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• 71. [Article] Net production, movement, and food of cutthroat trout (Salmo clarki clarki Richardson) in three Oregon coastal streams

  Unfished populations of cutthroat trout in three small coastal streams in Oregon were studied from April of 1962 until November of 1963. Population size, growth rate, and net production were estimated ...

  Citation × Citation Citation Abstract Copy Title: Net production, movement, and food of cutthroat trout (Salmo clarki clarki Richardson) in three Oregon coastal streams Author: Lowry, Gerald Roger Unfished populations of cutthroat trout in three small coastal streams in Oregon were studied from April of 1962 until November of 1963. Population size, growth rate, and net production were estimated for study areas in each stream. The nature of seasonal movement patterns within the study areas and at fish traps was examined. Food habits of trout during the time of emergence and early growth of coho fry were studied. The mean annual biomass of cutthroat trout for all streams was 4.2 grams per square meter. Growth in length was greatest in April and May and least in October and November. Net production averaged 4.1 grams per square meter for the three streams. Growth rates were about equal in the three streams, but production levels were about 20 percent higher in one stream. Upstream migrations of trout occurred from late October until March, with a maximum in December. Kelts returned downstream from December to April with the greatest numbers in January and February. More than 90 percent of the downstream movement of smolts occurred in February, March, April and May, with numbers being consistently greatest in April. Two-year-old smolts dominated the run in the two larger streams, while one-year-old smolts did so in the smallest stream. Small tributaries of the study areas were found to be very important to cutthroat trout reproduction. Young trout were noted to leave the tributaries at about one year of age. Trout 150 mm in length that had never left the study streams were found in a gravid condition near redd sites. Food samples taken during the period of coho fry emergence and early growth failed to show that cutthroat trout were important consumers of young coho. Aquatic arthropods were consistently an important part of the diet; earthworms decreased in importance; and terrestrial arthropods increased in importance during the period from February to June. Title: Net production, movement, and food of cutthroat trout (Salmo clarki clarki Richardson) in three Oregon coastal streams Author: Lowry, Gerald Roger Unfished populations of cutthroat trout in three small coastal streams in Oregon were studied from April of 1962 until November of 1963. Population size, growth rate, and net production were estimated for study areas in each stream. The nature of seasonal movement patterns within the study areas and at fish traps was examined. Food habits of trout during the time of emergence and early growth of coho fry were studied. The mean annual biomass of cutthroat trout for all streams was 4.2 grams per square meter. Growth in length was greatest in April and May and least in October and November. Net production averaged 4.1 grams per square meter for the three streams. Growth rates were about equal in the three streams, but production levels were about 20 percent higher in one stream. Upstream migrations of trout occurred from late October until March, with a maximum in December. Kelts returned downstream from December to April with the greatest numbers in January and February. More than 90 percent of the downstream movement of smolts occurred in February, March, April and May, with numbers being consistently greatest in April. Two-year-old smolts dominated the run in the two larger streams, while one-year-old smolts did so in the smallest stream. Small tributaries of the study areas were found to be very important to cutthroat trout reproduction. Young trout were noted to leave the tributaries at about one year of age. Trout 150 mm in length that had never left the study streams were found in a gravid condition near redd sites. Food samples taken during the period of coho fry emergence and early growth failed to show that cutthroat trout were important consumers of young coho. Aquatic arthropods were consistently an important part of the diet; earthworms decreased in importance; and terrestrial arthropods increased in importance during the period from February to June. Close

• 72. [Article] 2012 Trapper Creek Redd surveys

  Abstract -- Odell Lake was once directly connected to the upper Deschutes River basin, but recent geologic activity severed this connection with the creation of Davis Lake. Despite a lack of connection ...

