Study on phytoplankton ecology of earthen catfish ponds in Bangladesh

An experiment was conducted in the earthen catfish ponds using thai pangush (Pangushius Sutchi) to analyze the microalgal ecology and their variation in time and space. There were three treatments with three replicates. In treatment one (T1) pangush catfish were stocked at the rate of 120/decimal and in treatment two (T2) and treatment three (T3) pangush catfish and silver carp were stocked at a ratio of 1:1 and 2:1 respectively. Results showed that average water quality parameters were within suitable range for plankton production and fish culture. The phosphorus and nitrogen enrichment influenced the Cyanobacterial biomass in different treatments whereas the other microalgae were found to be markedly low. In the present study, Cyanophyceae showed positive response to the nitrate-nitrogen, phosphate-phosphorus and negative response with temperature, pH and dissolved oxygen. Euglenophyceae showed positive relation with temperature, dissolved oxygen and negative relation with pH. Chlorophyceae and Bacillariophyceae were positively correlated with the water temperature and dissolved oxygen and inversely related with nitrate-nitrogen (NO­3-N), phosphate-phosphorus (PO4­-P). It can be concluded that Cyanobacteria used most of the nutrients from the ponds for their growth and as a result growth of beneficiary plankton was inhibited markedly.