Black Sea Kalkan

The Black Sea Kalkan is a fish of the flounder family and is considered endemic to the Black Sea. This is a very tasty fish, which is a valuable object of mariculture, which is actively cultivated in some Black Sea countries. Kalkan fish is successfully grown in intensive mariculture in cages, recirculation systems, in pools, and in fenced-off areas of the sea. Let's take a closer look at what the Black Sea Kalkan looks like, what its habitat is like, and much more.

 

 

Content

 

• What does the Black Sea Kalkan look like?
• What kind of fish is the Black Sea Kalkan
• Description of the Black Sea Kalkan fish
• Where does the Black Sea Kalkan fish live?
• Lifestyle of Black Sea Kalkan fish
• Reproduction of Black Sea Kalkan fish
• Spawning of the Black Sea Kalkan
• Growing Black Sea Kalkan

 

 

What does the Black Sea Kalkan look like?

 

What kind of fish is the Black Sea Kalkan

The Black Sea Kalkan, also known as the Azov Kalkan, or may be called the Azov Diamond (Latin name Scophthalmus maeoticus) is a species of ray-finned fish from the family Scophthalmidae, which is located in the order Flounders. The Azov Kalkan, which lives in the Sea of Azov, is considered a subspecies of the Black Sea Kalkan. It is believed that the Black Sea Kalkan is a related species of turbot.

The Black Sea Kalkan is one of the most valuable fish species in the Black and Azov Seas. Kalkan has a delicious taste, for which the Black Sea kalkan is called “Black Sea turbot”. In the Black Sea basin, kalkan is one of the most expensive Black Sea fish products.

Description of the Black Sea Kalkan fish

The Black Sea kalkan fish has a tall body, the height of which is 80% of the length. The body of the Kalkan is covered with bony conical tubercles. The eyes of the Kalkan fish are on its left side, which is the top. The lower part of the body of the Kalkan is white, the color of the eye side is brownish, with reddish spots. The Black Sea Kalkan fish has no scales. Kalkan has the ability to change color, masquerading as the color of the seabed. In the jaws there are even, bristle-like teeth arranged like ribbons; teeth are also located on the vomer.

The maximum body length of the Kalkan fish is 85 cm, and the mass of the Kalkan reaches 12 kg.

 

Where does the Black Sea Kalkan fish live?

 

Kalkan is a Black Sea endemic and therefore is found only in the Black and Azov Seas and is found in the adjacent part of the Sea of Marmara, the kalkan enters the mouths of rivers such as the Dnieper and Dniester. The Black Sea Kalkan lives on the seabed, preferring sandy (shell) and silty soils and is found at depths of up to 100 m in the Black Sea shelf zone to the continental slope of the depths, distributed along the entire coast. The Black Sea Kalkan fish forms local herds that do not carry out large migrations, so the range of the Black Sea Kalkan occupies less than 25% of the Black Sea. Local populations of Kalkan mix in adjacent zones. The largest population of the Black Sea Kalkan is located in the western part of the Black Sea on the shelf of Ukraine, Romania, and Bulgaria. There are populations in Turkish waters, as well as in the northeastern part of the Black Sea, located on the shelf from Crimea to Georgia.

The Azov Kalkan lives in the Sea of Azov. In winter and summer, the kalkan stays in deep water, and in spring and autumn it moves to shallow water.

Kalkan fry appear in the bottom layer at a depth of 2 to 10 m in August; Kalkan fry live in these areas for two to three months. Then the juveniles of the Kalkan move away from the shores. Adult specimens of the Kalkan at the age of 4-7 years in early spring accumulate for spawning at a depth of 30-70 m, in July-August they move towards greater depths, and in October they again approach the shore to feed.

Lifestyle of Black Sea Kalkan fish

The Black Sea kalkan fish is characterized by a long life cycle and a change in habitat during the period from the caviar stage to adulthood. The adult Black Sea Kalkan leads a bottom lifestyle and lives at depths from 10 to 120 m; in the winter-spring period, the Kalkan fish prefers to stay at depths of 10–70 m; in the summer-autumn period, the Kalkan goes to depths of 40–90 m. Black Sea Kalkan fish prefers to stay in a layer of water with a temperature of 8–10°C; the kalkan migrates following the migration of the species of fish that the kalkan mainly feeds on.

