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• 8651. [Article] 2007 Oregon Chub Investigations Progress Reports 2007

  Abstract -- Oregon chub Oregonichthys crameri, small minnows endemic to the Willamette Valley, were federally listed as endangered under the Endangered Species Act in 1993. Factors implicated in the decline ...

  Citation × Citation Citation Abstract Copy Title: 2007 Oregon Chub Investigations Progress Reports 2007 Abstract -- Oregon chub Oregonichthys crameri, small minnows endemic to the Willamette Valley, were federally listed as endangered under the Endangered Species Act in 1993. Factors implicated in the decline of this species include changes in flow regimes and habitat characteristics resulting from the construction of flood control dams, revetments, channelization, diking, and the drainage of wetlands. The Oregon chub is further threatened by predation and competition by non-native species such as largemouth bass Micropterus salmoides, crappies Pomoxis sp., sunfishes Lepomis sp., bullheads Ameiurus sp., and western mosquitofish Gambusia affinis. We continued surveys initiated in 1991 in the Willamette River drainage to quantify the abundance of known Oregon chub populations, search for unknown populations, evaluate potential introduction sites, and monitor introduced populations as part of the implementation of the Oregon Chub Recovery Plan. We sampled a total of 70 sites in 2007. New populations of Oregon chub were discovered at Green Island in the lower McKenzie River and in the Muddy Creek drainage (Linn County). We confirmed the continued existence of Oregon chub at 34 locations. These included 23 naturally occurring and 11 introduced populations. We did not find Oregon chub at nine locations where they were collected on at least one occasion between 1991-2006. Nonnative fish were collected at most of these locations. We obtained abundance estimates of 18 naturally occurring populations and 11 introduced populations of Oregon chub located in the Middle Fork Willamette, Santiam, McKenzie, and Mid-Willamette drainages (Table 1). We introduced additional Oregon chub into the South Stayton Pond in the Santiam drainage and into Cheadle and Display Ponds in the Mid-Willamette drainage. The Oregon Chub Recovery Plan (U.S. Fish and Wildlife Service 1998) set recovery criteria for downlisting the species to “threatened” and for delisting the species. The criteria for downlisting the species are: 1) establish and manage 10 populations of at least 500 adult fish, 2) all of these populations must exhibit a stable or increasing trend for five years, and 3) at least three populations meeting criterion 1 and 2 must be located in each of the three recovery areas (Middle Fork Willamette River, Santiam River, and Mid-Willamette River tributaries). In 2007, there were 20 populations totaling 500 or more individuals (Table 1). Fifteen of these populations also met the second criteria. Of the 15 populations meeting criteria 1 and 2, eight were located in the Middle Fork Willamette drainage, four were located in the Mid-Willamette drainage, and three were located in the Santiam drainage. In 2007, we met the downlisting criteria. Findings to date indicate that Oregon chub remain at risk due to the loss of suitable habitat and the continued threats posed by the proliferation of non-native fishes, illegal water withdrawals, accelerated sedimentation, and potential chemical spills or careless pesticide applications. Their status has improved in recent years, resulting primarily from successful introductions and the discovery of previously undocumented populations. Title: 2007 Oregon Chub Investigations Progress Reports 2007 Abstract -- Oregon chub Oregonichthys crameri, small minnows endemic to the Willamette Valley, were federally listed as endangered under the Endangered Species Act in 1993. Factors implicated in the decline of this species include changes in flow regimes and habitat characteristics resulting from the construction of flood control dams, revetments, channelization, diking, and the drainage of wetlands. The Oregon chub is further threatened by predation and competition by non-native species such as largemouth bass Micropterus salmoides, crappies Pomoxis sp., sunfishes Lepomis sp., bullheads Ameiurus sp., and western mosquitofish Gambusia affinis. We continued surveys initiated in 1991 in the Willamette River drainage to quantify the abundance of known Oregon chub populations, search for unknown populations, evaluate potential introduction sites, and monitor introduced populations as part of the implementation of the Oregon Chub Recovery Plan. We sampled a total of 70 sites in 2007. New populations of Oregon chub were discovered at Green Island in the lower McKenzie River and in the Muddy Creek drainage (Linn County). We confirmed the continued existence of Oregon chub at 34 locations. These included 23 naturally occurring and 11 introduced populations. We did not find Oregon chub at nine locations where they were collected on at least one occasion between 1991-2006. Nonnative fish were collected at most of these locations. We obtained abundance estimates of 18 naturally occurring populations and 11 introduced populations of Oregon chub located in the Middle Fork Willamette, Santiam, McKenzie, and Mid-Willamette drainages (Table 1). We introduced additional Oregon chub into the South Stayton Pond in the Santiam drainage and into Cheadle and Display Ponds in the Mid-Willamette drainage. The Oregon Chub Recovery Plan (U.S. Fish and Wildlife Service 1998) set recovery criteria for downlisting the species to “threatened” and for delisting the species. The criteria for downlisting the species are: 1) establish and manage 10 populations of at least 500 adult fish, 2) all of these populations must exhibit a stable or increasing trend for five years, and 3) at least three populations meeting criterion 1 and 2 must be located in each of the three recovery areas (Middle Fork Willamette River, Santiam River, and Mid-Willamette River tributaries). In 2007, there were 20 populations totaling 500 or more individuals (Table 1). Fifteen of these populations also met the second criteria. Of the 15 populations meeting criteria 1 and 2, eight were located in the Middle Fork Willamette drainage, four were located in the Mid-Willamette drainage, and three were located in the Santiam drainage. In 2007, we met the downlisting criteria. Findings to date indicate that Oregon chub remain at risk due to the loss of suitable habitat and the continued threats posed by the proliferation of non-native fishes, illegal water withdrawals, accelerated sedimentation, and potential chemical spills or careless pesticide applications. Their status has improved in recent years, resulting primarily from successful introductions and the discovery of previously undocumented populations. Close

• 8652. [Article] Life history variability, habitat use, and migratory behavior of coastal cutthroat trout in the Salmon River, Oregon Annual Progress Report

  Abstract -- A previous study characterized a diversity of life history strategies of coastal cutthroat trout (Oncorhynchus clarki clarki) in Salmon River (Krentz 2007). In contrast to life history patterns ...

