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Threatened fishes of the world: Stenodus leucichthys leucichthys Güldenstädt, 1772 (Salmonidae)

Authors:
Abstract
This paper introduces the ecological and biological char-
acteristics of the Inconnu (Stenodus leucichthys leucichthys).
This is a Caspian Sea endemic species of the family
Salmonidae, listed as Extinct in the Wild in IUCN’s Red
Data Book due to restricted access to spawning grounds,
dam construction, illegal fishing, and environmental pol-
lution. This valuable species has considerable ecological
and economical importance for the region, but there are
little data for the Caspian Sea populations. We discuss its
distribution, ecological and reproductive characteristics,
and the causes of its extinction in the Caspian Sea.
Zusammenfassung
In dieser Arbeit werden die ökologischen und biologischen
Merkmale des Weißlachses („Inconnu“) Stenodus leucichthys
leucichthys einführend behandelt. Es handelt sich um eine
endemische Art des Kaspischen Meeres aus der Familie der
Lachsfische (Salmonidae), die in der Roten Liste des IUCN
als „ausgestorben“ geführt wird; als Gründe werden Ein-
schränkung der Laichgründe, Staudammbauten, illegale
Befischung und Umweltverschmutzung genannt. Die
wertvolle Art hat erhebliche ökologische und ökonomische
Bedeutung für die Region, aber es gibt wenige Daten über
die Populationen des Kaspischen Meeres. Wir diskutieren
die Verbreitung, die ökologischen und fortpflanzungsbiolo-
gischen Kennzeichen sowie die Gründe für die Ausrottung
im Kaspischen Meer.
Résumé
Cet article propose les caractéristiques écologiques et
biologiques du Stenodus (Stenodus leucichthys leucichthys). Il
s’agit d’une espèce endémique de la Caspienne, de la famille
de Salmonidae, répertoriée comme étiente dans la nature
selon l’IUCN’s Red Data Book, à cause de l’accès ma laisé
aux frayères, à la construction d’un barrage, à la che illé-
gale et à la pollution de l’environnement. Cette espè ce a une
importance considérable sur le plan éco logi que et écono -
mique dans la région,mais il y a peu de données concernat
les populations de la mer Caspienne. Nous trai tons de sa di -
stribution, de ses caractéristiques écolo giques et reproduc-
tives et des causes de son extinction en mer Caspienne.
Sommario
Questo articolo presenta le caratteristiche ecologiche e bio-
logiche del salmone bianco noto anche come “Inconnu
(Stenodus leucichthys leucichthys). Si tratta di una specie ende -
mica del Mar Caspio appartenente alla famiglia Salmonidae
e elencata come “Estinta in natura dallo IUCN Red Data
Book a causa delle limitazioni degli spazi riproduttivi, della
costruzione di dighe, della pesca illegale e dell’inquinamento
ambientale. Questa specie ha un’importanza considerevole
per la regione dal punto di vista ecologico ed economico, ma
esistono pochi dati per le popolazioni del Mar Caspio. Se ne
discutono la distribuzione, l’ecologia, la riproduzione e le
cause dell’estinzione nel Mar Caspio.
INTRODUCTION
The Inconnu (Stenodus leucichthys leucichthys
Güldenstädt) is the largest and fastest-growing
member of the whitefish subfamily Coregoninae
(Salmonidae). Two subspecies of Inconnu are rec-
ognized, with S. l. leucichthys isolated in the
Caspian Sea drainage of western Asia, while S. l.
nelma (Pallas) is found in the Arctic and sub-arctic
regions of north-western North America and north-
ern Eurasia (Stephenson et al. 2005). It is known by
a range of common names: Inconnu (English),
Belorybitsa (Russian), Mahi Ziba (Persian), Stenode
Blanc (French), Salmon Blanco (Spanish) Ak balyk
(Kazakh) and Azatmahy (Turkmenian).
Stenodus leucichthys leucichthys is the Caspian
endemic subspecies and mainly occurs along the
western and eastern coasts of the middle Caspian
aqua vol. 18 no. 1 - 15 January 2012
31
aqua, International Journal of Ichthyology
Threatened fishes of the world: Stenodus leucichthys leucichthys Güldenstädt,
1772 (Salmonidae)
Samaneh Poursaeid & Bahram Falahatkar*
Fisheries Department, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Guilan, Iran
* Corresponding author. Fisheries Dept., Faculty of Natural Resources, University of Guilan, Sowmeh
Sara, P.O. Box 1144, Iran. Tel.: +98 182 322 3599; Fax: +98 182 322 2102.
