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Title: The response of salmon populations to geomorphic measurements at three scales
Author: Bryant, M.D.; Woodsmith, R.D.;
Source: North American Journal of Fisheries Management 29:549-559.
Publication Series: Scientific Journal (JRNL)
Protocols to assess stream channel response to disturbances often focus on physical aspects of
the stream at the reach scale without measurements of fish populations. In this study, estimates of juvenile salmon abundance in 511 habitat units within 25 reaches of 12 streams were made over 4 years and juxtaposed with measurements of physical habitat at the habitat unit, reach, and watershed scales. Fish ranged in size from about 50 to 160 mm fork length. The amount of variation among densities differed by species and geographic scale. For most species, the habitat unit scale accounted for the most variation. Relationships between salmon density and measurements at the habitat unit scale varied. At the reach scale, we observed a negative relationship between abundance of coho salmon Oncorhynchus kisutch parr and number of pools. A positive relationship appeared between coho salmon parr and large wood. At the watershed scale, a positive relationship was observed between coho salmon parr and valley morphology. Valley morphology also entered
the model for cutthroat trout O. clarkii. Differences in salmonid densities observed between northern and southern watersheds were attributed to differences in landforms, geology, and soils among islands in southeast Alaska. Simple habitat measures, such as pool counts, were not good predictors of fish abundance. However, geomorphic measures from multiple scales that are accompanied by estimates of fish abundance can provide managers with an integrated picture of watershed productivity and a better means to evaluate features that influence productivity.
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Bryant, M.D., and R.D. Woodsmith. 2009. The response of salmon populations to geomorphic measurements at three scales. North American Journal of Fisheries Management 29:549-559.
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