in pond fishery, keeping adult and young fish in specially equipped hibernating ponds during the winter. In favorable wintering conditions with well-fed fish, carp fingerlings weighing 25-30 g are placed in hibernating ponds at the rate of 350,000-400,000 fish per hectare (ha) of pond area, pond and wild carp hybrids at the rate of 400,000-500,000 per ha, and crucian carp fry at 600,000-700,000 per ha. Older fish are placed in ponds by weight: 250-300 centners per ha. When the ponds freeze, the water temperature drops to 0.4-1°C, and the metabolic processes of the fish drop, they stop feeding, and the insufficiently fattened fingerlings die. The condition and behavior of the fish are observed through ice holes; the normal exchange of water and air, the oxygen content, and so on, are monitored. The water is aerated to saturate it with oxygen (pressure differentials are created in the water supply system, and so forth). Infectious diseases are controlled by the preventive measures of treating summer ponds and disinfecting wintering ones. Vegetation is removed from the bottom of the ponds.
REFERENCESMartyshev, F. G.Prudovoe rybokhoziaistvo, 2nded. Moscow, 1958.
Dorpkhov, S. M., S. P. Pakhomov, and G. D. Poliakov. Prudovoe rybovodstvo, 2nd ed. Moscow, 1962.
G. D. POLIAKOV