  Citation × Citation Citation Abstract Copy Title: 2012 Trapper Creek Redd surveys Abstract -- Odell Lake was once directly connected to the upper Deschutes River basin, but recent geologic activity severed this connection with the creation of Davis Lake. Despite a lack of connection to the Deschutes River, indigenous bull trout (Salvelinus confluentus) subsist in Odell Lake. The Odell Lake bull trout are now the only natural adfluvial bull trout population in Oregon. Despite their persistence; angling mortality, habitat degradation, hybridization, and competition with introduced species limit bull trout populations. Bull trout were listed as threatened under the Endangered Species Act in 1998 (Office of the Federal Register 63 [June 10, 1998]: 31647). ODFW has monitored this population closely by conducting weekly redd counts on an annual basis and mapping redd locations to identify areas of optimal spawning habitat in Trapper Creek. Title: 2012 Trapper Creek Redd surveys Abstract -- Odell Lake was once directly connected to the upper Deschutes River basin, but recent geologic activity severed this connection with the creation of Davis Lake. Despite a lack of connection to the Deschutes River, indigenous bull trout (Salvelinus confluentus) subsist in Odell Lake. The Odell Lake bull trout are now the only natural adfluvial bull trout population in Oregon. Despite their persistence; angling mortality, habitat degradation, hybridization, and competition with introduced species limit bull trout populations. Bull trout were listed as threatened under the Endangered Species Act in 1998 (Office of the Federal Register 63 [June 10, 1998]: 31647). ODFW has monitored this population closely by conducting weekly redd counts on an annual basis and mapping redd locations to identify areas of optimal spawning habitat in Trapper Creek. Close

• 73. [Article] Diamond Lake Fish Management Issues

  This document covers the massive decline in catch and return on trout stocked in Diamond Lake starting in the 90s and describes issues addressing the most likely cause, an increased Tui chub population ...

  Citation × Citation Citation Abstract Copy Title: Diamond Lake Fish Management Issues Author: Oregon. Department of Fish and Wildlife This document covers the massive decline in catch and return on trout stocked in Diamond Lake starting in the 90s and describes issues addressing the most likely cause, an increased Tui chub population competing for resources with the trout. The report discusses the persistent issue of Tui chub in Diamond Lake, and compares catch of Tui chub and Rainbow trout from Diamond Lake from 1985 through 1995. See also: A preliminary report on the Diamond Lake study, which discusses a similar issue in 1947. https://ir.library.oregonstate.edu/xmlui/handle/1957/42827 Title: Diamond Lake Fish Management Issues Author: Oregon. Department of Fish and Wildlife This document covers the massive decline in catch and return on trout stocked in Diamond Lake starting in the 90s and describes issues addressing the most likely cause, an increased Tui chub population competing for resources with the trout. The report discusses the persistent issue of Tui chub in Diamond Lake, and compares catch of Tui chub and Rainbow trout from Diamond Lake from 1985 through 1995. See also: A preliminary report on the Diamond Lake study, which discusses a similar issue in 1947. https://ir.library.oregonstate.edu/xmlui/handle/1957/42827 Close

• 74. [Article] A summary of coastal cutthroat trout studies, 1962-1965

  This report summarizes research on coastal cutthroat trout from the beginning of more intensive studies in 1962 through 1965. This report includes data on migration, survival/mortality, growth, and food ...

  Citation × Citation Citation Abstract Copy Title: A summary of coastal cutthroat trout studies, 1962-1965 Author: Bulkley, Ross V., Hansen, David, Skeesick, Del, Oregon. State Game Commission. Research Division This report summarizes research on coastal cutthroat trout from the beginning of more intensive studies in 1962 through 1965. This report includes data on migration, survival/mortality, growth, and food habits collected during this period. It also discusses the Siuslaw Estuary catch estimates. Title: A summary of coastal cutthroat trout studies, 1962-1965 Author: Bulkley, Ross V., Hansen, David, Skeesick, Del, Oregon. State Game Commission. Research Division This report summarizes research on coastal cutthroat trout from the beginning of more intensive studies in 1962 through 1965. This report includes data on migration, survival/mortality, growth, and food habits collected during this period. It also discusses the Siuslaw Estuary catch estimates. Close

• 75. [Article] Native Trout Studies, Annual Progress Report, Project # F-136-R-13

  Abstract -- We developed a proposal for studies to better describe 1) the seasonal movements and locations of adult westslope cutthroat trout in the mainstem John Day River subbasin, and 2) the characteristics ...

