Individuality matters for substrate-size preference in the Nile tilapia juveniles

Area of Science:

• Animal behavior
• Aquaculture
• Ethology

Background:

• Preference tests are common for assessing animal welfare and environmental enrichment.
• Traditionally, these tests focus on group-level preferences for resources or conditions.
• Individual variation in preferences has been noted in Nile tilapia for background colors.

Purpose of the Study:

• To investigate individual variability in Nile tilapia preferences for substrate size.
• To determine if Nile tilapia exhibit consistent group-level preferences for different substrate sizes.
• To inform best practices in fish rearing and environmental enrichment based on actual fish preferences.

Main Methods:

• Utilized a robust method for analyzing individual animal preferences.
• Presented Nile tilapia with different substrate sizes (e.g., gravel, sand).
• Recorded and analyzed fish choices to identify preferences at individual and group levels.

Main Results:

• Demonstrated clear individual variability in Nile tilapia preferences for substrate size.
• Observed a consistent group-level avoidance of small gravel.
• Found that fish strongly preferring one substrate size never chose gravel over sand-size substrate.

Conclusions:

• Nile tilapia avoid gravel and prefer smaller substrates, potentially due to mouth gap size.
• Current fish-rearing practices may misinterpret fish needs regarding substrate.
• Environmental enrichment should account for individual and species-specific substrate preferences.