The effects of electroshock on immune function and disease progression in juvenile spring Chinook salmon

Although much is known about the effects of electroshock on fish physiology , consequences to the immune system and disease progression have not receiv ed attention. Our objectives were to determine the effects of electroshock on selected immune function in juvenile spring chinook salmon Oncorhynchus tshawytscha, the mechanism of any observed alteration, and the effects of e lectroshock on disease progression. We found that the ability of anterior k idney leukocytes to generate antibody-producing cells (APC) was suppressed 3 h after a pulsed-DC electroshock (300 V, 50 Hz, 8 ms pulse width) but rec overed within 24 h. This response was similar in timing and magnitude to th at of fish subjected to an acute handling stress. The mechanism of suppress ion is hypothesized to be via an elevation of plasma cortisol concentration s in response to stress. Other monitored immune functions, skin mucous lyso zyme levels, and respiratory burst activity were not affected by exposure t o electroshock. The progression of a Renibacterium salmoninarum (RS) infect ion may have been altered after exposure to an electroshock. The electrosho ck did not affect infection severity or the number of mortalities, but may have accelerated the time to death. The limited duration of APC suppression and lack of effects on lysozyme and respiratory burst, as well as infectio n severity and mortality levels in RS-infected fish, led us to conclude tha t electrofishing under the conditions we tested is a safe procedure in rega rds to immunity and disease.