Fish Health (Jim Peterson, pers. conun.) 



No unusual incidences of physical abnormalities were 

 observed among golden trout in Montana. All were free of visible 

 signs of disease symptoms. No viral pathogens were isolated; 

 however, T.S.A. cultures revealed a general prevalence (six of 

 nine populations of Yersinia cucKeri, serotype 2. Samples from 

 Sylvan Lake were found to contain Y^ cucketif both serotypes 1 

 and 2. No type 1 was isolated from the other populations 

 sampled, and no Y^ lilcJifiil of either serotype was found in 

 samples from Fourmile Basin #4, Blue Danube or Lower Lightning 

 Lake (Table 9). Y^ ruckeri is the bacterial pathogen that causes 

 Enteric Redmouth (ERM) , a disease which often results in heavy 

 mortality, especially when introduced into a crowded situation 

 such as a fish hatchery. It is important to remember that ERM 

 was not observed in these fish, but the causative organism 

 (Y. ruckeri) was, and so the potential for disease exists. 

 Y^ ruckeri serotype 2 is much less pathogenic to trout than 

 serotype 1 and "...probably pose no more threat than many genera 

 of ubiquitous bacteria in the aquatic environment..." (Janeke, 

 pers . comm. ) . 



The first samples of 18 goldens from Sylvan Lake were live- 

 captured in gill nets, held from 5 to 48 hours in crowded live- 

 cars and artificially spawned. Fifteen of 18 samples were found 

 to contain Y^ ruckeri (serotypes 1 from 3 fish, serotype 2 from 

 11 fish, and serotypes 1 and 2 from 1 fish). A second sample 63 

 days later found Y^ ruckeri in 10 of 30 fish sampled (nine sero- 

 type 2, one serotype 1). These goldens were stressed by gillnet- 

 ting, but not to the degree of the first sample. 



The health samples collected from spawning goldens at the 

 time eggs were collected in 1981 were routine. No evidence of a 

 pathogen was apparent and there was no reason to suspect that Y_^ 

 rucker i was present. Another precaution taken at that time was 

 to water-harden all eggs collected in a 3 mg/L solution of ery- 

 thromycin (Abbot Labs). Erythromycin is commonly used in Montana 

 when collecting eggs from wild sources to help eliminate the 

 possible spread of bacterial fish pathogens. Y^ ruckeri is 

 transmitted fish to fish via the water and there is no conclusive 

 proof of egg transmissions (Klontz et al. 1976). However, 

 because this precaution was taken, we are hopeful that any possi- 

 bility of transmission of this pathogen from Sylvan Lake was 

 interrupted. Eggs collected in 1980 for Cave Lake were also 

 water hardened in erythromycin and the fish were found negative 

 for Y^ ruckeri . 



The eggs collected at Sylvan Lake in 1981 were hatched and 

 reared at the Washoe Park Trout Hatchery at Anaconda. These 

 goldens suffered from parasitic infections of Hexamitar Cost3 . a 

 and C yrodactvlus incurred from the hatchery water supply. Some 

 mortality was experienced, but treatment for the parasites con- 

 trolled the situation. These fish were sampled for Y^. i :ucke i :i 

 when they were 2,100/pound and again when 150/pound. No Y_.. 

 ruckeri was found. 



- 29 - 



