch with the bottom substrate, they become sticky and stick to it. The embryos take eight to fifteen days to grow into larval fish. They are completely reliant on their yolk sacs for nutrition throughout this time. The larvae are carried downstream by river currents into backwater areas like oxbows and sloughs, where the free-swimming fry feed on insect larvae and crustacea for their first year. They attain 18 to 20 cm (7.1 to 7.9 in) in length during their first year of development and move back into the swift-flowing currents of the main stem river.

Distribution of Sturgeon

From Scandinavia to the Mediterranean, the common Old World sturgeon (Acipenser sturio) can be found. Along the east coast of North America, there is a very similar, closely related variety that some authors regard to be a different species (A. oxyrhynchus). These fishes can grow up to 3 metres (10 feet) in length and weigh up to 227 kilos (500 pounds).

The Russian sturgeon, A. gueldenstaedtii, is one of the most valuable species found in Russia's rivers, and it may be found from Lake Baikal eastward. It's roughly the same size as a typical sturgeon and can be found in rivers that flow into the Black and Caspian seas. The sterlet (A. ruthenus) is a smaller species that lives in the Black and Caspian seas and is a desirable food fish that grows to be approximately 0.9 metres (3 feet) long. The stellate, or star, sturgeon, A. stellatus, is found in the Black and Caspian oceans, as well as the Sea of Azov's rivers. It, like the sterlet, has a long pointed snout, and its flesh, caviar, and isinglass are highly prized.

The Russian sturgeon, A. gueldenstaedtii, is one of the most valuable species found in Russia's rivers, and it may be found from Lake Baikal eastward. It's roughly the same size as a typical sturgeon and can be found in rivers that flow into the Black and Caspian seas. The sterlet (A. ruthenus) is a smaller species that lives in the Black and Caspian seas and is a desirable food fish that grows to be approximately 0.9 metres (3 feet) long. The stellate, or star, sturgeon, A. stellatus, is found in the Black and Caspian oceans, as well as the Sea of Azov's rivers. It, like the sterlet, has a long pointed snout, and its flesh, caviar, and isinglass are highly prized.

The North American lake, or rock, sturgeon (A. fulvescens) is found in the Mississippi River valley, the Great Lakes, and Canada, and can weigh up to 90 kg (200 pounds). The white, Oregon, or Sacramento sturgeon (A. transmontanus) is the largest of the North American sturgeons, weighing up to 820 kg. It lives along the Pacific coast (1,800 pounds).

The genus Scaphirhynchus, or shovelnose sturgeon, belongs to the Acipenseridae family, and three species are differentiated by their long, broad, flat snouts. The Mississippi River and its tributaries are home to these fish.

Types of Sturgeon 

There are 29 types of sturgeon species in which some of them have been discussed below:

Beluga Sturgeon

The Beluga Sturgeon is the world's largest sturgeon and one of the world's largest bony fishes, as well as one of the few sturgeon species that actively eat other fishes and one of the world's largest predatory fishes. Although adult beluga sturgeon have few natural predators, human fishing pressure has been intense. Unfortunately, the beluga sturgeon is cursed with producing some of the world's most sought-after caviar. The term "caviar" refers to fish eggs, and beluga sturgeon lay millions of them. Large individuals have been known to carry hundreds of pounds of caviar, with beluga sturgeon caviar fetching up to US$3500 per pound (US$8000 per kilogramme).

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This enormous value, along with the large number of eggs that a single beluga sturgeon can lay, makes the beluga sturgeon the most valuable fish in the world for anglers. That value could spell the end for the beluga sturgeon. The beluga sturgeon is easy to catch when ready to spawn upriver, either by harpoon or in nets. Despite the fact that it has been granted limited legal protection in several locations, its population is declining everywhere it resides. It has vanished entirely from some seas and rivers where it once thrived, and biologists believe it is highly endangered. To put it another way, it is extremely vulnerable to extinction throughout its whole range. Without additional protection and enforcement of present efforts, one of the world's biggest sturgeon and most intriguing species may perish forever.

White Sturgeon

The White sturgeon is the biggest fish in North America. The record-breaking fish was captured in 1898 and weighed around 1,500 pounds. Sturgeon skin is coated in bone plates called scutes instead of scales, which can be particularly sharp on young sturgeon. The skeletons of sturgeons, like sharks, are constructed of cartilage rather than bone.

When they're young, sturgeon devour molluscs and tiny invertebrates with their suction cup-like mouth. They are mostly fish eaters as adults.

