Sterlet

Sterlets are ancient fish species that are also suitable for keeping in the garden pond, provided that you know their special needs.

Characteristics

• Name: Sterlet (Acipenser ruthenus)
• System: Sturgeons (Acipenseridae)
• Size: 40-120 cm
• Origin: rivers in Northern Russia, Baltic Sea tributaries, Danube
• Posture: not very demanding
• Aquarium size: from 5000 liters
• pH value: 6.5-7.2
• Water temperature: 2-26 ° C
• Special requirements: clear, oxygen-rich water, gravelly subsoil, additional ventilation required above 15 ° C. No permanent high organic load and nitrate values above 100 mg / l.

Interesting facts about the Sterlet

Scientific name: Acipenser ruthenus

Systematics

• Class: Actinopterygii (ray fins)
• Subclass: Chondrostei (cartilage organoids)
• Order: Acipenseriformes (sturgeon)
• Family: Acipenseridae (sturgeon)
• Genus and species: Acipenser ruthenus

Size

When fully grown, sterlets are on average 40 cm and a maximum of 120 cm long. They then weigh an average of 2-4 kg, the largest specimens up to 16 kg.

Color

In nature, sterlets are dark gray-brown with whitish fin edges and a light side line formed by 60-70 side shields. The head has a lower mouth and a nose that is slightly bent upwards. The belly is light. There are also almost white albino forms from breeding in pond farms and circulatory systems.

Origin

• Northern Russia
• Baltic Sea tributaries
• Danube

Gender differences

• Males are sexually mature at 3-5 years, females from 7-9 years.
• Sexually mature females can be recognized by their physique because they are thicker.
• Before sexual maturity, differentiation is only possible for specialists.

Reproduction

Sterlets spawn in shallow water on gravel. To do this, they move upstream to the gravelly upper reaches of the rivers. The sticky eggs cling to the stones in the flowing water. After hatching, the stream of water drives the juvenile fish into nutrient-rich waters.

Life expectancy

Up to 20 years in good housing conditions.

Interesting facts

Nutrition

In the wild, sterlets feed on animal food, such as:

• Insect larvae
• Worms
• Snails
• Shellfish
• small fish (sometimes)
• now and then a few dried smelts
• Mussel meat (without salt!)
• River flea shrimp
• Sturgeon feed pellets

Brook fleas are real treats and can be used to tame the fish.

Sturgeon feed pellets, like natural food, are rich in protein (50-60% crude protein) and contain a lot of aquatic fat (up to 20%).

• It is important to have a high proportion of fish in the dry feed, which increases the energy content of the ration and contains many essential fatty acids. This applies to both sinking feed and swimming feed.
• Young sterlets in particular like to swim backward on the surface of the water and, after getting used to them, take the fish feed directly from the keeper. Particularly with this size of fish, it is important to ensure sufficient feed intake.
• It is absolutely necessary to feed a suitable sturgeon food in the above-mentioned composition, otherwise, there is a risk of malnutrition, vitamin deficiency, and starvation. For adequate nutrition one should feed 1% of the live weight of the sterlets.
• Because of its high-fat content, sturgeon feed cannot be stored for very long, it quickly becomes rancid and then dangerous for the fish. Small containers that should be stored in a cool and dark place are better protected from spoilage than large ones. After opening the package, the feed should be fed within 3 months. Older batches of feed should be disposed of.

Group size

Sterlets are loners and therefore also feel very comfortable alone in the pond.

Pond size and required water parameters

Pay attention to the following criteria for species-appropriate husbandry:

• Sterlets need a lot of free swimming space. Keep a sterlet in a pond with a capacity of 5,000 liters or more. From 20,000 liters, two or three copies also feel good.
• No thread algae, stones, or roots may protrude into the pond; because sturgeons cannot swim backward. If they get caught, they will suffocate because the swimming process helps them breathe.
• A good filter system must ensure clean and clear water with very good water quality. The high oxygen demand of the fish is taken into account by a high circulation rate and additional ventilation.
• The proportion of oxygen dissolved in the water must not fall below 5 mg / l.
• Guaranteed at temperatures above 15 ° C, oxygen concentrations above 6 mg / l.
• Make sure the water quality is good. The optimal pH range is between 6.5 and 7.2. Avoid strong algae formation, because it leads to high pH values ​​above 8. The ammonium and nitrite concentration values ​​must not exceed 0.1 mg / l, depending on the pH values.
• Check the nitrate levels regularly. Although these are hardly dangerous, high concentrations above 100 mg / l are generally a sign of old water that is overloaded with degradation products. The sturgeons cannot tolerate this water permanently.

Socialization with other pond fish

Since the fish are completely peaceful, they can easily be socialized with Koi, for example. Small fish, such as young goldfish, can, however, be eaten by large sturgeons. It should also be noted that sterlets are not very targeted when it comes to eating and that a large koi can easily push them away from the food. There is a risk that individual sturgeons in a large group of Koi will not get enough food. Therefore, be particularly careful when the sturgeons feed.