Fish Hatchery Management - fisheries & aquaculture

FISH HEAL'I'H MANAGEMENTmacronucleus. They can be especially troublesome on young catfish, centrarchids,and goldfish.Ambiphrya can cause problems anytime of year but most frequentlyoccurs when water quality deteriorates due to excessive amounts of organicmatter or low oxygen levels. This protozoan is not a parasite. It feeds onbacteria and detritus and may develop in high numbers. Heavy infestationson the gills cause the fish to act as if they were suffering from an oxygendeficiency. Large numbers of them can cause a reddening of the skin andfins. Fry and small fish may refuse to feed actively, flash, and becomelistless.Ambiphrya is controlled easily with formalin at 125-250 parts per millionfor up to I hour, or 15-25 parts per million as a pond treatment. Coppersulfate, at whatever concentration can be used safely, or potassium Permanganateat 2 parts per million, also give good results.TRICHOPHRTASpecies of Trichophrya sometimes are found on the gills of fish and cancause serious problems in catfish and occasionally in other warmwaterspecies. They have rounded to pyramid-shaped bodies (30 x 50 micrometers)and are distinguished by food-catching tentacles in the adult stage(Figure 94). Live organisms have a characteristic yellowish-orange oryellowish-brown color that makes them very conspicuous when wet mountsof gill tissue are examined under a microscope at 100x or 440x.Affected fish gills are pale and clubbed, and may be eroded. Infectedfish will be listless, as if they were suffering from an oxygen deficiency.Trichophrya is difficultto control in ponds but satisfactory results can beobtained with copper sulfate at whatever concentration is safe. Pond treatmentswith formalin or potassium permanganate give erratic results. A bathtreatment of 125-250 parts per million formalin for up to I hour usually iseffective, but may have to be repeated the next day.Internal Protoloan DiseasesHEXAMITAHexamita salmonis is the only common flagellated protozoan found in theintestine of trout and salmon. Although the pathogenicity of the organismis questioned by some researchers, most feel it can cause poor growth andelevated mortality in small (2-inch) fish. All species of salmonids are susceptibleto infection. Because there are no well-defined signs, a diagnosis of