Treating catfish diseases: walking the line between excess and moderation

Authors: Straus, David - Dave; Beck, Benjamin

Submitted to: Aquaculture America
Publication Type: Proceedings
Publication Acceptance Date: 12/14/2015
Publication Date: 2/22/2016
Citation: Straus, D.L., Beck, B.H. 2016. Treating catfish diseases: walking the line between excess and moderation. Proceedings of the Aquaculture America 2016, February 22-26, Las Vegas, Neveda 2016. p. 83.

Interpretive Summary:

Technical Abstract: Cost savings by using a cheaper disease treatment will increase profitability of any catfish farm. This invited producer presentation will discuss costs savings using copper sulfate in catfish production and a summation of our research, specifically in the hatchery. Copper sulfate is not approved by the FDA for use on food fish. But, regulatory action has been deferred pending ongoing research; so it is currently acceptable to use. The only FDA-approved compounds for fungus control are formalin and hydrogen peroxide; these are very expensive and have human safety concerns/storage precautions (formalin - carcinogen, severe skin and respiratory irritant, flammable, hydrogen peroxide - severe skin and respiratory irritant, corrosive). A comparison of costs for fungus control of one treatment of a catfish trough is as follows: Hydrogen Peroxide (approved) - $0.89 Formalin (approved) - $0.73 Copper Sulfate - $0.02 A range-finding study was designed to determine the optimum concentration of copper sulfate needed to control fungus (Saprolegnia sp.) on channel catfish eggs in 23 deg C well water at the Stuttgart National Aquaculture Research Center. Channel catfish were spawned on-site and spawns were moved to the hatching lab within 24 hrs. Similar portions (approximately 80 g) of a spawn were placed into mesh baskets of individual compartments of a custom hatching trough (n=4) and acclimated for 1 hr. Egg counts (eggs/approximately 10 g sample) were also determined for each spawn to estimate number of eggs in each portion. The study consisted of 5 copper sulfate concentrations (2.5, 5, 10, 20, and 40 mg/L) and an untreated control. Eggs were treated daily until the embryos developed eyes (after 5 treatments). Water chemistry for the well water was pH 7.5, 220 mg/L total alkalinity, and 90 mg/L total hardness. When hatching was complete for all viable eggs, fry were siphoned into individual jars containing 70% ethanol and counted within a few days to determine the percent of fry that hatched in each treatment. Fungus was severe in the untreated controls (2% survival) and an optimum treatment of 10 mg/L CuSO4 daily was sufficient to control fungus (63% survival) in 23.5 deg C well water. Very little fungus was present in treatments receiving 10 mg/L CuSO4 or higher (Table 1), except in 1 replication (1 spawn) that had numerous unfertilized eggs.