E-mail: falahatkar@guilan.ac.ir
Received: 24 April 2011 – Accepted: 30 July 2011
Sea at depths of 60-65 m (Berg 1984). Declining
natural populations in the Caspian Sea due to
heavy fishing pressure, increasing water pollution
and habitat alteration and destruction have
resulted in S. l .leucichthys being listed as “Extinct
in the wild” (IUCN Red List 2010). Concerns
about the decline of Stenodus l. leucichthys popula-
tions led Volga River hatcheries to carry out artifi-
cial reproduction and restocking in the Caspian
Sea (Belyaeva & Milstein 1959). The Arctic sub-
species, Stenodus leucichthys nelma, was introduced
into the northern Volga River drainage and is now
expanding, so may threaten surviving populations
and cultivated stocks through hybridization (Frey-
hof & Kottelat 2008).
Despite the ecological and economic importance
of this fish, very little is known about it in the
Caspian Sea. Therefore, the aim of this study is to
introduce and better understand the ecological and
biological characteristics of this valuable species.
Identification: D II-VI (9-13), A II-IV 9-15, dor-
sal fin high and pointed, adipose fin present, pelvic
fins with well developed axillary process, vertebrae
65-68, manubrium absent, with hook-shaped
processes on the capitulum, anterior edge of
hyomandibular round, only 19 to 26 gill rakers
present on lower limb of first gill arch. Scales large,
99-120 in lateral line. Body fusiform and moder-
ately slender, head relatively small, mouth large
and terminal, lower jaw long, tip projecting, hind
end reaching back behind eye, upper jaw reaching
to level of pupil, teeth present on jaws, vomer,
palatines and tongue. Pyloric caeca 191-193. Max-
imum length and weight 130 cm and 35 kg respec-
tively; much larger individuals have been recorded.
Sides of body silvery, belly silvery white without
spots, dorsum usually green, blue or pale brown
(Fig. 1). Sexual dimorphism develops during
spawning period, when epithelial tubercles appear
on head and side of body of males (Berg 1948;
Shariaty 2001).
Distribution: Stenodus l. leucichthys is found only
in rivers draining to the Caspian Sea, from which it
mainly ascends the Volga, while very few fish
ascend the Ural, and it is rarely found in the Terek.
It is widely found along the western coast north of
Makhach-kala and along the eastern coast
(Mangyshlak). Its closest relative, Stenodus leuci-
chthys nelma, penetrates into the Caspian Sea from
the Arctic Ocean basin through the Post-Glacial
ponded lakes which are situated between the basins
of the Volga and the Kama, on the one hand, and
of the Baltic Sea and the Arctic Ocean, on the other
(Berg 1948). Stenodus l. leucichthys spends the warm
season in the central and southern regions of the
Caspian Sea (Kottelat & Freyhof 2007) mainly in
Guilan and no record of this species has been
reported from the Mazandaran and Golestan coasts
(FAO 1991). Figure 2 shows the distribution of S.
l. leucichthys in the Caspian Sea basin.
Habitat and ecology: Stenodus l. leucichthys is a
pelagic species which inhabits open waters to the
depth 65 m, and has not been found below 65m
(its optimum depths are 25-45 m). This fish is an
oxyphilic species and prefers waters with tempera-
ture below 20°C. It is heterotrophic and an active
aqua vol. 18 no. 1 - 15 January 2012 32
Threatened fishes of the world: Stenodus leucichthys leucichthys Güldenstädt, 1772 (Salmonidae)
Fig. 1. Stenodus leucichthys leucichthys from the southern part of the Caspian Sea; weight 4300 g; total length 75 cm. Photo
by Samaneh Poursaeid.
predator. At 30 days after hatching, fingerlings
begin to feed on invertebrates and larvae and small
juveniles of other fishes. In the sea, adult S. l. leuci-
chthys feeds mainly on small fish (clupeids,
engraulids, juvenile cyprinids, atherinids, gobiids
etc) (Podlesny 1947; Svetovidov 1984; Shariaty
2001). Stenodus l. leucichthys is amphidromous.
However, amphidromy is not obligatory and non-
amphidromous populations have been described in
some locations (Petrova 1976). Mature adults
migrate from sea to the delta of the Volga in the fall,
winter and the early spring. Therefore, the species
has two seasonal forms, spring and autumn, which
are differentiated in time of entry to the Volga for
spawning (Berg 1948). Adults migrate downward
to the sea after spawning, but many of them die
(Freyhof & Kottelat 2008). The alevins immedi-
ately descend to the sea after hatching.
