Effects of suction dredge mining on anadromous salmonid habitat in Canyon Creek, Trinity County, California

Author

Gary R. Stern

Graduation Date

1988

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, 1988

Committee Chair Name

Thomas Hassler

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Humboldt State University -- Theses -- Fisheries, Salmonidae--Effect of habitat modification on, Mineral industries--Environmental aspects--California--Trinity County

Abstract

The effects of suction dredge gold mining on the stream habitat of chinook salmon (Oncorhynchus tshawytscha), coho salmon (0. kisutch), and steelhead trout (Salmo gairdneri) were investigated at Canyon Creek, Trinity County, California during 1984 and 1985. In 1984, a total of 1136 m2 of streambed was disturbed by 20 suction dredge operations. In 1985, 1075 m2 were disturbed by 15 dredge operations. Increased levels of stream turbidity and total suspended solids were detected 100 m below active dredges. Gravel and fine sediment deposited 10 to 50 m downstream of dredge outflows aggraded the channel, reduced substrate particle size, and increased substrate embeddedness. Other adverse effects on stream habitat included bank undercutting, bank sluicing, channelization, and riparian vegetation damage. A stream flow of approximately 24 cms during Water Year 1985 (October 1984 through September 1985) effectively obliterated instream mining disturbance from the previous season. At the onset of the 1985 dredge season less than ten percent of the area disturbed by 1984 dredging was visible. Direct observation of anadromous fish indicated that young—of—the—year steelhead abundance and the holding locations of adult spring—run chinook salmon and adult summer—run steelhead were not affected by dredge mining operations. Current California regulations limit suction dredge impacts by requiring permits, seasonal closures, aperture size restrictions, and exclusion from designated areas. Adverse dredging effects could be additionally reduced by establishing procedural guidelines, educating miners to the habitat needs of salmonids, and an increased presence of Department of Fish Game and U.S. Forest Service personnel.

https://scholarworks.calstate.edu/concern/theses/8p58pg62m

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