Effects of stream channel morphology on golden trout spawning habitat and recruitment
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Authors: R. A. Knapp, V. T. Vredenburg, and K. R. Matthews
Date: 1998
Journal: Ecological Applications
Volume: 8
Number: 4
Pages: 1104-1117
Summary of Methods: Channel width, depth, water velocity, vegetation cover, and substrate size were measured along two different streams in the Golden Trout Wilderness (118° 15' N, 36° 22' W), in Sierra Nevada Mountains, California to determine the effects of livestock grazing on California golden trout spawning habitat. Trout redds (nests) and juvenile trout were also counted on both streams. The first stream had five wide stream reaches paired with five narrow reaches. The other stream had a livestock exclosure that was constructed 10 years prior to the start of the study; and measurements were taken inside the exclosure and downstream from it. In a previous study (Knapp and Matthews 1996 (N Am J Fish Manage:805-820) also available in the RSIS database) in the Golden Trout Wilderness, authors found that grazing increased stream width; therefore, wide stream reaches were used to represent the effects of grazing. Grazing occurred on the first stream from July to September by 235 cow-calf pairs. The second stream, with the exclosure was grazed lightly by 700 cow-calf pairs in July and again at high intensity in October.
Article Summary / Main Points: Wide reaches and the reach outside the exclosure had more suitable spawing habitat, redds, and juvenile trout. The narrow reaches and the reach inside the exclosure had no redds. Where redds occurred and were counted there was less vegetation cover and wider streams. California golden trout seem to prefer wider streams that have less vegetation to spawn.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 18 Sierra Nevada Foothills 22A Sierra Nevada Mountains
Agrovoc Control Words: Riparian zones Rangelands Fish
Article Review Type: Refereed
Article Type: Documented Case History
Keywords: california golden trout, oncorhynchus mykiss aguabonita, livestock grazing, recruitment, reproduction, salmonids, sierra nevada, spawning habitat, stream alteration, stream morphology
Annotation: Even though the authors found that grazing typically widens streams, which increased trout redd density, they note that livestock grazing should be used with caution when trying to improve fish habitat as overgrazing can degrade riparian areas. This study is site specific due to the small number of streams sampled and the lack of understanding as to why there were no redds in the narrow reaches. More information on this study can be found in Knapp and Matthews, 1996 (N Am J Fish Manage:805-820) also available in the RSIS database.
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