Do predators influence the distribution of age-0 kokanee in a Colorado Reservoir?

Transactions of the American Fisheries Society
By: , and 



Seasonal changes in reservoir conditions such as productivity, light, and temperature create spatiotemporal variation in habitat that may segregate or aggregate predators and prey, producing implications for the distribution, growth, and survival of fishes. We used hydroacoustics to document the diel vertical distribution of age-0 kokanee Oncorhynchus nerka relative to environmental gradients at Blue Mesa Reservoir, Colorado, during May-August of 2002. Temperature, light, and zooplankton density profiles were examined relative to foraging conditions for kokanee and their primary predator, lake trout Salvelinus namaycush. Age-0 kokanee displayed large diel vertical migrations in May despite the lack of an energetic advantage before reservoir stratification. Age-0 kokanee minimized near-surface foraging at this time, perhaps to avoid predation by visual predators, such as lake trout, in the well-lit surface waters. Strong reservoir stratification in midsummer appeared to provide a thermal refuge from lake trout that the kokanee exploited. By August vertical migrations were shallow and most kokanee remained in the epilimnion throughout the day. Although the energetic implications of the late-summer strategy are unclear, it appears that kokanee were responding to changes in their predator environment. A robust model for kokanee diel vertical migration across a range of systems should include a predator avoidance component.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Do predators influence the distribution of age-0 kokanee in a Colorado Reservoir?
Series title Transactions of the American Fisheries Society
DOI 10.1577/T03-1234.1
Volume 133
Issue 6
Year Published 2004
Language English
Publisher Taylor & Francis
Contributing office(s) Western Fisheries Research Center
Description 13 p.
First page 1366
Last page 1378
Country United States
State Colorado
Other Geospatial Blue Mesa Reservoir
Online Only (Y/N) N
Additional Online Files (Y/N) N
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