Title
Using 'Travel Time' Data to Characterize the Behavior of Migrating Animals
Publication Date
2002
Keywords
behavior, migration, travel time, environmental factors, water currents, juvenile, chinook, salmon, seaward migration, fish length, life history, habitat
Journal or Book Title
The American Naturalist
Abstract
For migratory species, duration of migration, or "travel time," is often a critical variable in determining the cost of migration. Observed travel times are the result of both environmental factors such as air or water currents and the behavior of individuals. In an effort to distinguish among these components, I developed a migration model based on an advection-diffusion equation that characterizes population movements in terms of two biologically meaningful parameters: migration rate and rate of population spread. I applied the model to travel time data from juvenile chinook salmon (Oncorhynchus tshawytscha), which were tagged during their seaward migration. The tagged fish originated from three separate evolutionarily significant units (ESUs) as classified by the U. S. National Marine Fisheries Service. The model was expanded by allowing migration and diffusion rates to vary with fish length and river flow. Variability in travel times explained by these factors was strikingly similar from year to year within ESUs, and the migratory behavior revealed by the analysis was consistent with the life-history patterns that distinguish the ESUs. The approach presented here is easily adaptable to a wide range of migratory species and may be particularly useful for predicting how at-risk populations respond to variable conditions in regulated or otherwise disturbed migration habitats.
Pages
372-387
Volume
159
Issue
4