Abstract:
Although much is known about the effects of electroshock on fish physiology, consequences
to the immune system and disease progression have not received 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 electroshock on disease progression. We found that the ability of anterior kidney 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 recovered within 24 h. This response was similar
in timing and magnitude to that of fish subjected to an acute handling stress. The mechanism of
suppression is hypothesized to be via an elevation of plasma cortisol concentrations in response
to stress. Other monitored immune functions, skin mucous lysozyme levels, and respiratory burst
activity were not affected by exposure to electroshock. The progression of a Renibacterium salmoninarum
(RS) infection may have been altered after exposure to an electroshock. The electroshock
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 infection severity and mortality levels in RS-infected fish, led us to
conclude that electrofishing under the conditions we tested is a safe procedure in regards to
immunity and disease.
