Behavioral and Biochemical Studies of Onset and Recovery from Acid Stress in Arctic Char (Salvelinus alpinus)

Abstract

The time course of acid stress was followed in Arctic char (Salvelinus alpinus) exposed to pH 4.5 (HCl) for 2 wk and then returned to control conditions (pH 7.8). Behavioral parameters (activity, thigmotaxis, appetite, and attraction to a food extract) and blood parameters (hematocrit and plasma Cl−, Na+, osmolality, protein, cortisol, and glucose) were monitored. Reaction to the acid was evident in all parameters. Fish were initially hyperactive but became hypoactive with continued exposure. Thigmotaxis was generally greater in the acid-stressed fish than the controls. Feeding intensity and attraction to food extract were depressed throughout the exposure, but periods of partial recovery occurred. Hematocrit, protein, cortisol, and glucose increased, while osmolality, Cl−, and Na+ decreased in acid-exposed fish. Partial recovery occurred in some blood parameters during the latter part of the exposure. After return to control conditions, behavioral and blood parameters except cortisol recovered within 2 wk but might have recovered earlier if fish had not contracted a Saprolegnia infection. Extract attraction was negatively correlated with hematocrit, protein, cortisol, and glucose and positively correlated with plasma Cl. Activity was negatively correlated with plasma protein and glucose. Thigmotaxis was not correlated with any blood parameter.