The primary productivity by phytoplankton was determind durimg 1979-1981 for fishponds with the silver carp,bighead and tilapia as the major culture species. Tests were made on the vertical ,diel and seasonal changes in primary productivity in relation to major ecological factors and overall fish yield with the mean daily O2 production ranged from 3. 0 to 28. 9 gO2. m- 2d-1. The daily gross oxygen production usually exceeded oxygen, respiration The annual oxygen production was 2567-4197 gO2. m 2d-1.Monthly ...