SURVIVAL OF BROOK TROUT EMBRYOS IN 3 EPISODICALLY ACIDIFIED STREAMS

We evaluated, for brook trout Salvelinus fontinalis in three streams t hat undergo episodic acidification during critical periods of embryo d evelopment, survival of embryos from egg deposition to preemergence in natural redds and survival of sac fry in toxicity tests done in situ. Twenty-five natural redds were used for comparisons among streams. Me dian survival to preemergence (range, 16-68%) was different (P less-th an-or-equal-to 0.05) among streams and was inversely related to stream concentration of inorganic monomeric Al. Survival to preemergence was not related to intragravel dissolved oxygen concentration, gravel qua lity, or depth or velocity of stream water at redd sites. Median survi val of sac fry exposed to stream water for 39 d was different among st reams (range, 51-95%) and was inversely related to stream concentratio n of inorganic monomeric Al. Episodic acidification could lead to decl ines in populations of brook trout by causing decreased survival of ea rly life stages.