GROWTH AND STRESS IN FISH PRODUCTION

Considerable progress has been made towards increasing the growth rate and food conversion efficiency of a variety of fish species reared under aquaculture conditions. Essentially, two approaches have been adopted: the traditional approach of selective breeding from desirable phenotypes and, recently, the application of biochemical/molecular techniques such as genetic engineering. In all situations, however, the performance of the fish is governed not only by its genetic potential but also by its immediate environmental conditions. Certain environmental factors such as water temperature and food supply have an obvious and major influence on growth rate and food conversion efficiency but are not necessarily stressful in themselves. Other factors such as poor water quality, physical disturbance and social domination of one fish by another can act as powerful environmental stresses. thereby reducing the performance of the fish. This paper identifies some of the hormonal pathways linking deleterious environmental conditions to growth processes in fish and considers the implications of these pathways for aquaculture. It is suggested that the selection for broodstock of fish with a reduced cortisol response to common aquacultural stresses would have benefits for disease resistance, reproductive performance and growth rate.