Effects of Prolonged Exposure to Ammonia on Fertilized Eggs and Sac Fry of Rainbow Trout (Salmo gairdneri)

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Abstract
Effects of ammonia on fertilized eggs and resulting sac fry of rainbow trout (S. gairdneri) were tested at concentrations of un-ionized ammonia ranging from 0.05-0.37 mg/l (as NH3 - N). Exposure was continuous throughout the incubation period and for 42 days thereafter. There was no differential egg mortality or effect on incubation period. The lowest concentration of 0.05 mg/l NH3 - N caused some retardation of early growth and development and 0.1 mg/l caused similar but more severe effects throughout most of the test period. Hypertrophy of secondary gill lamellae epithelium occurred at 0.19 mg/l. Karyolysis and karyorrhexis occurred in the same tissue at 0.28 mg/l. Pale coloration and blue-sac disease occurred in sac fry at concentrations of 0.19 mg/l and higher. The estimated incipient LC50 (lethal threshold concentration) for rainbow trout sac fry was 0.25 mg/l NH3 - N.