Technical Report

 

Reduction of salmonid predators by chemical treatment Public Deposited

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https://ir.library.oregonstate.edu/concern/technical_reports/vm40xs61n

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  • The upper drainage of the John Day River system produces summer steelhead and spring chinook salmon. The fish are generally confined to the main stem and its tributaries above Prairie City. The spawning and rearing areas are comparatively free of undesirable fish species, but salmonid smolts migrating downstream must travel through populations of large predatory squawfish. The purpose of the study was to determine if salmonid smolt survival could be increased through removal of the large squawfish by treatment with rotenone. A 40-mile section of the John Day River between Dayville and John Day was selected for study. A pretreatment fish population inventory was conducted to determine the species and numbers of fish present within the test area. Significantly large populations of undesirable fish and correspondingly low numbers of salmonids were observed in the test area. In late August 1962 the 40-mile study area was treated with liquid rotenone. Observations indicated the kill of all fish species was greater than 99 percent in the river and irrigation ditches. None of the tributary streams were treated. It was necessary to use a detoxifying agent to prevent kill of fish populations downstream from the study area. Liquid potassium permanganate was successfully used for this purpose. Posttreatment inventory of fish populations within the study area has shown that average size and number of squawfish was effectively reduced and that salmonid numbers can be increased by temporary control of rough fish populations. There was a significant increase of resident rainbow trout within the study area. Steelhead fingerling and fry reared in the treated area© Most of the salmonid populations resulted from natural recruitment from upstream areas.
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  • 14-17-0001-1016
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  • File scanned at 300 ppi (256 Grayscale) using Capture Perfect 3.0.82 on a Canon DR-9080C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
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