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 at 100 cm·sec−1 (2–3 fork lengths·sec−1) for 5 min in freshwater and placed in flow-through holding boxes in a recovery tank at 25°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 O2 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 brackish water (10 g NaCl·L−1).