Sterlet (Acipenser ruthenus)

Photo by Jiry Bohdal

by Terry White

Comments: The Sterlet is the sturgeon best suited for keeping in garden ponds as it's slower growing and has a smaller maximum size than other species available. The Sterlet is a freshwater species that only rarely is found in brackish water; as such they are less tolerant of salt than the other species but can easily take doses suitable for koi. More sedentary than some of the other species the Sterlet tends to spend day times down in the deepest parts of the pond becoming more active as dusk approaches. It is often seen looking for food around the edges of shelves and drop-offs. Care must be taken when bowling or transporting this fish as it tends to produce a lot of mucus from the body when caught not only making it very slippery to handle but it also thickens the water during transportation. The name Sterlet refers to the small bony stars (Scutes) found in the skin.

Sometimes in shops you will see other sturgeon given the Sterlet title, normally Diamond Sterlet or Siberian Sterlet. Do not believe them, it is a ruse by the shops to make you think that the Diamond or Siberian sturgeon will stay small and they will not. It is a true sturgeon not a dwarf species. They can grow to around 1 meter after 10-12 years and attain a maximum of around 1.2m and 16kg. They can be kept in ponds of 1000 - 2000 gallons (4500 -9000 litres) for many years but bigger is better if you want to keep the fish into adulthood. Best-kept temperature range is from 10-18^oC (50-65^oF) but can tolerate higher temperatures if lots of oxygen is present.

Albino Sterlets can be found. They are a pale yellow, almost orange in colour, which is the flesh with all the pigment taken out. The eyes also are orange/yellow. It makes a great pond fish as not only is it highly visible it also is slightly smaller at around .75m - 1m long but they tend to be more expensive than the natural coloured ones.

As with all sturgeons avoid buying them too small, they may be cheaper but their survival chances are much better when they are 10 - 12" long.

Description: The Sterlet has 11-18 dorsal scutes, 56-71 lateral scutes, 10-20 ventral scutes, 32-54 dorsal fin rays and 16-34 anal fin rays. A long pointed snout, the barbels are fimbriated and the lower lip is split. Dark-brown to grey, sometimes a dark green tint on the back, with white fin edges ventrally white. The scutes are whitish and the scutical lines are visible running down the body.

Distribution map for Acipenser ruthenus

Wild Distribution: Sterlet are distributed in the Pronto-Caspian watershed as well as in rivers entering the White and Kara seas, in mainland Europe and Siberia tributaries of the Black sea, Azov and Caspian Seas; parts of the Polar sea; also some tributaries of the Baltic Sea. Sterlets are found from the Danube, the Don and Kuban, Dnjester and Dnjepr, Volga, Ural, Ob Irtysh and Jennessej rivers.

Vulnerability: The Sterlet is listed as 'Vulnerable' on the IUCN Red List of Threatened Species.

Dam on the Volga River at the point it flows out of Lake Volgo

Biology: The Sterlet is a potamodromous (freshwater only) species. During spawning migration Sterlets move upstream depending upon the water level. At high water levels migration is further upstream. Males appear on the spawning ground prior to the females and stay there over a longer period. Spawning takes place in April to June at water temperatures of 10-17^oC over gravel substrate of 1-7 cm diameter at a depth of 1-15 m along the ridges at water velocities of 1.5-5.0 m/s. Sexual maturity is reached after 3-5 years in males and 5-8 years in females.

A female carries 20,000 to 30,000 eggs per kg of body weight. The larvae hatch after 4-5 days at 13^oC and have a length of 6-7mm after additional 6-10 days exogenous feeding begins. Adults begin to migrate downstream immediately after spawning. Feeding is commenced in backwaters and basins during the migration. During the winter the fish tend rest up in pools where they can group together.

In Russia sturgeon culture and reproduction begun with the sterlet in 1869; nowadays the sterlet is frequently used for hybrids. In ponds the Sterlet is relatively undemanding to rear although the growth is slow reaching 50g in the first year 300 g in the second and 1kg in the third.

Natural feeding: The Sterlets natural food consists of insect larvae, crustaceans, oligochaetes and molluscs. Zooplankton and fish eggs are part of the diet if available.

Orchard Fisheries Sturgeon / Sterlet Food Pellets for sale. Buy online or order by phone.

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