324 FISH HATCHERY MANAGEMENT 



Figure 95. Hexamita salmonis. 



Figure 96. Henneguya 

 sp. 



hexamitiasis must be made by microscopic examination of gut contents 

 from the anterior portion of the intestine and pyloric caeca. The flagellates 

 (Figure 95) are minute, colorless, pear-shaped organisms that dart rapidly 

 in every direction. Gross signs of infected fish may include swimming in a 

 cork-screw pattern, and a dark emaciated condition commonly called 

 "pin- headed." The protozoan may become abundant in fish that are fed 

 meat diets, and can cause irritation of the gut lining. With the advent of 

 processed diets, incidence of the disease has greatly declined. 



Therapy is not recommended unless Hexamita salmonis is abundant. For 

 treatment, feed epsom salt (magnesium sulfate) at the rate of S'/o of the diet 

 for 2 or 3 days. 



HENNEGUYA 



Seventeen species of Henneguya have been described from a wide variety of 

 North American freshwater fishes. The following remarks are limited to the 

 relationship of these parasites to hatchery-reared species, primarily channel 

 catfish. 



