Management of Physiological Stress in Finfish Aquaculture

Abstract

AbstractPhysiological stress is a nonspecific response common to all vertebrate organisms initiated by many types of environmental changes. Stress in fish can be characterized by physiological changes such as plasma cortisol, glucose, lactate, and electrolyte concentrations and is quantitatively related to the severity and longevity of the stressor. A hierarchy is evident among the physiological changes, such that adrenalin from activation of the sympathetic nervous system is released most rapidly, followed by cortisol, and then glucose. Plasma electrolyte disturbances may not occur until the stress is severe and present for an extended time. Adrenalin increases plasma glucose by stimulating liver glycogenolysis, which represents a metabolic energy cost to the fish. The functions of cortisol include possible induction of gluconeogenesis and suppression of the inflammatory response. Maintaining osmoregulatory homeostasis is an energetically expensive process, and disturbances deplete energy reserves. Recent experiments have shown the importance of distinguishing between acute and chronic responses to stress. Acute responses to stressors may be beneficial to the fish and extend their normal adaptive ability, whereas chronic exposure to stressful conditions may result in decreased performance or survival. The physiological stress response in fish culture has been shown to be altered by hatchery conditions and genetic selection. Management practices and selection pressures affect the stress response, which requires that the ultimate use of the fish be considered during rearing. Commercial food fish aquaculture, which involves rearing fish at very high densities, requires minimizing stressors such as water‐quality deterioration, disease treatment, and handling to maintain healthy growing fish. Fish raised for stocking into the wild might benefit from a more robust stress response to prepare them for survival in a natural environment. Present information does not allow for the selection of the most desirable stress response profile that would benefit fish reared for different purposes.