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Overview

Brief Summary

Biology

Sturgeons are generally solitary, spending a number of years at sea before returning to the river where they were born, in order to breed in their turn. Entering the river in spring, mature individuals migrate upriver to the shallow spawning grounds (4). Females can produce between 200,000 and 6 million eggs, which are sticky so that they can attach to the gravel substrate (4). Mature individuals do not eat throughout the spawning migration (4). As the juveniles grow they begin to migrate downstream, and adult fish spend about seven to eight years at sea before reaching sexual maturity (7). Sturgeon feed opportunistically on bottom dwelling creatures, feeling for prey amongst the mud with the sensitive barbels on their chin. Their food consists mainly of invertebrates and small fish (4).
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Description

One of the largest European fish to breed in rivers, the European sea sturgeon has been fished to the brink of extinction principally as a source of caviar (2). This sturgeon has an olive-black upper body and a white belly (4). The elongated body tapers to a narrow pointed tip at the snout and lacks scales, apart from the five rows of whitish bony platelets, or scutes, which run the length of the fish (4). European sea sturgeon have sensitive barbels which are positioned on the lower jaw and are used to locate prey, which is then sucked into the mouth (4).
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Comprehensive Description

Biology

Amphihaline and anadromous fish (Ref. 51346, 51439), frequenting littoral zones (Ref. 2163, 51439, 51442). A long-lived and slow-growing species (Ref. 9988). It lives the major part of his life in sea but enters rivers for reproduction (Ref. 30578, 51442). Found on various substrates, from sand to rocks (Ref. 51346). At the sea, it occurs in coastal and estuarine zones. In freshwaters, it inhabits estuaries and large rivers (Ref. 59043). Juveniles found both in estuaries and in the sea (Ref. 2163), they slowly adapt to saltwater (Ref. 89103) and usually spend around 2-3 years in river estuaries before moving to the sea (Ref. 40152), some may migrate to the sea during their first summer (Ref. 59043). Usually solitary. Feeds on crustaceans, mollusks, polychaete worms and small fish. Today most males only reach 100-150 cm length, females 130-215 cm (Ref. 59043, 89104). Utilized fresh and frozen, and also for caviar; eaten steamed, pan-fried, broiled, boiled, microwaved and baked (Ref. 9988). A threatened species, mainly due to bycatch, poaching, habitat degradation (spawning grounds, nursery areas) and physical obstacles to migration (Ref. 26160).
  • Bauchot, M.-L. 1987 Poissons osseux. p. 891-1421. In W. Fischer, M.L. Bauchot and M. Schneider (eds.) Fiches FAO d'identification pour les besoins de la pêche. (rev. 1). Méditerranée et mer Noire. Zone de pêche 37. Vol. II. Commission des Communautés Européennes and FAO, Rome. (Ref. 3397)   http://www.fishbase.org/references/FBRefSummary.php?id=3397&speccode=2504 External link.
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Description

 Acipenser sturio is a solitary species with a distinct morphology. Quite a large species, it can reach a total length of up to 5 m and a weight of 120 kg. Acipenser sturio has an olive-black upper body and a white belly. It has an elongated body which tapers to a narrow pointed tip at the snout, and lacks scales. It can be easily recognised by five rows of light-coloured bony platelets that run the length of the fish. Possessing no teeth, it uses conspicuous sensitive barbels on the lower jaw to locate prey which are sucked into the mouth.Acipenser sturio is a long-lived (up to 100 years) and slow-growing species. This has left it vulnerable to fishing pressure, and is now severely threatened by commercial fishermen targeting, in particular, the caviar contained within the females (Elvira, 2000).
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Distribution