  Citation × Citation Citation Abstract Copy Title: Native Trout Studies, Annual Progress Report, Project # F-136-R-13 Abstract -- We developed a proposal for studies to better describe 1) the seasonal movements and locations of adult westslope cutthroat trout in the mainstem John Day River subbasin, and 2) the characteristics of habitats associated with these locations. We radio-tagged a total of 41 adult cutthroat trout, including six from Deardorff Creek, 18 from Roberts Creek, and 17 from Rail Creek to initiate efforts to describe their seasonal movements. We began to measure the characteristics of habitats used by these fish. In August, we helped survey Vinegar Creek (Middle Fork John Day River subbasin) for the presence of bull trout. Vinegar Creek was thought to no longer support bull trout, but these surveys led to the discovery of one. Title: Native Trout Studies, Annual Progress Report, Project # F-136-R-13 Abstract -- We developed a proposal for studies to better describe 1) the seasonal movements and locations of adult westslope cutthroat trout in the mainstem John Day River subbasin, and 2) the characteristics of habitats associated with these locations. We radio-tagged a total of 41 adult cutthroat trout, including six from Deardorff Creek, 18 from Roberts Creek, and 17 from Rail Creek to initiate efforts to describe their seasonal movements. We began to measure the characteristics of habitats used by these fish. In August, we helped survey Vinegar Creek (Middle Fork John Day River subbasin) for the presence of bull trout. Vinegar Creek was thought to no longer support bull trout, but these surveys led to the discovery of one. Close

• 76. [Article] Crooked River Fish Management Plan 1979

  Abstract -- The Crooked River is a major tributary to the Deschutes River and has the habitat to produce a good rainbow trout population, especially between Prineville Dam and Rice-Baldwin Dam. However, ...

  Citation × Citation Citation Abstract Copy Title: Crooked River Fish Management Plan 1979 Abstract -- The Crooked River is a major tributary to the Deschutes River and has the habitat to produce a good rainbow trout population, especially between Prineville Dam and Rice-Baldwin Dam. However, winter streamflow is minimal and high turbidity is common. The. river is not stocked but various ages and sizes of hatchery fish emigrate from Prineville Reservoir during periods of spill; and these fish constitute a sizable portion of the trout population in the river. The Crooked River has maintained a successful fishery on the combination of wild and hatchery (from Prinevi11e Reservoir) trout under general statewide regulations. In July 1979, the Oregon Fish and Wildlife Commission accepted the Department's recommendation to continue to manage this portion of Crooked River for wild and hatchery fish. Hatchery fish will not be stocked in this section of the river, but large numbers of hatchery trout migrate from Prineville Reservoir into the river below the dam. Title: Crooked River Fish Management Plan 1979 Abstract -- The Crooked River is a major tributary to the Deschutes River and has the habitat to produce a good rainbow trout population, especially between Prineville Dam and Rice-Baldwin Dam. However, winter streamflow is minimal and high turbidity is common. The. river is not stocked but various ages and sizes of hatchery fish emigrate from Prineville Reservoir during periods of spill; and these fish constitute a sizable portion of the trout population in the river. The Crooked River has maintained a successful fishery on the combination of wild and hatchery (from Prinevi11e Reservoir) trout under general statewide regulations. In July 1979, the Oregon Fish and Wildlife Commission accepted the Department's recommendation to continue to manage this portion of Crooked River for wild and hatchery fish. Hatchery fish will not be stocked in this section of the river, but large numbers of hatchery trout migrate from Prineville Reservoir into the river below the dam. Close

• 77. [Article] Biology and production of the red-band trout (Salmo sp.) in four southeastern Oregon streams

  The red-band trout is native to many small, isolated streams in southeastern Oregon. A study of the red-band population of Three- mile Creek and Reservoir was conducted from August 1973 to June 1975. Data ...

