Does experimental cortisol elevation mediate risk-taking and antipredator behaviour in a wild teleost fish?

Area of Science:

• * Fish Physiology and Behavior
• * Endocrinology and Stress Response

Background:

• * The hypothalamic-pituitary-interrenal (HPI) axis is vital for stress response in fish.
• * Elevated HPI axis activity can negatively impact fish physiology and increase mortality.
• * Stressed fish exhibit higher predator-induced mortality, but the behavioral mechanisms are unclear.

Purpose of the Study:

• * To investigate the influence of the HPI axis on risk-taking and antipredator behaviors in pumpkinseed sunfish (Lepomis gibbosus).
• * To determine if cortisol administration affects boldness, exploration, and shoaling tendencies.

Main Methods:

• * Juvenile pumpkinseed sunfish were implanted with either cortisol or a sham control (cocoa butter).
• * Behavioral assessments were conducted 48 hours post-implantation, including predation-risk, exploration, and shoaling tests.
• * Test order was randomized to minimize bias.

Main Results:

• * Cortisol treatment did not significantly alter antipredator, exploratory, or shoaling behaviors.
• * Body mass significantly affected post-attack swimming duration and exploratory activity.
• * No direct role for cortisol in mediating sociability, boldness, or risk-taking was found under laboratory conditions.

Conclusions:

• * Cortisol may not directly mediate sociability, boldness, and risk-taking behaviors in pumpkinseed sunfish in controlled settings.
• * The HPI axis's role in predator-prey interactions might be more complex and context-dependent in natural environments.