Assessment of the contamination of fresh water ecosystems by pesticides and herbicides in irrigated rice fields and effects on fish production (A review)
This paper assessed reports and records of the contamination of fresh water ecosystem by pesticides and herbicides in irrigated rice fields and their effects on fish production. It highlights pesticides and herbicides application in agriculture in view of the transfer and degradation processes. The pesticides often remain undegraded. Pesticides in fresh surface water can get into the food chain and affect the health of the people and animals consuming the aquatic foods produced from such water bodies. Pesticides and herbicides pose a threat to aquatic ecosystem; they are known to reduce fish growth, survival and reproduction. Some other effects of pesticides and herbicides on fish include loss of equilibrium, gasping for breath and erratic swimming behaviour. Filaments of fish in lower concentrations were pink while those in the higher concentrations were enlarged and eroded. Also, persistent application of pesticides and herbicides has caused financial and economic losses in rice/fish culture and decline of production. However, since the use of pesticides and herbicides is an important tool in agricultural practice in developing countries, recommended application regimes and regulations should be strictly adhered to in order to limit the excesses and dangers posed by these chemicals. The effect of pesticide and herbicide application to aquatic life is reviewed and discussed.
Keywords: Pesticides, herbicides, Ecosystem, fish.