2 - 3 weeks after hatching, a complex metamorphosis begins, as a result of which the right eye moves to the left side of the body, the spine of the fish curls, and the upper left side of the body becomes grayish-brown, and the right side becomes milky.
Kalkan radically changes its environment from plankton to a near-bottom habitat, adapting to its diet
new food organisms, under radically changed physical conditions (especially low light) and adaptation of the immune system to a completely new microbiota of the environment.
Kalkan fry sink to the bottom after metamorphosis at a shallow depth and still hold Throughout the warm season, they can be located in the splash zone; often, fry of the Kalkan are kept in thickets of macrophytes, or live on coastal banks, on silt-sandy soils. At the same time, the kalkan leads the lifestyle of a typical ambush predator: the kalkan can burrow into the ground and hide in it, both in case of danger and to hunt for active prey - crustaceans (copepods, gammarus, shrimp) and small fish (sultana, anchovy, sprat , horse mackerel, Black Sea haddock, sprat, herring), sometimes small shellfish. The favorite food of the Kalkan is polychaete worms - polychaetes. At the same time, the kalkan continues to feed on zooplankton organisms.

Growing up, the juveniles of the Kalkan move further and further from the shore into the sea with each season.

Reproduction of Black Sea Kalkan fish

Puberty of the Kalkan generation occurs at the age of 3–4 years, reaching a body length of 30–35 cm; mass maturation of Kalkan males occurs at 4–5 years of age, and Kalkan females at 5–7 years of age. During this period, they can already join the spawning stock, starting from the end of March, at a depth of 80–120 m, moving closer to the shore during the spawning peak. As the sea warms up, the spawning stock of Kalkan move away from the shore and disperse before the onset of autumn food migrations following schools of small fish.

The fertility of the Kalkan is high and ranges from 1.8 million eggs in females weighing 3-4 kg to 12-14 million eggs in females weighing 12-15 kg. Kalkan caviar is pelagic, caviar diameter is 1.1-1.2 mm, contains one fat drop.

Spawning of the Black Sea Kalkan

Kalkan spawning takes place from the end of March to mid-June in the bottom layers of the sea, at a depth of 90 to 40 m, when the water temperature ranges from 8° to 12°C, spawning is portioned, fertilized eggs rise to the surface of the sea, the temperature of which during the period Spawning season can vary from 8°C to 20°C. Kalkan eggs are pelagic, have positive buoyancy (at a water salinity of 18‰), eggs develop in the near-surface layer of the sea, maximum Kalkan eggs are found in the sea - at
water temperature ranging from 11 to 16°C.

 

Growing Black Sea Kalkan

Is Kalkan grown artificially or not? Natural populations of Kalkan have been severely undermined by fishing and need to be replenished with Kalkan grown under artificial conditions. Therefore, to saturate the market, Black Sea Kalkan is grown under artificial conditions. The biotechnology of the Black Sea Kalkan allows it to be successfully grown in RAS, pools, and cages.

Among the features of growing Kalkan in artificial conditions, the following can be noted:

• On the farm, the Kalkan feeds intensively at any time of the year, stopping feeding only when the water temperature ranges below 7 ºС or above 23 ºС.
• Kalkan, when grown in pools, is inactive; it only moves to grab food.
• The feed ratio is low; when feeding the Kalkan with low-value fish (serrat) or wet food, it is 1.5–2.0;
• The feed coefficient when feeding the Kalkan with granulated feed is less than 1.0.
• Kalkan reaches a marketable weight of 2 kg quickly.
• In Kalkan, sexual maturity occurs at 3–4 years of age, which is 2–3 years earlier than in natural conditions.
• In the Black Sea Kalkan, by changing the photoperiod and water temperature, it is possible to obtain young Kalkan in any season of the year; this increases the efficiency of the aqua farm several times, allowing the enterprise’s capacity to be used several times.

 

Where is Kalkan grown? Kalkan is grown in Romania, Bulgaria, Turkey; in the rest of the Black Sea countries there are still no large mariculture farms for growing Kalkan. In all countries of the region, it is necessary to develop artificial propagation of the white salmon to replenish natural populations.

How fast does Kalkan grow when grown? If you grow the Kalkan in ideal fish farming conditions, which include daily feeding with complete food, maintaining the water temperature at least 18 ° C, and maintaining a sparse planting density of the Kalkan at each segment of the production cycle, then the Kalkan grows very quickly, the Kalkan can grow to a marketable weight of 2 kg, in just 12 months. In less favorable conditions, the growth of the Kalkan is less rapid, it can reach a marketable weight only in 20 months of cultivation, while when the Kalkan grows in nature, it will take twice as long to reach a marketable weight.