Increasing Iodine Concentrations during Landlocked Fall Chinook Salmon Egg Disinfection Decrease Bacterial Numbers with No Impact on Egg Survival

Abstract

Egg disinfection is an important practice that prevents potential disease transfer, but currently allowable disinfection regimes do not completely eliminate external egg membrane microbes. In this experiment, newly fertilized and water‐hardened landlocked fall Chinook Salmon Oncorhynchus tshawytscha eggs were submersed for 10 min in povidone‐iodine solutions containing 0, 100, 200, and 400 mg/L active iodine. External egg bacterial numbers (CFUs) were quantified after each disinfection treatment, and egg survival (%) was calculated at the eyed stage. All of the disinfection treatments significantly reduced CFUs compared with untreated controls. However, eggs from the 400‐mg/L iodine treatment had significantly lower CFUs (2.20 ± 0.59 [mean ± SE]) than the 100‐mg/L (10.43 ± 8.01) and 200‐mg/L (8.10 ± 1.51) treatments. Percent survival was not significantly different among any of the treatments; survival was 18.86 ± 5.17%, 19.17 ± 4.76%, and 20.16 ± 5.27% in the eggs subjected to 100 mg/L, 200 mg/L, and 400 mg/L iodine, respectively. These results indicate that 10‐min treatments of 400 mg/L active iodine on landlocked fall Chinook Salmon eggs provide the most microbial reduction with no effect on subsequent egg survival.

Impacts of Zebra Mussel Veliger Control Treatments on the Survival of Water-Hardened Landlocked Fall Chinook Salmon Eggs

“…The experiment was conducted at McNenny State Fish Hatchery, Spearfish, South Dakota, USA using well water (11˚C; total hardness as CaCO 3 , 360 mg/L; alkalinity as CaCO 3 , 210 mg/L; pH, 7.6; total dissolved solids, 390 mg/L). Landlocked fall Chinook salmon eggs were obtained from twelve female broodfish spawned at Whitlocks Spawning Station on Lake Oahe, South Dakota, using techniques described by Huysman et al [11]. After four hours of transportation to McNenny Hatchery, the water-hardened fertilized eggs from each spawn were disinfected in 100 mg/L povidone iodine (Western Chemical, Ferndale, Washington, USA) for ten minutes and then rinsed in fresh water.…”

Comprehensive toxic effects of povidone iodine on microalgae Chlorella pyrenoidosa under different concentrations

“…In aquatic animal virus, PVP‐I can kill Tilapia Lake Virus and inactivate white spot syndrome virus in the concentration of 100 ppm (Chang et al, 1998; Soto et al, 2019). PVP‐I could be used to disinfect the chinook salmon egg and had good sterilization effect with no effect on subsequent egg survival (Huysman et al, 2018). It could also effectively kill protozoa when it was used to disinfect the embryos of the edible ascidian Halocynthia roretzi (Kumagai et al, 2016).…”

Water hardness does not influence iodine-induced mortality of rainbow trout eyed eggs

“…This treatment is effective in reducing, but not eliminating, all bacteria on the external egg membrane (Kumagai et al, 1998;Wagner et al, 2008;Barnes et al, 2009). Increasing iodophor concentrations above the standard 100 mg/L (United States Fish and Wildlife Service, 2021) results in more complete egg disinfection (Wagner et al, 2012;Loch and Faisal, 2016;Bergmann et al, 2018;Huysman et al, 2018). However, higher concentrations can lead to increased egg mortality (Wagner et al, 2010(Wagner et al, , 2012Huysman et al, 2018).…”

“…Increasing iodophor concentrations above the standard 100 mg/L (United States Fish and Wildlife Service, 2021) results in more complete egg disinfection (Wagner et al, 2012;Loch and Faisal, 2016;Bergmann et al, 2018;Huysman et al, 2018). However, higher concentrations can lead to increased egg mortality (Wagner et al, 2010(Wagner et al, , 2012Huysman et al, 2018). Although iodine toxicity and efficacy are not generally affected by overall water chemistry (Backer and Hollowell, 2000;Fraise et al, 2004), it is possible that specific chemical components of the water used to create the treatment solutions may impact subsequent egg survival.…”