Using "travel time" data to characterize the behavior of migrating animals

Area of Science:

• Ecology
• Population Dynamics
• Ichthyology

Background:

• Migration duration is a critical factor influencing the energetic costs for migratory species.
• Observed migration times result from environmental influences (e.g., currents) and individual behaviors.
• Understanding these components is crucial for effective conservation of migratory populations.

Purpose of the Study:

• To develop and apply a novel migration model to differentiate environmental and behavioral influences on travel time.
• To analyze travel time data from juvenile chinook salmon (Oncorhynchus tschawytscha) from distinct evolutionarily significant units (ESUs).
• To investigate how fish length and river flow affect migration and diffusion rates.

Main Methods:

• Developed a migration model based on an advection-diffusion equation.
• Characterized population movements using migration rate and rate of population spread parameters.
• Expanded the model to incorporate fish length and river flow as variables influencing migration and diffusion.

Main Results:

• The model successfully applied to chinook salmon travel time data from three ESUs.
• Migration and diffusion rates were found to vary with fish length and river flow.
• Year-to-year variability in travel times was consistently explained by these factors within ESUs.
• Migratory behavior aligned with the life-history patterns distinguishing the ESUs.

Conclusions:

• The advection-diffusion model provides biologically meaningful insights into migratory behavior.
• The model's findings are consistent with chinook salmon life-history patterns and ESUs.
• This approach is adaptable for diverse migratory species, aiding predictions in disturbed habitats.