Donald F. Amend

A Hematopoietic Virus Disease of Rainbow Trout and Sockeye Salmon

Abstract A previously undescribed virus disease epizootic of hatchery rainbow trout (Salmo gairdneri) in British Columbia, Canada is presented. In the same locality, a similar virus disease was experienced among hatchery sockeye salmon (Oncorhynchus nerka). Typical symptoms included flashing, fecal casts, hemorrhagic areas at the base of fins, and petechial hemorrhages on the visceral fat and membranes in the abdominal cavity. Histopathologic changes were typified by extensive degeneration and necrosis in the hematopoietic tissues of the kidney and spleen. A virus was isolated from both species of fish on tissue culture and the viruses showed cross-infectivity. Based upon the pathological changes in the hematopoietic tissue and the demonstration of a vital infection, a tentative descriptive name was designated Infectious Hematopoietic Necrosis. The isolated viruses were distinctly different from the infectious pancreatic necrosis or viral hemorrhagic septicemia viruses of trout, but did show similarities ...

Transportation of fish in closed systems: methods to control ammonia, carbon dioxide, pH, and bacterial growth

Abstract Methods to control the development of toxic by-products in the water were evaluated for various pet-fish species enclosed in polyethylene bags overlayed with oxygen. A formula of three components was developed that decreased the concentration of ammonia and carbon dioxide, controlled bacterial growth, and maintained a higher pH compared with untreated controls held under similar conditions. Clinoptilolite at 14 g/liter controlled the ammonia accumulation, tris buffer (0.017 M) at pH 8.0 controlled the accumulation of free CO2, and neomycin sulfate at 20 mg/liter prevented bacterial blooms. Fish were held up to 48 hours and at loading densities up to 180 g/liter with favorable results. Field tests of the formulation were conducted by air-transporting several species of pet fish from either Florida or east Asia to Seattle, Washington at loading densities that averaged 102 and 87 g/liter, respectively. The average transit time from Asia was longer than shipments from Florida, 36 hours compared to 22...

Heritability of tolerance for infectious hematopoietic necrosis in sockeye salmon (Oncorhynchus nerka)

Abstract A hierarchical breeding design was used to demonstrate the heritability of tolerance for infectious hematopoietic necrosis (IHN) in sockeye salmon. Oncorhynchus nerka. Heritability was about 30%, indicating that artificial selection may increase the number of fish that can tolerate the disease.

Comparative Toxicity of Two Iodophors to Rainbow Trout Eggs

Abstract Toxicity of Wescodyne(R) and Betadine(R) to eyed eggs was not adversely affected by water hardness (as calcium and magnesium) or by exposure periods up to 60 min. Both iodophors were much more toxic below pH 6.0 than at pH 8.0. In general Wescodyne was slightly more toxic than Betadine. Significant egg loss occurred if freshly fertilized eggs were water-hardened in either iodophor at 100 ppm of iodine, but egg loss at 25 ppm of iodine or at 100 ppm if the eggs were disinfected 30 min after water hardening was comparable to the control. Also, there was no effect on the egg mortality or fry development following single or multiple exposures after eggs were water hardened. At pH 6.0 and above, Wescodyne and Betadine at 100 ppm iodine in a 15-min dip would be safe to use on rainbow trout eggs at any stage of development after water hardening. Recommendations and precautions for hatchery use are given.

Etomidate: Effective Dosages for a New Fish Anesthetic

Abstract Etomidate (r-(+)-ethyl-1-(1-phenylethyl)-1H-imidazole-5-carboxylate) is a potent and safe anesthetic for fish. The minimum effective dose for four species of aquarium fish ranged from 2.0 to 4.0 mg/liter, and the maximum safe dose ranged from 7.0 to 20.0 mg/liter. In general, the lower the dose, the longer the time for anesthesia, but the faster the recovery time. At 4.0 mg/liter, fish typically entered anesthesia within 90 seconds and recovered within 40 minutes. Etomidate is more effective in alkaline water and higher water temperature but is not affected by total hardness. Test species varied in their ability to survive extended or repeated exposures to the drug. Etomidate has advantages over other commonly used fish anesthetics and should be evaluated further.

Some Factors Influencing Susceptibility of Rainbow Trout to the Acute Toxicity of an Ethyl Mercury Phosphate Formulation (Timsan)

Abstract This study determined the influence of water temperature (55–68° F), dissolved oxygen (4–12 ppm), water hardness as CaCO3 (20–256 ppm), and chloride ions (to 2 mM) on the susceptibility of rainbow trout (Salmo gairdneri) to the acute toxicity of ethyl mercury phosphate (EMP). The fish were exposed for one hour to 0.125 ppm EMP, the active ingredient of Timsan, a commercial EMP formulation. The death rate because of the exposure to EMP increased with an increase in water temperature, a decrease in dissolved oxygen, and an increase in chloride ions; calcium appeared to have no effect. The effect of water temperature and dissolved oxygen was ascribed to changes in the respiration rate of the fish, and a chemical explanation is presented for the effect of chloride ions.

An improved method for isolating viruses from asymptomatic carrier fish

Abstract This paper describes a method using elevated levels of penicillin, streptomycin, and nystatin instead of filters to control bacteria and mold contaminants in specimens processed for virus isolation. Filters were shown to significantly reduce the virus concentration. Virus and tissue cultures were not affected by this procedure. In field tests nearly three times more specimens were positive for virus with this method than with the widely used filter technique. Moreover, the cost of materials was less. This method is recommended for inspection and certification purposes.

Increase in Ocean Survival of Freely Migrating Steelheads Vaccinated Against Vibrio anguillarum

Abstract Steelheads (Salmo gairdneri) were vaccinated as juveniles against two serotypes of Vibrio anguillarum, marked, and allowed to migrate freely to the sea. A statistically significant (P ⩽ 0.01) 19.3% increase in return rate of adults to the hatchery occurred among the vaccinated group compared to the nonvaccinated control group. No difference between groups was found in the size or sex ratio of returning fish.