Recovery of cardiac and ventilatory frequencies after sub-acute pesticide (ABOL-X) treatment in rainbow trout, Salmo gairdneri Richardson.

Short term, sublethal changes in coughing rate, cardiac and ventilatory frequencies in hatchery-reared rainbow trout (27-34 cm) exposed to menazon and gamma BHC containing pesticide were monitored at 15 +/- 1 degree C during recovery period to investigate the effects of this chemical on fish respiratory and cardiovascular systems. Laboratory conditions simulated a rapid environmental pollution often occurring in running waters. The coughing response was particularly sensitive to water pollutants. Average rate of ventilation was lower in treated fish than in control specimens and decreased parallel with the time of recovery. Average heart rate was higher in treated trout as compared to the controls. These changes were characteristic for hypoxic conditions and provide useful sublethal physiological indications for a rapid environmental stress. Percentage coupling and phase angle of ECGs within the ventilatory cycle were also studied during recovery when significant differences were observed between treated and untreated groups of fish.