Dose-Confirmation of Copper Sulfate for Treating Fungus on Channel Catfish, Ictalurus punctatus, Eggs at a Commercial Hatchery

Abstract

This study at a commercial hatchery was required by the U.S. Food and Drug Administration to provide independent substantiation of the results of previous laboratory dose-confirmation studies on the use of copper sulfate (CuSO₄) to control fungus (Saprolegnia spp.) on the eggs of channel catfish, Ictalurus punctatus. The study compared an untreated control group of eggs to eggs treated with 10 mg/L CuSO₄ in a flow-through system; mean water temperature was 23.5°C. Eggs were treated once daily until the embryos reached the eyed stage (5 treatments). Hatching was complete by day 11, and fry were counted to determine the percentage of survival in each treatment. Fungus was identified by polymerase chain reaction (PCR) as Saprolegnia spp. The mean survival in the control treatments was 4% and 40% in the CuSO₄ treatments; the latter survival was significantly higher, but still lower than normal. This study confirms that 10 mg/L CuSO₄ is an effective treatment to control fungus on catfish eggs when used daily until the eggs are eyed. However, continued treatment of eggs until hatching occurs may be warranted based on fungal growth rates observed after treatments were discontinued.

Keywords:

• Channel catfish eggs
• effectiveness
• copper sulfate
• Saprolegnia spp

Acknowledgments

We appreciate the hospitality of the fish producer for allowing us to use their facility. We thank Freeport-McMoRan Copper & Gold Inc. (formerly Phelps Dodge Corporation) for supplying the Triangle Brand® copper sulfate. Thanks to Dale Jamison for maintaining the channel catfish brood stock at SNARC for this study. Cindy Ledbetter and her summer student Christen Proctor set up the experiment and took care of the daily activities of the study. Adam Fuller, Peter Perschbacher, Mack Fondren, and Matt McEntire provided critical reviews of the manuscript. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.

Notes

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