Stenodus leucichthys

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Stenodus leucichthys
Stenodus leucichthys.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Salmoniformes
Family: Salmonidae
Genus: Stenodus
Species:
S. leucichthys
Binomial name
Stenodus leucichthys
Synonyms
  • Salmo leucichthys Güldenstädt, 1772
  • Stenodus leucichthys leucichthys (Güldenstädt, 1772)
  • Salmo nelma (non Pallas, 1773)

Stenodus leucichthys, also known as the inconnu, sheefish, ak balyk, or beloribitsa, is a species of large, anadromous, freshwater whitefish in the family Salmonidae. In the strict sense its natural distribution is restricted to the Caspian Sea basin. It is now considered extinct in the wild, but survives in cultured stocks. [1] [2] The nelma (Stenodus nelma), a more widespread species of Eurasia and North America, is sometimes considered its subspecies. [3] [4]

Contents

Systematics

Alternatively, the name Stenodus leucichtys has previously been used in a broader sense, referring to a widespread species composed of two subspecies, which if true would make it the sole extant representative of the Stenodus genus. [2] In addition to the landlocked subspecies Stenodus leucichthys leucichthys, it comprises the nelma, Stenodus leucichthys nelma (Pallas, 1773) which lives in Eurasian and North American rivers of the Arctic basin. Despite this designation, nelma, similarly known as the sheefish or inconnu, is currently often considered to be a distinct species Stenodus nelma, which makes the legitimacy of this use case and its inclusion of both species as one debatable. [1] [3] [5] [4] [6]

At a higher level, the genus Stenodus is not considered phylogenetically distinct from the broader lake whitefish genus Coregonus , although it is phenotypically distinct due to its large size and specialized predator morphology. [7] This is due to conflicting evidence regarding the monophyly of the Coregonus genus and its relationship to Stenodus, either being sister to or nested within Coregonus, with several studies backing both arguments. Possible reasons for conflicting results include the relatively new age of the clade that contains both genera, which diverged approximately 10 million years ago, and the lack of sufficient data on the effect of hybridization between and within each genera. While the most recent mitogenomic analysis does support the monophyly of Coregonus, evidence of the Atlantic whitefish species, C. huntsmani, being more basal to the whitefish genus than the Stenodus genus suggests it being paraphyletic. [8]

Description

The inconnu has a large, terminal mouth with a protruding lower jaw, a high and pointed dorsal fin, a forked and homocercal tail, and possesses an adipose fin. It is generally silvery white on the body sides and underbelly with a green, blue, or pale brown back. The meat is white, flaky, sweet, and somewhat oily. [2] It has an elongate, fusiform body plan of up to 130 centimetres (51 in) in total length and weighing up to 35 kilograms (77 lb). [9] Males exhibit slight sexual dimorphism during spawning, developing nuptial tubercles on its head and body side. Additionally, Stenodus leucichthys, and the closely related nelma, are distinct among whitefish due to their more predatory morphologies. [7] In addition to being extremely closely related species, S. leucichthys and S. nelma are also largely indistinguishable in appearance, however, the two species should not be confused given their ranges occupy different continents.

Biology

Stenodus leucichthys is an anadromous fish, meaning it migrates up stream into fresh waters from the sea in order to spawn and reproduce externally. Egg development can last up to 200 days, culminating in the release of over 100 thousand eggs, with each individual spawning twice during their life cycle (every 2 to 3 years). Migrations can last up to or exceeding a year long, this is partially owing to the slow development of their gonads which can require up to 8 months spent in the river to fully mature, just in time for their spawning season. [2] [10] In terms of development, inconnu larvae reach the fingerling stage at approximately 30 to 40 days and have a maturation period lasting 3 to 6 years, with males typically reaching maturity about one year earlier. [2] Although historically calculated based on their scales, age is most accurately measured by analyzing the otolith or fin rays, particularly pectoral fin rays, of Stenodus as crowding of scales in old age fish reduces the accuracy and readability of these measurements. However, the accuracy of these measurements has only been analyzed in the North American populations of the closely related, or possible subspecies, Stenodus nelma. [11]

