Full Length Research Paper
Essien-ibok MA, Asuquo IE, 1Ek
Abstract
The toxicity Urea fertilizer against Heterobranchus bidorsalis fingerlings (mean total length, 6.98 ± 0.30cm SD; mean body weight 2.04 ± 0.35g SD) was investigated. The fingerlings were exposed to increasing concentrations of Urea (0.00g/l, 8.75g/l, 10.00g/l, 11.25g/l, 12.50g/l, 13.75g/l, 15.00g/l and 16.25g/l) fertilizer in the static renewal bioassay for 96 hours. Exposed fish showed initial stress responses such as erratic swimming, restlessness, loss of balance, frequent attempts at jumping out of the tank and quietness. Water quality examinations showed a decrease in the dissolved oxygen content and increase in total hardness and alkalinity as the concentration of fertilizer was increased. The 96hours LC50, associated confidence limits and safe concentrations for the fertilizer were (17.84, 11.88- 13.67, and 1.78g/l respectively). Mortality rates were concentration-dependent and death rate in the highest concentrations were significantly higher (P<0.05) than the others. Mortality rate was influenced by both concentration and time. The findings from this study show that Urea fertilizer could be classified as toxic to Heterobranchus bidorsalis fingerlings at certain concentrations.