Primary and Secondary Effects of Stress in Fish: Some New Data with a General Review

Abstract

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. Metabolic 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.