Atlantic sturgeon
| Atlantic sturgeon | ||||||||||||
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Atlantic sturgeon ( Acipenser oxyrinchus oxyrinchus ) |
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| Acipenser oxyrinchus | ||||||||||||
| Mitchell , 1815 |
The Atlantic sturgeon ( Acipenser oxyrinchus ) is a bony fish from the genus of the sturgeon (Acipenser), which occurs in two subspecies along the North American Atlantic and Gulf coast. Genetic studies indicate that the species was also found in the Baltic Sea until recently. The stocks have been endangered mainly due to overfishing since the end of the 19th century.
features
The Atlantic sturgeon can only be reliably distinguished from the European sturgeon ( Acipenser sturio ), which is probably its sister species, by means of molecular biological studies. The animals have the typical physique of the sturgeon with an elongated body, an under-lying proboscis mouth , heteroceric caudal fin and five rows of bone plates along the trunk, which are oval in the Atlantic sturgeon. Usually the animals reach a length of 1.30 to 2.20 meters and a weight of 30 to 45 kilograms for males and 50 to 110 kilograms for females. The reported maximum dimensions are 4.30 meters and almost 370 kilograms. The body of young animals is dark brown with a yellowish to whitish belly and dark bone plates, with the middle of the back plates being light. The lateral edges of the snout are clearly colored black and the rear edge of the caudal fin is white. Adults are dark brown or bluish-black to light brown or copper-colored with a whitish or slightly yellowish belly. Only adult animals have a black spot on the underside of the snout. This is always long and pointed in a V-shape. Two pairs of short, slender barbels sit halfway from the tip of the snout to the mouth. The upper lip has an indentation in the middle, the lower lip is interrupted. There is a bone ridge above the eye. The iris is bronze, gold or copper in color. The back row has 7 to 16 bone plates, the side rows 24 to 35, the abdominal rows 6 to 14 plates. Between the anus and anal fin there are 2 to 6 small plates in pairs, between 3 to 9 plates between the dorsal or anal fin and the caudal fin. Small platelets are also found next to the anal fin. There are numerous tiny, diamond-shaped plates between the large bone plates. The dorsal fin has 38 to 46 soft rays, the anal fin 23 to 30.
Way of life
Atlantic sturgeon are anadromous migratory fish that spend most of their adult life in the shallow waters above the continental shelf , sometimes undertaking long migrations along the coasts. Annelids , molluscs , bottom-dwelling crustaceans and small bony fish serve as food . The spawning migration begins in the south of the range in February or March, in the Central Atlantic from April to May and in Canadian waters in May to July. The animals migrate into estuaries and rivers, where the eggs are laid in weakly brackish or fresh water at temperatures from 13 to 18 ° C. These are about 2.5 millimeters in diameter and are likely to be placed on the ground in running water over firm ground. The young hatch after about a week and spend about three to five years in rivers or estuaries before they migrate into the sea with a length of 76 to 92 centimeters. The adult animals do not eat anything during their stay in the warm rivers and usually return to the sea from mid-November when the water cools below 20 ° C. The males reach sexual maturity at 6 to 14 years of age, the females at 8 to 28 years, whereby the southern populations reach sexual maturity earlier than the northern ones. Adult animals mate every three to four years and reach an age of up to 60 years.
Occurrence
The Atlantic sturgeon occurs with two subspecies along the North American Atlantic coast. The nominate form ( Acipenser oxyrinchus oxyrinchus ) occurs from the Labrador Peninsula in Canada to the St. Johns River in East Florida. The southern subspecies Acipenser oxyrinchus desotoi , the Gulf sturgeon , occurs in the Gulf of Mexico from the Mississippi River Delta to South Florida. Individual sightings have also been reported from waters further south. The golf sturgeon differs from the nominate form in the length of its head and fin as well as the shape of the bone plates, but the only statistically certain distinguishing feature is the size of the spleen , which is slightly larger than that of the nominate form.
