Pesticide residues in fish and aquatic invertebrates.

Over the past 6 years a great number of fish and aquatic invertebrates from experimental and commercial fishponds have been analyzed for the presence of organochlorine insecticides and polychlorinated biphenyls (PCBs). Invariably, all specimens contained DDE and PCBs and in many instances also DDT, DDD and BHC isomers. A study of the kinetics of the organophosphorus compound parathion in an experimental fishpond ecosystem revealed a rapid bioconcentration of the chemical in algae, zooplankton, aquatic invertebrates and fish. The time-course of parathion disappearance showed an exponential type decline of the chemical over a period of three weeks.