The sterlet (''Acipenser ruthenus'') is a relatively small species of
sturgeon
Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretace ...
from
Eurasia
Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago a ...
native to large rivers that flow into the
Black Sea
The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Roma ...
,
Azov Sea
The Sea of Azov ( Crimean Tatar: ''Azaq deñizi''; russian: Азовское море, Azovskoye more; uk, Азовське море, Azovs'ke more) is a sea in Eastern Europe connected to the Black Sea by the narrow (about ) Strait of Kerch, ...
, and
Caspian Sea
The Caspian Sea is the world's largest inland body of water, often described as the world's largest lake or a full-fledged sea. An endorheic basin, it lies between Europe and Asia; east of the Caucasus, west of the broad steppe of Central Asia ...
, as well as rivers in
Siberia
Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part of ...
as far east as
Yenisei
The Yenisey (russian: Енисе́й, ''Yeniséy''; mn, Горлог мөрөн, ''Gorlog mörön''; Buryat language, Buryat: Горлог мүрэн, ''Gorlog müren''; Tuvan language, Tuvan: Улуг-Хем, ''Uluğ-Hem''; Khakas language, K ...
. Populations migrating between fresh and salt water (
anadromous
Fish migration is mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousan ...
) have been
extirpated
Local extinction, also known as extirpation, refers to a species (or other taxon) of plant or animal that ceases to exist in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinct ...
.
Also known as Sterlet sturgeon.
Due to
overfishing
Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...
(for its flesh,
caviar
Caviar (also known as caviare; from fa, خاویار, khâvyâr, egg-bearing) is a food consisting of salt-cured roe of the family Acipenseridae. Caviar is considered a delicacy and is eaten as a garnish or a spread. Traditionally, the ter ...
, and
isinglass
Isinglass () is a substance obtained from the dried swim bladders of fish. It is a form of collagen used mainly for the clarification or fining of some beer and wine. It can also be cooked into a paste for specialised gluing purposes.
The E ...
), pollution, and dams, the sterlet has declined throughout its native range and is considered
vulnerable by the
IUCN
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
.
Restocking projects are ongoing, and it has been
introduced to some regions outside its native range, but the latter have generally not become self-sustaining.
Today, the majority of the international trade involves sterlets from
aquaculture
Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lot ...
.
Physical appearance
*The sterlet may reach 16 kg in weight and 100 to 125 cm in length, rarely exceeding a length of 90 cm.
*It is quite variable in coloration, but usually has a yellowish
ventral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...
side.
*It is distinguishable from other European species of sturgeons by the presence of a great number of whitish lateral
scutes
A scute or scutum (Latin: ''scutum''; plural: ''scuta'' "shield") is a bony external plate or scale overlaid with horn, as on the shell of a turtle, the skin of crocodilians, and the feet of birds. The term is also used to describe the anterior po ...
, fringed
barbel Barbel may refer to:
*Barbel (anatomy), a whisker-like organ near the mouth found in some fish (notably catfish, loaches and cyprinids) and turtles
*Barbel (fish), a common name for certain species of fish
**''Barbus barbus'', a species of cyprinid ...
s, and an elongated and narrow snout, highly variable in length.
Feeding habits
The sterlet's main source of food is
benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...
organisms; they commonly feed on
crustaceans
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...
,
worm
Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always).
Worms vary in size from microscopic to over in length for marine polychaete wor ...
s, and insect
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
e.
Life history
The sterlet commonly reaches the age of 22 to 25 years. Males reach sexual maturity at 3–7 years old and females at 4–12 years old. Spawning occurs from the middle of April to the beginning of June. Females may lay from 15,000–44,000 eggs, at water temperatures preferably 12–17 °C (54–63 °F).
As pond fish
Sterlets require relatively large ponds with good water conditions, and may get entangled in plants such as
blanketweed. They may require special food such as sterlet sticks, as they are unable to digest the vegetable proteins usually found in commercial fish foods.
As food
In Russia, it is held in high esteem on account of its excellent flesh, contributing also to the best kinds of caviar and
isinglass
Isinglass () is a substance obtained from the dried swim bladders of fish. It is a form of collagen used mainly for the clarification or fining of some beer and wine. It can also be cooked into a paste for specialised gluing purposes.
The E ...
.
History in the Danube
The sterlet (''Acipenser ruthenus'' in Linnaeus' classification) is the last of the five native sturgeon species inhabiting the Middle and Upper Danube River. Its population has dropped significantly, mainly due to the degradation of main habitats, spawning grounds and foraging grounds.
References
{{Authority control
Freshwater fish of Europe
Fish of Europe
Fish of the Black Sea
Fish of Central Asia
Fish of Russia
Fish described in 1758
Acipenser
Taxa named by Carl Linnaeus