Currently, in the Kapshagay Reservoir and the Ili River, along with commercial fish, there are small, non-commercial, random universes of the Chinese complex such as stone moroco, goby, false gudgeon, medaka, bitterling, beautiful sleeper. These small fishes, except specialist none of adult fish is not considered, the most consider them young or they are called “weed” (low value) fish. Therefore, we consider it appropriate to tell briefly about them.
In the late 50s and early 60s, the above fish in the Balkhash-Ili basin were accidentally, during the period of acclimatization of the young of herbivorous fishes from Amur River. Due to the rapid adaptation to the environment, they quickly spread across the basin and their number increased. They live in the shores, shallow, without flowing or little running water. Although these fish are small as juveniles, but they are already adults, and are considered mature fish. The biology of these fish is different and very interesting. The life cycle of small fish in comparison with other fish is short, that is, short-cycle, live up to 4-5 years and become mature at 1-3 years of age. Length 2,3 – 5,5 mm, and weight 0,2-3,4 g. Caviar is laid on stone, sand, vegetation the most interesting some of them, for example, mustard lays eggs in the mantle cavity of the clam. Unlike other fish, bitterling has an ovipositor and with the help of ovipositor they lay eggs in the mantle cavity of a live mollusk. Small “low-value” fish feed on young fish and are also competitors in the nutrition of young commercial fish species, while they themselves are the food of predatory fish. In aquaculture, these small fish are caught specifically for feeding predatory fish. Low-value fish are caught in the juvenile delirium during the period of research work on catching juveniles of commercial fish.