Fasting and Diet Content Affect Stress-Induced Changes in Plasma Glucose and Cortisol in Juvenile Chinook Salmon

Abstract

Juvenile chinook salmon (Oncorhynchus tshawytscha) reared on low-, medium-, or high-lipid diets for 18 weeks were either kept on their respective diets or fasted for 20 d; then they were subjected to a 30-s handling stress or to handling plus continuous confinement. In fish that were handled but not confined, poststress hyperglycemia was greatest in fed fish that received the high-lipid diet and was generally lower in fasted than in fed fish. Plasma cortisol elevations in response to handling or handling plus confinement stress were not appreciably affected by diet type or fasting. The results indicated that prior feeding regimes and the types of diet fed should be considered when one is interpreting the magnitude of hyperglycemic stress responses in juvenile chinook salmon.