  Citation × Citation Citation Abstract Copy Title: Life history variability, habitat use, and migratory behavior of coastal cutthroat trout in the Salmon River, Oregon Annual Progress Report Abstract -- A previous study characterized a diversity of life history strategies of coastal cutthroat trout (Oncorhynchus clarki clarki) in Salmon River (Krentz 2007). In contrast to life history patterns in other Oregon estuaries (Giger 1972), cutthroat trout of all sizes resided for extended periods of time throughout the available channel habitats in Salmon River estuary. The estuarine resident population appeared to represent a significant portion of the migratory individuals, and included all age classes. Estuary growth was similar to that of their ocean migrant counterparts, and survival in the estuary was high. Because cutthroat were collected and marked primarily within the estuary (Krentz 2007), it is unclear what portion of the migrant population remained in the estuary relative to the ocean migrants, or whether the tagged group was representative of the anadromous populations. The current study was designed to track a representative sample of the downstream migrant population, and assess the relative success (survival) of the estuary and ocean migrants. Similar studies in the Columbia River documented directed and rapid migration through the estuary (Zydlewski et al. 2008, Hering et al. 2009). With one exception, cutthroat trout were not observed to rear in the estuary. In addition, many fish disappeared before reaching the ocean and few of the ocean migrants returned to the site of release. In this study we replicated the study design used in the Columbia River studies to allow comparison of estuary migration and rearing strategies between the two estuaries. The primary objective of our work in the Salmon River was to increase understanding of coastal cutthroat trout biology and the relationship between resident and migratory cutthroat. Study objectives were to: 1. Estimate the distribution and abundance of coastal cutthroat trout in the Salmon River watershed 2. Quantify the proportions of the cutthroat populations that are migratory, identify which individuals migrate and describe the timing of migration 3. Describe habitats used by anadromous migrants and characterize migration behavior within the Salmon River estuary 4. Estimate growth rate of estuary resident cutthroat 5. Estimate estuarine/marine survival of anadromous individuals and document return to estuary 6. Compare migratory patterns and survival with cutthroat in the Columbia River In this report, we will discuss migration patterns, habitat use, and growth. The study will be continued in 2010 to meet objectives (1), (2), and (6), and provide more detail to objectives (3), (4), and (5). Title: Life history variability, habitat use, and migratory behavior of coastal cutthroat trout in the Salmon River, Oregon Annual Progress Report Abstract -- A previous study characterized a diversity of life history strategies of coastal cutthroat trout (Oncorhynchus clarki clarki) in Salmon River (Krentz 2007). In contrast to life history patterns in other Oregon estuaries (Giger 1972), cutthroat trout of all sizes resided for extended periods of time throughout the available channel habitats in Salmon River estuary. The estuarine resident population appeared to represent a significant portion of the migratory individuals, and included all age classes. Estuary growth was similar to that of their ocean migrant counterparts, and survival in the estuary was high. Because cutthroat were collected and marked primarily within the estuary (Krentz 2007), it is unclear what portion of the migrant population remained in the estuary relative to the ocean migrants, or whether the tagged group was representative of the anadromous populations. The current study was designed to track a representative sample of the downstream migrant population, and assess the relative success (survival) of the estuary and ocean migrants. Similar studies in the Columbia River documented directed and rapid migration through the estuary (Zydlewski et al. 2008, Hering et al. 2009). With one exception, cutthroat trout were not observed to rear in the estuary. In addition, many fish disappeared before reaching the ocean and few of the ocean migrants returned to the site of release. In this study we replicated the study design used in the Columbia River studies to allow comparison of estuary migration and rearing strategies between the two estuaries. The primary objective of our work in the Salmon River was to increase understanding of coastal cutthroat trout biology and the relationship between resident and migratory cutthroat. Study objectives were to: 1. Estimate the distribution and abundance of coastal cutthroat trout in the Salmon River watershed 2. Quantify the proportions of the cutthroat populations that are migratory, identify which individuals migrate and describe the timing of migration 3. Describe habitats used by anadromous migrants and characterize migration behavior within the Salmon River estuary 4. Estimate growth rate of estuary resident cutthroat 5. Estimate estuarine/marine survival of anadromous individuals and document return to estuary 6. Compare migratory patterns and survival with cutthroat in the Columbia River In this report, we will discuss migration patterns, habitat use, and growth. The study will be continued in 2010 to meet objectives (1), (2), and (6), and provide more detail to objectives (3), (4), and (5). Close

• 8653. [Article] 2009 Foskett Spring Speckled Dace Investigations Progress Report 2009

  Abstract -- Speckled dace (Rhinichthys osculus) are geographically widespread throughout the western United States and occur in many isolated subbasins and interior drainages in south-central Oregon. The ...