Sequencing of the mitochondrial DNA of museum specimens indicates that the sturgeon population of the Baltic Sea, which has meanwhile been exterminated by fishing, was also the Atlantic sturgeon and not the European sturgeon ( Acipenser sturio ), as had long been assumed . These had probably immigrated 1200 to 800 years ago and were able to prevail against the European sturgeon, which is more sensitive to cold, and displaced it during the Little Ice Age . Further genetic studies, which also included genes from the cell nucleus , suggest that only the females of the Atlantic sturgeon were actually successful in the Baltic Sea, where they produced a hybrid population together with males of the European sturgeon .
Use and protection
The Atlantic sturgeon has been fished for at least 4000 years, but more intensive fishing did not begin until the late 19th century, with the focus on spring migrations. The catch numbers for both subspecies fell by 90% within about 10 years and only recovered slowly despite increasingly strict controls. At the end of the twentieth century, bycatch catches for Atlantic sturgeon exceeded those of directed fisheries . Fishing has been banned in the United States since 1997 . In Canada , strict fishing regulations are checked. In addition to fishing, which is considered the main threat to the species, dam construction projects and water pollution threaten migrations and habitats.
The species is currently listed on the Red List of Threatened Species as Near Threatened , and the subspecies of the Gulf Sturgeon as Vulnerable . In the Washington Convention , the Atlantic sturgeon is listed as a species in need of protection in Appendix two. In addition to regulating capture and trade, protective measures include marking programs for research into distribution and migration as well as breeding experiments in aquaculture .
In 2005 a breeding program was started with the aim of repopulating the Atlantic sturgeon in the Baltic Sea, for which 20 sexually mature sturgeons were imported to Germany from St. Andrews in Canada . While the species is better suited for colonization attempts than the European sturgeon , of which there are not enough fish available, it is uncertain whether the animals are suitable for the now warmer Baltic Sea.
Web links
- Atlantic sturgeon on Fishbase.org (English)
Individual evidence
- ^ William E. Bemis, Eric K. Findeis, Lance Grande: An overview of Acipenseriformes . In: Environmental Biology of Fishes . tape 48 , 1997, pp. 25-71 (English).
- ^ Minister of Supply and Services Canada: CITES Identification Guide - Sturgeons and Paddlefish: Guide to the Identification of Sturgeon and Paddlefish Species Controlled under the Convention on International Trade in Endangered Species of Wild Fauna and Flora . Wildlife Enforcement and Intelligence Division, Environment Canada, 2001, ISBN 0-660-61641-6 (English, French, Spanish, full text [PDF; 10.9 MB ]).
- ↑ a b Atlantic sturgeon on Fishbase.org (English)
- ↑ a b c Species Fact Sheet of the FAO
- ^ A b c d Theodore IJ Smith & James P. Clugston: Status and management of Atlantic sturgeon, Acipenser oxyrinchus, in North America . In: Environmental Biology of Fishes . tape 48 , 1997, pp. 335-346 (English).
- ^ Entry in the IUCN Red List for Acipenser oxyrhinchus
- ^ Vadim J. Birstein, William E. Bemis: How many species are there within the genus Acipenser? In: Environmental Biology of Fishes . tape 48 , 1997, pp. 157-163 (English).
- ↑ a b Arne Ludwig, Lutz Debus, Dietmar Lieckfeldt, Isaac Wirgin, Norbert Benecke, Ingo Jenneckens, Patrick Williot, John R. Waldman, Christian Pitra: When the American sea sturgeon swam east . In: Nature . tape 419 , 2002, pp. 447 (English).
- ↑ Ralph Tiedemann, Katja Moll, Kirsten B. Paulus, Michael Scheer, Patrick Williot, Ryszard Bartel, Jörn Gessner, Frank Kirschbaum: Atlantic sturgeons (Acipenser sturio, Acipenser oxyrinchus): American females successful in Europe . In: Natural Sciences . tape 94 , 2007, p. 213-217 (English).
- ↑ Acipenser oxyrinchus (Gulf Sturgeon). IUCN, accessed December 12, 2015 .
- ↑ Acipenser oxyrinchus ssp. desotoi (Gulf Sturgeon). IUCN, accessed December 12, 2015 .
- ↑ Stör is coming back to Germany. Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, accessed on March 31, 2014 .