Behavioral Modifications in Arctic Char (Salvelinus alpinus) Chronically Exposed to Sublethal pH

The effects of acid stress on the locomotor and chemoreceptive behavior of Arctic char were determined by quantifying their movements within a laboratory trough. Three behavioral parameters were measured: activity, spatial preference within the trough, and the attraction to a plume of food extract presented at different concentrations. Char were preexposed for 14 days to pH 7.8 (controls), 7.0, 5.5, 5.0, 4.75, or 4.5, and then individually tested in the trough at the same pH. The behavior of pH 7.0 and 5.5 char was not statistically different from the controls. Char exposed to pH 5.0 behaved much like control fish but were more active and less responsive to the extract. Marked behavioral changes occurred when char were exposed to either pH 4.75 or 4.5. At these levels activity was sharply reduced, time spent at the ends of the trough increased, and attraction for the extract was highly depressed. Some individuals were strongly affected, while others were affected only moderately. We suggest that behavioral abnormalities brought on by acid stress are responsible, in part, for the disappearance of fish populations from lakes and streams where pH's have been chronically depressed by acid pollution.