  Citation × Citation Citation Abstract Copy Title: 2009 Foskett Spring Speckled Dace Investigations Progress Report 2009 Abstract -- Speckled dace (Rhinichthys osculus) are geographically widespread throughout the western United States and occur in many isolated subbasins and interior drainages in south-central Oregon. The Foskett Spring speckled dace (R. osculus ssp.) is represented by a single population that inhabits Foskett Spring (Figure 1) on the west side of Coleman Lake (Warner Lakes subbasin) in Lake County, Oregon. Foskett speckled dace was listed as threatened under the federal Endangered Species Act in 1985 (U.S. Fish and Wildlife Service 1985). The Foskett speckled dace became isolated in Foskett Spring at the end of the Pluvial period (~9,000-10,000 years ago). Foskett Spring is a natural spring that rises from a springhead pool, flows through a narrow spring brook into a series of shallow marshes, and then disappears into the soil of the normally dry Coleman Lake (Figure 1). A second population in Dace Spring, located approximately 0.8 kilometer south of Foskett Spring, was established from an introduction of 100 fish from Foskett Spring in 1979-1980 (Williams et al. 1990); however recent surveys have failed to document their continued existence at this location. In 1987, the U.S. Bureau of Land Management (BLM) acquired, through exchange, the 65 hectare parcel of land containing Foskett and Dace Springs. Both sites were fenced to exclude livestock. The Recovery Plan for the threatened and rare native fishes of the Warner Basin and Alkali Subbasin states that Foskett speckled dace will probably not be delisted in the near future because of its extremely isolated range and potential for degradation of its habitat from localized events (USFWS 1997). The primary recovery objective for this species is long-term persistence through preservation of its native ecosystem. The plan further states that the conservation and long term sustainability of this species will be met when: 1) long-term protection of its habitat, including spring source aquifers, springpools and outflow channels, and surrounding lands is assured; 2) long-term habitat management guidelines are developed and implemented to ensure the continued persistence of important habitat features and guidelines include monitoring of current habitat and investigation for and evaluation of new spring habitats; and 3) research into life-history, genetics, population trends, habitat use and preference, and other important parameters is conducted to assist in further developing or refining criteria 1) and 2), above. Actions needed to meet these criteria include protecting the fish population and its habitat, conserving genetic diversity of the fish population, ensuring adequate water supplies are available, monitoring of the dace population and habitat conditions, and evaluating long-term effects of climatic trends on recovery of this fish population. The purpose of this investigation was to determine the status of the federally listed Foskett Spring speckled dace and its habitat. This report updates a monitoring program initiated in 2005 by ODFW (Scheerer and Jacobs 2005) by providing results of monitoring conducted in 2009. Specifically, this monitoring program calls for biannual estimates of population abundance, assessments of distribution and demographic parameters and assessments of physical habitat conditions. Title: 2009 Foskett Spring Speckled Dace Investigations Progress Report 2009 Abstract -- Speckled dace (Rhinichthys osculus) are geographically widespread throughout the western United States and occur in many isolated subbasins and interior drainages in south-central Oregon. The Foskett Spring speckled dace (R. osculus ssp.) is represented by a single population that inhabits Foskett Spring (Figure 1) on the west side of Coleman Lake (Warner Lakes subbasin) in Lake County, Oregon. Foskett speckled dace was listed as threatened under the federal Endangered Species Act in 1985 (U.S. Fish and Wildlife Service 1985). The Foskett speckled dace became isolated in Foskett Spring at the end of the Pluvial period (~9,000-10,000 years ago). Foskett Spring is a natural spring that rises from a springhead pool, flows through a narrow spring brook into a series of shallow marshes, and then disappears into the soil of the normally dry Coleman Lake (Figure 1). A second population in Dace Spring, located approximately 0.8 kilometer south of Foskett Spring, was established from an introduction of 100 fish from Foskett Spring in 1979-1980 (Williams et al. 1990); however recent surveys have failed to document their continued existence at this location. In 1987, the U.S. Bureau of Land Management (BLM) acquired, through exchange, the 65 hectare parcel of land containing Foskett and Dace Springs. Both sites were fenced to exclude livestock. The Recovery Plan for the threatened and rare native fishes of the Warner Basin and Alkali Subbasin states that Foskett speckled dace will probably not be delisted in the near future because of its extremely isolated range and potential for degradation of its habitat from localized events (USFWS 1997). The primary recovery objective for this species is long-term persistence through preservation of its native ecosystem. The plan further states that the conservation and long term sustainability of this species will be met when: 1) long-term protection of its habitat, including spring source aquifers, springpools and outflow channels, and surrounding lands is assured; 2) long-term habitat management guidelines are developed and implemented to ensure the continued persistence of important habitat features and guidelines include monitoring of current habitat and investigation for and evaluation of new spring habitats; and 3) research into life-history, genetics, population trends, habitat use and preference, and other important parameters is conducted to assist in further developing or refining criteria 1) and 2), above. Actions needed to meet these criteria include protecting the fish population and its habitat, conserving genetic diversity of the fish population, ensuring adequate water supplies are available, monitoring of the dace population and habitat conditions, and evaluating long-term effects of climatic trends on recovery of this fish population. The purpose of this investigation was to determine the status of the federally listed Foskett Spring speckled dace and its habitat. This report updates a monitoring program initiated in 2005 by ODFW (Scheerer and Jacobs 2005) by providing results of monitoring conducted in 2009. Specifically, this monitoring program calls for biannual estimates of population abundance, assessments of distribution and demographic parameters and assessments of physical habitat conditions. Close

• 8654. [Article] Hood River Bull Trout Abundance, Life History, and Habitat Connectivity, 2007 Progress Reports 2007

  Abstract -- Hood River bull trout are thought to exist as two independent reproductive units (USFWS 2004), known as local populations (Rieman and McIntyre 1995). The Clear Branch local population is isolated ...

