Control of euglenophyte bloom and fish production enhancement using duckweed and lime

 Euglenophyte bloom is a common problem in most of the aquaculture ponds in Bangladesh. In the present study we conducted an experiment to control euglenophyte bloom for achieving better fish production using duckweed (Lemna minor) and lime. The experiment was carried out using four treatments, i.e., ponds were supplied with duckweed (T1), lime treatment (T2), both duckweed and lime (T3) and without supply of duckweed and lime (T4). Rohu, catla, mrigal, silver carp and silver barb were stocked and their gut contents were analyzed monthly. The ranges of water quality parameters were analyzed within the productive limit during the experimental period. The mean abundance of euglenophyte was significantly highest in T4 (17.62 ± 1.97 x 104 cells/L), followed by T2 (2.96 ± 0.20 x 104 cells/L), T1 (1.94 ± 0.35 x 104 cells/L) and T3 (1.53 ± 0.42 x 104 cells/L). Gut content analysis revealed that considerable amounts of euglenophyte were consumed by silver carp and silver barb, but not preferred by rohu, catla and mrigal. The gross yields of fish were 2133.37, 1967.76, 2816.52 and 1725.62 kg/ha/5 months in T1, T2, T3 and T4 respectively. The highest fish production in T3 and lowest fish production in T4 indicated the use of duckweed and lime is economically sustainable for controlling euglenophytes bloom, maintaining water quality and getting higher fish production.