Streamlining boldness measurement in fish: A practical approach to field studies

Area of Science:

• Fish ecology
• Animal behavior
• Behavioral ecology

Background:

• Fish personality, particularly boldness, influences ecological processes.
• Traditional boldness assessments in labs can cause stress, affecting natural behaviors like feeding.
• A simplified field method for assessing fish boldness is needed.

Purpose of the Study:

• To develop and validate a simplified field-based test for measuring boldness in fish.
• To assess the relationship between boldness and size in juvenile brown trout.
• To investigate if boldness differs between early and late migrating sea trout.

Main Methods:

• A modified open field test was adapted for field use near natural habitats.
• A startle response to sudden light exposure in a novel environment measured boldness.
• The method was applied to juvenile brown trout and sea trout.

Main Results:

• Boldness in brown trout was negatively correlated with size; smaller individuals were bolder.
• Early migrating sea trout exhibited greater boldness than late migrants.
• The field test proved effective in identifying behavioral differences.

Conclusions:

• The modified open field test provides a feasible and less stressful method for assessing fish boldness in situ.
• This approach can be valuable for ecological studies, especially when laboratory transport is impractical.
• Findings highlight the ecological relevance of fish personality traits and their variation.