  Citation × Citation Citation Abstract Copy Title: Hood River Bull Trout Abundance, Life History, and Habitat Connectivity, 2007 Progress Reports 2007 Abstract -- Hood River bull trout are thought to exist as two independent reproductive units (USFWS 2004), known as local populations (Rieman and McIntyre 1995). The Clear Branch local population is isolated above Clear Branch Dam, which provides limited downstream fish passage during infrequent and sporadic periods of spill and no upstream passage. Bull trout in this population inhabit Laurance Lake Reservoir and tributaries upstream of Clear Branch Dam. The Hood River local population occurs in the mainstem Hood River and Middle Fork Hood River downstream of the Clear Branch Dam and a small number of adult bull trout migrate each year into the Hood River from the Columbia River (Figure 1). The status of both populations is extremely precarious. The Clear Branch population is at risk of a random extinction event due to low numbers, negative interactions with non-native smallmouth bass, isolation and limited spawning habitat (USFWS, 1998). The Hood River population also appears to be small and is threatened by passage barriers, unscreened irrigation systems, impaired water quality and periodic siltation of spawning substrate by glacial outbursts. Clear Branch bull trout spawn in Clear Branch and Pinnacle Creek. After rearing in these two natal streams for an unknown time period, most are believed to migrate downstream to Laurance Lake Reservoir. Clear Branch bull trout have been documented passing over the dam spillway during high water events (Pribyl et al. 1996) and may provide a recruitment source for the Hood River local population. Adult bull trout tagged at Powerdale Dam have been observed at Coe Branch irrigation diversion and in a trap at the base of Clear Branch dam. These fish may have been attempting to reach spawning areas located upstream of the dam. However, the success of bull trout migrating downstream via the spillway or the possibility of successfully navigating through the diversion network has never been determined. Depending on the water year, the Middle Fork Irrigation District (MFID) may not spill at all, or the timing of the spill may not coincide with the timing of downstream migration, which is currently unknown (East Fork Hood River and Middle Fork Hood River Watershed analysis). Smallmouth bass were discovered in Lake Laurance Reservoir in the 1990s. Creel surveys have shown that large adult bass are caught occasionally in the reservoir and schools of bass fry have been seen by district fish biologist (Rod French, ODFW, personal communication), suggesting that they are spawning successfully. This illegal introduction poses a potential threat to the Clear Branch bull trout population, but its magnitude is unknown because the bass population size and degree of interaction between the two species are unknown. Bull trout and smallmouth bass have significantly different temperature preferences and tolerances, with bull trout being one of the most sensitive coldwater species and bass being a warm water species. Lake Laurance, a relatively high-altitude reservoir at 890 m (2,920 feet), does not provide ideal bass habitat so these two species may have largely non-overlapping distributions or differing activity periods (Terry Shrader, ODFW warmwater fish biologist, personal communication). However, based on past reservoir temperature data (Berger et al. 2005), there are periods in the reservoir when there is potential for bull trout and bass interaction: periods when bull trout are susceptible to bass predation and when juvenile fish might compete for resources. Spawning activity of the Hood River local population has been observed in a few locations within the Middle Fork of Hood River (Figure 1). Although consistent and extensive spawning areas for this population are not known, some of the locations where juvenile rearing or potential bull trout redds have been observed include the Middle Fork Hood River and some of its tributaries: Bear Creek, Compass Creek and Coe Branch (USFWS 2004). However, Coe Branch, Compass Creek, and the Middle Fork are glacial streams with a high volume of sand and silt which may compromise spawning success. No bull trout spawning or rearing has been observed on the East and West Forks of Hood River. The Middle Fork and mainstem Hood River provide foraging, migration and overwintering habitat. Hood River bull trout are also known to migrate into the Columbia River. Two bull trout tagged at Powerdale Dam (RK 7.2 of mainstem Hood River) were recovered near Drano Lake in Washington State; and one was captured 11 kilometers downstream of the confluence of the Hood and Columbia Rivers (USFWS 2004). Every year (usually between May and July), adult bull trout, presumably migrating upstream from the Columbia River, are captured and anchor tagged at Powerdale Dam. Although some of these tagged fish have been observed upstream (one in Coe Branch and three below Clear Branch dam), the spawning destination of fluvial adults within the Hood River basin is largely unknown. Dispersing juvenile bull trout and migrating adults in this local population are threatened by flow diversions with inadequate screening and passage facilities. Several structures are suspected to impede upstream migration or entrain juvenile and adult bull trout into irrigation works (Pribyl et al. 1996, HRWG 1999). These structures include: the diversion at Clear Branch Dam (passage and screening), Coe Branch (passage and screening), and the Farmers Irrigation District diversion (screening) on the mainstem Hood River (HRWG 1999). However, little research has been conducted to assess the impacts of these structures on migrating bull trout. Beyond a general knowledge of the distribution of Hood River bull trout and the nature of anthropogenic factors that potentially restrict their life history and habitat connectivity, little is known about this recovery unit. Baseline information about adult abundance is lacking for both local populations, the potential of a source (Clear Branch) and sink (Hood River) relationship between the two local populations has not been explored, and the migratory life history of adult fish caught at Powerdale Dam is unknown. The degree to which irrigation and hydropower diversions hamper connectivity within the Hood River basin is also poorly understood. Migratory life histories have been viewed as key to species persistence (Rieman and McIntyre 1995; Dunham and Rieman 1999), and understanding movement patterns and associated habitat requirements are critical to maintaining those migratory forms (Muhlfeld and Morotz 2005; Hostettler 2005). Gaining this information is also critical to evaluating bull trout recovery in the Hood River Subbasin (Coccoli 2004). The Oregon Department of Fish and Wildlife (ODFW) initiated a study in 2006 to improve our understanding of the abundance, life history, and potential limiting factors of the bull trout in this recovery unit. This report describes findings for the first two years of the study (2006-2007). Specific study objectives for the first two years were: 1. Determine the migratory life history of Hood River bull trout and assess the potential impacts of flow diversions and two new falls on the Middle Fork Hood River (scoured by the November 2006 glacial outburst) on bull trout migrations. 2. Determine current distribution of bull trout reproduction and early rearing in historical and potential bull trout streams in the Hood River Subbasin. 3. Determine the juvenile and adult life history the Clear Branch local population and develop a statistically reliable and cost-effective protocol for monitoring the abundance of adult Clear Branch bull trout. 