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Response of Juvenile Coho Salmon and Steelhead to Placement of Large Woody Debris in a Coastal Washington Stream
Author(s) -
Cederholm C. J.,
Bilby R. E.,
Bisson P. A.,
Bumstead T. W.,
Fransen B. R.,
Scarlett W. J.,
Ward J. W.
Publication year - 1997
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1997)017<0947:rojcsa>2.3.co;2
Subject(s) - oncorhynchus , large woody debris , debris , juvenile , fishery , environmental science , tributary , habitat , sound (geography) , fish <actinopterygii> , geography , ecology , oceanography , biology , geology , riparian zone , cartography
Many fish habitats have been altered in Pacific Northwest streams and rivers over the past century by a variety of land use practices, including forestry, urbanization, agriculture, and channelization. There are research and management needs for evaluation of the effectiveness of rehabilitation projects intended to enhance stream fish habitat recovery. The response of populations of juvenile coho salmon Oncorhynchus kisutch and steelhead O. mykiss to addition of large woody debris (LWD) was tested in North Fork Porter Creek (NFPC), a small coastal tributary of the Chehalis River, Washington. The NFPC was divided into three 500‐m study sections; two sections were altered with two approaches (engineered and logger's choice) to adding LWD, and the third was kept as a reference site. Immediately after LWD addition, the abundance of LWD pieces was 7.9 times greater than the pretreatment level in the engineered site and 2.7 times greater in the logger's choice site; abundance was unchanged in the reference site. Subsequent winter storms brought additional LWD into all three study sites. In the years that followed, the amount of pool surface area increased significantly in both the engineered and logger's choice sites, while it decreased slightly in the reference site. After LWD addition, winter populations of juvenile coho salmon increased significantly in the engineered and logger's choice sites, while they remained the same in the reference site. There were no significant differences in the coho salmon populations during spring and autumn within the reference, engineered, or logger's choice sites. The coho salmon smolt yield from the engineered and logger's choice sites also increased significantly after LWD addition, while it decreased slightly in the reference site. After LWD addition, the reference site and the engineered site both exhibited increases in age‐0 steelhead populations; however, the population in the logger's choice site did not change. There was no difference in age‐1 steelhead abundance among sites, or before and after enhancement during any season. Winter populations of juvenile coho salmon and age‐0 steelhead were related inversely to maximum and mean winter discharge.