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White sturgeon are born in freshwater and, while they can enter seawater to complete their life cycle, it is not essential. When it comes to spawning, white sturgeon rely on water temperature, day length, and the intensity of the water current. Males and females both participate in broadcast spawning, which involves releasing sperm and eggs into the water current at the same time. Fertilized eggs stick to the river bottom as soon as they come into touch with it. Females can discharge up to 3 million eggs. White sturgeon can live for over a century and continue to grow throughout their lives.

Lake Sturgeon 

The lake sturgeon (Acipenser fulvescens) is a temperate fish that can be found in North American freshwater systems from Hudson Bay to the Mississippi River drainages. Lake sturgeon prefer sand or gravel habitat along the riverbed or lake's bottom. Populations are falling across the species' native range, and 19 of the species' 20 states are categorised as threatened. Overharvesting and habitat loss due to dam construction are two factors contributing to the decline.

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Sturgeon in lakes are slow-moving fish that move up rivers to spawn during the spawning season. Between the ages of 20 and 26, female sturgeons spawn. Males reach sexual maturity between the ages of 8 and 12. The average lifespan of a male sturgeon is 50 to 60 years, although a female sturgeon can live up to 150 years.

Sterlet Sturgeon 

The sterlet (Acipenser ruthenus) is a small sturgeon native to Eurasia's main rivers, including those that run into the Black Sea, Azov Sea, and the Caspian Sea, as well as rivers in Siberia as far east as the Yenisei. Anadromous populations (those that migrate between fresh and saltwater) have become extinct.

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The sterlet has plummeted across its native range due to overfishing (for the flesh, caviar, and isinglass), pollution, and dams, and is now classified as vulnerable by the IUCN. There are continuing restocking operations, and it has been introduced to several areas outside of its natural range, but they have not proven to be self-sustaining. Today, aquaculture sterlets account for the majority of international trade.

Conservation Status

The flesh, eggs, and swim bladder of sturgeons are prized. Fresh, pickled, or smoked flesh is available. Caviar is made out of the eggs that are stripped from fertile females and then released. Isinglass, an extremely pure form of gelatin used for numerous industrial purposes, is made from the inner membrane of the sturgeon's swim bladder. Southern Russia, Ukraine, and Iran have the greatest commercial sturgeon fisheries, while the sector is also active in the United States and western Europe.

Sturgeons are easily overfished, with more than half of the surviving species listed as severely endangered by the International Union for Conservation of Nature and Natural Resources (IUCN). The Chinese sturgeon is considered the most endangered fish, with a population drop of roughly 98 percent between 1973 and 2010. Water pollution in the Yangtze and dam building that has barred access to or changed the flow regime near the sturgeon's remaining spawning grounds have been linked to the species' decline. Because there was no evidence of reproduction in the wild in 2013 and 2014, some researchers believe the species is on the verge of extinction.

Interesting Facts About Sturgeon 

• The common term for the 27 species of fish in the Acipenseridae family is sturgeon.

• Sturgeons with a length of 2 to 3.5 metres (7–12 feet) are common, with some species reaching 5.5 metres (18 feet).

• The majority of sturgeons are bottom-feeding anadromous fish that migrate upstream to spawn but spend most of their life feeding in river deltas and estuaries.

• Almost all caviar is derived from the remains of dead fish. On the Caspian, fishermen wait until a mature female sturgeon (at least 10 years old) is ready to go upstream and lay their eggs before catching them. The sturgeon will be captured and transported to a huge boat where workers will slit her open and extract her eggs. The caviar is cleaned and packaged to avoid spoiling; the rest of the fish is sold for flesh.

• The name "caviar" comes from the Persian khavyar, which comes from the word khaya, which means "egg." In 1591, the word was first printed in English.

• Caviar can be heard. When you brush two fish eggs together, you can hear the friction. The sound of good caviar is distinct and similar to a cat's purr.

• Despite having survived on Earth for millions of years, sturgeon are now threatened by overfishing and habitat disruption.

• Their evolution may be traced back to the Triassic period, which lasted between 245 and 208 million years.

• Over 85 percent of sturgeon species are classed as highly endangered by the IUCN, making them the most critically endangered category of species.

• A sturgeon is an emblem on Saint Amalberga of Temse's coat of arms in art.

Sturgeons are known for their eggs, known as caviar, which lay in the fresh waters of the northern hemisphere. Sturgeons can reach a length of 6 metres, weigh over 100 kilograms, and live for over a century. Previously, females were slaughtered to take the eggs from their abdomens, but modern techniques allow the eggs to be gathered without the fish being killed. Because the species is endangered, sturgeon aquaculture has grown in popularity in recent decades.