Effects Of Addition Of Tilapia And Periphyton Substrates On Water Quality And Abundance Of Plankton In Freshwater Prawn Culture Ponds.

Abstract

Abstract: The research investigated the effects of addition of tilapia and periphyton substrates on water quality and abundance of plankton in freshwater prawn culture ponds. The absence and presence (0 and 0.5 individual/m 2) of tilapia were investigated in 40m 2 ponds stocked with 3 prawn juveniles (5.023 ±0.04g)/m 2 with or without added substrates for periphyton development. A locally formulated and prepared pellet feed (2mm) containing 30% protein with C/N ratio close to 10 was used. The feed was applied at the rate of the 10 % body weight and gradually decreased to 3 % at the end of the culture period. Water quality parameters and the abundance of plankton and periphyton biomass were measured. The abundance of plankton and periphyton biomass was significantly higher in tilapia-free ponds comparing to tilapia added ponds. The addition of substrates did not influence size at harvest but improved the survival of prawn from 54.4 to 76.9%. Substrates contributed an increase in gross and net yield of prawn by 33 % and 42.5%, respectively. Addition of tilapia and periphyton substrates benefited the freshwater prawn culture through reducing toxic inorganic nitrogenous compounds in water, enhancing the utilization of natural foods and improving survival, production and economic benefit