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Incorporating movement patterns to improve survival estimates for juvenile bull trout

North American Journal of Fisheries Management

By:
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DOI: 10.1080/02755947.2012.720644

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Abstract

Populations of many fish species are sensitive to changes in vital rates during early life stages, but our understanding of the factors affecting growth, survival, and movement patterns is often extremely limited for juvenile fish. These critical information gaps are particularly evident for bull trout Salvelinus confluentus, a threatened Pacific Northwest char. We combined several active and passive mark–recapture and resight techniques to assess migration rates and estimate survival for juvenile bull trout (70–170 mm total length). We evaluated the relative performance of multiple survival estimation techniques by comparing results from a common Cormack–Jolly–Seber (CJS) model, the less widely used Barker model, and a simple return rate (an index of survival). Juvenile bull trout of all sizes emigrated from their natal habitat throughout the year, and thereafter migrated up to 50 km downstream. With the CJS model, high emigration rates led to an extreme underestimate of apparent survival, a combined estimate of site fidelity and survival. In contrast, the Barker model, which allows survival and emigration to be modeled as separate parameters, produced estimates of survival that were much less biased than the return rate. Estimates of age-class-specific annual survival from the Barker model based on all available data were 0.218±0.028 (estimate±SE) for age-1 bull trout and 0.231±0.065 for age-2 bull trout. This research demonstrates the importance of incorporating movement patterns into survival analyses, and we provide one of the first field-based estimates of juvenile bull trout annual survival in relatively pristine rearing conditions. These estimates can provide a baseline for comparison with future studies in more impacted systems and will help managers develop reliable stage-structured population models to evaluate future recovery strategies.

Geospatial Extents

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Incorporating movement patterns to improve survival estimates for juvenile bull trout
Series title:
North American Journal of Fisheries Management
DOI:
10.1080/02755947.2012.720644
Volume
32
Issue:
6
Year Published:
2012
Language:
English
Publisher:
American Fisheries Society
Publisher location:
Lawrence, KS
Contributing office(s):
Utah Cooperative Fish and Wildlife Research Unit
Description:
14 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1123
Last page:
1136
Number of Pages:
14
Country:
United States
State:
Oregon
Other Geospatial:
Blue Mountains;Skiphorton Creek;South Fork Walla Walla River;Walla Walla River