Acipenseriformes

(vertebrate zoology) An order of the subclass Actinopterygii represented by the sturgeons and paddlefishes.

(Sturgeons and paddlefishes)

Class: Actinopterygii

Order: Acipenseriformes

Number of families: 2

Evolution and systematics

The order Acipenseriformes includes 25 species of sturgeons in four genera (Acipenser, Huso, Scaphirhynchus, and Pseudoscaphirhynchus) in the family Acipenseridae and two living species of paddlefishes in the family Polyodontidae. The Acipenseriformes are primitive fish; recognizable fossils date to the early Cretaceous (144–65 million years ago). The Acipenseridae and Polyodontidae probably diverged from each other during the Jurassic (208–146 million years ago).

Physical characteristics

Acipenseriformes are some of the largest freshwater fishes, with species ranging in maximum size from 2.5 ft (0.76 m) to nearly 28.2 ft (8.6 m). Their bodies are elongate with large heads, small eyes, and fins positioned towards the posterior. A lateral line and scales are absent. Sturgeons and paddlefishes are dark on the tops of their bodies, but pigmentation fades to much lighter ventral colors, and many have white bellies. Species of sturgeon take on a variety of dull colors: gray, brown, dark blue, olive-green, and nearly black. Paddlefishes may appear bluish gray, brown, or black on their dorsal surface.

All Acipenseriformes share relict characteristics, including a largely cartilaginous endoskeleton and heterocercal caudal fin. The only ossified bones are found in the skull, jaws, and pectoral girdle. Other common anatomical features include an elongated snout with sensory barbels, a ventral mouth, an unconstricted notochord, and a lack of scales covering their skin.

Although they share many similar characteristics, anatomical and ecological distinctions exist between sturgeons and paddlefishes. Sturgeons have four barbels used for detecting prey, and the ventral mouth is protrusible. Paddlefishes have only two small sensory barbels and nonprotrusible mouths. Another major anatomical difference between sturgeons and paddlefishes is in their body coverings. The skin of paddlefishes is largely naked, with patches of minute scales. In contrast, sturgeons are armored with five rows of bony shields along their bodies.

Distribution

Acipenseriformes are found throughout the Northern Hemisphere in North America, Europe, and Asia. Among the sturgeons, nine species inhabit North America, four are found in Europe, ten live in Asia, and four have Eurasian distributions. One species of paddlefish is found in North America; the other paddlefish species is endemic to China.

Habitat

Acipenseriformes inhabit seas, rivers, and lakes. Some species spend a large portion of their lives at sea but enter coastal rivers to spawn. Other species live strictly in freshwater rivers and lakes. Sturgeons are typically associated with sand, gravel, or rock substrates.

Behavior

Most sturgeons spend their lives in their native river or in nearshore areas of adjacent seas, but some individuals move long distances through coastal habitats. Sturgeons exhibit seasonal and spawning migrations. They may move from shallow to deep water in the summer and return to shallow areas in the winter. All sturgeons spawn in fresh water; thus, those that live in the sea migrate to fresh water for spawning. Paddlefishes swim constantly, both day and night, and migrate upstream to spawn.

Sturgeons are active primarily during the day, and many species congregate in discrete seasonal feeding areas.

Observations of lab-reared juveniles suggest that certain species may establish a dominance hierarchy based on size, with large fish acting aggressively towards smaller fish in disputes over limited foraging space. Although sturgeons and paddlefishes are solitary for most of their life, some aggregation has been observed in larvae, which migrate in unorganized groups.

Feeding ecology and diet

Sturgeons locate food by swimming close to the bottom with their sensory barbels dragging the substrate. They selectively ingest slow-moving benthic invertebrates, including insects, worms, crustaceans, and mollusks, and feed on other fishes to a limited extent. Paddlefishes feed by swimming through the water with their mouths open and filtering large amounts of water through their gill rakers. Paddlefishes primarily consume microcrustaceans and insect larvae in the plankton, but they occasionally eat benthic invertebrates and other fishes.

Because of their large size and protective bony scutes, adult sturgeons and paddlefish have few predators except humans. However, sturgeons may be attacked, and possibly killed, by the parasitic sea lamprey, Petromyzon marinus.

Reproductive biology

Sturgeons typically spawn during spring and summer months. Prespawning activities involve rolling near the bottom and leaping out of the water. Spawning takes place in groups of two to three fish, with one or two males per female. Female sturgeons produce large quantities of eggs (up to several million), which are deposited over shallow shoals or rocky areas and fertilized by males. No nests are constructed, but the eggs are adhesive and stick to the substrate. Sturgeons do not devote any parental care to their offspring. Adults of some species spawn every year, but most species allow longer intervals between spawning events.

