Sensitivity of Endemic Snake River Cutthroat Trout to Acidity and Elevated Aluminum

Abstract

Abstract Acidic episodes in waters of the western USA, do not last as long and are not as intense as those in the eastern USA, but we found that the native western cutthroat trout Oncorhynchus clarki is sensitive to even brief reductions in pH. In laboratory studies, fish were exposed to acidity (pH 4.5–6.5) alone or in the presence of aluminum during the first 7 d of the freshly fertilized egg, eyed embryo, alevin, or swim-up larva stages of development. Following exposure to acidity and aluminum, eggs and fish were held under control water quality conditions to 40 d posthatch to assess effects of the exposure on subsequent development. Reductions in pH from 6.5 to 6.0 in low-calcium water (1.4 mg/L) did not affect survival, but reduced growth offish in the early life stages. The presence of as little as 50 μg A1/L at low pH further decreased growth and reduced survival. The most sensitive indicators of stress were loss of ions (determined from whole-body sampling) and reduced swimming in alevins, reduct...