Survival response of Sarotheron melanotheron (Ruppel, 1852) fingerlings to various concentration levels of perfkthion under laboratory condition

Survival response of sarotheron melanotheron fingerlings to various concentration levels of perfkthion was studied under laboratory condition using five concentration levels, 0.0mg/l, 0.7mg/l, 1.4mg/l, 2.8mg/l, 5.5mg/l and 11.2mg/l. mortality increased with increase in concentration level and exposure time. ten percent mortality was observed in the control (0mg/l), 3% mortality was recorded after 12 hours and 7% at the end of 36 hours. at the lowest concentration of 0.7mg/l, 27% mortality occurred after 12 hours and 30% mortality occurred after 24 hours. at the 48th hour, the rate increased to 37%, 47% after 72 hours and afterwards no further death was observed till the end of the experiment. at 1.4mg/l, 20% mortality occurred after 12 hours, this increased to 37% after 24 hours, 43% after 36 hours, 53% after 60 hours, 63% after 72 hours, 73% after 84 and 77% after 96 hours. mortalities occurred in concentration level 2.8mg/l at the rate of 7% after 12 hours, 13% after 24 hours, 20% after 36 hours and 7% mortality after 48 hours. this increased to 43% after 60 hours and remained at 47% mortality from the 72nd hour till the end of experiment. at concentration level 5.6mg/l, mortality was 43% within 12 hours, this increased to 47% after 24 hours and 50% at the end of the 36th hour. no further mortality occurred till the 60th hour when 60% was observed. this continued to 63% after 84 hours and 67% at the end of the toxicity test. at concentration level 11.2mg/l, mortality was 43% at the 12th hour. it increased to 70% at the 48th hour and 97% at the 96 hour. there was significant effect of perfekthion on s. melanotheron fingerlings. there was delayed mortality at concentration 2.8mg/l. lc50 was not reached within 12 hours. as exposure time increased, lc50 reduced. the median lethal time (lt50) values for concentration levels, 1.4mg/l, 2.8mg/l, 5.6mg/l and 11.2mg/l was 57.85 hours, 91.52 hours, 48.35 hours and 27.61 hours respectively. lt50 increased with decrease in concentration level with the least value (27.61) at the highest concentration of 11.2 mg/l as compared to 57.85 hours at 1.4mg/l. the safe concentration of perfekthion organophosphate insecticide was 0.119mg/l. there were strong positive correlations between concentrations(r = 0.9982 – r = 0.9999). the correlation of ph with total alkalinity was r = 0.9379, total hardness with salinity (r = 0.6705). weak positive correlations occurred for ph and temperature (r = 0.3516), temperature and ta (r = 0.2572) and; temperature and th (r = 0.0419). negative correlations occurred for ph and do (r =– 0.0604), ph and th (r = -0.7524), ph and salinity (r = - 0.6369) and do with salinity (r = - 0.1759). strong positive correlation existed between mortality and th (r = 0.7795) and between mortality and salinity (r = 0.8062). negative correlation existed between mortality and ph, ta (r =- 0.7681, r = -0.7977) and in mortality with do and temperature (r = -0.4479 and r = -0.2288).