Paddlefishes spawn in the early spring as water levels are rising. They migrate from lakes and rivers into streams to locate spawning sites in shallow water. Males and females broadcast eggs and sperm over gravel substrates while swimming in groups. No parental care is provided to the offspring. Female paddlefishes produce very large numbers of eggs (up to 600,000) and do not spawn annually.

Conservation status

Overexploitation and habitat alteration, particularly the construction of dams, threaten and limit populations of Acipenseriformes throughout their range. The commercial landings of sturgeons exceeded 3,000 tons (2,721 tonnes) in 1890, but landings declined by 99% over the next century. Overfishing threatened many populations with local extinction, and stock enhancement programs have been introduced to maintain many sturgeon fisheries. Dams limit access to spawning sites and isolate populations. Other human activities on the shores of rivers increase siltation and contaminate rock or gravel spawning areas.

All Acipenseriformes are cited on the IUCN Red List. While some species are considered Lower Risk/Near Threatened (2 species) by the IUCN, most species are at greater risk and are classified as either Critically Endangered (6 species), Endangered (11 species), or Vulnerable (8 species). The international trade of Acipenseriformes is regulated through the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES). The short-nose sturgeon (Acipenser brevirostrum) and the common sturgeon (Acipenser sturio) are considered threatened with extinction and are listed on Appendix I of CITES. All other species of sturgeon and paddlefish are listed on Appendix II of CITES. The shortnose sturgeon is listed as an endangered species in the United States.

Significance to humans

Sturgeons have been valued for their caviar, the unfertilized eggs of the female, since the times of the ancient Persian, Greek, and Roman empires. The Chinese began trading caviar during the tenth century. It became popular as a luxury food in Europe during the seventeenth and eighteenth centuries and remained prized as a culinary delicacy at the end of the twentieth century. The smoked meat of sturgeons also is highly valued, particularly in European and Asian markets. In the late 1800s, paddlefish eggs and flesh also were sought commercially.

Species accounts

Resources

Birstein, Vadim J., John R. Waldman, and William E. Bemis, eds. Sturgeon Biodiversity and Conservation. Dordrecht, The Netherlands: Kluwer Academic Publishers, 1997.

Billard, Roland, and Guillaume Lecointre. "Biology and Conservation of Sturgeon and Paddlefish." Reviews in Fish Biology and Fisheries 10 (2000): 355–392.

Jennings, Cecil A., and Steven J. Zigler. "Ecology and Biology of Paddlefish in North America: Historical Perspectives, Management Approaches, and Research Priorities." Reviews in Fish Biology and Fisheries 10 (2000): 167–181.

Kynard, B., and M. Horgan. "Ontogenetic Behavior and Migration of Atlantic Sturgeon, Acipenser oxyrinchus oxyrinchus, and Shortnose Sturgeon, A. bervirostrum, with Notes on Social Behavior." Environmental Biology of Fishes 63 (2002): 137–150.

Kynard, B., E. Henyey, and M. Horgan. "Ontogenetic Behavior, Migration, and Social Behavior of Pallid Sturgeon, Scaphirhynchus albus, and Shovelnose Sturgeon, S. platorynchus, with Notes on the Adaptive Significance of Body Color." Environmental Biology of Fishes 63 (2002): 389–403.

Peterson, Douglas L., Mark B. Bain, and Nancy Haley. "Evidence of Declining Recruitment of Atlantic Sturgeon in the Hudson River." North American Journal of Fisheries Management 20, no.1 (2000): 231–238.

Wilkens, L. A., D. F. Russell, X. Pei, and C. Gurgens. "The Paddlefish Rostrum Functions as an Electrosensory Antenna in Plankton Feeding." Proceedings of the Royal Society of London B 264 (1997): 1723–1729.

"Lake Sturgeon Fact Sheet." New York State Department of Environmental Conservation. . 30 Sept. 1999 (25 Oct. 2002). "White Sturgeon." Pacific States Marine Fisheries Commission. 25 Oct. 2002 (16 Dec. 1996).

"Fish: Paddlefish." Tennessee Aquarium. 25 Oct. 2002.

[Article by: Katherine E. Mills, MS]

An archaic order of actinopterygian fishes, represented by the sturgeons and paddlefishes. The characters include a highly chondrified internal skeleton; fins which are archaic and sharklike in appearance, with more than one ray per pterygiophore; a caudal fin which is strongly hete-rocercal; scales which are reduced and often form five lengthwise series of bony plates; rostrum produced; and weak jaws (see illustration). Fleshy barbels are present on the lower surface of the snout. The cartilaginous skeleton of the acipenseri form fishes was long regarded as primitive, and was taken as indicative of alliance with the Chondrichthyes. Research reveals, however, that this is secondary, and the true relationship is with the typical bony fishes.