4. Assess the potential impact of smallmouth bass on bull trout in Laurance Lake Reservoir. Title: Hood River Bull Trout Abundance, Life History, and Habitat Connectivity, 2007 Progress Reports 2007 Abstract -- Hood River bull trout are thought to exist as two independent reproductive units (USFWS 2004), known as local populations (Rieman and McIntyre 1995). The Clear Branch local population is isolated above Clear Branch Dam, which provides limited downstream fish passage during infrequent and sporadic periods of spill and no upstream passage. Bull trout in this population inhabit Laurance Lake Reservoir and tributaries upstream of Clear Branch Dam. The Hood River local population occurs in the mainstem Hood River and Middle Fork Hood River downstream of the Clear Branch Dam and a small number of adult bull trout migrate each year into the Hood River from the Columbia River (Figure 1). The status of both populations is extremely precarious. The Clear Branch population is at risk of a random extinction event due to low numbers, negative interactions with non-native smallmouth bass, isolation and limited spawning habitat (USFWS, 1998). The Hood River population also appears to be small and is threatened by passage barriers, unscreened irrigation systems, impaired water quality and periodic siltation of spawning substrate by glacial outbursts. Clear Branch bull trout spawn in Clear Branch and Pinnacle Creek. After rearing in these two natal streams for an unknown time period, most are believed to migrate downstream to Laurance Lake Reservoir. Clear Branch bull trout have been documented passing over the dam spillway during high water events (Pribyl et al. 1996) and may provide a recruitment source for the Hood River local population. Adult bull trout tagged at Powerdale Dam have been observed at Coe Branch irrigation diversion and in a trap at the base of Clear Branch dam. These fish may have been attempting to reach spawning areas located upstream of the dam. However, the success of bull trout migrating downstream via the spillway or the possibility of successfully navigating through the diversion network has never been determined. Depending on the water year, the Middle Fork Irrigation District (MFID) may not spill at all, or the timing of the spill may not coincide with the timing of downstream migration, which is currently unknown (East Fork Hood River and Middle Fork Hood River Watershed analysis). Smallmouth bass were discovered in Lake Laurance Reservoir in the 1990s. Creel surveys have shown that large adult bass are caught occasionally in the reservoir and schools of bass fry have been seen by district fish biologist (Rod French, ODFW, personal communication), suggesting that they are spawning successfully. This illegal introduction poses a potential threat to the Clear Branch bull trout population, but its magnitude is unknown because the bass population size and degree of interaction between the two species are unknown. Bull trout and smallmouth bass have significantly different temperature preferences and tolerances, with bull trout being one of the most sensitive coldwater species and bass being a warm water species. Lake Laurance, a relatively high-altitude reservoir at 890 m (2,920 feet), does not provide ideal bass habitat so these two species may have largely non-overlapping distributions or differing activity periods (Terry Shrader, ODFW warmwater fish biologist, personal communication). However, based on past reservoir temperature data (Berger et al. 2005), there are periods in the reservoir when there is potential for bull trout and bass interaction: periods when bull trout are susceptible to bass predation and when juvenile fish might compete for resources. Spawning activity of the Hood River local population has been observed in a few locations within the Middle Fork of Hood River (Figure 1). Although consistent and extensive spawning areas for this population are not known, some of the locations where juvenile rearing or potential bull trout redds have been observed include the Middle Fork Hood River and some of its tributaries: Bear Creek, Compass Creek and Coe Branch (USFWS 2004). However, Coe Branch, Compass Creek, and the Middle Fork are glacial streams with a high volume of sand and silt which may compromise spawning success. No bull trout spawning or rearing has been observed on the East and West Forks of Hood River. The Middle Fork and mainstem Hood River provide foraging, migration and overwintering habitat. Hood River bull trout are also known to migrate into the Columbia River. Two bull trout tagged at Powerdale Dam (RK 7.2 of mainstem Hood River) were recovered near Drano Lake in Washington State; and one was captured 11 kilometers downstream of the confluence of the Hood and Columbia Rivers (USFWS 2004). Every year (usually between May and July), adult bull trout, presumably migrating upstream from the Columbia River, are captured and anchor tagged at Powerdale Dam. Although some of these tagged fish have been observed upstream (one in Coe Branch and three below Clear Branch dam), the spawning destination of fluvial adults within the Hood River basin is largely unknown. Dispersing juvenile bull trout and migrating adults in this local population are threatened by flow diversions with inadequate screening and passage facilities. Several structures are suspected to impede upstream migration or entrain juvenile and adult bull trout into irrigation works (Pribyl et al. 1996, HRWG 1999). These structures include: the diversion at Clear Branch Dam (passage and screening), Coe Branch (passage and screening), and the Farmers Irrigation District diversion (screening) on the mainstem Hood River (HRWG 1999). However, little research has been conducted to assess the impacts of these structures on migrating bull trout. Beyond a general knowledge of the distribution of Hood River bull trout and the nature of anthropogenic factors that potentially restrict their life history and habitat connectivity, little is known about this recovery unit. Baseline information about adult abundance is lacking for both local populations, the potential of a source (Clear Branch) and sink (Hood River) relationship between the two local populations has not been explored, and the migratory life history of adult fish caught at Powerdale Dam is unknown. The degree to which irrigation and hydropower diversions hamper connectivity within the Hood River basin is also poorly understood. Migratory life histories have been viewed as key to species persistence (Rieman and McIntyre 1995; Dunham and Rieman 1999), and understanding movement patterns and associated habitat requirements are critical to maintaining those migratory forms (Muhlfeld and Morotz 2005; Hostettler 2005). Gaining this information is also critical to evaluating bull trout recovery in the Hood River Subbasin (Coccoli 2004). The Oregon Department of Fish and Wildlife (ODFW) initiated a study in 2006 to improve our understanding of the abundance, life history, and potential limiting factors of the bull trout in this recovery unit. This report describes findings for the first two years of the study (2006-2007). Specific study objectives for the first two years were: 1. Determine the migratory life history of Hood River bull trout and assess the potential impacts of flow diversions and two new falls on the Middle Fork Hood River (scoured by the November 2006 glacial outburst) on bull trout migrations. 2. Determine current distribution of bull trout reproduction and early rearing in historical and potential bull trout streams in the Hood River Subbasin. 3. Determine the juvenile and adult life history the Clear Branch local population and develop a statistically reliable and cost-effective protocol for monitoring the abundance of adult Clear Branch bull trout. 4. Assess the potential impact of smallmouth bass on bull trout in Laurance Lake Reservoir. Close