Range Description

This species was once known from the North and Baltic Seas, English channel, European coasts of Atlantic, northern Mediterranean west of Rhodos, and western and southern Black Sea. It was occasionally recorded in Algeria, Morocco and Tunisia. The last record from the Rioni (Georgia) was in 1991, although further surveys have failed to find the species (J. Gessner, pers comm.). Today this species is restricted only to the Garonne River (France).
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Eastern Atlantic: the only remaining spawning population occurs in the Garonne drainage in France (Ref. 59043, 89072). Used to range from Norway to the Bay of Biscay, including the North Sea, European coasts of Atlantic, northern Mediterranean eastward to Rhodos, western and southern Black Sea; occasionally recorded from the White Sea, Iceland, Morocco and Algeria. Anadromous, in most large rivers, but not recorded from Danube upriver of delta. Recent DNA studies using museum specimens revealed that this species co-exists with A. naccarii from the Adriatic Sea to the Iberian Peninsula (Ref. 52173). Several DNA sequence differences were found between individuals of the species from the Gironde River population and from the North and Baltic Seas showing that different populations of A. sturio are genetically divergent (Ref. 82476). Appendix II of the Bern Convention (2002). Appendix I and II of the Bonn Convention (2009). Annex II and IV of the EC Habitats Directive (2007). International trade banned (CITES I, since 29.7.83; CMS Appendix II).
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Eastern Atlantic, Europe, Middle East: Western and southern Europe (including western Baltic Sea, North Sea, Mediterranean Sea, Black Sea, Sea of Marmara and adjacent watersheds).
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Coastal waters from the St. Lawrence River to the Gulf of Mexico, running up into rivers to spawn; reported from Hudson Bay, also Scandinavia to the Mediterranean.
  • Bigelow, H.B.and Schroeder,W.C.,1953; Bauchot, M.-L., 1987; Allardi, J. and P. Keith, 1991; Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea and W.B. Scott, 1991; Billard, R., 1997; Frimodt, C., 1995 ; Lepage, M. and E. Rochard, 1995.
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Range

Previously abundant along all European coasts, this sturgeon is today restricted to a single, reproductive population that breeds in the Gironde River, France (5).
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Physical Description

Morphology

Dorsal spines (total): 0; Dorsal soft rays (total): 30 - 44; Analspines: 0; Analsoft rays: 23 - 30
  • Bauchot, M.-L. 1987 Poissons osseux. p. 891-1421. In W. Fischer, M.L. Bauchot and M. Schneider (eds.) Fiches FAO d'identification pour les besoins de la pêche. (rev. 1). Méditerranée et mer Noire. Zone de pêche 37. Vol. II. Commission des Communautés Européennes and FAO, Rome. (Ref. 3397)   http://www.fishbase.org/references/FBRefSummary.php?id=3397&speccode=2504 External link.
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Size

Maximum size: 3500 mm TL
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Max. size

600 cm TL (male/unsexed; (Ref. 59043)); max. published weight: 400.0 kg (Ref. 556); max. published weight: 120 kg; max. reported age: 100 years (Ref. 556)
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to 350.0 cm TL (male); 220.0 cm TL (female); max.weight: 400 kg (male); max.weight: 120 kg (female)
  • Bigelow, H.B.and Schroeder,W.C.,1953; Bauchot, M.-L., 1987; Allardi, J. and P. Keith, 1991; Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea and W.B. Scott, 1991; Billard, R., 1997; Frimodt, C., 1995 ; Lepage, M. and E. Rochard, 1995.
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Diagnostic Description

Body elongated, pentagonal section (Ref. 51442). Snout moderate with tip narrow and pointed (Ref. 3397), mouth inferior (Ref. 59043). Lower lip not continuous, interrupted at center (Ref. 3397). Four barbels halfway between snout tip and mouth but not reaching the latter (Ref. 3397, Ref. 51442). No scales, but 5 rows of scutes on the body: dorsal 9-16, lateral 24-39 on each side, ventral 9-14 on each side, with dense cross-lines of smaller rhombic plates between the dorsal and lateral rows (Ref. 2196, Ref. 3397, Ref. 40476, Ref. 51442). Dorsal side greenish-brown to blackish with golden tints, flanks light with silvery tints, belly white (Ref. 3397).
  • Bauchot, M.-L. 1987 Poissons osseux. p. 891-1421. In W. Fischer, M.L. Bauchot and M. Schneider (eds.) Fiches FAO d'identification pour les besoins de la pêche. (rev. 1). Méditerranée et mer Noire. Zone de pêche 37. Vol. II. Commission des Communautés Européennes and FAO, Rome. (Ref. 3397)   http://www.fishbase.org/references/FBRefSummary.php?id=3397&speccode=2504 External link.
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Ecology

Habitat

Seine River Demersal Habitat

This taxon is one of a number of demersal species in the Seine River system of Western Europe. Demersal river fish are found at the river bottom, feeding on benthos and zooplankton

The Marne and Yonne exhibit the greatest torrential flows, due to the percentage of their courses underlain by impermeable strata, in combination with the river gradients. Although the Loing manifests the highest percentage of impermeable strata of all the tributaries, its low gradient mitigates against torrential velocities. Thus the majority of the Seine and its tributaries exhibit a relaxed generally even flow rate.

