To boldly climb: behavioural and cognitive differences in migrating European glass eels

Area of Science:

• Ecology
• Animal Behavior
• Neuroscience

Background:

• The European eel (Anguilla anguilla) population has declined significantly over the past three decades.
• Habitat fragmentation from structures like dams and weirs is a major contributing factor.
• Fish passage devices on these structures may selectively impact young eels based on their climbing behavior.

Purpose of the Study:

• To investigate the relationship between individual climbing tendency and prior fishway passage experience in European eels.
• To analyze brain gene transcription related to neurogenesis and synaptic plasticity in relation to climbing profiles.
• To understand how environmental obstacles influence eel behavior and potential coping mechanisms.

Main Methods:

• Classified European eels into climbing profiles: 'leaders', 'followers', 'finishers', and 'no climbers'.
• Assessed climbing propensity and repeatability of behavior in eels from upstream and downstream river segments.
• Analyzed brain gene transcription levels associated with neurogenesis and synaptic plasticity.

Main Results:

• Eels from upstream segments of an impounded river exhibited higher and more repeatable climbing propensities.
• 'Leaders' displayed lower transcription levels of synapse-related genes compared to 'followers'.
• Differences in climbing behavior and gene expression suggest distinct coping styles (proactive vs. reactive).

Conclusions:

• Climbing propensity differences exist in glass eels separated by water obstacles.
• Eels may adopt varied climbing strategies influenced by environmental stress and cognitive abilities.
• Fish passage devices can impose selective pressures on eel populations, potentially altering their behavioral and neurological traits.