Influences of summer water temperatures on the movement, distribution, and resources use of fluvial Westslope Cutthroat Trout in the South Fork Clearwater River basin

North American Journal of Fisheries Management
By: , and 

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Abstract

Although many Westslope Cutthroat Trout Oncorhynchus clarkii lewisi populations in Idaho are robust and stable, population densities in some systems remain below management objectives. In many of those systems, such as in the South Fork Clearwater River (SFCR) system, environmental conditions (e.g., summer temperatures) are hypothesized to limit populations of Westslope Cutthroat Trout. Radiotelemetry and snorkeling methods were used to describe seasonal movement patterns, distribution, and habitat use of Westslope Cutthroat Trout in the SFCR during the summers of 2013 and 2014. Sixty-six radio transmitters were surgically implanted into Westslope Cutthroat Trout (170–405 mm TL) from May 30–June 25, 2013, and June 20–July 6, 2014. Sedentary and mobile summer movement patterns by Westslope Cutthroat Trout were observed in the SFCR. Westslope Cutthroat Trout were generally absent from the lower SFCR. In the upper region of the SFCR, fish generally moved from the main-stem SFCR into tributaries as water temperatures increased during the summer. Fish remained in the middle region of the SFCR where water temperatures were cooler than in the upper or lower regions of the SFCR. A spatially explicit water temperature model indicated that the upper and lower regions of the SFCR exceeded thermal tolerance levels of Westslope Cutthroat Trout throughout the summer. During snorkeling, 23 Westslope Cutthroat Trout were observed in 13 sites along the SFCR and at low density (mean ± SD, 0.0003 ± 0.0001 fish/m2). The distribution of fish observed during snorkeling was consistent with the distribution of radio-tagged fish in the SFCR during the summer. Anthropogenic activities (i.e., grazing, mining, road construction, and timber harvest) in the SFCR basin likely altered the natural flow dynamics and temperature regime and thereby limited stream habitat in the SFCR system for Westslope Cutthroat Trout.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Influences of summer water temperatures on the movement, distribution, and resources use of fluvial Westslope Cutthroat Trout in the South Fork Clearwater River basin
Series title North American Journal of Fisheries Management
DOI 10.1080/02755947.2016.1141124
Volume 36
Issue 3
Year Published 2016
Language English
Publisher American Fisheries Society
Contributing office(s) Coop Res Unit Seattle
Description 19 p.
First page 549
Last page 567
Country United States
State Idaho
Other Geospatial South Fork Clearwater River,
Online Only (Y/N) N
Additional Online Files (Y/N) N
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