Responses of Two Life Stages of Oreochromis niloticus to Acute Toxicity of Ridoff (Organophosphat Insecticide)

Abstract

The acute toxicity of Ridoff (Insecticide dichlorvos) on two life stages of Oreochromic niloticus of mean standard length and weight (fingerlings - 4.20 ± 0.60 cm and weight - 7.00±0.20g and juveniles - 12.04 ± 0.20cm and 14.04±0.05g) were investigated under laboratory condition at the concentrations of 0.05, 0.08, 0.10, 0.13 and 0.15ml/l. All the physicochemical parameters (ammonia, dissolved oxygen, pH, temperature and nitrite) under consideration were within acceptable limits. LC50 of Ridoff was calculated at 24, 48, 72 and 96 hours using probit test. Mortality was observed in all treatments of the two life stages exposed from 0.08mg/l at 96 hours. In the first life stage (fingerlings), LC50 was 0.058 within 24 and 96hours and the second life stage (post fingerlings) LC50 was 0.019 within 24 and 96 hours. At a close watch the two life stages exhibited agitated swimming, loss of equilibrum, air gulping, period of quiescence, and turned on flank and swarm in circles and finally died. Accumulation of mucus also was observed on the gill filaments and body surface of the dead fish on exposure to toxicant. Ridoff (Dichlorvos) indeed is harmful to Oreochromis niloticus, which could be a non-target organism in an aquatic ecosystem

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