Effect of malathion in Ignacio Ramirez Dam sediments on rainbow trout (Onchorhynchus mykiss)

Above the Ignacio Ramirez Dam (IRD), malathion (MA) Is used in agricultural activities to control pests. This compound is one of the most widely used organophosphate pesticides in Mexico. Both acute and sublethal toxicity, as well as insecticide kinetic uptake and depuration in juvenile trout (Oncorhynchus mykiss) were determined using spiked natural sediments, Lipid peroxidation level and acetylcholinesterase activity (AChE) were used as indicator param-eters of sublethal toxicity. The results of acute toxicity of MA in rainbow trout showed that 96h-LC 50 in water was 0.1164 mg/l while in sediments was 0.7650 mg/kg. All MA concentrations produce an increase in lipid peroxidation level and a decrease in AChE activity. The results of the kinetic model showed that the maximum rate of absorption was at 12 h with a rapid bioconcentration. When MA was desorbed from the sediment, the pesticide concentration was increased in the trout gill. The gills are organs with a great capacity of MA uptake in Oncorhynchus mykiss to produce a toxic effect in this organism.