Abstract
Moving 4-5 in coho salmon (O. kisutch) held in soft (20 ppm CaCO3) water from the relatively light loading density of 0.5 lb/ft3 to 1.2 or 4 lb/ft3 (density index, DI = 0.1, 0.2, 0.4, 0.8) caused stress as indicated by loss of feeding behavior, but only minimal physiological disturbances, as indicated by lack of hyperglycemia or hypochloremia. Moving them to 6 or 12 lb/ft3 (DI = 1.2, 2.4) caused physiological stress which required at least a week for recovery. Smolting coho salmon were physiologically stressed by population densities of 1 lb/ft3 or more and a subclinical corynebacterial kidney infection was activiated. Rainbow trout (S. gairdneri) (4-5 in.) were physiologically stressed when moved and held at 1 lb/ft3 or more but retained normal feeding behavior. This indicates that handling and crowding stress will be minimized in softwater areas if densities in fish distribution trucks or in ponds or raceways during disease treatments are held to 0.1-0.5 lb/gal.

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