Stress in rainbow trout, <i>Salmo gairdneri:</i> effects upon phagocyte chemiluminescence, circulating leucocytes and susceptibility to <i>Aeromonas salmonicida</i>

Abstract

Rainbow trout were inoculated with Aeromonas salmonicida (AS) and 24 h later the tanks were drained off and the trout were kept for 30 min in 3 cm of water on the bottom of the tanks. This manipulation was considered as handling and anoxic stress. Twenty four hours later the stressed fish showed a leucopenia, mainly a lymphopenia. The chemiluminescence (CL) response of the head kidney phagocytes was lower in stressed fish. The inoculated‐unstressed fish showed a greater CL response than the controls (non inoculated‐unstressed). The mortality rate after AS inoculation was greater in the stressed than in the unstressed fish. When the stress was repeated four times for 15 min during 2 days, the CL response was lower; no difference was observed when the fish were stressed eight times for 15 min over 4 days.