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FISH HATCHERY MANAGEMENT 



Figure 87. hhtyobodo (Costia), 400x magnification. (Courtesy G. 

 L. Hoffman, Fish Farming Experimental Station, Stuttgart, Arkan- 

 sas.) 



Ichtyobodo can be a serious problem on all species and sizes of warmwater 

 fish, particularly channel catfish. This flagellate can cause problems any- 

 time of year, but is most common on warmwater fish from February to 

 April. 



Pond treatments for Ichtyobodo that give good results, if they can be used 

 in the particular situation, include: formalin at 15-25 parts per million; po- 

 tassium permanganate at 2 parts per million (may have to be 

 repeated depending on organic load in the pond); or copper sulfate at 

 whatever concentration can be used safely. For a prolonged bath treatment 

 for salmonids or warmwater fish, best results are obtained from formalin at 

 125 to 250 parts per million for up to 1 hour; the concentration depends 

 on water temperature and species and size of fish to be treated. 



ICHTHYOPHTHIRIUS 



Ichthyophthirius multifilis, or "Ich," is a large ciliated protozoan exclusively 

 parasitic on fish. It probably is the most serious disease of catfish, but also 

 is a common parasite of other warmwater fishes and can be a serious prob- 

 lem of salmonids. Ich is the only protozoan parasite that can be seen by 

 the naked eye; when fully grown it may be as large as 1.0 millimeter in di- 

 ameter and appear as gray-white pustules much like grains of salt. Positive 

 identification is based on the finding of a large, ciliated protozoan with a 

 horseshoe- shaped macronucleus embedded in gills, skin, or fin tissue. 



The feeding stages, or trophozoites, of Ich are found in the epithelium of 

 the skin, fins, and gills (Figures 89 and 90). When mature, the adult 

 parasites drop off the host and attach to the bottom or sides of the pond. 

 Once encysted, they reproduce by multiple fission and, within two to 



