Balkhash Perch - Perca schrenki
In the water bodies of Kyrgyzstan, representatives of this family were absent until the late 1950s, although the common river perch is native to the lower reaches of the Chu River (within Kazakhstan). In the 1960s, amateur fishermen introduced Balkhash perch into the water bodies of the Chui Valley.
It is an endemic species of the Balkhash-Alakol water system. It differs from the common river perch — Perca fluviatilis — by its more elongated body, the absence of a black spot on the dorsal fin and transverse dark stripes in adult fish, gray fins, a lower first dorsal fin, and a protruding lower jaw. Young fish have 10–13 noticeable transverse dark stripes on their bodies, which disappear with age.
This species lives in a variety of conditions, found both in fast-flowing mountain rivers, such as the Chu, and in heavily overgrown lakes and ponds of the Chui Valley, where it sometimes has an almost black coloration. The Balkhash perch is a predator, feeding on small fish, young of larger fish, but also preying on its own young. It grows slowly, reaching a length of 50 cm and a weight of 1.5 kg.
The perch is a commercially important species, harvested in salted, dried, and frozen forms. However, it has recently been included in the international Red Book.
In the lower reaches of the Chu (from the village of Furmanovka to the lowland lakes), this species is widely distributed, both in the riverbed and in the floodplains and floodplain lakes. The perch likely entered the Chu from the north via the Ishim River through the Nuru and Sary-Su rivers, which once formed a single hydrographic network connected to the Aral Sea basin when the Chu and Sary-Su were tributaries of the Syr Darya.
Perch - A Type of Fish
By appearance, the common perch is difficult to confuse with other fish species. The body of the perch is covered with fine ctenoid (with spines) scales, which are quite dense. The back rises steeply just behind the head and smoothly descends to the tail stem at the level of the pectoral fins. There are two fins on the back. The first consists of sharp spines connected by a membrane. At the end of this fin, there is a dark spot. Small teeth are arranged in several rows on the jaws. The pectoral, ventral, and anal fins are red, while the dorsal and caudal fins are greenish-brown; the back is dark with a blue metallic sheen, and the sides of the body are greenish-bronze with dark transverse stripes. The iris of the eyes is red.
In the water bodies of the lower Chu, perch reaches sexual maturity by the third year of life. It spawns early — in March to early April when the water temperature is 8–10°C. Spawning is communal. In the spawning schools, females outnumber males (10:1 and even 17:1). The perch lays its eggs on underwater vegetation — bulrush, sedge, and submerged stems of reeds.
The eggs are adhesive and are enclosed in gelatinous ribbons in the form of a net. At the time of spawning, fish sometimes gather in large schools (up to several hundred individuals) at spawning grounds. The spawning grounds of the perch are usually located in channels and backwaters with clean water.
The fecundity of perch caught in Lake Bolshie Kamkaly, measuring 19–22 cm and weighing 152–232 g, ranged from 2,184 to 60,310 eggs. Young perch feed on plankton, benthic invertebrates, and young shoots of aquatic plants. Mature perch primarily feed on fish (young roach, rudd, etc.) and even on their own young. Particularly active feeding occurs in the post-spawning period (April - May) and in autumn (September - October). In the lower reaches of the Chu, perch has commercial significance. It is sold to the local population in fresh, salted, and frozen forms during winter.
Fish