Title: Safety of copper sulfate to channel catfish eggs Authors
Submitted to: North American Journal of Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 23, 2011
Publication Date: January 30, 2012
Citation: Straus, D.L., Mitchell, A.J., Carter, R.R., Mcentire, M.E., Steeby, J.A. 2012. Safety of copper sulfate to channel catfish eggs. North American Journal of Aquaculture. 74:60-64. Interpretive Summary: Copper sulfate is used in catfish hatcheries to prevent fungus from growing on eggs while they are incubated in hatching troughs. Nothing has been published about how safe it is to fish eggs. In previous studies we showed how effective it is at controlling fungus when treating eggs daily with 10 parts per million of copper sulfate. This rate is very low and copper is flushed out of the troughs within a few hours. This concentration is also very safe for eggs at even 3 and 5 times this dose. Research like this is important information that is needed by the catfish industry to fight fungus problems on eggs and to help the FDA in approving this low-cost, safe and effective compound for use in aquaculture.
Technical Abstract: Copper sulfate (CuSO4) is commonly used in the catfish industry to control saprolegniasis (caused by watermolds) on eggs. This study was designed to establish the safety of CuSO4 when applied to hatching troughs containing channel catfish eggs in 26 degrees C flow-through well water at 10, 30, and 50 mg/L for three times the normal treatment duration (N = 4). Eggs were treated daily until the embryos reached the eyed stage. A small amount of watermold was detected on control treatment eggs in three of the replicates and on the 10 mg/L CuSO4 - treated eggs in the other replicate by day 3. The safety of CuSO4 was indicated by the percent of fry that hatched from the eggs. Fry survivals in the control, 10 mg/L, 30 mg/L, and 50 mg/L CuSO4 treatments were 41, 81, 64 and 80%, respectively. The control treatment was significantly different from all CuSO4 treatments. Treating channel catfish eggs with up to 50 mg/L CuSO4 did not adversely affect the hatch rates in this study. There appears to be an adequate margin of safety above 10 mg/L; therefore, CuSO4 should be considered a safe treatment to mitigate losses caused by saprolegniasis.