Development and testing of a rapid method for measuring shoal size discrimination

Area of Science:

• Animal Behavior
• Cognitive Ecology
• Ethology

Background:

• The shoal-choice test assesses quantity discrimination in social fish, but its long duration (20-30 min) limits large-scale application due to infrequent shoal switching.
• Limited switching reduces opportunities for fish to compare shoal sizes, hindering efficient behavioral analysis.

Purpose of the Study:

• To develop and validate a modified shoal-choice test to accelerate the assessment of quantity discrimination in fish.
• To enhance the frequency of shoal switching and reduce observation time for improved efficiency in behavioral studies.

Main Methods:

• A novel shoal-choice test was designed, confining the subject fish in a central transparent cylinder to maintain proximity to stimulus shoals and encourage switching.
• The method was tested on guppies (Poecilia reticulata) using discrimination tasks (e.g., 4 vs. 6 fish).

Main Results:

• The new method reduced observation time to under 5 minutes for preference assessment.
• Guppies exhibited significantly higher switching frequency (5x) and spent less time near their initial choice (10x less) compared to the traditional method.
• Guppies successfully discriminated 5 vs. 6 fish using the new method, a task not achieved with the classical approach.

Conclusions:

• The modified shoal-choice test offers a rapid and efficient alternative for large-scale behavioral screenings of quantity discrimination in fish.
• Methodological adjustments can profoundly impact findings, underscoring the need for careful consideration when comparing quantitative abilities across species.