Reproduction: The main spawning sites of S. l.
leucichthys are located in the basin of the Kama, in
the Ufa River, 3000 km upstream from the mouth
of the Volga (Shariaty 2001). The secondary spawn-
ing grounds are situated in the Belaya between Ufa
and Sterlitamak. The spawning season in the Ufa
begins from the middle of October to the begin-
ning of November. Males mature at +5 to +6 years
while females reach maturity at the age of +6 to +7
years (Freyhof & Kottelat 2008). Stenodus l. leuci-
chthys spawns twice during its life cycle with an
interval of two years (Berg 1948). Its optimum tem-
perature for reproduction is 0.1 to 6°C. Semi-adhe-
sive eggs are deposited on the gravel and rock sub-
strate (Kottelat & Freyhof 2007). The sex ratio of
brooders in the natural spawning grounds is almost
1:1 as for the subspecies Stenodus leucichthys nelma
(Brown 2000). The average fecundity is 250× 103
eggs per individual (104.5-400× 103). On average,
about 26% of the total weight of each fish is egg
weight (Berg 1948). Embryonic development takes
about 180-200 days. Fry hatch from March up to
the early May (mostly the second half of April).
From the seventh day onward, fry begin to feed on
plankton. The fry stage lasts around two months
and then they develop into fingerlings (Berg 1948).
Threats: The sharp decline in their abundance
due to the construction of dams, insufficient
spawning areas, increasing illegal fishing, unstable
hydrological conditions, river contamination and
damage caused by other fish (especially kilka) and
crustaceans has resulted in this species being listed
as extinct in the wild (Letichevski 1983; IUCN
2010).
BRIEF DISCUSSION
Unfortunately, the published data on different
aspects of S. l. leucichthys is limited and most stud-
ies on the species has been carried out on North
American and Eurasian populations of Stenodus
leucichthys nelma (Scott & Crossman 1973; Alt
1977; Morrow 1980; Brown 2000; Howland et al.
2000; Underwood et al. 2000; Stephenson et al.
2005). Therefore, much effort from scientists and
aqua vol. 18 no. 1 - 15 January 2012
33
Samaneh Poursaeid & Bahram Falahatkar
Fig. 2. Distribution of Stenodus leucichthys leucichthys in
the Caspian Sea basin (red circles).
governments should be made in understanding the
biology, ecology and behaviour for managing this
valuable species. One key objective in working
with endangered species is to increase the number
of individuals of the species concerned by artifi-
cially/controlled reproduction in captivity. Unfor-
tunately, there is no policy for preserving this
species in the Caspian Sea from illegal fishermen
by countries bordering the Sea and this should be
done according to fishing methods, size of net
mesh and time/place prohibition. Previously, the
Russian federation enhanced the spawning areas in
the lower parts of the Volgograd hydroelectric
power station for increased efficiency of natural
reproduction.
In connection with the present study, the negative
influences of the modern environment needs to be
studied (i.e. all possible causes of stress, environ-
mental changes, destruction of spawning grounds)
in order to better organize protection of this species
and thus develop the necessary strategies for action.
Findings from this preliminary data suggest that
further research is needed for the future, including
population genetics, artificial spawning, domesti-
cation for future aquaculture activities, natural
behaviour during migration and spawning, as well
as ionic balance and osmoregulation. The collec-
tive goal of this research should enhance the effec-
tiveness of breeding programs, increase popula-
tions of remaining wild stock, and to improve our
understanding of the biological knowledge of this
species. Since stocks have declined, much effort is
needed to rehabilitate the wild populations by all
countries around the Caspian Sea.
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aqua vol. 18 no. 1 - 15 January 2012 34
Threatened fishes of the world: Stenodus leucichthys leucichthys Güldenstädt, 1772 (Salmonidae)
... Recently (June 2018) we saw a single specimen of this species (about 55 cm and 3,500 gr) in the fish market at Freydonkenar city. In addition, Poursaeid and Falahatkar (2012) recorded from Gilan coast. ...
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Rearing of Inconnu fingerlings in the Volga river delta
  • V N Belyaeva
  • V V Milstein
BELYAEVA, V. N. & MILSTEIN, V. V. 1959. Rearing of Inconnu fingerlings in the Volga river delta. Moscow: "Rybnoye Khozyaistvo". Fish Industry Journal: 1-18.
Fishes of freshwaters of USSR and adjacent countries. Vol I. USSR Academy of Sciences publishers
  • L S Berg
BERG, L. S. 1948. Fishes of freshwaters of USSR and adjacent countries. Vol I. USSR Academy of Sciences publishers, Moscow-Leningrad.