The effects of common laboratory and husbandry practices on the stress response of greenback flounder Rhombosolea tapirina (Gunther, 1862)

This study examined the stress response of the greenback flounder Rhombosolea tapirina to common laboratory and aquaculture practices. Plasma levels of cortisol in wind fish sampled within 2 min of capture were comparable to plasma cortisol values in other species captured from the wild and sampled immediately. Plasma levels of cortisol were significantly higher in wild fish sampled after capture, confinement and transport. The latency of the plasma cortisol response to stress was approximately 10 min. Cultured greenback flounder, exposed to normal husbandry conditions, had low plasma cortisol levels, however, 3 h of crowding combined with 5 min chasing (simulated grading) resulted in significantly elevated cortisol levels for up to 48 h. Plasma cortisol was significantly higher in fish held at medium and high stocking density than at low density. The plasma cortisol stress response of greenback flounder is similar to that shown by other marine teleosts. Plasma lactate levels in wild fish sampled after capture, confinement and transport, were considerably higher than levels in fish sampled within 3 min of capture, or exposed to 30-min exercise. No significant changes in muscle lactate were observed in response to exercise; however, there were significant increases in plasma lactate, and muscle [H+] and a significant decrease in plasma [H+] following exercise, indicating that muscle and blood physiology of greenback flounder do change in response to exercise. Unlike other flatfish, there was little evidence for in situ glycogenesis within white muscle tissue after exercise and there was some indication that greenback flounder have higher aerobic scope than other flatfish studied to date. This study showed that some routine husbandry practices have the capacity to stress greenback flounder.