ACIPENSER (STURGEON)

Contents hide

1) Classification of Acipenser (Sturgeon)

2) Geographical distribution

3) Habit and habitat

4) General Characteristics of Acipenser (Sturgeon)

5) Ecological Importance of Acipenser:

6) Conservation Status of Acipenser:

7) Special features

8) Identification

Classification of Acipenser (Sturgeon)

Phylum :- Chordata (Dorsal tubular nerve cord, notochord and gill-slits present.)
Group :- Craniata (Cranium with brain present.)
Sub phylum :- Vertebrata (Vertebral column present.)
Division :- Gnathostomata (Jaws and paired appendages present.)
Super Class :- Pisces (Paired fins, gills and skin with scales.)
Class :- Osteichthyes (Bony fishes. Skin contains dermal scales. Paired lateral fins present. Gills, air bladder present. Cleavage meroblastic.)
Sub-Class :- Palaeopterygii (Ancient fishes. Dermal fin rays numerous. Clavicles present. Nostrils free from mouth cavity.)
Order :- Chondrostei (Body covered with bony scutes or naked. Tail heterocercal. Skeleton largely cartilaginous. Notochord unsegmented. Vertebrae acentrous.)
Family :- Acipenseridae
Genus :- Acipenser

Geographical distribution

Acipenser is abundantly distributed in Black Sea, Sea of Azor, Caspian Sea, in rivers of Europe, China and on the Atlantic coasts of North America. Lower Jurassic to Recent.

Habit and habitat

Acipenser is a marine, bottom-dwelling fish. They stir the bottom with their snout in search of small invertebrates, worms, molluscs, small fishes and aquatic plants for feeding. They are migratory fishes, anadromous, ascending rivers for spawning.

General Characteristics of Acipenser (Sturgeon)

Commonly known as Sturgeon, measuring 2 to 4 metres in length.
Body is elongated, cylindrical and bulky and is divided into head, trunk and tail.
In the body scales are represented by five longitudinal rows of bony scutes with small intervening ossification.
Each plate is provided with a pointed and partly-conical and backwardly-directed spine.
Head is produced ahead as a long flattened rostrum or snout.
It contains a pair of eyes and functional spiracles.
Well developed rostrum with 4 ventral barbels is used to stir the bottom mud in search of small invertebrates.
Barbels detect the food and direct the rostrum to dig the mud.
Food is sucked through the ventral surface of the snout.
Mouth is ventral and transverse and without teeth in jaws.
Narrow crevices between scutes contain dermal denticles like those of Elasmobranchi.
Spiracles open and skeleton cartilaginous.
Operculum represented by opercular bone.
Dorsal fin single and posteriorly placed.
Paired fins are pectoral and pelvic fins.
Ventral fin opposite to dorsal fin. Caudal fin bilobed.
2 to 3 million eggs are laid by a single fish during the breeding season. The air bladder is smooth, oval and contains ciliated epithelium.

Acipenser is a genus of fish within the family Acipenseridae, commonly referred to as sturgeons. These ancient fish are often called “living fossils” due to their evolutionary history, which dates back over 200 million years. They are primarily found in freshwater and coastal ecosystems in the Northern Hemisphere, including rivers, lakes, and estuaries. Sturgeons are known for their large size, long lifespans, and importance in commercial fisheries for their meat and caviar (roe).

Ecological Importance of Acipenser:

Nutrient Cycling:
- Sturgeons contribute to nutrient cycling by foraging at the bottom of rivers and lakes, stirring up sediments, and redistributing nutrients in aquatic ecosystems.
Trophic Role:
- As opportunistic feeders, they consume a variety of benthic organisms, such as mollusks, crustaceans, and small fish, helping regulate these populations.
- Sturgeons are also prey for larger aquatic predators, including seals and large fish species, playing a critical role in the food web.
Indicator Species:
- The presence and health of sturgeon populations often indicate the overall health of freshwater and estuarine ecosystems, as they are sensitive to pollution and habitat changes.

Conservation Status of Acipenser:

Global Status:
- Most sturgeon species are listed as Endangered or Critically Endangered on the IUCN Red List, making them one of the most threatened groups of animals in the world.
Threats:
- Overfishing: High demand for sturgeon caviar has led to significant overharvesting, pushing many species to the brink of extinction.
- Habitat Loss: Dams, river channelization, and habitat degradation disrupt sturgeon migration and spawning, reducing their reproductive success.
- Pollution: Agricultural and industrial pollutants degrade water quality, affecting sturgeon health and habitat.
Conservation Efforts:
- Fishing Regulations: Many countries have imposed bans or strict regulations on sturgeon fishing and caviar trade.
- Restoration Programs: Conservationists are restoring spawning habitats and implementing captive breeding and restocking programs.
- International Agreements: Sturgeons are protected under the Convention on International Trade in Endangered Species (CITES) to control and monitor their trade.

Special features

Primitive Characteristics:
- Sturgeons are among the most primitive ray-finned fish, with features such as cartilaginous skeletons, lack of scales, and a heterocercal (asymmetrical) tail.
Long Lifespan:
- Sturgeons are exceptionally long-lived, with some species, like the beluga sturgeon (Huso huso), living over 100 years.
Anadromous Behavior:
- Many sturgeon species are anadromous, meaning they migrate from saltwater to freshwater to spawn, similar to salmon.
Large Size:
- Sturgeons are among the largest freshwater fish, with species like the beluga sturgeon reaching lengths of over 20 feet (6 meters) and weights of up to 3,500 pounds (1,600 kilograms).
Economic Importance:
- Black eggs of European sturgeons are used to prepare a delicacy called as caviar. Their air bladder is used to prepare isinglass meant for cleaning wines and beers.