Experimental Culture of the Giant Freshwater Prawn, Macrobrachium vollenhovenii (Herklots, 1857) around the FUTO Axis of Otamiri River, Imo State, Nigeria

: Culture trial of 7,488 juveniles of the giant freshwater prawn, Macrobrachium vollenhovenii (Herklots, 1857) was carried out for 180 d in concrete tanks to determine their adaptability, survival, feed utilization and growth performance under culture condition. Twelve experimental concrete tanks each measuring 10 m × 5 m × 1.0 m were used for the experiment from March to August 2016. The prawns were stocked two weeks after treatment of tanks with agricultural lime at the rate of 2,279 kg/ha and poultry manure at the rate of 114 kg/ha. Four experimental diets tested were designated as T 1 : powdered broiler starter, T 2 : commercial brine shrimp, T 3 : combination of broiler starter and brine shrimp and T 4 : Mississippi Agricultural and Forestry Experimental Station (MAFES) diet formula. Diets were randomly assigned to the four treatment tanks and replicated three times in a 4 × 3 = 12 experimental units as a completely randomized design experiment (CRD). Each tank was stocked with 624 juvenile prawns with mean total length of 1.5 cm and body weight of 10.0 g. Prawns were fed at 5% body weight and twice at 0600 h and 1800 h. Sampling for growth was carried out bi-weekly while water quality was tested weekly. Results were statistically evaluated with one way analysis of variance (ANOVA). Water quality of the four tanks was not significantly different ( p > 0.05) from one another throughout the culture period and conformed to recommended tolerable limits in prawn culture ponds. Growth performance was best in diet T 4 (the MAFES formula), with a survival rate of 75%, mean weight gain (MWG) of 65 g, relative growth rate (RGR) of 650%, specific growth rate (SGR) of 1.12%, average daily growth (ADG) of 0.3 g/day and food conversion ratio (FCR) of 1.44. The above values differed quite significantly ( p < 0.05) from growth responses of other diets. The computed gross ratio (GR) of 0.62 suggests that prawn culture is a highly lucrative business.