Evaluation of Hydrogen Peroxide and Temperature to Control Mortality Caused by Saprolegniasis and to Increase Hatching Success of Largemouth Bass Eggs

We evaluated the use of hydrogen peroxide (H 2 O 2 ), temperature, or both, to control mortality presumptively caused by fungus Saprolegnia in Florida largemouth bass Micropterus salmoides floridanus eggs in a flow‐through hatchery system. Four treatments—ambient water (AW; control), ambient water and H 2 O 2 (AWHP), heated water (HW), and both heated water and H 2 O 2 (HWHP)—were tested on each of 30 replicate spawns. Four 8 cm × 5 cm sections of spawning mat, one for each treatment, were cut from each of the 30 selected spawns. Egg counts on each cut mat section were recorded. Water temperature in all AW and HW trial tanks ranged from 17.9°C to 19.2°C and from 22.1°C to 23.6°C, respectively, during treatment. The water temperature difference between treatments averaged 4.4°C. Hydrogen peroxide trial tanks received two, 100 mg/L H 2 O 2 treatments 8 h apart, until hatch. The 7.5 L/min incoming water flow was not reduced during treatment. The addition of HW, H 2 O 2 , or both, significantly increased mean percent hatch (79, 79, and 91%, respectively) over that of the untreated controls (49%). Significant differences were found in mean percent hatch levels between AW and the other three treatment groups ( P < 0.05). The combination of higher incubation temperature and H 2 O 2 administration also resulted in significantly greater hatch than did either higher incubation temperature or increased H 2 O 2 administration alone; percent hatch did not differ significantly between eggs that either were only incubated at the higher temperature or received only H 2 O 2 administration. Increasing incubation water temperature to 22–23°C instead of using only water at ambient temperature (18–19°C) or adding 100 mg/L H 2 O 2 twice daily in a flow‐through system significantly increased hatching percentage of Florida largemouth bass eggs.