Seine water pollutant loads of heavy metals, nutrients, sediment and bacteria are relatively high, especially influnced by wastewater and surface runoff from Paris and its suburbs. Parisian pollutant loadings are noted to be particularly high during periods of high rainfall, not only due to high runoff, but also from the inadequate sewage treatment facilities in periods of high combined wastewater/stormwater flow.

Heavy metal concentrations at Poses weir reveal the following levels: copper, 1.9 milligrams per liter; cadmium, 32 mg/l; and lead, 456 mg/l. Concentrations of zinc are also quite high, making the Seine Estuary one of the most highly contaminated estuaries in the world with respect especially to lead and cadmium. Significant amounts of toxic pollutants are also attached to sediments deposited in the Seine during the last two centuries, including mercury, nickel, chromium, toluene, DDT and a variety of herbicides and pesticides. Downriver from Paris, significant quantites of ammonium are discharged into the Seine from effluent of the Achères wastewater treatment plant.

There are a total of 37 fish species inhabiting the Seine, and another two taxa that are known to have been extirpated in modern times. Two of the largest aquatic fauna known to have lived in the Seine are now locally extinct: the 500 centimeter (cm) long sturgeon (Acipenser sturio) and the 83 cm long allis shad (Alosa alosa).

The largest extant native demersal (species living on or near the river bottom) taxa in the Seine are:

the 133 cm European eel (Anguilla anguilla);

the 150 cm northern pike (Esox lucius);

the 120 cm sea lamprey (Petromyzon marinus); and,

the 152 cm Burbot (Lota lota).

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Habitat and Ecology

Habitat and Ecology
Biology: Anadromous (spends at least part of its life in salt water and returns to rivers to breed).

Males reproduce for the first time at 10-12 years, females at 14-18. There are indications for a reproduction at two year intervals for males and 3-4 years for females in April-July. Adults do not eat during migration and spawning. The distance of the spawning migration seems to be positively correlated with water level, and a distance of 1000 km or more may be covered during years of high water. Spent fishes immediately return to the sea (FAO 2009).

Potential spawning grounds have been mapped. Juveniles migrate downstream and are present in upper estuary at one year old. They continue a slow downstream migration and penetrate the sea at 2-3 years. For the next 4-6 years, they leave the sea to enter the lower estuary at summer time where movements and feeding were determined. At sea, this species feeds on a variety of molluscs, crustaceans and small fish. Atlantic population feed benthically.

Systems
  • Freshwater
  • Marine
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Environment

demersal; anadromous (Ref. 51243); freshwater; brackish; marine; pH range: 7.5; dH range: 10 - 20; depth range 4 - 93 m (Ref. 51346), usually 5 - 60 m (Ref. 26160)
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Depth range based on 1 specimen in 1 taxon.
Water temperature and chemistry ranges based on 1 sample.

Environmental ranges
  Depth range (m): 89 - 89
  Temperature range (°C): 7.020 - 7.020
  Nitrate (umol/L): 8.857 - 8.857
  Salinity (PPS): 35.129 - 35.129
  Oxygen (ml/l): 6.192 - 6.192
  Phosphate (umol/l): 0.765 - 0.765
  Silicate (umol/l): 4.624 - 4.624
 
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 Acipenser sturio is a demersal species. It can tolerate a wide range of salinities. Most of its life is spent at sea, relatively close to the coast, but it enters rivers to spawn.
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Depth: 5 - 60m.
From 5 to 60 meters.

Habitat: demersal. Amphihaline and potamodromous fish frequenting litoral zones. Juveniles found both in estuaries and in the sea (Ref. 2163). This species is usually solitary. Becoming rare (Ref. 4537). Feeds on crustaceans, molluscs, polychaete worms and small fishes. Eggs deposited on sand or gravel. A long-lived and slow-growing species (Ref. 9988). Utilized fresh and frozen, and also for caviar; eaten steamed, pan-fried, broiled, boiled, microwaved and baked (Ref. 9988).
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demersal; freshwater; brackish; marine; pH range: 7.5; dH range: 10.0 - 20.0; depth range 5 - 60 m . Amphihaline and potamodromous fish frequenting littoral zones. Juveniles found both in estuaries and in the sea. Enters rivers to reproduce. Usually solitary.
  • Bigelow, H.B.and Schroeder,W.C.,1953; Bauchot, M.-L., 1987; Allardi, J. and P. Keith, 1991; Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea and W.B. Scott, 1991; Billard, R., 1997; Frimodt, C., 1995 ; Lepage, M. and E. Rochard, 1995.
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Sturgeons are found near to the bottom of the water column, over a soft sandy or muddy substrate (6). Adults are found in the lower sections of large rivers and in the open sea, whilst spawning occurs upriver in shallow pools with a gravel base (6).
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Migration

