Handling in fish induces perturbations of various biological parameters which have been investigated or reviewed in an attempt to analyse and quantify the resulting stress. Endocrine changes, being early consequences of stress, are referred to as primary effects. Original data obtained on coho (Oncorhynchus kisutch), sockeye (O. nerka), and chinook (O. tshawytscha) salmon show that all types of stress result in an increase in circulating catecholamines, mainly adrenaline. There is no quantitative difference in response intensity between the species studied but large individual variations exist. In mature male coho salmon, struggling and hypoxia also resulted in an increase of plasmatic corticosteroids. Secondary effects occur as a result of these endocrine changes. Metabohc disturbances include a pronounced increase in blood glucose, and either a decrease or an increase of plasmatic free fatty acid (FFA) according to the species. These metabolic disturbances brought about by stress of short duration are shown to be of relatively long duration. Recent advances in the understanding of osmoregulatory processes show that the action of catecholamines on gill permeability may explain the stress-induced water imbibition of fish in fresh water and the dehydration of fish in seawater. Beyond some practical considerations, the results reported open up the possibility for genetic selection of varieties of high or low response to stress. The aquaculture of captive fish or the resource enhancement of natural stocks cannot be undertaken without the use of various handling procedures in the field, in the hatchery, or in the laboratory. These techniques such as capture, transportation, freshwater-saltwater transfer, and vaccination result in several types of stress which induce struggling, hypoxia, temperature, and osmotic shock. Many types of stress reviewed by Love (1970) have lethal consequences. Moreover death can be delayed and a distressed condition may remain unapparent for a while after the application of stress (Parker et al. 1959; Bouck and Ball 1966). In order to minimize the effects, and if necessary, modify the procedures of handling, it is necessary to be able to quantify the degree of stress and obtain an underi Present Address: Institut Oceanographique, 195, Rue Saint-Jacques, 75005 Paris, France. standing of the underlying mechanisms. From this standpoint, in an actual or potential situation of stress, neuroendocrine responses (primary effects) are elicited which in turn induce metabolic and osmotic disturbances referred to as secondary effects. PRIMARY EFFECTS Earlier studies have shown that stress in fish is accompanied by rapid changes in the plasma concentrations of catecholamines and corticosteroids. Adrenaline and noradrenaline are present in the plasma of fish in high concentration at rest and rapidly increase after a few minutes of hypoxia or struggling in cyclostoma (Mazeaud, M. 1969a), selachians (Mazeaud, M. 1969b), or telcosts (Mazeaud, M. 1964, 1971; Nakano and Tomlinson 1967), adrenaline or noradre...
