Those that are quickly degradable influence only the organisms that are killed immediately. Because of the rapid disappearance of the chemical, survivors tend to be relatively unaffected. Because persistent organochlorine insecticides are not used in broadcast applications, problems of food chain accumulation will not occur as they have in the past. Thus, predators will not pick up toxic burdens. They may have a temporary decreased food supply.
Fish are particularly sensitive to certain insecticides.
Very low concentrations can cause heavy mortality, particularly in slow moving streams. The extreme sensitivity of fish is attested to by the very small amounts of such insecticides that will dissolve in water. The ability of a stream to support fish is not impaired after the insecticide is gone. Insecticides may be flushed out or inactivated by adsorption to the organic surfaces, where they are usually degraded to relatively harmless materials. An exception is in lakes, where they may persist in low, but possibly harmful, concentrations.