Striped bass exercise and handling stress in freshwater: Physiological responses to recovery environment

Freshwater-acclimated subadult striped bass Morone saxatilis that had undergone cannulation of the dorsal aorta were exercised against a water current al 100 cm . sec(-1) (2-3 fork lengths-sec(-1)) for 5 min in freshwater and placed in Row-through holding boxes in a recovery tank at 25 degrees C. Recovery tanks contained water with either 0 (freshwater, FW), 10 (brackish water, BW), or 30 (seawater, SW)g NaCl . L(-1) or 10 mM NaHCO3-. L(-1) (buffered freshwater, BFW). A postexercise metabolic acidosis (decreased postexercise blood pH and increased blood lactate) was compensated within 2-4 h in all recovery environments except SW. Arterial O-2 tension and cortisol, glucose, and hemoglobin concentrations transiently increased immediately after exercise, and arterial CO2 tension and HCO3- generally decreased. Plasma Cl- did not change until 2-4 h postexercise, when decreases (FW and BFW), an increase (SW), or no change (BW) indicated passive fluid or Cl- exchanges with the recovery environment. Increasing plasma Cl- in the SW recovery environment inhibited HCO3- retention or uptake, which slowed pH compensation. In summary, postexercise acidoses were corrected and ionic imbalances were minimized by recovery in brackishwater (10 g NaCl . L(-1)).