The fish eat plankton and aquatic insect larvae as juveniles and then become predators of smaller fish almost exclusively in adulthood. However, 30-day old fingerlings stomach contents have been observed to contain the larvae and juveniles of smaller fish species, indicating that this predatory transition occurs during very early life stages. As an adult, its primary food source, comprising over 90% of its diet, is small pelagic fish which mainly consisted of native kilka and silverside, with less reliance on Caspian roach and gobiids, prior to its extirpation. [2] [4]

Distribution

Endemic to the Caspian Sea, the Caspian inconnu is now considered extinct in the wild, with current populations confined to hatcheries or only maintained due to stocking. [3] Within the Caspian, inconnus live primarily in the central and southern parts of the sea during summer months but are also often found in the Northern Caspian for feeding during autumn and winter months. [12]

Historically, ak balyk used to inhabit particularly the Volga, Ural and Terek rivers, and migrate up to 3,000 kilometres (1,900 mi) upstream from the Caspian to their main spawning grounds Kama River until dam construction and river contamination limited migration past the city of Volgograd. [2] [9] [13] In addition to the Kama tributary, their major spawning grounds included the Oka and Sura tributaries among others along the greater Volga River. [12] Alternatively, the closely related nelma has a broad, arctic and sub-arctic distribution extending from northern Eurasia to north-west North America.

Habitat

Inconnus are pelagic fish that do not exceed depths of 60 to 65 metres (197 to 213 ft), typically inhabiting 25 to 45 metres (82 to 148 ft) depths. [2] [9] It is euryhaline given its anadromous spawning migration, allowing them to survive in fresh and brackish waters with increased salinity tolerances developing in fingerlings around the age of 30 to 50 days. A primarily cold-water species, inconnu prefer temperatures below 20°C and will only be found in the North Caspian when temperatures reach around 10°C. [2]

Conservation Status

Following the construction of dams and hydropower reservoirs, particularly the Volgograd dam in 1959, the migration and natural reproduction of this species has been completely impeded with no efforts to reestablish their natural migration routes. [9] [12] [13] Historically, their food supply was sustained by native small fish until the introduction of invasive comb jelly Mnemiopsis into the Caspian and the decline of prey fish stocks, especially kilka, degraded their food supplies, which contributed to its decline as well. [2] Today, the taxon is considered to be extinct in the wild by the IUCN Red List. [1] [9] The stock however survives in hatcheries, particularly those established in the Volga River, and some populations are maintained by stocking. [3]

Human Use

In the past, inconnu was a very important commercial fish, with its fat-rich meat making it ideal for smoking. Smoked whitefish is typically referred to as balyk in the Turkic-speaking areas of this region and is likely the origin for the species’ Kazakh name, ak balyk. While annual commercial catch rates used to exceed 1000 tons in the early to mid-20th century, the rapidly declining population has led to a ban on commercial fishing of Stenodus leucichthys, with fishing only done for reproductive purposes in support of hatcheries and only at special fishing sites. While this ban was lifted in the 1980s due to artificial reproduction efforts, it was reestablished because of continued population decline from illegal fishing, river contamination, and hatcheries releasing fewer fingerlings. [9] During this ban lift, the inconnu served as an important fish for restocking in the Caspian, however these efforts were largely reduced in the 1990s due to further population decline. [2] The widespread, closely related Stenodus nelma is a historically important subsistence food for Native Alaskans in the Yukon and Mackenzie River basins. [14]

Related Research Articles

<i>Coregonus</i> Genus of fishes

Coregonus is a diverse genus of fish in the salmon family (Salmonidae). The Coregonus species are known as whitefishes. The genus contains at least 68 described extant taxa, but the true number of species is a matter of debate. The type species of the genus is Coregonus lavaretus.

