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United States Department of Agriculture

Agricultural Research Service

Research Project: STRATEGIES FOR FISH DISEASE CONTROL AND PREVENTION

Location: Harry K. Dupree Stuttgart National Aquaculture Research Center

Title: Treating sunshine bass eggs with copper sulfate controls fungus and increases survival

Authors
item Straus, David
item Beck, Benjamin
item Farmer, Bradley
item Ledbetter, Cynthia
item Williams, Rick -
item Clark, Mike -
item Freeze, Mike -

Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 2013
Publication Date: February 10, 2014
Citation: Straus, D.L., Beck, B.H., Farmer, B.D., Ledbetter, C.K., Williams, R.S., Clark, M.L., Freeze, M.T. 2014. Treating sunshine bass eggs with copper sulfate controls fungus and increases survival [abstracts]. Book of Abstracts Aquaculture America 2014: Taking Aquaculture to New Heights through Technology, Marketing, Collaboration, February 9-12. 2014, Seattle, Washington. p.504.

Technical Abstract: A major obstacle to sunshine bass production is fungal growth on eggs. Copper sulfate (CuSO4) is commonly used for fungus control in channel catfish hatcheries that use troughs, but the effectiveness of it on fish eggs hatched using different systems was not known. Female white bass Morone chrysops and male striped bass M. saxatilis were spawned, and sunshine bass eggs were transferred immediately to 6 L McDonald jars. Tannic acid was added to the jars and they were aerated for 4 min. Well water flowed through the jars for 2 h. Next, iodine was added to each jar and they were aerated for 10 min in a static bath; ovary tissue was removed with a sieve following this bath. Water flow was resumed for 1 h to purge the iodine before proceeding. Approximately 120 ml of eggs were counted with an optoelectronic XperCount (TM) enumerator and transferred to each hatching chamber of our experimental system (below, left); water volume was 1.5 L. Water flow maintained the rolling action of the eggs per industry standards. The study consisted of three CuSO4 concentrations (10, 20, and 40 mg/L) and an untreated control (n=3). Because eggs start hatching after 2 d, treatment began immediately the afternoon of spawning with a 10 min aerated, static bath and was repeated morning and afternoon on Day 2. Eggs were not treated after hatching began. Fry were counted with the XperCount (TM) on Day 4. Water parameters were: pH 7.9, 216 mg/L alkalinity, and 266 mg/L hardness. Fungus samples from the control chambers were identified as Saprolegnia ferax. Fungus was severe in the untreated controls (28% survival). Very little fungus was present in treatments receiving 10 mg/L CuSO4 (32% survival) or higher. The best survival was at 40 mg/L CuSO4 (50% survival); however, the 20 mg/L CuSO4 treatment (46% survival) gave similar results and allows for a greater margin of safety. We developed an in vitro assay (below, right) that confirmed maximum fungal inhibition was achieved at 20 mg/L CuSO4.

Last Modified: 10/23/2014
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