Lake sturgeon (Acipenser fulvescens).

The Acipenseriformes include three families: the extinct Chondrosteidae; the sturgeon family, Acipenseridae, with 4 Recent genera and about 23 species; and the paddlefish family, Polyodontidae, consisting of two Recent species, Psephurus gladius of China and Polyodort spathula of the eastern United States. See also Actinopterygii; Osteichthyes; Sturgeon.

This article is in need of attention from an expert on the subject. WikiProject Science or the Science Portal may be able to help recruit one. (November 2008)

Acipenseriformes Fossil range: Late Jurassic–Recent PreЄ Є O S D C P T J K Pg N [1]
Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Acipenseriformes
Families
Acipenseridae—sturgeons Polyodontidae—paddlefishes Chondrosteidae—extinct Errolichthyidae—extinct

Acipenseriformes (pronounced /æsɨˈpɛnsərɨˈfɔrmiːz/) are an order of primitive ray-finned fishes that includes the sturgeons and paddlefishes, as well as some extinct families.^[2]

Notable characteristics of Acipenseriformes include:

• Cartilaginous endoskeleton
• Lack of vertebral centrum
• Spiral valve intestine
• Conus arteriosus

Species

Acipenseriformes

Order Acipenseriformes

• Family Acipenseridae
  • Subfamily Acipenserinae
    • Genus Acipenser
      • Acipenser baerii
        • Siberian sturgeon, Acipenser baerii baerii
        • Baikal sturgeon, Acipenser baerii baicalensis
      • Shortnose sturgeon, Acipenser brevirostrum (USA)
      • Yangtze sturgeon, Acipenser dabryanus
      • Lake sturgeon, Acipenser fulvescens (USA)
      • Russian sturgeon, Acipenser gueldenstaedtii
      • Green sturgeon, Acipenser medirostris
      • Sakhalin sturgeon, Acipenser mikadoi
      • Japanese sturgeon, Acipenser multiscutatus
      • Adriatic sturgeon, Acipenser naccarii
      • Fringebarbel sturgeon, Acipenser nudiventris
      • Acipenser oxyrinchus (USA)
        • Gulf sturgeon, Acipenser oxyrinchus desotoi
        • Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus
      • Persian sturgeon, Acipenser persicus
      • Sterlet, Acipenser ruthenus
      • Amur sturgeon, Acipenser schrenckii
      • Chinese sturgeon, Acipenser sinensis
      • Starry sturgeon, Acipenser stellatus
      • European sturgeon, Acipenser sturio (also "Baltic sturgeon")
      • White sturgeon, Acipenser transmontanus
    • Genus Huso
      • Beluga sturgeon, Huso huso
      • Kaluga sturgeon, Huso dauricus
  • Subfamily Scaphirhynchinae
    • Genus Scaphirhynchus
      • Pallid sturgeon, Scaphirhynchus albus
      • Shovelnose sturgeon, Scaphirhynchus platorynchus
      • Alabama sturgeon, Scaphirhynchus suttkusi
    • Genus Pseudoscaphirhynchus
      • Dwarf sturgeon, Pseudoscaphirhynchus hermanni
      • Syr Darya sturgeon, Pseudoscaphirhynchus fedtschenkoi
      • Amu Darya sturgeon, Pseudoscaphirhynchus kaufmanni
• Family Polyodontidae (Paddlefish)
  • Genus Polyodon
    • American paddlefish, Polyodon spathula (USA)
  • Genus Psephurus
    • Chinese paddlefish, Psephurus gladius

External links

• Photos and illustrations of Acipenseriformes
• CITES finalizes 2006 caviar export quotas

References

1. ^ Wiley, Edward G. (1998). Paxton, J.R. & Eschmeyer, W.N.. ed. Encyclopedia of Fishes. San Diego: Academic Press. pp. 76-79. ISBN 0-12-547665-5. 
2. ^ "Acipenseriformes". FishBase. Ed. Ranier Froese and Daniel Pauly. 05 2006 version. N.p.: FishBase, 2006.

• Martin Hochleithner and Joern Gessner, The Sturgeons and Paddlefishes of the World: Biology and Aquaculture
• Martin Hochleithner, Joern Gessner, and Sergej Podushka, The Bibliography of Acipenseriformes

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