SURVIVAL, SUBLETHAL RESPONSES, AND TISSUE RESIDUES OF ATLANTIC SALMON EXPOSED TO ACIDIC PH AND ALUMINUM

Early life stages of Atlantic salmon (Sabno salar) were continuously exposed to pHs ranging from 4.5 to 7.2 in one study, and to A1 concentrations ranging from 33 to 264 mu g/l at pH 5.5 in a second study. The tests were begun with eyed eggs and conducted until 60 d post-hatch. The exposure water contained about 3.0 mg/l calcium and was representative of acid-sensitive surface waters with low acid-neutralizing capacity. Hatching success, mortality, growth, behavior, and tissue residues of aluminum were determined during the tests. Egg hatching and the growth of larvae were reduced significantly al pH 4.5 and 5.0, and larval mortality increased at pH 4.5. Larval feeding and swimming behavior were impaired at pH 6.5 and lower. Hatching was not affected at pH 5.5 in the presence of Al; however, larvae exposed to 124 mu g Al/l at pH 5.5 incurred significant increases in mortality. The inhibition of feeding observed among fish exposed to pH 5.5 was intensified at all concentrations of Al tested. At pH 5.5, reduced growth occurred among larvae exposed to 71 mu g Al/l and higher. Concentrations of Al in whole-body tissue ranged from 3 mu g/g for fish exposed to 33 mu g Al/l to 96 mu g/g for those exposed to 264 mu g Al/l. At 60 d of exposure, bioconcentration factors ranged from 76 to 190 and were directly related to exposure concentration. Sublethal exposure of Atlantic salmon to acidic pH alone, and in combination with Al, may significantly reduce their fitness and may also play a significant role in recruitment failure in some acid-sensitive waters in the northeastern United States.