Columnaris (Flavobacterium columnare) challenge using Fathead minnows (Pimephales promelas) in an ultra-low flow system
Arkansas baitfish farms routinely struggle with columnaris disease, which is caused by Flavobacterium columnare. Columnaris is ubiquitous in fathead minnows (Pimephales promelas) especially after harvest while they are being held in vats and during the transport prior to being sold. Columnaris disease is transmitted horizontally from fish to fish is one of the most serious bacterial infections affecting the aquaculture industry today. The disease is highly contagious and may be spread through contaminated nets, specimen containers, and even food. Outbreaks are commonly caused by stress such as overcrowding, low dissolved oxygen, high ammonia and nitrite concentrations. In order to further examine this issue, a columnaris challenge tank study was devised with three different densities (400/m3, 800/m3 and 1600/m3) and at two different temperatures (22°C and 28°C) using an ultra-low flow system. The experiment was performed with three replicates. LSU- 04-066 stain was used to challenge fathead minnows during the trail. Dissolved oxygen, flow, ammonia and fish mortality were recorded following the challenge. Fish mortality following the challenge was almost 100% in all the densities at 28°C within 24 hours and at 22°C within 28-30 hours. Tank water and fish tissue (gills, kidney, and spleen) samples were collected and processed for the presence of columnaris using real time PCR and flow cytometry. Data are currently being analyzed and results will be presented and discussed in the context of baitfish industry.