Efficacy of Treatments of "ich" Infestations in Channel Catfish. The parasite "ich" is very devastating in commercial catfish ponds and most research comparing possible treatments has been seriously flawed. We did an aquarium study to investigate the ability of a variety of legal or potentially legal treatments that might be used for ich in ponds or holding facilities. We found that (at the concentrations tested) chloramine-T, iodine compounds, potassium permanganate, and salt were completely ineffective. In experiments using daily treatments for up to three weeks, copper sulfate blocked the transmission of ich to uninfested fish but did not cure fish already carrying the parasite. Formalin was effective only at high doses and repeated treatments and concentrations that were sufficient to poison many of the fish. None of the compounds legal for use in food fish appeared to be effective in curing heavily infested channel catfish fingerlings.

Yersinia ruckeri: An Emerging Pathogen of Channel Catfish. Project was completed this year. We discovered that Yersinia ruckeri, the bacterium that causes enteric red mouth in trout, is sometimes responsible for losses of cultured channel catfish. The catfish isolates are identical to trout isolates and the type culture. After 2 years of Yersinia cases in catfish, the disease disappeared. Diagnostic tools develop din this study will speed identification and containment of this disease should it reoccur.

Molecular Methods for the Diagnosis of Viral Diseases in Cyprinids. Previous work done in our lab has discovered a number of reoviruses in shiners and grass carp. This year PCR-based assays have shown that our isolates, and the type strain of Golden Shiner Virus, are all probably Chinese Grass Carp Reovirus, a serious pathogen of grass carp that has not been previously reported in the US. This is the thesis project of Matt McEntire.

"Prevention of Disease Transmission During Japanese-Style Koi Shows. In this type of show, all of the koi are held in a single tank. A number of virulent diseases have been spread to champion koi (sometime valued at 5-10 thousand dollars!) through this mechanism including a new koi herpes virus. Our work has shown that sodium chlorite kills bacteria and viruses at concentrations that are well tolerated by fish and that this compound may be useful in the reduction of disease transmission from infected fish to healthy fish living in the same tank."

Toxic Algae: HCTC. This work confirmed the link between A. marina and HCTC and demonstrated that prevention of HCTC-related losses was possible. We also identified the conditions required for the growth of the toxic algae A. marina. Additionally, we demonstrated that the HCTC syndrome is not related to microcystin. This work was done with Don Freeman of the USDA-ARS and was the thesis project of Scott Snyder.

Prevention of Algal Toxicosis in Channel Catfish. This work was funded by the catfish promotion board. Along with Larry Dorman , Martha Fitz, and Peter Perschbacher we sampled ponds on a dozen farms and tried to establish relationships between algal populations and the occurrence of HCTC, VTC, and anemia. Several thousand samples were collected and analyzed and the data led to an improved understanding of the impact of algal toxins in aquaculture. We were not able to demonstrate a conclusive link between algae and VTC or anemia but did document several major fish losses that could be directly attributed to aquatic toxins.

Toxicity of Hydrogen Sulfide. We produced gaseous hydrogen sulfide by reacting iron sulfide with sulfuric acid and used the gas to validate or analysis techniques and to do LC50 determinations in shiners and goldfish. We found that it was necessary to use zinc sulfide concentrating methods to reliably measure levels of less than 100 ppb. We determined that the LC50 for baitfish held at pH 6.5 was about 500 ppb following a single dose in static aquariums. The half-life of hydrogen sulfide under these conditions is greater than 24 h.

Koi Herpes Virus. In collaboration with Wayne Gray of UAMS and Scott Lepatra of Clear Springs Trout, we developed a PCR method to detect KHV. We have used this method to diagnose KHV cases and have published a manuscript describing it. This assay provides a fast and unambiguous diagnosis of KHV.

Resistance of flukes to Dylox. Melanie Newman of the UAPB Lonoke Diagnostic Laboratory and I are checking the sensitivity of populations of flukes to Dylox. There is very good anecdotal evidence of resistance. We are trying to document it.

Treatment of columnaris infections in warmwater fish. This is the thesis project of Swapna Thomas. We have collected a large group of columnaris isolates and are characterizing them with RAPD (a PCR based technique) to see how closely related they are. When that is complete, we will work on an experimental infection model with the different isolates and determine which treatments work best in catfish and baitfish. Results to date indicate considerable variability in the DNSA sequences of our columnaris isolates. This is the thesis project of Swapna Thomas

Toxicity of Commonly Used Rice, Cotton and Soybean Pesticides to Commercial Aquaculture Species. We are treating catfish, shiners, bass, and shrimp with agricultural chemicals to screen for those that have the potential to cause mortality with accidental aerial over spray. We have completed tests using facet and Prowl alone and in combination and have found no toxicity even when it is applied to aquariums at 100% of the field dose.

Age Structure in Commercial Catfish Ponds. We are just beginning this study. We are looking at the age structure of catfish populations in old ponds and to see if there is an accumulation of poorly growing fish. If found, these fish will be examined to see if they might serve as a disease reservoir. A graduate student and a source of known-age fish have been found.

Incidence of LMBV in Arkansas. We have worked with Arkansas game and Fish to inspect fish in most major lakes and state hatcheries in Arkansas for largemouth bass virus. The virus is widespread in natural waters but has not been detected in bass fingerlings destined for stocking.

Ion Requirements for Raising Marine Shrimp in Fresh Water. We are investigation the importance of individual ions and ion ratios for farming marine shrimp in Arkansas.

Susceptibility of Temperate Fishes to SVCV. We are looking to see if SVCV is dangerous to North American fishes.

Early Cross Protection form Fish Vaccines: We are investigating the surprising ability of some DNA vaccines to protect against very different viruses and at a very short period after vaccination.