The effectiveness of a specific piscicides for the control of an invasive fish Coptodon zillii in an urban lake

Redbelly tilapia (Coptodon zillii) poses a significant threat to aquatic ecosystem security and water quality, severely impeding ecological restoration efforts for the aquatic ecosystem.But effective control methods for redbelly tilapia, particularly within riverine and lacustrine habitats, have been scarce."Miefeiling" an organophosphorus pesticide, has demonstrated specificity as a piscicide for tilapia species.However, there was little information regarding the application of this compound in natural water bodies, such as lakes.This study aimed to evaluate the efficacy and safety of "Miefeiling" in Dongshan Lake of Guangzhou City, where redbelly tilapia constituted 79.41% of the biomass of all the fish species.A concurrent control experiment was conducted in ponds.The application of "Miefeiling" at a concentration of 0.20 ml/m resulted in a substantial reduction of the redbelly tilapia population within a 30-hour period, achieving an eradication rate of 88.7 g/m and totaling 1598.2 kg of the redbelly tilapia removed from Dongshan Lake.Post-treatment population dynamics were as follows: no redbelly tilapia was detected 20 days post-treatment; 180 days post-treatment, redbelly tilapia accounted for 7.22% of the fish biomass; and 630 days post-treatment, comprised 14.03% of the fish biomass.This was significantly lower compared to the control lake without piscicide application, where redbelly tilapia made up 75.43% of the fish biomass.Additionally, total phosphorus and chemical oxygen demand levels reverted to baseline within seven days, with no detectable presence of malathion or dichlorvos throughout the experimental period.The application of "Miefeiling" did not adversely affect other native fish species, and the pond experiment indicated minimal impacts on phytoplankton and water quality.These results suggest that "Miefeiling" can effectively eradicate redbelly tilapia without compromising water quality and the native biota in the lake.