|Straus, David - Dave|
Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: 11/1/2008
Publication Date: 2/8/2009
Citation: Mitchell, A.J., Straus, D.L., Radomski, A.A., Carter, R.R. 2009. Hydrogen peroxide treatments for channel catfish eggs infected with water molds [abstract]. Book of Abstracts Aquaculture America. p.227.
Technical Abstract: Fungi, or water molds Saprolegnia spp., on channel catfish Ictalurus punctatus eggs can lower fry production. This requires the producer to spawn more catfish or face fingerling shortages. Few treatments have been tested against channel catfish eggs infested with an identified fungus. Hydrogen peroxide treatments were evaluated to determine their affect on egg survival and their efficacy against naturally occurring Saprolegnia spp. infestations. Three samples (12.8 g average) taken from each egg mass (less than 24-h old) were weighed and the eggs counted to determine the number of eggs per gram (overall average of 28.8 eggs/g). Egg masses were separated into about 90 g portions and placed in hatching troughs with nine separate compartments; each compartment had its own water inlet, drain and paddle. The compartments contained 35 L of water with an inflow of about 1.25 L/min (28 min water exchange rate). Water temperatures (23.2-24.0 degrees C) were monitored continually, dissolved oxygen (4.5 to 6.4 mg/L) and water flows were taken daily (adjusted if needed), and total alkalinity (215 mg/L) and total hardness (110 mg/L) were taken at the beginning of each study. Hydrogen peroxide was applied once daily as a flow through treatment at ten concentrations (0, 15.6, 31.3, 62.5, 250, 500, 1,000, 2,000, and 4,000 mg/L) in three studies until the eggs were clearly in the eyed-egg stage (5 or 6 treatments). In the last two studies, identical treatments (0 to 500 mg/L) were applied for 6 d in each study. Observations for fungal development were made daily until hatching began. The maximum measure of fungal growth (nearest 0.5 cm) was recorded from the egg mass in each compartment. This value was used as the fungal coverage measurement. Hatched fry, at the termination of each test run, were counted and percent survival determination counted fry/number of potential fry X 100) for each treatment was made. Concentrations above 500 mg/L drastically lowered egg survival and were dropped after the first study. Concentrations of 125, 250 and 500 mg/L were significantly different from the controls and all treatments significantly reduced fungal coverage when compared to the controls but were not different from each other. The 250 mg/L treatment had the highest average survival (64.4 percent compared to 24.7 percent for the controls), lowest incidence of fungi (27.3 percent compared to 100 percent for the control) and the lowest average fungal coverage (0.95 cm compared to 7.09 cm for the controls).