Submitted to: North American Journal of Aquaculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/1/2002
Publication Date: 6/1/2002
Citation: Zimba, P.V., Tucker, C.S., Mischke, C.C., Grimm, C.C. 2002. Short-term effects of diuron on catfish pond ecology. North American Journal of Aquaculture 64:16-23. Interpretive Summary: Diuron has been approved for control of off-flavor producing cyanobacteria in catfish production ponds. We examined what effect diuron has on the community structure of ponds. Dissolved nutrient concentrations (particularly nitrogen) increased in the treated ponds. Filamentous cyanobacteria decreased in diuron-treated ponds. Zooplankton composition was not significantly altered in terms of constituent species. Diuron had little overall negative impact on water quality in the catfish ponds.
Technical Abstract: 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 nine 0.4-ha experimental ponds; six ponds served as controls. Water and fish samples were collected from all ponds each week for chemical and biological analysis. Water and fish samples were analyzed for off-flavor compounds. Ammonia-nitrogen, nitrite-nitrogen, nitrate-nitrogen and soluble reactive phosphorus concentrations were determined from the weekly water samples. Phytoplankton community composition was analyzed by algal pigment concentration and cell counts. Zooplankton populations were monitored by identification and counting under light microscopy. All measured variables were compared between diuron-treated ponds and control ponds (P<0.1). A specific off-flavor compound was significantly reduced in both water and fish fillets in diuron-treated ponds. Some of the water quality variables (ammonia-nitrogen, nitrite-nitrogen, and soluble reactive phosphorus) were different on specific dates, but concentrations in both sets of ponds were within the normal range of values reported for commercial catfish ponds. Overall, there was not a strong treatment effect on water quality variables. Diuron altered the phytoplankton composition within the ponds by reducing filamentous blue-green alga biomass. However, overall phytoplankton biomass was not different between treatment and control ponds; filamentous blue-green algae was (in part) replaced by diatom biomass. Zooplankton populations were not dramatically altered. It appears that diuron can be an effective control for one specific type of fish flavor problem, while having negligible effects on the overall water quality or other environmental variables measured in this study.