Stenodus leucichthys

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White Salmon ( Stenodus leucichthys )

The White Salmon ( Stenodus leucichthys ) is an important Palesti and nearktischer edible fish from the relationship of the whitefish ( Coregoninae or how increasingly prized now, Coregonidae ). It is the largest member of the subfamily Coregoninae and feeds mainly predatory ( piscivor ), while feeding the other species of the subfamily of plankton and benthic invertebrates. It can be 1,5 m long, 40 kg and about 22 years old. In Russia, he was also called Tsar or angelfish.

Features

The pointed head takes up almost 1/5 of a total length of. The upper permanent mouth is larger than that of Coregonus and Prosopium ( maxilla and Supramaxillare are stretched). It extends to the height of the pupil. Very small but distinct teeth marks (" close ", so Stenodus, " Engzähner " ) on the jaws ( maxilla: only at the upper end ), the Palatines ( in bands ), the vomer and the Glossohyale (each a small group ). Old animals have lost their teeth for the most part, they do not also need to snap. The color is bright silver with a little darker back ( olive green to gray- blue, including dorsal fin ), as with all Coregoniden.

The skull is medioparietal, that is, the median parietals come together - but among them reaches an extension of the supraoccipital but always up to the frontalia (see Boulenger 1895). A narrow Supra orbitals is present. The Dentalia front form a small hook or knob that fits into a pit of Praemaxillen and is helpful when packing the loot -. The fish has on each side (about ) ten gill skin rays. The rakers are bony, dentate rather pointed and partly fine; stand on the first gill arch 5-7 and 13-17 (with its narrowing, the young fish still catch even nauplius larvae if needed) -. Stenodus has 64-69 vertebrae. The hull is little Kompress.

The dorsal fin (D 11-19 ) is high and shorter, the anal fin (A 14-19) but slightly longer than in Coregonus. P ~ 17; V ~ 14 ( with a clear Axillarfortsatz at the base). At the caudal fin (C 19) sometimes falls on a somewhat elongated Ventrallappen, which (as already the mouth position) suggests that Stenodus ( too) near-surface hunting.

The tail skeleton is in contrast to the related genera a pair Urodermalia (Kendall and Behnke 1984). The scales are quite small (about 88-118 along the entire side line). The output of the S-shaped stomach is an asymmetric pair of tuft Pylorusschläuchen ( about 100 to about 200).

Development and ecology

After hatching in late spring, the larvae need (11-13 mm long) initially about two weeks their yolk sack, before they start to eat ( Harpacticiden and other small crustaceans, chironomid larvae and other insects ). Once they are able to, however, they go to the fish - eating over ( eg eggs and larvae ) - they behave from then quite " wild, greedy ," so that Albert Günther for the genre today invalid name Luciotrutta, so " pike trout " could dominate.

The aim of anadromous specimens is the sea ( where they certainly rarely get too far out of the mouths of rivers; until 50 m depth and at temperatures below 18 ° C) - but there are in the whole distribution area also resident populations ( "voluntarily" or due to insurmountable barriers) in fresh water ( in lakes - stay or rivers ) - for example, in Great Slave Lake. After several years ( minimum of five [ male ] to a maximum of fifteen [ females ] ) they rise then fall back into the rivers to spawn, where they but usually not penetrate like the real salmon also high in the mountains or in the headwaters; Rapids and waterfalls they do not tempt to overcome. However, the upgrade can take several months (eg, earlier in the Volga even over a year ); it happens sometimes under ice.

Many questions about the biology of the different populations are still to be clarified. Food intake is clearly set during the turn. On Laichort behave the males and the slightly larger females as other Salmoniformes, but the eggs are not buried, but expelled in the open water and inseminated - they then sink to the bottom and stick here laid on gravel and the like. Is spawned at water temperatures below 6 ° C (usually September, October ). Large females can readily donate 500,000 eggs per season in several stages. However, the ausgelaichten fish die in low numbers, but return to their state biotopes back - they can walk five times ( but probably not every year ) and join in more often. So wear - in contrast to Oncorhynchus - to feed their young with hardly. The incubation period for months, up to the Arctic spring.

