FISH HEALTH MANAGEMENT 323 



macronucleus. They can be especially troublesome on young catfish, cen- 

 trarchids, and goldfish. 



Ambiphrya can cause problems anytime of year but most frequently 

 occurs when water quality deteriorates due to excessive amounts of organic 

 matter or low oxygen levels. This protozoan is not a parasite. It feeds on 

 bacteria and detritus and may develop in high numbers. Heavy infestations 

 on the gills cause the fish to act as if they were suffering from an oxygen 

 deficiency. Large numbers of them can cause a reddening of the skin and 

 fins. Fry and small fish may refuse to feed actively, flash, and become 

 listless. 



Ambiphrya is controlled easily with formalin at 125-250 parts per million 

 for up to 1 hour, or 15-25 parts per million as a pond treatment. Copper 

 sulfate, at whatever concentration can be used safely, or potassium perman- 

 ganate at 2 parts per million, also give good results. 



TRICHOPHRYA 



Species of Trichophrya sometimes are found on the gills of fish and can 

 cause serious problems in catfish and occasionally in other warmwater 

 species. They have rounded to pyramid-shaped bodies (30 x 50 microme- 

 ters) and are distinguished by food-catching tentacles in the adult stage 

 (Figure 94). Live organisms have a characteristic yellowish-orange or 

 yellowish- brown color that makes them very conspicuous when wet mounts 

 of gill tissue are examined under a microscope at lOOx or 440 x. 



Affected fish gills are pale and clubbed, and may be eroded. Infected 

 fish will be listless, as if they were suffering from an oxygen deficiency. 



Trichophrya is difficult to control in ponds but satisfactory results can be 

 obtained with copper sulfate at whatever concentration is safe. Pond treat- 

 ments with formalin or potassium permanganate give erratic results. A bath 

 treatment of 125-250 parts per million formalin for up to 1 hour usually is 

 effective, but may have to be repeated the next day. 



Internal Protozoan Diseases 



HEXAMITA 



Hexamita salmonis is the only common flagellated protozoan found in the 

 intestine of trout and salmon. Although the pathogenicity of the organism 

 is questioned by some researchers, most feel it can cause poor growth and 

 elevated mortality in small (2-inch) fish. All species of salmonids are sus- 

 ceptible to infection. Because there are no well-defined signs, a diagnosis of 



