HPI Axis (Stress Response)

The hypothalamus-pituitary-interrenal axis - the fish stress response, analogous to the mammalian HPA axis.

System: Endocrine Level: Advanced Discipline: Endocrinology

📖 Overview

In fish, the interrenal tissue (not a discrete adrenal gland) produces cortisol under stress. The pathway - hypothalamus signals pituitary, pituitary releases ACTH, ACTH stimulates interrenal cortisol - is functionally identical to human stress physiology. Cortisol elevation is the definitive stress biomarker in fisheries and aquaculture.

🔑 Key Concepts

Cortisol, ACTH, interrenal cells, chronic stress vs acute stress.

🎯 Applications

Catch-and-release survival, aquaculture welfare, and fish transport all depend on managing the HPI axis.

✨ Fun Fact

A hooked and released trout can carry elevated cortisol for 24+ hours. This is why gentle handling and quick release make the difference between survival and delayed mortality.