Acute toxicity of monocalm 400sl (monocrotophos) and profenalm 720ec (profenofos) on Oreochromis niloticus (Linnaeus, 1758)

Abstract

Objective: This study aimed at assessing acute toxicity of Monocalm 400SL (monocrotophos) and Profenalm 720EC (profenofos), two organophosphorous pesticides widely used in the Far North region of Cameroon, to fight against insects and mites parasitizing cotton, rice, maize, sorghum, beans and potatoes.
Methodology and results: A 48 h static acute toxicity test was carried out, to determine the LC₅₀ of commercial formulations of monocrotophos (Monocalm 400SL) and profenofos (Profenalm 720EC) on the freshwater Oreochromis niloticus and its behaviours, during the exposition. The fishes were exposed to increasing concentrations of the two pesticides, in a non-renewed medium. The numbers of dead fishes were recorded, after 48 h and the behaviours observed, during the exposition. The 48h-LC₅₀ values, estimated by probit analysis, were of 20.42 and 0.046 mgL^-1, for monocrotophos and profenofos, respectively. Lowest Observed Effect Concentration (LOEC) means were of 10 and 0.02 mgL^-1, for monocrotophos and profenofos, respectively. Elsewhere, fish behaviours such as slow opercular movements, loss of balance, increased surfacing activities, loss of pigmentation; increased aggression and erratic swimming were observed, during exposition to the pesticides.
Conclusion and application of results: Monocrotophos was found to be slightly toxic and profenophos highly toxic to Oreochromis niloticus. Water contamination with these products can represent a great threat for fish and aquatic invertebrates. So it is recommended to apply these pesticides with caution.

Keywords: Acute toxicity; LC_50; monocrotophos; profenofos; Oreochromis niloticus.