Acute toxicity of Trichlorfon (Dipterex) to fry of Cichlasoma urophthalmus Günther

Abstract. Fry of Cichlasoma urophthalmus Günther were exposed to various concentrations of the organophosphate pesticide Trichlorfon, ranging from 1·25 to 80 mg/l in laboratory conditions. Mortality reached 100% in the highest concentrations (60 and 80 mg/l) in the first 24h. The intermediate concentration (40 mg/l) resulted in 50% mortality after 24h, and no mortality was observed in lower levels of the pesticide. LC50 at 24, 48 and 72h were 26·5, 23·7 and 17·2 mg/l respectively.
Some of the surviving fish were transferred to clean fresh water for a post-treatment growth trial. All the fish grew well with no apparent adverse effects as judged by their growth indices after 8 weeks.