METHANOGENESIS IN FISH HATCHERY PONDS AND ITS ROLE IN ORGANIC-MATTER DECOMPOSITION

Results of long-term studies of gas formation in silts of fish hatcher y ponds under different operating conditions are presented. Methane co nstituted up to half of the total volume of bottom gas. Methanogenesis proceeded most actively in July and August (up to 8 mg C/liter/day). Methanogenesis from acetate was slightly dominant, conceivably due to a high rate of acetogenesis (5 mg C/liter/day). Methanogenesis contrib uted about 20% to the total anaerobic process of organic matter destru ction in silt. Bottom gas content depended on the intensities of fish feeding and water exchange. Up to 25% of generated methane was oxidize d in upper silt layers and near-bottom water, which affected the oxyge n regime of fish hatchery ponds and the condition of fish brood.