Abstract:
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.
