Stress in fish: phiysiology of the stress-response, causes and consequences (review)

Abstract

ln intensive fish production, the stress is inevitable. During the cuIture period, the fish is exposed to several potential stressors such as management and environmental conditions. The consequences are the reduction of growth and the reproductive performance and low resistance to disease. The stress response involves several physiological changes. Those changes are divided in primary, secondary and tertiary effects. The primary effects are the elevation of the plasma concentration of catecholamines and corticosteroids. Among the secondary effects can be related the metabolic changes such as glycaemia, lactic acid and hepatic glycogen, the hematological effects, such as in hematocrit and in the number of circulating lymphocytes, and the hydromineral effects, such as in plasma chloride, sodium, potash and protein levels, and in the osmolarity of the plasma. Among the tertiary effects can be related the reduction of growth, reproduction performance and resistance to disease. ln the teleost fish the elevation of the plasmatic cortisol is recognized as a principal hormonal response to stress and it is widely utilized as a stress response indicator. Several situations of the modern commercial aquacuIture are potentially stressful for fish. With the intensification of the fish production, the frequency of stressor managements increases. The physiological responses to stress are evolutionary developed in natural environment, and in artificial conditions imposed by commercial aquaculture this response may be extremely deleterious for the fish health and for the economic viability of the fish production.