Jeff J. Rach, Steven Redman, Dale Bast, and  Mark P. Gaikowski.  2004.  A comparison of the 
efficacy of hydrogen peroxide versus formalin treatments to control mortality associated with 
saprolegniasis on lake trout eggs (Salvelinus namaycush).  Submitted to the U.S.Fish andWildlife 
Service on July 02, 2004.

Increasing concerns over user safety and environmental discharge following formalin use at fish 
culture facilities are causing fish culturists to consider alternative drugs, such as hydrogen 
peroxide, to control saprolegniasis on fish eggs.  We compared the efficacy of hydrogen peroxide 
versus formalin treatments to control fungal infections on lake trout eggs (Salvelinus namaycush) 
incubated at the Iron River National Fish Hatchery (Iron River, Wisconsin).  Four strains of lake 
trout eggs were incubated in six vertical flow Heath incubators; three replicate incubators for 
each chemical.  Each incubator had 13 trays containing eggs and there was approximately 25,000 
to 30,000 eggs per tray.  Formalin (1,667 mg/L) or hydrogen peroxide (1,000 mg/L) treatments 
were applied once daily for 15 min up to the development of visible eye spots in the eggs (eyed 
egg stage).  Eyed eggs and dead eggs were separated using a photoelectric egg sorter and the 
number of live and dead eggs was determined volumetrically.  In the hydrogen peroxide test 
group, the bottom trays of each incubator had fungus present on the eggs, while no fungus was 
observed on eggs treated with formalin.  The mean percent egg eye-up for an incubator treated 
with formalin (75%) was significantly greater (P < 0.05) than one treated with hydrogen peroxide 
(70%).  Formalin was the most efficacious therapeutant, however, both therapeutants were 
effective in increasing lake trout egg survival up to the eyed egg stage.  In species requiring 
lengthy incubation periods at cold water temperatures, higher hydrogen peroxide concentration 
may be required than the 500 mg/L concentration currently allowed under the Low Regulatory 
Priority statues of hydrogen peroxide.