<i>Coregonus lavaretus</i> Species of fish

Coregonus lavaretus is a species of freshwater whitefish, in the family Salmonidae. It is the type species of its genus Coregonus.

<span class="mw-page-title-main">Pollan (fish)</span> Species of fish

The pollan or Irish pollan is a freshwater whitefish known only from five Irish lakes, Lough Neagh, Lower Lough Erne, Lough Ree, Lough Derg and Lough Allen. The pollan faces competition from introduced species such as pike, roach and zebra mussel, and the populations rely on restocking for survival.

<span class="mw-page-title-main">Arctic cisco</span> Species of fish

The Arctic cisco, also known as Arctic omul, is an anadromous species of freshwater whitefish that inhabits the Arctic parts of Siberia especially Yenisey Gulf. It can also be found in Alaska and Canada. It has a close freshwater relative in several lakes of Ireland, known as the pollan, alternatively regarded as conspecific with it, or as a distinct species.

<span class="mw-page-title-main">Broad whitefish</span> Species of fish

The broad whitefish is a freshwater whitefish species. Dark silvery in colour, and like a herring in its shape. Its distinctive features includes: a convex head, short gill rakers, and a mild overbite. It is found in the Arctic-draining streams, lakes, and rivers of far eastern Russia and North America. Its prey includes larval insects, snails, and shellfish. It is eaten by humans and brown bears.

<span class="mw-page-title-main">Round whitefish</span> Species of fish

The round whitefish is a freshwater species of fish that is found in North American drainages from Alaska to New England, including the Great Lakes except for Lake Erie, and in Arctic tributaries of northeast Asia, as well as northern Kamchatka Peninsula and the northern coasts of the Sea of Okhotsk. It has an olive-brown back with light silvery sides and underside and its length is generally between 9 and 19 inches. They are bottom feeders, feeding mostly on invertebrates, such as crustaceans, insect larvae, and fish eggs. Some other fish species, like white sucker in turn eat their eggs. Lake trout, northern pike and burbot are natural predators. Other common names of the round whitefish are Menominee, pilot fish, frost fish, round-fish, and Menominee whitefish. The common name "round whitefish" is also sometimes used to describe Coregonus huntsmani, a salmonid more commonly known as the Atlantic whitefish.

<span class="mw-page-title-main">Atlantic whitefish</span> Species of fish

The Atlantic whitefish is a coregonine fish inhabiting some freshwater lakes within Nova Scotia, Canada. It is known to survive only in the Petite Rivière watershed as landlocked populations. Earlier it was also found in the Tusket and Annis rivers of Nova Scotia. Those populations were anadromous, migrating to the estuary to feed while breeding in freshwater.

Stenodus is a genus of large-sized whitefish in the family Salmonidae. It consists of two species; one of them (beloribitsa) is extinct in the wild. The two species have alternatively been considered subspecies of the single species Stenodus leucichthys.

<span class="mw-page-title-main">Freshwater whitefish</span> Subfamily of fishes

The freshwater whitefish are fishes of the subfamily Coregoninae, which contains whitefishes and ciscoes, and is one of three subfamilies in the salmon family Salmonidae. Apart from the subfamily Coregoninae, the family Salmonidae includes the salmon, trout, and char species of the subfamily Salmoninae, and grayling species of the subfamily Thymallinae. Freshwater whitefish are distributed mainly in relatively cool waters throughout the northern parts of the Northern Hemisphere.

<span class="mw-page-title-main">Gravenche</span> Extinct species of fish

The gravenche, also known as the Lake Geneva whitefish or the little fera, is a presumably extinct freshwater fish from Lake Geneva in Switzerland and France.

<span class="mw-page-title-main">Peled (fish)</span> Species of fish

The peled, also called the northern whitefish, is a species of freshwater whitefish in the family Salmonidae. It is found in northern Europe and Asia.

