Bull Trout (Salvelinus confluentus) Population and Habitat Surveys in the Middle Fork Willamette and McKenzie River Systems Amy M. Ambrosier, Stephen D. Hammond and Giles C. Thelen Oregon Department of Fish and Wildlife Springfield, OR 97478 November 30, 1995 CONTENTS Page ABSTRACT............................................................................................................. 1 INTRODUCTION..................................................................................................... 1 DESCRIPTION OF PROJECT AREA ..................................................................... 2 METHODS .............................................................................................................. 3 Distribution Surveys........................................................................................... 3 Transplants........................................................................................................ 5 Genetic Sampling .............................................................................................. 5 Spawning Surveys ............................................................................................. 5 Redd Characterization ....................................................................................... 6 Creel Surveys .................................................................................................... 6 RESULTS................................................................................................................ 7 Mainstem McKenzie Population......................................................................... 7 Anderson Creek Downstream Migrant Trap ................................................. 7 Juvenile Transfers ........................................................................................ 8 Distribution Surveys...................................................................................... 9 Standard Hole Counts .................................................................................. 9 Spawning Surveys........................................................................................ 10 Genetic Sampling ......................................................................................... 12 Trail Bridge Reservoir Population ...................................................................... 12 Juvenile Transfers ........................................................................................ 12 Distribution Surveys...................................................................................... 12 Spawning Surveys........................................................................................ 13 South Fork McKenzie Population....................................................................... 13 Distribution Surveys...................................................................................... 13 Standard Hole Counts .................................................................................. 13 Spawning Surveys........................................................................................ 14 Genetic Sampling ......................................................................................... 14 Middle Fork Willamette Population .................................................................... 14 DISCUSSION AND CONCLUSIONS ...................................................................... 15 Mainstem McKenzie Population......................................................................... 15 Trail Bridge Reservoir Population ...................................................................... 16 South Fork McKenzie Population....................................................................... 17 Middle Fork Willamette Population .................................................................... 17 ACKNOWLEDGMENTS.......................................................................................... 18 REFERENCES........................................................................................................ 19 APPENDIX A Water velocity, depth, substrate and cover types over bull trout redds in Anderson Creek Oregon, 1994 ............................................ 21 FIGURES and TABLES Page Figure 1. Length frequency histogram for juvenile bull trout captured in a downstream migratory trap from February through September 1995. ... 8 Figure 2. Bull trout observed during snorkel surveys of eight standard pools in the McKenzie River, 1994................................................................ 9 Figure 3. Bull trout observed during snorkel surveys of eight standard pools in the McKenzie River, 1995................................................................ 10 Figure 4. Number of bull trout observed during snorkel surveys of 15 pools on the South Fork McKenzie, 1995. ............................................... 14 Table 1. Table 1. The capture of bull trout fry and juveniles in the downstream ..... 7 migrant trap on Anderson Creek, 1994-1995.................................................... Table 2. Anderson Creek redds cumulative totals, 1995.......................................... 10 Table 3. Anderson Creek redds in index area, 1989-1995....................................... 11 ABSTRACT Populations of bull trout (Salvelinus confluentus) in the McKenzie and Middle Fork Willamette River basins were studied to determine their relative abundance, distribution, and habitat requirements. The bull trout population in the Upper McKenzie system appeared to be the largest and fastest growing population surveyed. In one day, up to 33 adults were observed in eight pools in the mainstem of the Upper McKenzie. The number of redds in Anderson Creek, which is believed to provide the majority of spawning habitat in the Upper McKenzie system, continues to increase. Redds were also observed in Olallie Creek, upstream of Highway 126, after the installation of a fish passage culvert. Bull trout fry, transferred to sections of Sweetwater Creek and Olallie Creek above two fish passage culverts, were observed one to three years later near their release sites and appeared healthy. The trend of the bull trout population in the South Fork McKenzie is unknown. In 1995 up to 17 adult bull trout were sighted in one day where only three adults were observed in 1994. Roaring River is the only tributary on the South Fork McKenzie in which bull trout redds and juveniles have been located. It is believed to be the major spawning tributary above Cougar Reservoir. Despite recent, unverified sightings by anglers, no bull trout were located on the Middle fork Willamette River. INTRODUCTION In 1980, the American Fisheries Society designated bull trout (Salvelinus confluentus) a distinct species from dolly varden (S. malma). Bull trout are large predators weighing up to fifteen pounds. Historically they were held in low regard due to their piscivorous nature. Anglers and resource managers implemented eradication efforts, blaming bull trout for contributing to declines in populations of more desirable species such as Pacific salmon (Oncorhynchus spp), rainbow trout (O. mykiss), and cutthroat trout (O. clarki). Bull trout are now thought of as a valuable indicator of the status and health of an ecosystem. This is because they require very cold spring fed water, high quality pristine habitat (usually associated with old growth forests), and unrestricted interbasin migrations (Ratliff and Howell 1992). Listing under the Endangered Species Act was recently judged to be warranted but was precluded by higher priority species and limited resources. Bull trout are extinct in Oregon from all areas west of the Cascades except the McKenzie drainage and possibly the Middle Fork Willamette drainage. Bull trout in the McKenzie River basin were either a contiguous population from the lower McKenzie River to Tamolitch Falls or two populations with some overlapping distributions. If two populations did exist, one spawned in the upper reaches of the South Fork and one in the upper reaches of the mainstem. The South Fork population was cut off from the mainstem McKenzie in 1963 by the construction of Cougar Dam. Historically, bull trout were reported in the Middle Fork Willamette basin in the Middle Fork and North Fork Willamette Rivers as well as Salt, Swift, and Staley Creeks.. This 1 population was isolated in 1961 by Hills Creek Dam and has since declined. Chemical treatment to remove non-game fish above the dam, habitat alteration from road construction and timber harvests, loss of juvenile spring chinook as a food source, and mortality from angling all may have contributed to the decline of this population. The last confirmed sighting was a photograph taken by an angler in 1990. The objectives of this study are to determine the status of bull trout populations in the McKenzie and Middle Fork Willamette River basins and to ascertain how to secure healthy populations with long-term sustainability. This study is funded by the Bonneville Power Administration. It began in June 1994 and will continue through November 1998. Substantial contributions of funds and personnel were made by the Willamette National Forest, Eugene Water and Electric board, Oregon Department of Transportation, Oregon Council of the Federation of Fly Fishers, and Trout Unlimited. DESCRIPTION OF PROJECT AREA The project area includes the South Fork McKenzie River above Cougar Reservoir, the McKenzie River above McKenzie Bridge, and the Middle Fork Willamette