Stress Responses in Pallid Sturgeon Following Three Simulated Hatchery Stressors

Abstract

AbstractBecause sturgeon populations are in critical decline, many species are artificially propagated in hatcheries with the goal of increasing wild stocks. Capture, transport, handling, confinement, and environmental fluctuations are just a few of the possible stressors Pallid Sturgeon Scaphirhynchus albus can be exposed to in conservation hatcheries. The objectives of the present study were to elucidate the effects of acute exposure to high ammonia concentrations, low dissolved oxygen (DO) concentrations, and crowding on stress responses in Pallid Sturgeon, quantified by changes in plasma cortisol and glucose. Exposure to un‐ionized ammonia‐nitrogen concentrations of 0.6 mg/L for 24 h resulted in no significant (P > 0.05) change in plasma cortisol concentrations, suggesting these fish do not perceive the buildup of toxins. Exposure to 2 mg/L DO over a 0.5‐h period resulted in a significant (P < 0.05) increase in plasma cortisol concentrations during the low DO challenge, with levels decreasing (P > 0.05) within 30 min of recovery and returning to prestress levels within 2.5 h of recovery. Plasma cortisol concentrations increased (P < 0.05) within 0.25 h of crowding and remained elevated after 0.5 h of crowding. Removal of the crowding stressor did not result (P > 0.05) in decreased circulating cortisol within 30 min. Regardless of the stressor, Pallid Sturgeon plasma glucose levels were unaffected (P > 0.05). As such, glucose does not appear to be a reliable indicator of stress in Pallid Sturgeon. Defining the effects of stress on Pallid Sturgeon physiology is a critical first step toward understanding how stress affects fish health and well being and optimization of propagation practices.