SENSITIVITY OF EARLY-LIFE-STAGE GOLDEN TROUT TO LOW PH AND ELEVATED ALUMINUM

Early-life-stage golden trout (Oncorhynchus aguabonita aguabonita) wer e exposed to acid and Al to examine the response and determine the sen sitivity of a western, alpine salmonid to conditions simulating an epi sodic pH depression. Freshly fertilized eggs, alevins, and swim-up lar vae were exposed for 7 d to one of 12 combinations of pH and Al, and s urviving fish were held to 40 d post-hatch to determine the effect of exposure on subsequent survival and recovery. Golden trout are sensiti ve to conditions simulating episodic acidification events typically ob served in the field. Significant mortality occurred when the pH of tes t waters was below 5.0 in the absence of Al or when pH was 5.5 in the presence of 100 mug/L total Al. Behavioral impairments were sensitive indicators of low pH and Al stress. Impaired locomotory and feeding be havior occurred at pH 5.5 without Al and at Al concentrations greater- than-or-equal-to 50 mug/L. In contrast, growth, RNA-to-DNA ratio, and whole-body ion concentration were relatively less sensitive indicators of sublethal acid and Al stress.