EFFECT OF BACTERIAL KIDNEY-DISEASE ON SALTWATER ADAPTATION OF COHO SALMON SMOLTS

Coho salmon Oncorhynchus kisutch with clinical infections of bacterial kidney disease (BKD) had poorer survival in the laboratory after 30 d in salt water (50%) than in freshwater (85%). Osmoregulatory ability of infected fish was better after acclimation in 10 parts per thousand salinity water before transfer to 30 parts per thousand salinity wate r. Infected fish exercised overnight (3.0 body lengths/s) were unable to survive the seawater challenge, whereas uninfected fish similarly e xercised survived with the same plasma Na+ levels as unexercised fish. Because BKD is present in most salmonid stocks, stress of seawater tr ansfers should be minimized through acclimation and reduced exertion.