THE EFFECTS OF LOW PH AND ELEVATED ALUMINUM ON YELLOWSTONE CUTTHROAT TROUT (ONCORHYNCHUS-CLARKI-BOUVIERI)

Although acid deposition is not considered a problem in the western United States, surface waters in high elevations and fish inhabiting these waters may be vulnerable to acidification. This study examined the sensitivity of a western salmonid to acid and aluminum stress. Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri; YSC) were exposed for 7 d during each of four early life stages, or continuously from fertilization to 40 d post-hatch, to decreased pH and elevated Al. We monitored survival, growth, whole-body ion content, and behavior of the exposed fish. Sensitivity of early life stages of YSC may be expressed by survival or by survival and sublethal effects. In our study, eggs were the most sensitive life stage of YSC to low pH if survival alone was considered. However, the sublethal effects on growth, tissue ion content, and behavior revealed the alevins and swim-up larvae were more sensitive to reduced pH and increased Al than eggs or eyed embryos. We also observed that survival was significantly decreased if YSC were exposed to pH 6.0 and 50 mug Al per liter continuously from fertilization to 40 d post-hatch.