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FISH HATCHERY MANAGEMENT 



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Figure 97. The interlamellar form of Henneguya with resultant spore-filled cysts 

 (arrow) between gill lamellae. Gill lamellae may become greatly hypertrophied 

 and lose all of their normal appearance. 175x magnification. (Courtesy Charlie 

 E. Smith, FWS, Bozeman, Montana.) 



CERA TOMYXA 



Ceratomyxa shasta is a serious myxosporidian parasite of salmonids in the 

 western United States that causes severe losses of rainbow and cutthroat 

 trout, steelhead, and coho and chinook salmon. Heavy mortalities of adult 

 salmon have occurred just prior to spawning. Severe hatchery epizootics, 

 resulting in 100% mortality, were reported as early as 1947 in California. 

 Many epizootics have been reported, including significant losses among 

 some wild salmonid populations. Infections also have been found in brook 

 and brown trout, and sockeye and Atlantic salmon. 



The spores of Ceratomyxa shasta are tiny and elongated and can be found 

 in great numbers in the lining of the gut and in cysts in the liver, kidney, 

 spleen, and muscle. The disease is contracted by adult salmon upon enter- 

 ing infected fresh water. Lake conditions are believed to be vital to the 

 development of the infective stage of the parasite. The entire life cycle, 

 which is poorly known, may be completed in 20 to 30 days at 53°F. Some 

 researchers feel that infection will not occur below 50°F. 



The first signs of infection in domestic rainbow trout include lack of ap- 

 petite, listlessness, and movement to slack water. The fish may darken and 

 shed fecal casts. The abdomen often swells with ascites. Exophthalmia 

 often occurs. The first internal changes appear as small, whitish, opaque 



