|Straus, David - Dave|
Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: 11/17/2006
Publication Date: 2/26/2007
Citation: Straus, D.L., Mitchell, A.J., Aime, M.C. 2007. Optimizing copper sulfate treatments for fungus control on channel catfish eggs in high alkalinity/moderate hardness water [abstract]. Book of Abstracts Aquaculture America. p. 885.
Technical Abstract: Interest in the use of copper sulfate (CuSO4) for fungus (Saprolegnia sp.) control in catfish hatcheries has developed over the past few years. A range-finding study was designed to determine the optimum concentration needed for fungus control on channel catfish eggs in 23.5°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 - 48 hrs. Similar portions (~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/~10 g sample) were also determined for each spawn to estimate number of eggs in each portion. The study consisted of 5 CuSO4 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°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. Table 1. Daily treatment concentration (until eggs were ‘eyed’), mean percent hatch and total fungus area after treatments were stopped until the end of the study. CuSO4 (mg/L) Mean % Hatch Fungus (cm2) 0 1.76 6.1 2.5 32.98 3.8 5 44.13 1.7 10 62.78 0.7 20 51.44 0.1 40 45.57 0.8