Differences in behaviour between rainbow trout selected for high- and low-stress responsiveness.

Area of Science:

• Animal Behavior
• Aquaculture Science
• Endocrinology

Background:

• Plasma cortisol responsiveness varies in rainbow trout (Oncorhynchus mykiss).
• Selective breeding can alter physiological and behavioral traits in fish.
• Understanding stress responses is crucial for optimizing aquaculture practices.

Purpose of the Study:

• To investigate behavioral differences between rainbow trout lines selected for high (HR) and low (LR) plasma cortisol responsiveness.
• To assess the impact of social isolation and intruder presence on locomotor activity and feeding behavior.
• To confirm differential hypothalamus-pituitary-interrenal axis activity between the selected lines.

Main Methods:

• Generation of two F1 rainbow trout lines divergent for post-stress cortisol levels through individual selection.
• Quantification of locomotor activity in isolated fish and in the presence of a conspecific intruder.
• Measurement of plasma cortisol concentrations following a confinement stress test.
• Observation of feed intake incidence under isolation conditions.

Main Results:

• HR fish showed significantly higher plasma cortisol concentrations than LR fish after stress.
• HR fish exhibited increased locomotor activity in the presence of an intruder, unlike in isolation.
• LR fish demonstrated a higher incidence of feed intake in isolation, suggesting better acclimation.
• No aggressive behavior towards intruders was observed in either line.

Conclusions:

• Selection for stress responsiveness in rainbow trout influences behavioral patterns, including activity levels and acclimation to environmental conditions.
• These behavioral alterations have potential implications for the performance and management of salmonid fish in aquaculture.
• The study highlights the link between physiological stress responses and observable behaviors in farmed fish.