• 8655. [Article] Population Assessment of Lahontan Cutthroat Trout, 2005 Progress Report 2006

  Abstract -- Five of the six native Lahontan cutthroat trout (Oncorhynchus clarki henshawi) populations in Oregon exist in the Coyote Lakes basin of southeast Harney County (ODFW 2005). The major drainage's ...

  Citation × Citation Citation Abstract Copy Title: Population Assessment of Lahontan Cutthroat Trout, 2005 Progress Report 2006 Abstract -- Five of the six native Lahontan cutthroat trout (Oncorhynchus clarki henshawi) populations in Oregon exist in the Coyote Lakes basin of southeast Harney County (ODFW 2005). The major drainage's in the Coyote Lakes Basin are Willow and Whitehorse Creeks. Both drainage's originate on the north slope of Trout Creek Mountain, terminate in the dry Coyote lake bed and are currently isolated from each other or any other basin. Populations of Lahontan cutthroat in Willow and Whitehorse Creeks have been protected under the ESA as a threatened species since 1991 and are also listed as threatened under State of Oregon statute (Hanson et al.1993). Along with changes in management and land use activities, the federal recovery plan for Lahontan cutthroat trout requires the assessment of habitat conditions and population abundance at five year intervals (Coffin and Cowan 1995). Population monitoring of cutthroat in Willow and Whitehorse creeks was initiated in 1985 and has occurred on a five year interval since then (Jones et al. 1998, ODFW Aquatic Inventory Project unpublished data). The goals of this project was to continue population monitoring by obtaining an estimate of Lahontan cutthroat trout in Willow Creek and Whitehorse Creek, and to test the application of the EMAP sampling design (Stevens and Olsen 2004) to obtain this estimate. Additionally, we determined distribution of cutthroat trout in tributaries where presence was suspected but not verified, and monitored distributions of the Antelope Creek populations. Title: Population Assessment of Lahontan Cutthroat Trout, 2005 Progress Report 2006 Abstract -- Five of the six native Lahontan cutthroat trout (Oncorhynchus clarki henshawi) populations in Oregon exist in the Coyote Lakes basin of southeast Harney County (ODFW 2005). The major drainage's in the Coyote Lakes Basin are Willow and Whitehorse Creeks. Both drainage's originate on the north slope of Trout Creek Mountain, terminate in the dry Coyote lake bed and are currently isolated from each other or any other basin. Populations of Lahontan cutthroat in Willow and Whitehorse Creeks have been protected under the ESA as a threatened species since 1991 and are also listed as threatened under State of Oregon statute (Hanson et al.1993). Along with changes in management and land use activities, the federal recovery plan for Lahontan cutthroat trout requires the assessment of habitat conditions and population abundance at five year intervals (Coffin and Cowan 1995). Population monitoring of cutthroat in Willow and Whitehorse creeks was initiated in 1985 and has occurred on a five year interval since then (Jones et al. 1998, ODFW Aquatic Inventory Project unpublished data). The goals of this project was to continue population monitoring by obtaining an estimate of Lahontan cutthroat trout in Willow Creek and Whitehorse Creek, and to test the application of the EMAP sampling design (Stevens and Olsen 2004) to obtain this estimate. Additionally, we determined distribution of cutthroat trout in tributaries where presence was suspected but not verified, and monitored distributions of the Antelope Creek populations. Close

• 8656. [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

• 8657. [Article] 2006 OPRD- Oregon Chub Population Monitoring on Oregon State Park Lands Progress Reports 2006

  Abstract -- Oregon chub Oregonichthys crameri, small minnows endemic to the Willamette River drainage of western Oregon (Markle et al. 1991), were federally listed as endangered under the Endangered Species ...

