ARS | Publication request: The safety of copper sulfate to channel catfish eggs

Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: December 10, 2008
Publication Date: February 16, 2009
Citation: Straus, D.L., Mitchell, A.J., Carter, R.R., Mcentire, M.E., Radomski, A.A., Steeby, J.A. 2009. The safety of copper sulfate to channel catfish eggs [abstract]. Book of Abstracts Aquaculture America. p.337.

Technical Abstract: Copper sulfate (CuSO4) is an economical treatment to control fungus (Saprolegnia spp.) on channel catfish eggs and is widely used by the industry. The purpose of this study was to determine the safety of copper sulfate to channel catfish eggs when treated at the therapeutic rate (10 mg/L), and also at 30 and 50 mg/L CuSO4. Catfish were spawned on-site and egg masses were used in the study within 24 hrs. Similar intact portions (approximately 100 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/approximately 15 g sample) were also determined for each of the egg masses to estimate number of eggs in each portion. Eggs were treated daily until the embryos developed eyes; exchange rate of the water was 90 minutes during treatments. Water chemistry during the study was pH 7.5, 208 mg/L total alkalinity, and 106 mg/L total hardness; water temperature was 26 deg C. When hatching was complete for all viable eggs, fry of each compartment were preserved in 70 percent ethanol for counting to determine the percent hatch in each treatment. Some fungus developed in the controls at this temperature and mean percent hatch was 40.8 percent. The mean percent hatch of the 10, 30, and 50 mg/L CuSO4 was 80.1, 64.2 and 80.2 percent, respectively. The difference between the 10 and 30 mg/L CuSO4 treatments was statistically significant, while the difference was not significant between the 10 and 50 mg/L CuSO4 treatments. The lower hatch-rate of the 30 mg/L treatment is attributed to the random sampling within the original egg masses and the range of hatching rates that are common in the industry. A separate experiment looked at the hatching success when eggs were treated daily until the embryos developed eyes with 100 mg/L CuSO4. The water temperature was 24 deg C and the exchange rate during the treatment was 30 minutes. The individual percent hatch of each replication was 62.7, 94.9, 59.7 and 64.8 percent.