Whole-Animal Physiological Processes for the Assessment of Stress in Fishes

General stress in fish often can be indirectly revealed by standardized laboratory tests in which stressed and healthy individuals are compared. In this paper, various techniques by which selected physiological processes of whole animals are used to detect stress are reviewed and evaluated. Reviewed tests fall into three categories. In the first, the resistance is measured in fish challenged by clearly definable stressors such as temperature, oxygen, and salinity. These methods have the advantage of economy of time, effort, and equipment. In the second category, highly integrative physiological activities such as growth and swimming are quantified. Here more complicated equipment and testing procedures are required. Methods of measuring swimming capacity range from the simple bench top “fish wheel” to elaborate swimming performance tunnels in which the oxygen consumption of the fish is simultaneously measured. The third category comprises methods of monitoring experimental subjects exposed to water-borne pollutants. The cough reflex test, for instance, estimates stress from relationships between chemical concentration and cough frequency. A more sophisticated, state-of-the-art approach is multiparameter monitoring which may lead to an understanding of the nature of the morbidity of stressed fish. Here continuous records are made of many body functions simultaneously. Although no single method appears to be the most sensitive for all stressors, there is a best method for each stressor, depending upon its effects. Investigators have the task of choosing among an array of methods, a technique which is both suitable to the fish species, their laboratory facility, and the potential stressor.