A farmer was using pesticides on his farm

A farmer was using pesticides on his farm. He used the product of his farm as food for rearing fishes. He was told that fishes were not fit for human consumption because large amount of pesticides had accumulated in the tissues of fishes. Explain how did this happen?

Pesticides from the soil are transferred into the crops and from the crops these are transferred into fish food. Pesticides entered into water through fish food and finally entered into the bodies of the fishes. Therefore, pesticides are transferred from lower trophic level to higher trophic level through food chain. Over the time, the concentration of pesticides in fishes reach a level which causes serious metabolic and physiological disorders.