<span class="mw-page-title-main">Humpback whitefish</span> Species of fish

The humpback whitefish, also referred to as the bottom whitefish, the Arctic whitefish or the pidschian, is a species of freshwater whitefish with a northern distribution. It is one of the members in the broader common whitefish complex, or the Coregonus clupeaformis complex. This fish lives in estuaries and brackish water near river mouths, in deltas and in slowly running rivers, in large lakes with tributaries, and floodplain lakes. It can migrate long distances upriver for spawning.

Coregonus trybomi is a freshwater whitefish in the family Salmonidae. It is a spring-spawning type of cisco, which probably has evolved from sympatric vendace independently in a number of Swedish lakes. Only one of those populations survives, and it is therefore considered Critically Endangered by the IUCN Red List. The status of Coregonus trybomi as a distinct species is however questionable. By Swedish authorities it is treated as a morphotype or ecotype, not an independent species. It was listed as "Data Deficient" in 2010 but excluded from the national red list in 2015.

The Caspian lamprey, Caspiomyzon wagneri, is a species of lamprey native to the Caspian Sea, and a member of the Petromyzontidae family. This species is a non-parasitic lamprey that feeds on animal carcasses.

Stenodus nelma, known alternatively as the nelma, sheefish, siifish, inconnu or connie, is a commercial species of freshwater whitefish in the family Salmonidae. It is widespread in the Arctic rivers from the Kola Peninsula eastward across Siberia to the Anadyr River and also in the North American basins of the Yukon River and Mackenzie River.

Coregonus fontanae, also known as the Stechlin cisco, Fontane cisco, or Fontane's cisco, is a putative species of freshwater whitefish in the family Salmonidae endemic to the Großer Stechlinsee in northern Germany. It is believed to have recently evolved from the sympatric vendace, Coregonus albula.

Coregonus bavaricus, the Ammersee kilch, is a species of freshwater whitefish endemic to Lake Ammersee in the German state of Upper Bavaria. A small, silver-colored fish, it typically lives between 60–85 m (197–279 ft) deep, though shallower in the summer months. In the early 20th century the Ammersee kilch was an important commercial species, but its population declined drastically in the 1930s onward due to overfishing and eutrophication of the only lake in which it is found. Today it is listed as Critically Endangered by the International Union for Conservation of Nature (IUCN) and may be on the verge of extinction.

Alosa kessleri, also referred to as the Caspian anadromous shad, the blackback, or the black-spined herring, is a species of alosid fish. It is one of the several species of shad endemic to the Caspian Sea basin.

<i>Coregonus maraena</i> Species of fish

Coregonus maraena, referred to in English as the maraene, maraena whitefish, vendace, cisco, lake herring, lake whitefish or the whitefish, is a whitefish of the family Salmonidae that occurs in the Baltic Sea basin - in the sea itself and the inflowing rivers, and in several lakes as landlocked populations. It is found in Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Netherlands, Norway, Poland, Slovakia, Russia and Sweden. As of 2013, it has been listed as a vulnerable species by the IUCN and as endangered by HELCOM. It is an extremely important fish within the Baltic Sea ecosystem, both for population equilibrium and for the local diets of the surrounding human population. Due to a variety of factors, mostly overfishing, the maraena's population dwindled to near-extinction levels. Thus, rampant repopulation was enacted to preserve this important fish.

<i>Coregonus widegreni</i> Species of fish

Coregonus widegreni, also called the Valaam whitefish, is a putative species of freshwater whitefish, a part of the common whitefish complex from Northern Europe. It is a demersal form of freshwater whitefish that feeds on benthic invertebrates. It spawns in late autumn, and can reach a length of 55 cm maximum. It is characterized by a low gill raker density.

