Cumulative effects of riparian disturbances along high desert trout streams of the John Day Basin, Oregon
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Authors: H. W. Li, G. A. Lamberti, T. N. Persons, C. K. Tait, J. L. Li, and J. C. Buckhouse
Date: 1994
Journal: Transactions of the American Fisheries Society
Volume: 123
Number: 4
Pages: 627-640
Summary of Methods: The collective effects of riparian disturbance (such as overgrazing) on the standing crop of rainbow trout (Oncorhynchus mykiss), in high desert trout streams of John Day Basin, Oregon were investigated. Focal reaches located near shaded and unshaded reaches of stream were used to observe cumulative effects of riparian cover upstream. It was assumed that unshaded reaches of the stream were grazed. These reaches were grouped together into two clusters [cluster N (Mountain, Rock, and Field Creeks) and cluster S (Service and Alder Creeks)] based on the type and distribution of riparian canopy. Sites were sampled in July of 1988 and 1989 for algal, invertebrate, rainbow trout standing crops, and trophic comparisons (combining both clusters data to examine the relations among solar insolation, water temperature, discharge, and standing crop).
Article Summary / Main Points: Higher rainbow trout standing crop populations, lower daily maximum temperatures, and perennial flow were observed in watersheds with greater riparian canopy. Focal reaches of watersheds used more intensively for cattle production i.e., Mountain and Alder Creeks were biologically different from focal reaches of Rock and Fields Creeks and Service Creek, respectively. In all watershed clusters positive associations were found between algal biomass and solar input, total invertebrate biomass, and herbivorous invertebrate biomass. There was no relation between trout biomass and invertebrate biomass. Increases in stream temperature can be lethal to rainbow trout which may negate the higher food availability.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 10 Central Rocky and Blue Mountain Foothills 9 Palouse and Nez Perce Prairies
Agrovoc Control Words: Riparian zones Watersheds Invertebrate
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: rainbow trout, oncorhynchus mykiss, invertebrate biomass, algal biomass, fish habitat, grazing, trophic structure
Annotation: This study is applicable to riparian areas, streams, and desert watersheds of intermountain West, but the results should be used with caution as the authors assumed that unshaded reaches of the stream were grazed by livestock. There was no direct measurement of livestock impact and other things can cause a stream reach to have an open canopy.
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