Title: Trials and tribulations of dose confirmation: Using copper sulfate for fungus control on channel catfish eggs Authors
Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: December 12, 2007
Publication Date: February 9, 2008
Citation: Straus, D.L., Mitchell, A.J., Carter, R.R. 2008. Trials and tribulations of dose confirmation: Using copper sulfate for fungus control on channel catfish eggs [abstract]. Book of Abstracts Aquaculture America. p.381. Technical Abstract: Range-finding and dose confirmation studies on the use of copper sulfate (CuSO4) for fungus control in channel catfish hatcheries were attempted during the catfish spawning season of 2007. Catfish were spawned on-site and egg masses were used in the study within 24 - 48 hrs. Similar portions (~80 g) of an egg mass were placed into mesh baskets of individual compartments of a custom hatching trough and acclimated for 1 hr. Egg counts (eggs/~10 g sample) were also determined for each egg mass to estimate number of eggs in each portion. The range-finding studies consisted of five CuSO4 concentrations and an untreated control. Eggs were treated daily until the embryos developed eyes. Range-finding studies were performed at 26°C in a commercial hatchery and also in our labs. During the studies, a small amount of fungus grew initially at this temperature, but not on all portions and it usually disappeared within a few days. This suggests that fungus does not grow well at this temperature, at least not in the present studies. The FDA/CVM required dose confirmation study in 23.5°C well water at SNARC was next, and was designed to test the optimal concentration (10 mg/L CuSO4) found during last year’s range-finding studies against a control. Catfish eggs were obtained as described above; eggs were treated daily until the embryos developed eyes. Water chemistry during the study was pH 7.7, 212 mg/L total alkalinity, and 95 mg/L total hardness. When hatching was complete for all viable eggs, fry of each compartment were preserved in 70% ethanol for counting to determine the percent hatch in each treatment. Fungus was severe in the untreated controls (8% survival) and 10 mg/L CuSO4 daily gave 55% survival; this difference was statistically significant. Independent substantiation will be performed next year.