  Citation × Citation Citation Abstract Copy Title: Biology and production of the red-band trout (Salmo sp.) in four southeastern Oregon streams Author: Kunkel, Clair The red-band trout is native to many small, isolated streams in southeastern Oregon. A study of the red-band population of Three- mile Creek and Reservoir was conducted from August 1973 to June 1975. Data were collected concerning population size, age composition, growth, biomass, recruitment, fecundity, and habitat. During the spring of 1975 similar data were collected for red-band populations in Home, Rattlesnake, and Buck creeks. The average trout biomass in Threemile Creek was 24.2 g/m2 and average production was 17.2 g/m2/yr. The production rate of 17.2 g/m2/yr is among the highest reported for salmonids in small streams and is probably in part due to the stable environment afforded by the springs which feed Threemile Creek. Biomass in the other study streams ranged from 2.4 to more than 6.7 g/m2 and production ranged from 1.2 to more than 4.2 g/m2/yr, not including production of age O-I fish. Trout biomass in Threemile Reservoir was 84 kg/ha in September 1974, and annual production was 80 kg/ha. The presence of the reservoir has increased the total production of the Threemile system by at least 12 times. Most female trout in the streams and reservoir matured at age III. Egg production in the Threemile system was considerably greater than in the other study streams. Spawners from the reservoir contributed nearly five times as many eggs to Threemile Creek as did the stream-dwelling females during the spring of 1974. The egg contribution of reservoir fish was probably greater than that required to perpetuate the observed trout densities in the stream. However, the resulting high density of fry may insure adequate contribution of young trout to the reservoir. Reservoir trout could serve as an egg source for rehabilitation of native trout in southeastern Oregon streams, where desirable. During spring more than 250 reservoir trout averaging 39.8 cm in length migrated into Threernile Creek to spawn, and provided excellent opportunity for anglers. Terminal reservoirs might be considered as management tools for trout populations in small streams, providing larger trout than the stream would normally produce. Such reservoirs could serve as multiple purpose water storage facilities for irrigation, stock watering, and trout production. The status of the trout populations studied was relatively good in stream sections that had not been disturbed by man's activities. Title: Biology and production of the red-band trout (Salmo sp.) in four southeastern Oregon streams Author: Kunkel, Clair The red-band trout is native to many small, isolated streams in southeastern Oregon. A study of the red-band population of Three- mile Creek and Reservoir was conducted from August 1973 to June 1975. Data were collected concerning population size, age composition, growth, biomass, recruitment, fecundity, and habitat. During the spring of 1975 similar data were collected for red-band populations in Home, Rattlesnake, and Buck creeks. The average trout biomass in Threemile Creek was 24.2 g/m2 and average production was 17.2 g/m2/yr. The production rate of 17.2 g/m2/yr is among the highest reported for salmonids in small streams and is probably in part due to the stable environment afforded by the springs which feed Threemile Creek. Biomass in the other study streams ranged from 2.4 to more than 6.7 g/m2 and production ranged from 1.2 to more than 4.2 g/m2/yr, not including production of age O-I fish. Trout biomass in Threemile Reservoir was 84 kg/ha in September 1974, and annual production was 80 kg/ha. The presence of the reservoir has increased the total production of the Threemile system by at least 12 times. Most female trout in the streams and reservoir matured at age III. Egg production in the Threemile system was considerably greater than in the other study streams. Spawners from the reservoir contributed nearly five times as many eggs to Threemile Creek as did the stream-dwelling females during the spring of 1974. The egg contribution of reservoir fish was probably greater than that required to perpetuate the observed trout densities in the stream. However, the resulting high density of fry may insure adequate contribution of young trout to the reservoir. Reservoir trout could serve as an egg source for rehabilitation of native trout in southeastern Oregon streams, where desirable. During spring more than 250 reservoir trout averaging 39.8 cm in length migrated into Threernile Creek to spawn, and provided excellent opportunity for anglers. Terminal reservoirs might be considered as management tools for trout populations in small streams, providing larger trout than the stream would normally produce. Such reservoirs could serve as multiple purpose water storage facilities for irrigation, stock watering, and trout production. The status of the trout populations studied was relatively good in stream sections that had not been disturbed by man's activities. Close

• 78. [Article] Biophysical factors driving the distribution and abundance of redband/steelhead trout (Oncorhynchus mykiss gairdneri) in the South Fork John Day River Basin, Oregon, USA

  The overall goal of this study was to identify multiple scales of habitat use and habitat electivity by redband/steelhead trout and define the limiting factors affecting the distribution patterns of this ...