Stenodus decreases in buying that stronger floods destroy a lot of eggs and brood, but in the spring, the number of predators is on the other hand still low and later the food situation for the young fish cheaper ( than for spring-spawning - which by the way at the subspecies leucichthys in the Volga lower reaches also were or are ). Some waters " dominated " the Njelma as the sole peak predator; after strong Oncorhynchus Rises, serve their salmon larvae and young fish as feed, also their population can often develop very well. You can compete with salmon, burbot or pike than predatory Coregone well. The food of fish older than 2 consists almost exclusively in all manageable fish, such as the Caspian Sea, especially in Gobiiden and clupeids, otherwise also coregonids, smelt, Dallia and young salmon. However, it also noted occasionally, you would begin Njelmy whose stomach was filled with small shells ( Finsch 1879).

Subspecies and (former) distribution

As usual with the Coregoniden there is taxonomic uncertainty also in this genus. Usually applies Stenodus as monotypic; but some authors want the "race" ( leucichthys ) recognize the catchment area of the Caspian Sea species status: they (the " Weißfischlein ", Russian белорыбица / Caspian inconnu ) have about a shorter head, opposite the North European- Siberian "race" ( nelma, Njelma, нельма ), which is also identical to the North American ( first described by Richardson in 1823 as mackenzii; Nearctic vernacular are whitefish, she ( e) fish ( "Mrs. fish " ), l' inconnu ("The Unknown " - hence " Conny " ) and " sii ", or more precisely siiriroaq (including the Inuit ) and others. Stenodus forms Coregonus spp., and Prosopium spp. spawners in the light all sorts of hybrids.

Stenodus leucichthys nelma occurs in many streams and rivers of Siberia, whose rich watersheds to China. The Njelma is also from northern European rivers known ( eastward from White Sea), but not from Scandinavia (despite expectation). In the Nearctic it is to the Northwest (Alaska, Yukon and parts of Northwestern Territories of Canada to the Anderson River, particularly in the Yukon and Mackenzie area) and limited the upstream stretches of the coast of the Arctic Ocean. She lives in the North Pacific or its tributaries such as the Anadyr and some rivers in northern British Columbia.

Since the Ice Age is the Bjelorybitsa, so the Nominat subspecies, S. leucichthys leucichthys, endemic to the Caspian Sea and its largest tributary, the Volga ( in which she could very well walk uphill because low gradient, were particularly important as spawning rivers but their tributaries Ufa and Belaya ), also of the Ural River, while Terek and Kura sparsely populated (although it is also stated as, indigenous ' for Turkey, which would relate to the Kura as a feeder ). Even on the Persian coast of the sea, the Bjelorybitsa is not entirely unknown, although only in the summer can be fished out of the cool deep region here. In Central Asia ( to Mongolia ) site- faithful populations were located in several reservoirs.

Use

As the Europeans this fish from Siberia and North America was known, the descriptions of travelers awakened (eg Brehm's Animal Life, Vol 8 ( 3rd ed 1892, pp. 349-352 ) ) the impression of inexhaustible swarms. The gold rush in the Yukon at the turn of the 19th to 20th century was entertained for a good part nutritionally by the savory and strong oily flesh of the Inconnu. We now know that giant swarms of large fish in the Arctic are particularly easy überfischbar because of temperature-induced low productivity. They were so used to just subsistence indigenous Inuit, Native Americans, Samoyeds. But even more drastic measures later worked on the river- regulation and energy on the populations. The Bjelorybitsa is today (especially by Volga - ropes that have prevented the spawning migration ) exterminated as a wild form and consists practically only in fish populations. These are but not completely transparent manner interspersed with nelma - genome, which is especially true for the Kazakh, Turkmen, etc. populations.

From the Anadyr population ( in the Chukchi ) are due to large dams only the freshwater portions in the upper reaches. In North America, the situation is slightly better, because there are large "river extensions " only in the planning stage. " Ladders " ( fish ladders ) would be hardly adopted by Inconnu (unlike salmon ). So currently tolerate the " Connie " still just the sports fishermen. The export (especially smoked, less frozen) is necessarily low - " production numbers " are rare.

Ambiguities still exist with regard to health concerns against fish from waters with inflows from (former) heavy metal mines. It has been found that so-called heat shock proteins ( HSP), which, inter alia, were considered as markers of exposure to mercury and easier to quantify than the metals themselves, so much less correlated than previously thought safe.