John Wiley & Sons, Ltd.

Ecological impacts of fluridone and copper sulphate in catfish aquaculture ponds

Fluridone and copper sulphate are often used for controlling macrophytes and algae in aquaculture ponds. The present study examined the ecological effects of these chemicals on macrophyte, phytoplankton, and zooplankton biomass, plankton community structure, water quality parameters, and fish survival and yield in catfish culture ponds using a randomized complete block design. The estimated half‐life of fluridone in the individual ponds ranged from 1.6 to 10.8 d. Free copper ion activity in ponds treated with copper sulphate was dynamic, ranging from pCu of 7.7 to 8.9 after each application and decreasing to ∼12 (1 × 10−12M) within a week after each application, approaching observed values in control ponds (pCu = 12.3 to 13.4). No difference in macrophyte biomass was observed among treatments. Fluridone and copper treatments elicited different responses within the phytoplankton community. Copper treatments reduced Cyanophyta biomass, but increased biomass of more tolerant taxa among the Chlorophyta and Chrysophyta. Fluridone treatments reduced total phytoplankton biomass including Cyanophyta and increased the sensitivity of Chlorophyta and Chrysophyta to copper. Copper also affected zooplankton community composition due to direct toxic effects on sensitive zooplankton taxa (e.g., Cladocera), whereas Copepoda biomass in copper‐treated ponds exceeded that in controls. Catfish survival and yield were not significantly different among treatments. The results of the present study suggest that fluridone and copper interact at realistic application rates, increasing the ability to control algae compared to treatments where they are applied alone. This article is protected by copyright. All rights reserved

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