Short-Term Effect of Diuron on Catfish Pond Ecology

We examined the effects of diuron treatment on catfish pond ecology under commercial culture conditions. Nine weekly treatments of diuron (0.01 mg/L) were applied to eight 0.4-ha experimental ponds; seven ponds served as controls. Water and fish samples were collected from all ponds each week for chemical and biological analysis. Data on mechanical aeration (hours of supplemental aeration required by each pond) were supplied by the pond manager. A compound (2-methylisoborneol) that is known to cause off-flavor was significantly reduced in both water and fish fillets in diuron-treated ponds. Overall, diuron did not strongly affect water quality variables. No differences in supplemental aeration were detected between the pond groups. Diuron altered the phytoplankton composition within the ponds by reducing the biomass of filamentous blue-green algae. However, overall phytoplankton biomass was not different between treatment and control ponds; filamentous blue-green algae were replaced by diatoms. Zooplankton populations were not dramatically altered, but rotifers tended to increase in diuron-treated ponds while copepod nauplii and cladocerans tended to decrease. It appears that diuron can be an effective control for 2-methylisoborneol, while having negligible effects on the overall water quality or other environmental variables measured in this study.