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Flowing Water: An Effective Treatment for Ichthyophthiriasis
Author(s) -
Bodensteiner Leo R.,
Sheehan Robert J.,
Wills Paul S.,
Brandenburg Alan M.,
Lewis William M.
Publication year - 2000
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1577/1548-8667(2000)012<0209:fwaetf>2.0.co;2
Subject(s) - catfish , ictalurus , biology , zoology , ichthyophthirius multifiliis , water flow , mortality rate , hatchery , fishery , fish <actinopterygii> , medicine , environmental engineering , engineering
Ichthyophthiriasis, or ich, is a disease of freshwater fish that is difficult to treat chemotherapeutically because the causative agent, Ichthyophthirius multifiliis , is protected by the host's epithelium during much of its life cycle. In our experiments, a modified standard formalin treatment (25 mg/L for 4 h, 4 d/week) conferred partial protection but failed to prevent 40–70% mortality among channel catfish Ictalurus punctatus. A water velocity of 20.3 cm/min in 5‐m‐long raceways and a turnover rate of 2.5/h reduced mortality of ich‐infected channel catfish fingerlings to less than 10%. A water velocity of 36.5 cm/min and a turnover rate of 4.5/h held mortalities to 7% and eliminated ich from the raceways. When turnover rate fell below 1.9/h (water velocity < 75 cm/min) in 24.4‐m‐long raceways, ich outbreaks occurred, but higher water velocities reversed the epizootics. Prophylactic increases in water flow (> 85 cm/min, turnover rate > 2.1/h) resulted in no losses caused by ich during 2 years at Little Grassy State Fish Hatchery, Illinois, where ich has historically caused 40–60% mortality of channel catfish fingerlings. Turnover rate may be more important than water velocity in controlling ich.