Diel patterns of baseline glucocorticoids and stress responsiveness in a teleost fish (bluegill, Lepomis macrochirus)

Little is known about whether glucocorticoids (GC) and GC responsiveness vary on a diel basis in the wild, especially for fish. Using bluegill (Lepomis macrochirus Rafinesque, 1819) as a model freshwater teleost fish, we tested whether baseline concentration and stress responsiveness of GCs (i.e., plasma glucose and cortisol) varied over a 24 h period. Blood samples from lake-dwelling wild bluegill were obtained across six periods representing …