Survival and sublethal responses of early life stages of pike exposed to low pH in artificial post-mining lake water

The threshold pH for survival of early life stages of pike Esox lucius in post-mining lakes was determined in a laboratory experiment using artificial water characterized by high concentrations of dissolved Ca, Al, Fe, Mn and SO 4 2- At pH 3.50-4.00, high mortality was observed before hatching. At pH 4.00 and 4.25, hatching rates were reduced compared with the controls (pH 7.40), and many embryos died in a partly hatched state. Hatching success of embryos exposed to pH levels of 4.50 or higher was not affected. However, at pH 5.00 many newly hatched embryos were deformed. Furthermore, pike exposed to pH 4.00-5.00 did not start feeding. At pH 4.75 and below, mortality increased to 100%, and at pH 5.00, only few eleutheroembryos which were in extremely poor condition survived to the end of the experiment. At pH 5.50, survival was in the same range as in the control group, but growth was reduced. Therefore, early life stages of pike are expected to survive in Lustian post-mining lakes when a pH of 5.50 and above is reached and maintained.