ARS | Publication request: Using copper sulfate to control fungus on fish eggs

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 8, 2013
Publication Date: February 8, 2013
Citation: Straus, D.L., Mitchell, A.J., Farmer, B.D., Ledbetter, C.K., Carter, R.R., Steeby, J.A. 2013. Using copper sulfate to control fungus on fish eggs [abstract]. Lonoke Aquaculture Workshop Book of Abstracts, February 7, 2013, Lonoke, Arkansas. p.7.

Technical Abstract: Copper sulfate (CuSO4) is widely used by the catfish industry as an economical treatment to control fungus (Saprolegnia spp.) on catfish eggs. This is an overview of our effectiveness and safety studies. Channel catfish spawns were 24 - 48 hrs old. Comparable portions of a single spawn were placed into mesh baskets of individual compartments of a customized hatching trough; each trough was one replication. Eggs were acclimated for 1 hr in 74 degrees F flow-through well water; the exchange rate was 30 min as in a commercial hatchery. The Effectiveness range-finding study consisted of 3 replications of 5 CuSO4 concentrations (2.5, 5, 10, 20, and 40 ppm) and an untreated control. Eggs were dosed every morning until the embryos developed eyes. Chemistry of the well water was pH 7.5, 220 ppm alkalinity, and 90 ppm hardness. When hatching was complete, fry were counted to determine the percent of fry that hatched in each treatment (based on counts from the original egg mass). Fungus was severe in the untreated controls (2% survival), and the most effective treatment of 10 ppm controlled fungus (63% survival). Two dose-confirmation studies have been completed and submitted to FDA to verify the optimum dose of 10 ppm, both in the lab and at a commercial hatchery. We are currently working on the effectiveness of CuSO4 to control fungus on hybrid striped bass eggs. The Target Animal Safety study was designed to test the safety of CuSO4 to catfish eggs at the proposed label rate (10 ppm), and also at 30 and 50 ppm. Catfish eggs (obtained as above) were dosed once daily until the embryos developed eyes; exchange rate of the 79 degrees F water was 90 minutes (3X the normal rate) during treatments. When hatching was complete, the percent hatch in each treatment was determined. Some fungus developed in the controls at this temperature and mean percent hatch was 40.8%. The percent hatch of the 10, 30, and 50 ppm CuSO4 was 80.1, 64.2 and 80.2%, respectively, indicating all treatments were safe to the eggs. A separate experiment looked at the hatching success when catfish eggs were dosed once daily until the embryos developed eyes with 100 ppm CuSO4. The percent hatch of each replication was 62.7, 94.9, 59.7 and 64.8%, which demonstrates the variability across spawns.