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 p ost-mining lakes was determined in a laboratory experiment using artificial water characterized by high concentrations of dissolved Ca, Al, Fe, Mn and SO 2/4(-). At pH 3.50-4.00, high mortality was observed before hatching. A t 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 stare. Hatching succes s of embryos exposed to pH levels of 4.50 or higher was not affected. Howev er, 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, mortal ity 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 L ustian post-mining lakes when a pH of 5.50 and above is reached and maintai ned. (C) 2000 The Fisheries Society of the British Isles.