  Citation × Citation Citation Abstract Copy Title: Biophysical factors driving the distribution and abundance of redband/steelhead trout (Oncorhynchus mykiss gairdneri) in the South Fork John Day River Basin, Oregon, USA Author: Madrinan, Luis Francisco The overall goal of this study was to identify multiple scales of habitat use and habitat electivity by redband/steelhead trout and define the limiting factors affecting the distribution patterns of this species during summer flows. The main objective in chapter 2 was to identify the most important habitat associations that control the distribution patterns of threatened populations of redband/steelhead trout in the South Fork John Day River Basin. I found that the factors influencing the distribution patterns of trout in the basin were dependent on the thermal context and spatial extent of analysis. The inclusion of water temperature alone at large spatial scales explained most of the distribution of trout at the basin scale and that channel morphology was a very important factor at small spatial scales. The main objective in chapter 3 was to identify geophysical factors influencing the distribution pattern of threatened populations of redband/steelhead trout in the basin at multiple spatial scales. I found that the trout distribution patterns in the area could be described as a clustered distribution, with a strong selection for upstream-cold water reaches and small, well oxygenated, running water pools. My study reveals that the most influential factor at large spatial scales was water temperature and smaller scale channel morphology. Chapter 4 examines whether longitudinal-summer-stream temperature profiles in semi arid-environment streams can be used to index carrying capacities of threatened populations of redband/steelhead trout. My results show that, in the South Fork John Day Basin, stream temperature can be used as indicator of trout carrying capacity. The distribution redband/steelhead trout in summer is largely determined by the- physiologically influenced-preference that individuals have for habitats within specific temperature ranges. Title: Biophysical factors driving the distribution and abundance of redband/steelhead trout (Oncorhynchus mykiss gairdneri) in the South Fork John Day River Basin, Oregon, USA Author: Madrinan, Luis Francisco The overall goal of this study was to identify multiple scales of habitat use and habitat electivity by redband/steelhead trout and define the limiting factors affecting the distribution patterns of this species during summer flows. The main objective in chapter 2 was to identify the most important habitat associations that control the distribution patterns of threatened populations of redband/steelhead trout in the South Fork John Day River Basin. I found that the factors influencing the distribution patterns of trout in the basin were dependent on the thermal context and spatial extent of analysis. The inclusion of water temperature alone at large spatial scales explained most of the distribution of trout at the basin scale and that channel morphology was a very important factor at small spatial scales. The main objective in chapter 3 was to identify geophysical factors influencing the distribution pattern of threatened populations of redband/steelhead trout in the basin at multiple spatial scales. I found that the trout distribution patterns in the area could be described as a clustered distribution, with a strong selection for upstream-cold water reaches and small, well oxygenated, running water pools. My study reveals that the most influential factor at large spatial scales was water temperature and smaller scale channel morphology. Chapter 4 examines whether longitudinal-summer-stream temperature profiles in semi arid-environment streams can be used to index carrying capacities of threatened populations of redband/steelhead trout. My results show that, in the South Fork John Day Basin, stream temperature can be used as indicator of trout carrying capacity. The distribution redband/steelhead trout in summer is largely determined by the- physiologically influenced-preference that individuals have for habitats within specific temperature ranges. Close

• 79. [Article] Distribution and characteristics of an isolated population of coastal cutthroat trout (Oncorhynchus clarki) in streams of Triangle Lake Basin, Oregon

  This research focused on features of a genetically isolated population of cutthroat trout (Oncorhynchus clarki) in the Triangle Lake basin of coastal Oregon. A falls at the outlet of Triangle Lake has ...

