Effects of biofloc technology on water quality and growth performance of Macrobrachium rosenbergii

Abstract

This study aimed to evaluate the effects of biofloc technology on the water quality and growth performance of Macrobrachium rosenbergii. The experiment was carried out over 165 days at the hatchery complex of the College of Fisheries and Aquatic Sciences, Mindanao State University-Marawi, Philippines. Postlarvae of M. rosenbergii (0.011±0.05 g) were stocked in 18 circular tanks (1200 L) consisting of six treatments under biofloc and non-biofloc systems in a completely randomized experimental design with tapioca flour as the carbohydrate source. Commercial pelletized sinking prawn feed with three dietary protein levels, viz., 42, 38, and 35% were chosen as experimental feeds. Results of the present study show that the water parameters were within the optimum range required in the culture of freshwater prawns. However, biofloc technology (BFT) did not influence sediment and water samples’ dissolved oxygen, temperature, and pH values. On the other hand, total ammoniacal nitrogen (TAN) and nitrate showed significant variation (p<0.05) among treatments, with higher values in the control treatment compared to the biofloc treatments. Moreover, the dietary protein level and carbohydrate addition had no significant effect on soil pH and organic carbon except for the soil total nitrogen value, where higher values were observed in the biofloc treatments. Furthermore, significantly higher mean prawn weight gain, net prawn yield, specific growth rate (SGR), and average daily weight gain (ADG) were recorded in the biofloc treatments compared to non-biofloc treatments. At the end of the culture period, there was 100% survival in all of the tanks. On the other hand, no significant variations were observed in feed conversion ratio (FCR) and protein efficiency ratio (PER) in the control treatment compared to the treatment with biofloc except in tanks using feed of 42% CP under the biofloc system. Therefore, based on the results of the present study, the use of BFT in the culture system of M. rosenbergii, helped reduce the protein percentage from 42 to 35, while maintaining the yield.