Survival Of Yolk Sac Larvae And Gonad Development Of Oreochromis Niloticus In Serially Diluted Solutions Of Layer (Chicken) Manure

ABSTRACT

Survival of yolk-sac larvae and gonad development of Oreochromis niloticus in serially diluted solutions of layer (chicken) manure were evaluated. The experiment was a complete randomised design with five treatments and three replicates. Levels of layer manure concentrations were introduced to 70 litre containers at the concentration of 8.4mg/l, 19.6mg/l, 28mg/l, 42mg/l and 84mg/l and the control devoid of any toxicant. The acute toxicity lasted for 4 days (96hrs LC₅₀). The survival larvae were reared for three months with the larvae being fed twice a day to satiation at a stocking density of 10 fish per treatment. From the toxicity result the median lethal concentration (LC₅₀) value of layer (chicken) manure for O. niloticus larvae was 30.90mg/l and the threshold is 1.49mg/l. The pH and temperature varied from control (p<0.05) while the dissolved oxygen decreased as the concentration increased. At the end of the rearing period, fish were dissected and gonad obtained for histological analysis. From the result, it could be attributed histologically that layer manure reduced the maturity of the gonads. The highest concentration (84mg/l) had more immature ovaries with mean value of 98.21±0.50, while control had the least (30.89±1.38). Maturing ovaries were highest in the control with mean value of 69.11±1.39 as compared to 84mg/l concentrations (1.75±0.52). There was significant difference between the means of dissolved oxygen, pH and temperatures (p<0.05).