Impacts of cypermethrin and deltamethrin’s use on aquatic invertebrates in commercial aquaculture ponds

Abstract

Agricultural pyrethroid insecticides especially cypermethrin and deltamethrin are being used
regularly for the control of aquatic insects in commercial carp aquaculture ponds in northwest Bangladesh.
Thisstudy was conducted in a farmer’s ponds under commercial aquaculture to know the impact of
cypermethrin and deltamethrin on aquatic invertebrates (insects, zooplanktons and benthos). Commercial
aquaculture ponds were treated with cypermethrin and deltamethrin @ 5 ?g (active ingredient)/liter pond
water in presence of fish. Required amount of each of the insecticides were diluted with water in big
aluminium pots and broadcasted over the pond water. Water quality parameters of the experimental ponds
were measured at pretreatment stage. Sampling of aquatic invertebrateswasdone pretreatment and after 1 day,
2 days, 5 days, 10 days, 15 days, 21days and 28 days of the application of insecticides. No fish mortality was
recorded after the treatment. Aquatic insect population was found to be most affected;number count
declined89.87% and 86.24% for cypermethrin and deltamethrin respectively within one day after treatment.
The insect count recovery began after day 10 and day 5 of cypermethrin and deltamethr in treatment
respectively. Loss of insect diversity was observed in cypermethrin treatment and diversity count did not
recover within observation period of 28 days.Zooplankton populationwas relatively less impacted (21.10%
and 26.33% declined respectively in cypermethrin and deltamethrin treatment). Benthos population count and
diversity was not affected, possibly due to the high organic carbon content and clay soil of the pond bottom.