12/11/2007. WI DNR egg disinfection methods. Points covered in this presentation. Spawning Ovarian fluid sampling Egg disinfection

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1 WI DNR egg disinfection methods Points covered in this presentation Spawning Ovarian fluid sampling Egg disinfection Disinfection site selection Iodine solutions Egg handling Egg disinfection in the field Susan Marcquenski with a lot of help from the hatchery crews at Wild Rose and Nevin Reducing pathogen risk starts with spawning Cull broodfish with lesions Handle broodfish with care Collect ovarian fluids for virology testing Spawn eggs into a collander to drain ovarian fluids away from eggs Fertilize eggs, water harden in clean water 1

2 Choose the egg disinfection site Away from fish and water containing fish Must have a clean, fish free water source Must be able to neutralize the spent iodine solution (sodium thiosulfate, or sunlight) before discharging it All gear used must be clean and disinfected. Staff who disinfect the eggs do not put up the eggs in the incubators. Egg disinfection is isolated from other hatchery operations. Iodine is toxic to live fish. Make sure the iodine solution will not contact live fish. Prepare iodine disinfection solution Measure desired amount of water into tub. The shape of the tub should maximize surface area, not volume. Sources of povidone iodine Western Chemical - Ovadine Argent - Argentyne Aquatic Ecosystems Ovadine Sources of povidone iodine Be sure to note the concentration of the iodine on the label and adjust your calculations accordingly. Accurately measure iodine Calculate the amount of iodine needed to obtain a 100 ppm iodophor solution. 38 mls of a 1% iodine solution per gallon water = 100 ppm iodophor 2

3 Mix iodine into clean water Decant water from eggs after water hardening. This water should not come in contact with fishpour into a drain or on the ground Gently pour eggs into a net that is set in the tub containing the iodine solution. Minimize the depth of the layers of eggs. Disinfect the eggs for 15 minutes. Carefully lift net, drain iodine solution and rinse eggs in fresh clean water. Mix up new iodine solutions as the brown color weakens. Test strips are available to estimate iodine concentrations. After eggs are disinfected Eggs are transferred to the incubation area by a different person. Eggs are measured out into the incubators using disinfected equipment. Neutralize and discard iodine solutions after all the eggs are disinfected each day. Solutions are neutralized when the brown color becomes clear. Use sodium thiosulfate or sunlight to neutralize iodine. 3

4 Egg disinfection in the field All spawning gear is disinfected daily in 100 ppm iodophor for 15 minutes Eggs can be disinfected in the field, but as an added precaution, should be disinfected again at the hatchery before they enter incubation facilities. Coolwater Egg Iodophor Treatments Jeff Kampa WDNR Treatment Iodophor Treatments Lake Sturgeon Walleye White Sucker Northern Pike Water Harden 100 ppm Iodine * * * * Water Harden 100 ppm Iodine/clay * * * Surface Disinfect 100 ppm Iodine * * * * Control * * * * Methods Eggs from each female apportioned to each treatment and controls Eggs dipped in 100 ppm solution prior to treatment exposure Treatment Exposure Time Results Water Hardening Surface Disinfection hours 15 minutes Monitored iodine concentration and ph during treatment Incubated with controls and measured eye-up 4

5 Walleye Walleye 1-hour Iodine Iodine hour Iodine/clay hour Iodine 15 minute 84 Control 84 Control 59 White Sucker White Sucker 1-hour Iodine Iodine hour Iodine/clay hour Iodine 15 minute 81 Control 82 Control 45 Lake Sturgeon Lake Sturgeon Iodine/clay >1.5 hours Not Available 21 Control 38 Iodine 15 minute 42 Control 38 5

6 Northern Pike Northern Pike Iodine hour Control 27 Iodine 15 minute 25 Control 26 Conclusions Water hardening treatments resulted in poor eye-up for walleye, white sucker, and lake sturgeon Surface disinfection treatments did not result in poor eye-up for any species Iodine concentrations tended to decline in all treatments, but did not drop below 50 ppm until after 1.5 hours of exposure No buffering was required in any treatment solutions due to depressed ph Conclusions Walleye and white sucker eggs treated during water hardening were more fragile and smaller than control eggs Premature hatching was noted for both treatments of northern pike and white sucker and water hardening for walleye Lower than expected eye-up for controls may have been related to extra handling to eliminate confounding effect of varying fertility among females Acknowledgements Governor Tommy Thompson State Fish Hatchery Wild Rose State Fish Hatchery Lake Mills State Fish Hatchery Black River Falls Operations Sue Marcquenski, Fish Health Specialist (Madison) Gene Hatzenbeler, Fish Research Technician (Spooner) 6