Dietary Tryptophan Supplementation Made No Difference on the Cannibalism, Survival and Growth of Heterobranchus longifilis fingerlings

Heterobranchus longifilis is a popular cultured and food fish but its cannibalism greatly reduces harvest thus necessitating proactive control measures. Tryptophan is believed to raise the serotogenic activity in the brain at certain levels leading to reduced aggression and cannibalism in certain species of fish which possibilities this research tried to explore in Heterobranchus longifilis. Fingerlings (0.58 ± 0.123g mean weight and 3. 8 ± 0.52cm mean length) were stocked in 18 round plastic tanks, each 45 litres containing 40 litres of water, at 45 fish per tank. Tryptophan was incorporated at 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 % in commercial Catfish feed by spraying each tryptophan - 70% alcohol solution to separate feed samples to form six different experimental feeds. The dried feeds were fed to the fish daily at 4 % body weight for 8 weeks. The experiment used a complete randomized design with 6 feed treatments and 3 replications. Water quality, growth, mortality and feed utilization data noted and at the end, their associated indices were determined and subjected to the analysis of variance for significant differences (P= 0.05). The results revealed that tryptophan supplementation at the levels used in the diets of Heterobranchus longifilis did not have any significant effects on all the parameters examined excepting mean weight gain. This was discussed in the context of growth and cannibalism.