Rattlesnake Creek "Research Project 1986 Final Report" - Montana, USA

Book excerpt: Normal 0 The Rattlesnake Creek fishery is unique due to its closure to fishing 45-years ago. Since that time, Rattlesnake Creek has been protected because it supplied Missoula, Montana with municipal water. In 1983, a 25-kilometer section of Rattlesnake Creek above the confluence of Beeskove Creek was opened to catch and release fishing; approximately 12-km immediately below this section remains closed. This study was designed to document the dynamics of an unfished trout population and their response to catch and release angling. The results will provide a point of reference for comparing trout populations in pristine systems with those in heavily impacted and managed streams. Until we understand the structure of undisturbed fisheries and their habitats, our present protection and enhancement efforts will lack both a rational context and effective direction. Objectives for the 1986 study were: 1. Document trout population abundance, size, and species composition, in two unfished sections and two fished sections of Rattlesnake Creek. 2. Evaluate the effects of catch and release fishing on the trout population in Rattlesnake Creek. 3. Document and compare changes in angler catch and pressure on Rattlesnake Creek upstream from Beeskove Creek. 4. Identify early spring and late fall movement patterns of Rattlesnake Creek trout populations. 5. Describe winter habitat used by Westslope Cutthroat Trout. Objectives This one year study was designed to collect baseline data necessary to evaluate the effects of catch and release fishing above Beeskove Creek and the population dynamics of an unfished population of Westslope Cutthroat Trout below Beeskove Creek in western Montana. The objectives for the first year were: 1. Determine wild trout species composition, distribution, size, abundance, and age in four sections of Rattlesnake Creek. 2. Document angler catch and pressure on Rattlesnake Creek upstream of Beeskove Creek. 3. Four sections of Rattlesnake Creek were studied from March, 1985 through February, 1987 to document species composition, distribution, size, and abundance of trout. The effects of catch and release fishing seasonal and diel habitat use were also evaluated. 4. Westslope Cutthroat Trout, Bull Trout, and Brook Trout were present in Rattlesnake Creek. Size and abundance of Westslope Cutthroat Trout and Bull Trout were large compared to other small, relatively infertile streams in western Montana. Catch and release angling (300 anglers per year) had no measurable effect on size and abundance of trout in Rattlesnake Creek. Twenty-one percent of all Westslope Cutthroat Trout tagged were recaptured and 68% of the Westslope Cutthroat Trout over 400-millimeters were caught and released. These and other data collected on Rattlesnake Creek indicate the extreme vulnerability of Westslope Cutthroat Trout to angling. 5. Diel and seasonal changes in Westslope Cutthroat Trout behavior and habitat use were documented. Westslope Cutthroat Trout behavior during late spring days was related to spawning. Feeding was the dominant activity during summer days and cover seeking dominated during winter days. Diel shifts were most noticeable from winter days to winter nights. Twice as many trout were seen at night under harsh winter conditions. Winter night counts correlated well with the summer day counts. Study Area The upper Rattlesnake Creek drainage is located in west central Montana, 8.3-kilometers (5.6-miles.) north of Missoula. The drainage encompasses approximately 21,053 ha (81.3-miles²), and is within the Lolo National Forest. Rattlesnake Creek originates on the flanks of McLeod and Triangle peaks, flowing south-southwest to its confluence with the Clark Fork of the Columbia River at Missoula. The creek descends 1,613-meters (5,291.0-ft) in 37.0-kilometers and has a mean gradient of 4.3%, with a gradient of 1.75% in the study sections (USFS-Lolo, 1976). There are nine perennial tributaries to Rattlesnake Creek. Wrangle, Lake, and High Falls creeks originate from glacial lakes while Porcupine, East Fork of Rattlesnake, Beeskove, Pilcher, Fraser and Spring Creeks originate from springs. More than 40 lakes are located in the upper drainage. The geologic parent material in the area includes argillite, quartzite, and limestone of the Precambrian Belt series as well as Cambrian shales and limestones (Nelson & Dobell 1961). The watershed is characterized by relatively high peak discharge per unit area (Van der Poel 1979). The general topography of the drainage is steep and mountainous. Vegetation varies from a spruce-fir forest in the upper drainage to an open pine-larch forest below Franklin Bridge. Cottonwood trees and shrubs are found in the lower riparian zone and occasionally the valley bottom opens up to small grassy meadows. Rattlesnake Creek is a 3rd order stream with a rubble-gravel bottom and an average annual discharge of 45 to 50-cubic feet per second. The Rattlesnake Creek drainage is managed primarily as a watershed and secondarily as a recreational area (USFS Management Plan 1984). Although Rattlesnake Creek is not currently used as a municipal water supply, plans of building a filtration plant and again using the water municipally are being discussed. A water company dam located 4.0-kilometers upstream from the mouth of Rattlesnake Creek would be the most probable site for a filtration plant. The 12.2-meters high dam prevents all upstream fish migration from the Clark Fork River.