Eggs of lake herring (Coregonus artedii) were incubated in a continuous-flow system at four constant water temperatures (2-8°C) and five dissolved oxygen (DO) concentrations (1-12 mg/L). In comparison with incubation time at 12 mg/L DO, time to median hatch was significantly longer (P<0.05) at 2 mg/L at 6°C (no hatch at 1 mg/L), at 3 mg/L or less at 4°C, and at 4 mg/L or less at 2°C. The time between hatching of the first and last eggs varied inversely with temperature. Mean total lengths of newly hatched fry were significantly shortened (P < 0.05) at 1 and 2 mg/L DO. At 6 and 8°C, percent survival through hatching was greater than at 2 and 4°C at DO of 4 mg/L or more, but fell to zero at 1 mg/L. The percentage of normal fry produced decreased noticeably below 4 mg/L DO. The optimum temperature for highest percentage survival of normal fry decreased directly with the level of dissolved oxygen. The temperatures at which the highest percentages of normal fry hatched from eggs incubated at DO concentrations of 4 or 8, 2, and 1 mg/L, were 6, 4, and 2°C, respectively-indicating a decreasing DO demand by embryos incubated at the lower temperatures. Our findings supported a previously published hypothesis that DO concentrations below 4 mg/L can be adverse to survival and development of coregonid embryos in nature.
