Effects of Routine Handling and Tagging Procedures on Physiological Stress Responses in Juvenile Chinook Salmon

—Juvenile chinook salmon Oncorhynchus tshawytscha were subjected to handling and tagging protocols typical of normal hatchery operations and monitored for their physiological response to stress. Treatments included coded-wire-tagging, counting, ventral fin clipping, adipose fin clipping, and a procedure simulating a pond split. Treatment fish were also subjected to a standardized stress challenge (1 h confinement) to evaluate their ability to deal with disturbances subsequent to a handling or tagging procedure. Circulating levels of cortisol and glucose were used as indicators of stress. Each of the treatments elicited very similar responses among treatment groups. Cortisol increased from resting levels of about 20 ng/mL to about 90 ng/mL by 1 h poststress and returned to near resting levels by 8 h poststress. Glucose levels increased from 50 mg/dL to about 80 mg/dL by 1 h poststress and remained elevated for much of the experiment. The cortisol and glucose responses to the confinement stress did not differ over time or among treatments. However, the confinement stress results do suggest a small but significant cumulative response, indicating small residual effects of the original handling protocols. No deaths were noted among treatment groups. The handling of fish is a necessary component of fish culture. For example, juvenile spring chinook salmon Oncorhynchus tshawytscha are sub* Corresponding author: [email protected] 1 Present address: Washington Department of Fish and Wildlife, 600 Capitol Way North, Olympia, Washington 98501-1091. 2 Supported cooperatively by the U.S. Geological Survey, Biological Resources Division; the Oregon Department of Fish and Wildlife; and Oregon State University. jected to a variety of handling protocols before release from hatcheries in order to implant or attach tags, otherwise mark fish, assess fish quality or developmental status, and adjust rearing densities (Wood 1968; Nielsen 1992). Such procedures are important elements in salmonid culture programs because they permit monitoring of migrations and the efficacy of rearing regimens. However, any physical handling or psychological disturbance is known to be stressful to fish (Don-