Rates of cortisol increase and decrease in channel catfish and sunshine bass exposed to an acute confinement stressor

Area of Science:

• Comparative physiology
• Aquatic toxicology
• Endocrinology

Background:

• Stress response in fish is critical for survival.
• Cortisol is a key stress hormone in teleosts.
• Understanding cortisol dynamics aids aquaculture and conservation.

Purpose of the Study:

• To investigate cortisol secretion and clearance in channel catfish and sunshine bass after low-water stress.
• To evaluate the effect of metomidate on cortisol dynamics during recovery.
• To compare stress responses between channel catfish and sunshine bass.

Main Methods:

• Fish were exposed to low-water stress and allowed to recover in freshwater or metomidate solution.
• Plasma cortisol and glucose levels were monitored over time.
• Cortisol secretion and clearance rates were calculated.

Main Results:

• Both fish species showed increased plasma cortisol and glucose under stress, with greater changes in sunshine bass.
• Metomidate treatment during recovery caused a transient glucose increase but minor overall differences.
• Cortisol decreased immediately in catfish but peaked later in sunshine bass, regardless of recovery conditions.

Conclusions:

• Rapid cortisol decrease post-stress involves reduced secretion, uptake, and enhanced renal clearance.
• Sunshine bass exhibit a more prolonged cortisol elevation compared to channel catfish.
• Metomidate's effect on cortisol clearance is minimal, highlighting intrinsic clearance mechanisms.