  Citation × Citation Citation Abstract Copy Title: Distribution and characteristics of an isolated population of coastal cutthroat trout (Oncorhynchus clarki) in streams of Triangle Lake Basin, Oregon Author: Hurley, Steven M. This research focused on features of a genetically isolated population of cutthroat trout (Oncorhynchus clarki) in the Triangle Lake basin of coastal Oregon. A falls at the outlet of Triangle Lake has blocked upstream migration of trout and anadromous salmonids into the basin. Cutthroat trout were found throughout the six study streams of the Triangle Lake basin in association with other native fishes and introduced warmwater fishes. Warmwater species (e.g. Centrarchidae) were restricted largely to the lakes of Triangle Lake basin, and did not comprise a significant part of the stream fish fauna. Salmonids and cottids dominated the upper forested reaches of the basin, whereas nonsalmonids dominated the lower reaches. The middle reaches contained a transitional fish community between the upper and lower reaches. Reach type was a major factor influencing cutthroat trout density and size distribution. Areal densities of cutthroat trout were highest in the upper reaches and lowest in the lower reaches with the exception of 0+ cutthroat trout, which occurred at similar densities in all reaches. The highest frequency of 1+ cutthroat trout occurred in the middle reaches, whereas the highest frequency of 0+ cutthroat occurred in the lower reaches. Within reaches, channel unit type influenced the density and age structure of cutthroat trout. Pools and rapids had the highest densities of cutthroat trout, whereas riffles, glides, and cascades had lower densities. Larger trout were found primarily in pools and rapids. Planted steelhead fry (Oncorhynchus mykiss) were found in two streams, Congdon Creek and Lake Creek. Although most steelhead fry leave the basin as smolts, some steelhead appear to become resident and may hybridize with native cutthroat trout. Cutthroat trout spawning was observed from late December 1987 through late May 1988. Differences in the time and place of spawning may serve to genetically isolate two populations of cutthroat trout in Triangle Lake basin. One population may be lake dwelling as adults and spawn lower in the basin in late spring. The other population may be stream dwelling and spawn in the winter during higher flows, which allows them to spawn in the upper reaches of the basin. Title: Distribution and characteristics of an isolated population of coastal cutthroat trout (Oncorhynchus clarki) in streams of Triangle Lake Basin, Oregon Author: Hurley, Steven M. This research focused on features of a genetically isolated population of cutthroat trout (Oncorhynchus clarki) in the Triangle Lake basin of coastal Oregon. A falls at the outlet of Triangle Lake has blocked upstream migration of trout and anadromous salmonids into the basin. Cutthroat trout were found throughout the six study streams of the Triangle Lake basin in association with other native fishes and introduced warmwater fishes. Warmwater species (e.g. Centrarchidae) were restricted largely to the lakes of Triangle Lake basin, and did not comprise a significant part of the stream fish fauna. Salmonids and cottids dominated the upper forested reaches of the basin, whereas nonsalmonids dominated the lower reaches. The middle reaches contained a transitional fish community between the upper and lower reaches. Reach type was a major factor influencing cutthroat trout density and size distribution. Areal densities of cutthroat trout were highest in the upper reaches and lowest in the lower reaches with the exception of 0+ cutthroat trout, which occurred at similar densities in all reaches. The highest frequency of 1+ cutthroat trout occurred in the middle reaches, whereas the highest frequency of 0+ cutthroat occurred in the lower reaches. Within reaches, channel unit type influenced the density and age structure of cutthroat trout. Pools and rapids had the highest densities of cutthroat trout, whereas riffles, glides, and cascades had lower densities. Larger trout were found primarily in pools and rapids. Planted steelhead fry (Oncorhynchus mykiss) were found in two streams, Congdon Creek and Lake Creek. Although most steelhead fry leave the basin as smolts, some steelhead appear to become resident and may hybridize with native cutthroat trout. Cutthroat trout spawning was observed from late December 1987 through late May 1988. Differences in the time and place of spawning may serve to genetically isolate two populations of cutthroat trout in Triangle Lake basin. One population may be lake dwelling as adults and spawn lower in the basin in late spring. The other population may be stream dwelling and spawn in the winter during higher flows, which allows them to spawn in the upper reaches of the basin. Close