Anadromous. Fish that ascend rivers to spawn, as salmon and hilsa do. Sub-division of diadromous. Migrations should be cyclical and predictable and cover more than 100 km.
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Trophic Strategy

Solitary at present because rare (Ref. 231). Feeding ceases during migration and spawning (Ref. 89072). Adults feed on benthic invertebrates and fish (Ref. 231, 51442), larvae and juveniles feed on small crustaceans and insect larvae (Ref. 51442, 89072).
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Feeds on crustaceans, mollusks, polychaete worms and small fishes.
  • Bigelow, H.B.and Schroeder,W.C.,1953; Bauchot, M.-L., 1987; Allardi, J. and P. Keith, 1991; Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea and W.B. Scott, 1991; Billard, R., 1997; Frimodt, C., 1995 ; Lepage, M. and E. Rochard, 1995.
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Life History and Behavior

Life Cycle

Anadromous species, with adults migrating to the middle reaches of large rivers mainly in spring and early summer. Spawning occurs between March and August, when water temperature rises above 20 °C at depths of 2-10 m over stony bottoms in areas with strong current (1.5-2.0 m/s) (Ref. 51442, 59043, 89103).Mature individuals do not feed during spawning migration (Ref. 3193). Number of spawned eggs increases with age. After spawning adults return to the sea (Ref. 51442). The development of the sticky dark grey eggs (2.6-3.0 mm diameter) takes about one week at 17°C (Ref. 26160, 35388). It is suggested that males spawn every 2 years, females every 3-4 years (Ref. 89072). Upstream spawning migrations appear to be positively correlated with water levels in rivers and distances of 1,000 kilometres or more may be covered when water levels are high (Ref. 89104). Sturgeons in general have a high capacity for hybridization and most species are able to cross-breed (Ref. 89103, 89117). This species has been reported to cross-breed (albeit rarely) with the Danube sturgeon (Acipenser gueldenstaedti) (Ref. 89105).
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Reproduction

Enters rivers from March/April to June/July, spawning over stones and gravel. Produces between 200,000 and 6 million eggs, with the numbers increasing with age; a fish of 150 kg may produce 4 million eggs . Mature individuals do not feed during spawning migration. The development of sticky eggs (2.6-3.0 mm diameter) takes about one week at 17°C.
  • Bigelow, H.B.and Schroeder,W.C.,1953; Bauchot, M.-L., 1987; Allardi, J. and P. Keith, 1991; Robins, C.R., R.M. Bailey, C.E. Bond, J.R. Brooker, E.A. Lachner, R.N. Lea and W.B. Scott, 1991; Billard, R., 1997; Frimodt, C., 1995 ; Lepage, M. and E. Rochard, 1995.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Acipenser sturio

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 3
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
CR
Critically Endangered

Red List Criteria
A2cde; B2ab(ii,iii,v)

Version
3.1

Year Assessed
2010

Assessor/s
Gesner, J., Williot, P., Rochard, E., Freyhof, J. & Kottelat, M.

Reviewer/s
Pourkazemi, M. & Smith, K.

Contributor/s

Justification
Once a very wide ranging species from the North and (Eastern) north Atlantic and Mediterranean coast of Europe and the Black Sea (one record from the White Sea in the 1950s), the last remaining population (in the Garonne in France) is still declining. The species last spawned in 1994 in the Garonne, where dams, pollution and river regulation has degraded and destroyed spawning sites. There are also plans to start gravel extraction. The current population size is between 20-750 wild, mature individuals (in the past three years there has been substantial stocking, but these animals will not reproduce until ~2016). Under normal population circumstances, the average reproductive age is suspected to be about 25 years. There has been more than a 90% population decline in the past 75 years based mainly on loss of habitat, along with pollution and exploitation.

This species now remains in just one location, where 27 spawning grounds (less than 10 km²) remain potentially accessible (the major threat to this species is bycatch). As this species continues to be caught as bycatch, the population is still decreasing.