  Citation × Citation Citation Abstract Copy Title: 2006 OPRD- Oregon Chub Population Monitoring on Oregon State Park Lands Progress Reports 2006 Abstract -- Oregon chub Oregonichthys crameri, small minnows endemic to the Willamette River drainage of western Oregon (Markle et al. 1991), were federally listed as endangered under the Endangered Species Act in 1993 (Markle and Pearsons 1990; Rhew 1993). This species was formerly distributed throughout the Willamette River Valley (Snyder 1908) in off-channel habitats such as beaver ponds, oxbows, backwater sloughs, and flooded marshes. These habitats usually have little or no water flow, have silty and organic substrate, and have an abundance of aquatic vegetation and cover for hiding and spawning. In the last 100 years, off-channel habitats have disappeared because of changes in seasonal flows and habitat characteristics resulting from the construction of flood control dams, revetments, channelization, diking, and the drainage of wetlands for bottomland agriculture. This loss of habitat combined with the introduction of non-native species to the Willamette Valley resulted in a restricted distribution and sharp decline in Oregon chub abundance. The Oregon chub is further threatened by predation and competition by non-native species such as largemouth bass Micropterus salmoides, crappies Pomoxis sp., sunfishes Lepomis sp., bullheads Ameiurus sp., and western mosquitofish Gambusia affinis. To evaluate abundance and distribution of Oregon chub populations, the Oregon Department of Fish and Wildlife has conducted surveys since 1991. Information collected also included the presence of non-native and native species, the characteristics of Oregon chub habitats, the characteristics of potential introduction sites, evaluation of Oregon chub introductions, and life history characteristics (Scheerer 2002, Scheerer and McDonald 2003, Scheerer et al. 2006). The Oregon Chub Recovery Plan (U.S. Fish and Wildlife Service 1998) set recovery criteria for downlisting the species to “threatened” and for delisting the species. The criteria for downlisting the species are: 1) establish and manage 10 populations of at least 500 adult fish, 2) all of these populations must exhibit a stable or increasing trend for five years, and 3) at least three populations meeting criterion 1 and 2 must be located in each of the three recovery areas (Middle Fork Willamette River, Santiam River, and Mid-Willamette River tributaries). In 2006, there were 18 populations totaling 500 or more individuals. Thirteen of these populations met the above criteria. Eight were located in the Middle Fork Willamette drainage, three were located in the Mid-Willamette drainage, and two were located in the Santiam drainage (Scheerer et al. 2006). The status of this species has improved substantially over the past decade and with the addition of a single Santiam population, the downlisting criteria will be met (Scheerer et al. 2006). Title: 2006 OPRD- Oregon Chub Population Monitoring on Oregon State Park Lands Progress Reports 2006 Abstract -- Oregon chub Oregonichthys crameri, small minnows endemic to the Willamette River drainage of western Oregon (Markle et al. 1991), were federally listed as endangered under the Endangered Species Act in 1993 (Markle and Pearsons 1990; Rhew 1993). This species was formerly distributed throughout the Willamette River Valley (Snyder 1908) in off-channel habitats such as beaver ponds, oxbows, backwater sloughs, and flooded marshes. These habitats usually have little or no water flow, have silty and organic substrate, and have an abundance of aquatic vegetation and cover for hiding and spawning. In the last 100 years, off-channel habitats have disappeared because of changes in seasonal flows and habitat characteristics resulting from the construction of flood control dams, revetments, channelization, diking, and the drainage of wetlands for bottomland agriculture. This loss of habitat combined with the introduction of non-native species to the Willamette Valley resulted in a restricted distribution and sharp decline in Oregon chub abundance. The Oregon chub is further threatened by predation and competition by non-native species such as largemouth bass Micropterus salmoides, crappies Pomoxis sp., sunfishes Lepomis sp., bullheads Ameiurus sp., and western mosquitofish Gambusia affinis. To evaluate abundance and distribution of Oregon chub populations, the Oregon Department of Fish and Wildlife has conducted surveys since 1991. Information collected also included the presence of non-native and native species, the characteristics of Oregon chub habitats, the characteristics of potential introduction sites, evaluation of Oregon chub introductions, and life history characteristics (Scheerer 2002, Scheerer and McDonald 2003, Scheerer et al. 2006). The Oregon Chub Recovery Plan (U.S. Fish and Wildlife Service 1998) set recovery criteria for downlisting the species to “threatened” and for delisting the species. The criteria for downlisting the species are: 1) establish and manage 10 populations of at least 500 adult fish, 2) all of these populations must exhibit a stable or increasing trend for five years, and 3) at least three populations meeting criterion 1 and 2 must be located in each of the three recovery areas (Middle Fork Willamette River, Santiam River, and Mid-Willamette River tributaries). In 2006, there were 18 populations totaling 500 or more individuals. Thirteen of these populations met the above criteria. Eight were located in the Middle Fork Willamette drainage, three were located in the Mid-Willamette drainage, and two were located in the Santiam drainage (Scheerer et al. 2006). The status of this species has improved substantially over the past decade and with the addition of a single Santiam population, the downlisting criteria will be met (Scheerer et al. 2006). Close

• 8658. [Article] Warner Valley Fish Investigations- Warner Suckers Progress Reports 2008

  Abstract -- The Warner sucker (Catostomus warnerensis) is endemic to the Warner Valley, an endorheic subbasin of the Great Basin in southeastern Oregon and northwestern Nevada. This species was historically ...

