Tests of theory for diel variation in salmonid feeding activity and habitat use

Authored by Steven F Railsback, Bret C Harvey, JW Hayse, KE LaGory

Date Published: 2005

DOI: 10.1890/04-1178

Sponsors: United States Department of Energy (DOE) Western Area Power Administration

Platforms: Swarm

Model Documentation: Other Narrative

Model Code URLs: Model code not found

Abstract

For many animals, selecting whether to fora e during day or night is a critical fitness problem: at night, predation risks are lower but feeding is less efficient. Habitat selection is a closely related problem: the best location for nocturnal foraging could be too risky during daytime, and habitat that is safe and profitable in daytime may be unprofitable at night. We pose a theory that assumes animals select the combination of daytime and night activity (feeding vs. hiding), and habitat, that maximizes expected future fitness. Expected fitness is approximated as the predicted probability of surviving starvation and predation over a future time horizon, multiplied by a function representing the fitness benefits of growth. The theory ` s usefulness and generality were tested using pattern-oriented analysis of an individual-based model (IBM) of stream salmonoids and the extensive literature on observed diel behavior patterns of these animals. Simulation experiments showed that the IBM reproduces eight diverse patterns observed in real populations. (1) Diet activity (whether foraging occurs during day and/or night) varies among a population ` s individuals, and from day to day for each individual. (2) Salmonids feed in shallower and slower water at night. (3) Individuals pack more tightly into the best habitat when feeding at night. (4) Salmonids feed relatively more at night if temperatures (and, therefore, metabolic demands) are low. (5) Daytime feeding is more common for life stages in which potential fitness increases more rapidly with growth. (6) Competition for feeding or hiding sites can shift foraging between day and night. (7) Daytime feeding is more common when food availability is low. (8) Diet activity patterns are affected by the availability of good habitat for feeding or hiding, We can explain many patterns of variation in diel foraging behavior without assuming that populations or individuals vary in how inherently nocturnal or diurnal they are. Instead, these patterns can emerge from the search by individuals for good trade-offs between growth and survival under different habitat and competitive conditions.

Tags

Brown trout Light-intensity Brook trout Cutthroat trout Rainbow-trout Grayling thymallus-arcticus Winter Microhabitat use Juvenile atlantic-salmon Diurnal activity