References

  1. 1 2 3 4 Freyhof, J. & Kottelat, M. (2008). "Stenodus leucichthys". IUCN Red List of Threatened Species . 2008: e.T20745A9229071. doi: 10.2305/IUCN.UK.2008.RLTS.T20745A9229071.en . Retrieved 19 November 2021.
  2. 1 2 3 4 5 6 7 8 9 10 11 Belyaeva, E. S. "Stenodus leucichthys leucichthys". caspianenvironment.org. Archived from the original on 2013-07-03.{{cite web}}: CS1 maint: unfit URL (link)
  3. 1 2 3 4 Kottelat, M.; Freyhof, J. (2007). Handbook of European Freshwater Fishes. Publications Kottelat. ISBN   978-2-8399-0298-4.
  4. 1 2 3 Froese, Rainer; Pauly, Daniel (eds.). "Species in genus Stenodus". FishBase . February 2013 version.
  5. ↑ Freyhof, J. & Kottelat, M. (2008). "Stenodus nelma". IUCN Red List of Threatened Species . 2008: e.T135545A4141935. doi: 10.2305/IUCN.UK.2008.RLTS.T135545A4141935.en .
  6. ↑ Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Species in the genus Stenodus". Catalog of Fishes . California Academy of Sciences . Retrieved 15 March 2012.
  7. 1 2 Bernatchez, L.; Colombani, F.; Dodson, J. J. (1991). "Phylogenetic relationships among the subfamily Coregoninae as revealed by mitochondrial DNA restriction analysis" (PDF). Journal of Fish Biology. 39: 283–290. Bibcode:1991JFBio..39S.283B. doi:10.1111/J.1095-8649.1991.TB05091.X . Retrieved 2012-05-05.
  8. ↑ Campbell, M.A.; Buser, T.J.; Alfaro, M.E.; López, J.A. (2020). "Addressing incomplete lineage sorting and paralogy in the inference of uncertain salmonid phylogenetic relationships". PeerJ. 8: e9389. doi: 10.7717/peerj.9389 . PMC   7337038 . PMID   32685284.
  9. 1 2 3 4 5 6 Poursaeid, F.; Falahatkar, B. (2012). "Threatened fishes of the world: Stenodus leucichthys leucichthys Güldenstädt, 1772 (Salmonidae)". Aqua (International Journal of Ichthyology). 18 (1): 31–34. S2CID   86104330.
  10. ↑ Dyubin, V.P. (2007). "The state of the reproductive system in Caspian inconnu Stenodus leucichthys (Salmoniformes, Coregonidae) with the sexual cycle completed under conditions of fish hatchery". Journal of Ichthyology. 47 (7): 533–537. doi:10.1134/S0032945207070077.
  11. ↑ Howland, K.L.; Gendron, M.; Tonn, W.M.; Tallman, R.F. (2004). "Age determination of a long-lived coregonid from the Canadian North: comparison of otoliths, fin rays and scales in inconnu (Stenodus leucichthys)". Annales Zoologici Fennici. 41 (1): 205–214. JSTOR   23736204.
  12. 1 2 3 Aladin, N.V.; Chida, T.; Chuikoy, Y.S.; Ermakhanov, Z.K.; Kawabata, Y.; Kubota, J.; Micklin, P.; Plotnikov, I.S.; Smurnov, A.O.; Zaitev, V.F. (2018). "The history and future of the biological resources of the Caspian and the Aral Seas". ". Journal of Oceanology and Limnology. 36 (6): 2061–2084. doi:10.1007/s00343-018-8189-z.
  13. 1 2 Dyubin, V.P. (2007). "The state of the reproductive system in Caspian inconnu Stenodus leucichthys (Salmoniformes, Coregonidae) with the sexual cycle completed under conditions of fish hatchery". ". Journal of Ichthyology. 47 (7): 533–537. doi:10.1134/S0032945207070077.
  14. ↑ Kuhnlein, H.V. (2017). "Traditional Animal Foods of Indigenous Peoples of North America". Centre for Indigenous Peoples’ Nutrition and Environment (CINE). McGill University. Retrieved October 17, 2024.
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