• 80. [Article] Effects of kokanee (Oncorhynchus nerka) redd superimposition on bull trout (Salvelinus confluentus) reproductive success in the Deschutes River Basin, Oregon.

  Oregon's only remaining non-reservoir population of adfluvial bull trout (Salvelinus confluentus) is found in Odell Lake, in the headwaters of the Deschutes River. The population size is unknown, but ...

  Citation × Citation Citation Abstract Copy Title: Effects of kokanee (Oncorhynchus nerka) redd superimposition on bull trout (Salvelinus confluentus) reproductive success in the Deschutes River Basin, Oregon. Author: Weeber, Matthew A. Oregon's only remaining non-reservoir population of adfluvial bull trout (Salvelinus confluentus) is found in Odell Lake, in the headwaters of the Deschutes River. The population size is unknown, but appears to be quite small. Limited spawning and rearing habitats, combined with the effects of introduced species and other anthropogenic changes to the basin have raised concerns as to the population's viability. The lower section of Trapper Creek, a tributary of Odell Lake, is the only known spawning habitat used by this species throughout the system. Large numbers of kokanee salmon (Oncorhynchus nerka) also spawn in the same reach, superimposing their redds on those dug earlier by bull trout. After superimposition by kokanee, bull trout redds are virtually undetectable. The objective of the study was to assess the effect of kokanee redd superimposition on bull trout egg-to-fry survival. Due to uncertainty in the size of the Odell Lake bull trout population much of the study was conducted on bull trout and kokanee of the Metolius River system, a neiboring Deschutes sub-basin. Emergent fry traps were used, in combination with egg burial depth measurements, scour monitors, and gravel characterization to establish actual physical overlap between both species and degree of bull trout egg pocket disturbance caused by kokanee. Results indicate that most bull trout egg pockets are dug deeper than depths reached by spawning kokanee. Kokanee were found to be very superficial spawners in the streams studied. Bull trout fry emergence data suggest that kokanee redd superimposition does not affect egg-to-fry survival rates. Title: Effects of kokanee (Oncorhynchus nerka) redd superimposition on bull trout (Salvelinus confluentus) reproductive success in the Deschutes River Basin, Oregon. Author: Weeber, Matthew A. Oregon's only remaining non-reservoir population of adfluvial bull trout (Salvelinus confluentus) is found in Odell Lake, in the headwaters of the Deschutes River. The population size is unknown, but appears to be quite small. Limited spawning and rearing habitats, combined with the effects of introduced species and other anthropogenic changes to the basin have raised concerns as to the population's viability. The lower section of Trapper Creek, a tributary of Odell Lake, is the only known spawning habitat used by this species throughout the system. Large numbers of kokanee salmon (Oncorhynchus nerka) also spawn in the same reach, superimposing their redds on those dug earlier by bull trout. After superimposition by kokanee, bull trout redds are virtually undetectable. The objective of the study was to assess the effect of kokanee redd superimposition on bull trout egg-to-fry survival. Due to uncertainty in the size of the Odell Lake bull trout population much of the study was conducted on bull trout and kokanee of the Metolius River system, a neiboring Deschutes sub-basin. Emergent fry traps were used, in combination with egg burial depth measurements, scour monitors, and gravel characterization to establish actual physical overlap between both species and degree of bull trout egg pocket disturbance caused by kokanee. Results indicate that most bull trout egg pockets are dug deeper than depths reached by spawning kokanee. Kokanee were found to be very superficial spawners in the streams studied. Bull trout fry emergence data suggest that kokanee redd superimposition does not affect egg-to-fry survival rates. Close