Cypermethrin is gaining popularity among fish farmers community to control aquatic insect pests and ectoparasites. Effect of cypermethrin application at farmer select dose (@0.003 ppm) on aquaculture pests (Notonecta & small prawn) commonly found in tropical ponds along with fish fry was assessed. Effect of cypermethrin application on the composition and survivability dynamics of aquatic microfauna namely rotifer, copepod and cladocera for 8 days was studied in tropical pond conditions. Cypermethrin cause significantly higher mortality to notonecta and prawn compared to fish fry within 24 h of exposure (P<0.05). Mortality of notonecta, prawn & fish fry became insignificant only after 72 h of cypermethrin application. During the 8 days span after application of cypermethrin, while population density Rotifer sp. remain unaffected (P>0.05), population density of Cladocera sp. and Copepod sp. reduced significantly (P<0.05). However, presence of dead zooplankton in the samples on the 8th day suggests that the presence of cypermethrin toxicity of beyond the period of study. Our results suggest that nursery pond stocking with fish fry after 72 h (three days) of application of cypermethrin might offer the triple advantage of predator elimination, prey availability and reduction in pesticide induced mortality of fish fry.

Highlights

• Cypermethrin toxicity to zooplanktons in pond water may persists beyond 8th day’s.
• Cypermethrin affect density of Copepda and Cladocera but not Rotifers.
• Cypermethrin effectively kills predatory notonecta and prawn.
• Cypermethrin might offer the triple advantage of predator elimination, prey availability and reduction in pesticide induced mortality of fish fry.