Common Catfish - Zhayán
Common Catfish - Silurus glanis
In the republics of Central Asia, the catfish is found in the basin of the Aral Sea (Syr Darya with its tributaries). In Kyrgyzstan, it inhabits the Kara-Darya River from its confluence with the Syr Darya to the mouth of the Kurshab-Darya, in the Naryn River up to Uch-Kurgan, and in the Chu River from the city of Tokmak to the lower reaches, where in floodplains (uzyaki) and floodplain lakes it is one of the main commercial fish. Although within Kyrgyzstan, in the water bodies of the Chui Valley and in the Chu River itself, the catfish has become quite rare due to the deterioration of living conditions, mainly because of the diversion of water from the Chu and its tributaries for irrigated agriculture.
In the basin of the Talas River (the lakes Biylikol, Akkol, and others), as well as in Lake Balkhash, catfish have been artificially bred and have become an important object of fishing.
The catfish is the largest of the fish inhabiting freshwater (not including migratory sturgeon species — beluga and kaluga, individual specimens of which can reach up to 500 kg or more). Ichthyological literature indicates that catfish weighing 600 kg have been found in the Amu Darya and Syr Darya. Veteran fishermen from the village of Furmanovka (formerly Gulyaevka), located 100 km downstream of the Chu River from the Chu railway station, claim that as early as the early 1930s, catfish up to 3-4 m long were caught in the river's floods.
The external appearance of the catfish indicates that it leads a bottom-dwelling lifestyle. It has small eyes located on the upper sides of its head, allowing it to easily monitor everything that swims above it while resting on the bottom of the water body. Upon noticing a school of fish or some other prey, it makes a powerful thrust with its tail and almost vertically propels itself upwards with its mouth open, grabbing its victim and immediately returning to its original position in a hole or depression in the river under a steep bank. Its dirty gray body, with dark blurred spots on the top and sides, effectively camouflages the catfish against the dark bottom of the water body.
Typical habitats for catfish are deep river or lake floods with extensive holes containing submerged roots or shrubs, sandy or slightly silted bottoms. The catfish avoids areas densely overgrown with reeds or bulrush and heavily turbid water. Large catfish are solitary and are very reluctant to leave their chosen spots, even during hunting and spawning.
In the water bodies of the Chui Valley, the lakes of the Jambyl region, and Lake Balkhash, catfish reach sexual maturity at 3-4 years of age. They spawn from the first decade of May until the end of June, with some individuals spawning even in July. In the ovaries of females, along with large eggs, there is a small portion (10-15% of the total number of eggs) of small eggs, which, by the way, indicates the catfish's tendency for batch spawning. The fecundity is high: for females measuring 60-140 cm, there are 20-25 thousand eggs per 1 kg of body weight. They lay their eggs on the roots of plants, submerged reed clumps, and shrubs.
A. P. Sabaneev, in his book "Life and Fishing of Freshwater Fish," referring to fishermen's observations, writes that large catfish engage in courtship games during the spawning period, which are accompanied by unusual noise. Catfish chase each other, leap out of the water, which, according to the mentioned author, helps to "break up the eggs." During these "games," the female catfish selects a male, the strongest one, with whom she goes to find a "tyrlo," meaning a spawning site. Upon finding a suitable location, the female catfish uses the stiff rays of her pectoral fins to create a hole ("mazlo"), where she lays her eggs. Both the male and female catfish guard the nest of developing eggs until the larvae hatch.
The hatched fry initially feed on small organisms from the zooplankton, worms, Gammarus, and larvae of aquatic insects. However, after just two months, the young catfish switch to feeding on the fry of other fish species, which are often found in shallow bays and channels. Interestingly, the young catfish migrate far from their birthplace before reaching sexual maturity. Unlike large catfish, young catfish can disperse through channels, streams, and irrigation canals beyond their native water body, which should be viewed as an advantageous biological adaptation aimed at reducing competition within the species for food.
Large catfish tend to stay alone in holes, making forays into shallow areas during feeding frenzies. From the age of one, catfish feed exclusively on animal food. Analysis of the stomach contents of a catfish caught in the floods of the lower Chu River showed that its fish diet mainly consisted of roach, rudd, young carp, and bream. Other animals found in the stomachs of catfish included frogs, water chickens, and water rats.
The most active feeding of catfish is observed immediately after winter hibernation, when they leave their wintering holes. In Kyrgyzstan and southern Kazakhstan, this occurs in the second half of March to the first half of April. During this period, catfish feed intensively on fish, which serves as the best bait when fishing for catfish with hooks. In May-June, when catfish spawn, their appetite sharply declines, but after spawning, they feed vigorously again until the onset of autumn cold (October-November).
It should be noted that catfish are quite sensitive to changes in weather, even in summer. Experienced fishermen have long noticed that many fish somehow sense the approach of a thunderstorm, stop taking bait, and retreat deeper into the water body. The minnow, on the other hand, rises to the surface during stormy weather and begins to catch insects blown into the water by the wind. According to P. Sabaneev, catfish behave extremely restlessly before and during a thunderstorm. They leave their holes and start swimming near the surface, making loud splashes.
In autumn, as the water temperature drops to +14-15°C, catfish migrate to deep wintering holes with sandy bottoms and fresh water. In Kyrgyzstan, catfish do not have commercial stocks, but in the water bodies of the Chui Valley, they are a desirable, albeit rare, trophy for amateur fishermen. It is a pity that, due to their biological merits (rapid growth) and excellent taste qualities of their meat, catfish deserve much more attention from fish farmers and practitioners of fisheries in the republic.
Catfish can and should be bred in the reservoirs of the Chui Valley, which are heavily polluted with small non-commercial fish — the main food for this fish. As a biological ameliorator, young catfish can be introduced into carp grow-out ponds to suppress the population of Amur sleeper and other nuisance fish.
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