|Straus, David - Dave|
Submitted to: Catfish Farmers of Arkansas
Publication Type: Abstract Only
Publication Acceptance Date: 1/12/2015
Publication Date: 1/16/2015
Citation: Straus, D.L., Farmer, B.D., Beck, B.H., Bosworth, B.G., Torrans, E.L., Tucker, C.S. 2015. Water hardness affects catfish susceptibility to columnaris [abstract]. Arkansas 2015 Aquaculture, January 15-16, 2015, Hot Springs, Arkansas. Catfish Farmers of Arkansas. p. 3.
Technical Abstract: Columnaris disease can cause tremendous losses of freshwater fish. While it has been studied exhaustively, little is known about its affinity to specific water chemistries that affects attachment. Recent studies in our labs have illuminated this subject. In the first experiment, two waters were used: unfiltered well waters from the Stuttgart National Aquaculture Research Center (SNARC; Stuttgart, Arkansas) and from the Warmwater Aquaculture Research Unit (WARU; Stoneville, Mississippi). Fingerling channel catfish (Ictalurus punctatus) were exposed to an F. columnare suspension in aquaria for 4 days; each aquarium contained 10 L of water and ½ was replaced daily. No fish died in the WARU water, but 100% of the fish died in SNARC water. Using qPCR, we found that there were approximately 1900 times more F. columnare attached to the gills of the fish in SNARC water (P = 0.0001). In the second experiment, four waters were used: the above waters, WARU water filtered through a carbon bed to remove tannins and SNARC water filtered through a water softener to remove hardness. No fish died in the WARU or filtered waters, but 17% of the fish died in SNARC water. Again using qPCR, we found that there were approximately 1600 times more F. columnare attached to the gills of the fish in SNARC water (P = 0.0001). Filtered SNARC water had less F. columnare than unfiltered SNARC water (P = 0.0809) and filtered WARU water had more F. columnare than unfiltered WARU water (P = 0.6191). Results suggest tannins have minimal involvement, and water analyses suggest that calcium and hardness are two parameters influencing bacterial attachment and ultimately pathogenesis. Results of ongoing tests will be discussed