Locomotor Activity and Blood Plasma Parameters of Acid-Exposed Lake Whitefish, Coregonus clupeaformis

In laboratory experiments, lake whitefish (Coregonus clupeaformis) were exposed to acidified water of pH 5.0 4.7, 4.4, and 4.1 for 2 wk; controls were held at pH 7.6. Continuous recordings of locomotor activity over 4 days and nights at the end of each treatment showed a consistent trend towards reduced daytime activity and loss of diel rhythmicity with increasing ambient acidity. Feeding was observed to decrease at pH 4.7, and to cease at pH 4.4 and 4.1. Associated with these behavioral effects were changes of blood plasma variables. Plasma cortisol and glucose levels increased with lowered pH; sodium, chloride, and their fractional contribution to osmolality decreased.