author(s)
Mohammad Sadequr Rahman Khan, Mst. Mansura Khan, Nahida Akter and Md. Abdul Wahab

abstract
The effect of tilapia inclusion on the plankton abundance, water quality parameters and growth performance of freshwater prawn (Macrobrachium rosenbergii) was evaluated in 120 days of grow-out in nine earthen ponds. Simultaneously, the performance of two tilapia strain (Chitralada and GIFT) was compared in prawn-tilapia polyculture system. There were three treatments: only freshwater prawn (T₁), prawn + Chitralada (T₂), and prawn + GIFT (T₃) with three replications of each. A total 47 genera of plankton was identified. The total phytoplankton abundance was significantly higher in T₁ (3.4×10⁴ cells l-¹) than T₂ (2.7×10⁴ cells l^-1) and T₃ (2.6×10⁴ cells l-¹). Higher abundance of Chlorophyceae and Euglenophyceae in T₁ was attributed with lower water transparency and higher Chlorophyll-α content. Tilapia inclusion had no negative effect on prawn performance rather tilapia controlled phytoplankton overgrowth, supported better prawn survival and increased combined production. Chitralada gained higher individual weight than GIFT, but their net production did not vary significantly.