The effects of electroshock on immune function and disease progression in juvenile spring chinook salmon (Oncorhynchus tshawytscha)

• Main Author: VanderKooi, Scott P
• Format: Dissertation
• Language: English
• Published: 16.06.1999
• Subjects: Chinook salmon > Immunology; Electric fishing > Physiological effect

Electrofishing is a sampling tool commonly used by fisheries researchers. While much is known about the effects of electroshock on fish physiology, consequences to the immune system and disease progression have not received attention. To understand the effects of electroshock on immune function we undertook a comparison of electroshock and handling stress in regards to selected immune functions and disease progression in juvenile spring chinook salmon (Oncorhynchus tshawytscha). The handling stress treatment was included to insure the responsiveness of the fish. Our objectives were to determine the effects of electroshock on immune function, determine the mechanism of any observed alteration, and to determine the effects of electroshock on disease progression. Skin mucous lysozyme concentrations were not affected by exposure to electroshock. Respiratory burst activity may be enhanced in leukocytes immediately after an in vitro electroshock. Any effect in vivo, however, appears to be brief given the lack of differences observed 3 h after exposure. The specific immune response, measured as the ability of anterior kidney leukocytes togenerate antibody producing cells (APC), was suppressed 3 h after electroshock, 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 elevation of plasma cortisol concentrations. The ability to generate APC may be suppressed 7 d after electroshock, but it is not evident what mechanism is responsible for this suppression. There was some evidence that the progression of a Renibacterium salmoninarum (RS) infection was altered after exposure to an electroshock. Exposure to electroshock did not have a clear affect on the severity of infection or the number of mortalities, but may have accelerated the time to death in infected fish that died. The limited duration of specific immune suppression and lack of effect on mortality in RS infected fish lead us to conclude that electrofishing under the conditions we tested is a safe procedure in regards to immunity and disease.