Effect of hydrogen sulfide on northern pike eggs and sac fry

A series of bioassays were conducted to test the effect of H₂S at two concentrations of oxygen on northern pike (Esox lucius L.) eggs and sac fry. At an oxygen concentration of approximately 2 ppm mean median tolerance limits (TLm) for eggs were 0.411, 0.076, 0.038, 0.034, and 0.030 ppm H₂S for 24, 48, 72, 96 hours, and for the duration of the embryonic period, respectively. At an oxygen concentration of approximately 6 ppm mean median tolerance limits (TLm) were 0.181, 0.046, 0.041, 0.037, and 0.032 ppm H₂S for 24, 48, 72, 96 hours, and for the duration of the embryonic period, respectively. Mean TLm values for sac fry were 0.035, 0.016, 0.012, and 0.009 ppm H₂S at 2 ppm oxygen and 0.160, 0.047, 0.030, and 0.026 ppm H₂S at 6 ppm oxygen for 24, 48, 72, and 96 hours, respectively. Eggs subjected to H₂S resulted in increasing percentages of sac fry with anatomical malformations. Sac fry hatched from eggs held at the higher H₂S concentrations were smaller than the controls. Sac fry subjected to H₂S showed decreased growth rates at the higher concentrations. The maximum possible safe level of H₂S for eggs is between 0.014 and 0.018 ppm and for sac fry between 0.004 and 0.006 ppm for 96 hours exposure.