History
  • 1996
    Critically Endangered
  • 1994
    Endangered
    (Groombridge 1994)
  • 1990
    Endangered
    (IUCN 1990)
  • 1988
    Endangered
    (IUCN Conservation Monitoring Centre 1988)
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Status

Classified as Critically Endangered (CR) on the IUCN Red List 2007 (1), and listed on Appendix I of CITES (3).
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Population

Population
The sturgeon was an important commercial fish until the beginning of the 20th century (Debus 2007). The last natural reproduction was in 1994 (previous reproduction in 1988). A population assessment in 2005 estimated 2,000 individuals remain. It is estimated that bycatch took around 200 fish per year (gill net and trawling at sea) (Rochard et al. 1997).

The size of the population today is much smaller (approximately 20-750 native wild adult fish, based on an assessment of the size the cohort before they leave the estuary). There are more individuals from stocking (7,000 in 2007; 80,000 in 2008; and 46,000 in 2009) (Rouault et al. 2008; Rochard 2010). These have not yet bred in the wild and first breeding (from the releases of 1995) is expected by 2014, F1 generation of 2007 and later releases around 2021. The limiting factor is the availability of females which won't reproduce until ~2016 (Rochard, pers. comm).

Population Trend
Decreasing
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Threats

Major Threats
Bycatch is the major threat and the extraction of gravel in the Garonne is a potential threat to the species. Dam construction, pollution and river regulation have led to loss and degradation of spawning sites.
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Critically Endangered (CR) (A2cde; B2ab(ii,iii,v))
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These long-lived and slow-growing fish are very vulnerable to exploitation; the European sea sturgeon has been extensively fished for its highly prized flesh and for the eggs, which are sold as caviar (6). The development of river systems, in particular the construction of hydroelectric dams, destroys the breeding habitat of this species and adults are no longer able to return to their natal rivers to breed (8). Today only a single reproductive population remains and the species is consequently extremely vulnerable to extinction (5).
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Management

Conservation Actions

Conservation Actions
An ongoing in situ conservation programme is in place. Ex-situ conservation is carried out in France and Germany. Bern Convention Action Plans have been developed, while National Action Plans are to come.

Restocking was initiated in 1995 and later in 2007 until 2009. Survival rate for the 1995 stocking is 3-5%; the survival rate for recent releases is unknown. For the first time in 2007, progenies were obtained from farmed specimen (Williot et al. 2009).

There is a fisheries awareness programme co-ordinated between National Fishermen Associations in Atlantic North Sea and WWF.

This species was listed on CITES Appendix II in 1975, and moved to Appendix I in 1983.
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Conservation

The European sea sturgeon is protected from international trade by its listing on Appendix I of the Convention on International Trade in Endangered Species (CITES) (3). A captive breeding programme (8) for the species is being undertaken with the long-term goal of reintroducing this 'dinosaur of the sea' to some of its former range.
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: commercial; aquaculture: commercial
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Wikipedia

European sea sturgeon

The European sea sturgeon (Acipenser sturio), also known as the Atlantic sturgeon, Baltic sturgeon or common sturgeon, is a species of sturgeon found on most coasts of Europe. It is currently a critically endangered species.[1]

The wedge-shaped head of this sturgeon ends in a long point. There are many sensitive barbels on the facial area. The dorsal fins are located very far back on the body. Five longitudinal lines of large osseous plates are found on the body of the fish. The stomach is yellow and the back is a brownish grey.

Head

This sturgeon can reach 6 m (20 ft) and 400 kg (880 lb) in weight, but a more common length is 1.25 m (4 ft 1 in).[2] They can reach an age of 100 years,[2] and have a late sexual maturity (12 to 14 years for the males and 16 to 18 years for the females).

They are found on the coasts of Europe, except the Black Sea, and have even been known to cross the Atlantic Ocean to the coasts of North America. Like many other sturgeons, they spawn in the rivers inland from the coast. Despite their estimated range of distribution, they have become so rare that they only breed in the Garonne river basin in France. However, in 2012 some 50 sturgeons were reintroduced in the Rhine near Nijmegen.

Like other sturgeons, they eat mollusks and crustaceans which they find with their barbels.

At the beginning of the 19th century, these fish were used extensively to produce caviar, but have been a protected species in Europe since 1982.

References[edit]

  1. ^ a b Gesner, J., Williot, P., Rochard, E., Freyhof, J. & Kottelat, M. (2010). "Acipenser sturio". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 24 February 2013. 
  2. ^ a b Froese, Rainer and Pauly, Daniel, eds. (2005). "Acipenser sturio" in FishBase. 10 2005 version.
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