  Citation × Citation Citation Abstract Copy Title: Warner Valley Fish Investigations- Warner Suckers Progress Reports 2008 Abstract -- The Warner sucker (Catostomus warnerensis) is endemic to the Warner Valley, an endorheic subbasin of the Great Basin in southeastern Oregon and northwestern Nevada. This species was historically abundant and its historical range includes three permanent lakes (Hart, Crump, and Pelican), several ephemeral lakes, a network of sloughs and diversion canals, and three major tributary drainages (Honey, Deep, and Twentymile Creeks). Warner sucker abundance and distribution has declined over the past century and it was federally listed as threatened in 1985 due to habitat fragmentation and threats posed by the proliferation of piscivorous non-native game fishes (U.S. Fish and Wildlife Service 1985). The Warner Valley is a northeast-southwest trending endorheic basin which extends approximately 90 km (Figure 1). The elevation of the valley floor is approximately 1,370 m and the basin is bound by fault block escarpments, the Warner Rim on the west and Hart Mountain and Poker Jim Ridge on the east. The Warner basin was formed during the middle Tertiary and late Quaternary geologic periods as a result of volcanic and tectonic activity (Baldwin 1976). Abundant precipitation during the Pleistocene Epoch resulted in the formation of Pluvial Lake Warner (Hubbs and Miller 1948). At its maximum extent approximately 11,000 years ago, the lake reached approximately 100 m in depth and 1,300 km2 in area (Snyder et al. 1964, Weide 1975). In 2008, precipitation and snow pack were near average and Hart and Crump Lakes never filled completely. In 2007, Crump Lake water levels were very low with less than a quarter of the surface area wetted during the winter. Both lakes have been watered continuously since 1993. The Warner sucker inhabits the lakes and low gradient stream reaches of the Warner Valley. Two life history forms are present that comprise the metapopulation of Warner suckers: lake and stream morphs. The lake suckers are lacustrine adfluvial or potamodromous fish which normally spawn in the streams. However, upstream migration may be blocked by low stream flows during dry water years or by irrigation diversion dams and spawning may occur in nearshore areas of the lakes (White et al. 1990). The stream suckers inhabit and spawn in the three major tributary drainages (Honey, Deep, and Twentymile Creeks). Large lake-dwelling populations of introduced fishes in the lakes likely reduce sucker recruitment by predation on young suckers (U.S. Fish and Wildlife Service 1998). The Recovery Plan for the Threatened and Rare Native Fishes of the Warner Basin and Alkali Subbasin (U.S. Fish and Wildlife Service 1998) sets recovery criteria for delisting the species. These criteria require that (1) a self-sustaining metapopulation is distributed throughout the Twentymile, Honey, and Deep Creek (below the falls) drainages, and in Pelican, Crump, and Hart Lakes, (2) passage is restored within and among the Twentymile, Honey, and Deep Creek (below the falls) drainages so that the individual populations of Warner suckers can function as a metapopulation, and (3) no threats exist that would likely threaten the survival of the species over a significant portion of its range. In 2008, we conducted investigations in Hart and Crump Lakes to quantify the abundance and distribution of Warner suckers, to search for evidence of recent recruitment, and to estimate sucker abundance relative to nonnative fish abundance. In addition we investigated growth and movement patterns. We used Passive Integrated Transponder (PIT) tagged suckers to determine growth rates and movements, tracked radio-tagged suckers to document seasonal spawning migrations, fished a screw trap in Twelvemile Creek to monitor downstream movements, and operated a trap at the Dyke diversion dam on Twentymile Creek to monitor upstream movements. Title: Warner Valley Fish Investigations- Warner Suckers Progress Reports 2008 Abstract -- The Warner sucker (Catostomus warnerensis) is endemic to the Warner Valley, an endorheic subbasin of the Great Basin in southeastern Oregon and northwestern Nevada. This species was historically abundant and its historical range includes three permanent lakes (Hart, Crump, and Pelican), several ephemeral lakes, a network of sloughs and diversion canals, and three major tributary drainages (Honey, Deep, and Twentymile Creeks). Warner sucker abundance and distribution has declined over the past century and it was federally listed as threatened in 1985 due to habitat fragmentation and threats posed by the proliferation of piscivorous non-native game fishes (U.S. Fish and Wildlife Service 1985). The Warner Valley is a northeast-southwest trending endorheic basin which extends approximately 90 km (Figure 1). The elevation of the valley floor is approximately 1,370 m and the basin is bound by fault block escarpments, the Warner Rim on the west and Hart Mountain and Poker Jim Ridge on the east. The Warner basin was formed during the middle Tertiary and late Quaternary geologic periods as a result of volcanic and tectonic activity (Baldwin 1976). Abundant precipitation during the Pleistocene Epoch resulted in the formation of Pluvial Lake Warner (Hubbs and Miller 1948). At its maximum extent approximately 11,000 years ago, the lake reached approximately 100 m in depth and 1,300 km2 in area (Snyder et al. 1964, Weide 1975). In 2008, precipitation and snow pack were near average and Hart and Crump Lakes never filled completely. In 2007, Crump Lake water levels were very low with less than a quarter of the surface area wetted during the winter. Both lakes have been watered continuously since 1993. The Warner sucker inhabits the lakes and low gradient stream reaches of the Warner Valley. Two life history forms are present that comprise the metapopulation of Warner suckers: lake and stream morphs. The lake suckers are lacustrine adfluvial or potamodromous fish which normally spawn in the streams. However, upstream migration may be blocked by low stream flows during dry water years or by irrigation diversion dams and spawning may occur in nearshore areas of the lakes (White et al. 1990). The stream suckers inhabit and spawn in the three major tributary drainages (Honey, Deep, and Twentymile Creeks). Large lake-dwelling populations of introduced fishes in the lakes likely reduce sucker recruitment by predation on young suckers (U.S. Fish and Wildlife Service 1998). The Recovery Plan for the Threatened and Rare Native Fishes of the Warner Basin and Alkali Subbasin (U.S. Fish and Wildlife Service 1998) sets recovery criteria for delisting the species. These criteria require that (1) a self-sustaining metapopulation is distributed throughout the Twentymile, Honey, and Deep Creek (below the falls) drainages, and in Pelican, Crump, and Hart Lakes, (2) passage is restored within and among the Twentymile, Honey, and Deep Creek (below the falls) drainages so that the individual populations of Warner suckers can function as a metapopulation, and (3) no threats exist that would likely threaten the survival of the species over a significant portion of its range. In 2008, we conducted investigations in Hart and Crump Lakes to quantify the abundance and distribution of Warner suckers, to search for evidence of recent recruitment, and to estimate sucker abundance relative to nonnative fish abundance. In addition we investigated growth and movement patterns. We used Passive Integrated Transponder (PIT) tagged suckers to determine growth rates and movements, tracked radio-tagged suckers to document seasonal spawning migrations, fished a screw trap in Twelvemile Creek to monitor downstream movements, and operated a trap at the Dyke diversion dam on Twentymile Creek to monitor upstream movements. Close

• 8659. [Article] Information Report 2018-01; Winter Habitat Condition of Oregon Coast Coho Salmon Populations, 2007-2014

  Abstract -- In this report we summarize results of eight years (2007-2014) of habitat surveys for 18 independent Oregon coast coho salmon populations across four monitoring strata (North Coast, Mid Coast, ...

  Citation × Citation Citation Abstract Copy Title: Information Report 2018-01; Winter Habitat Condition of Oregon Coast Coho Salmon Populations, 2007-2014 Abstract -- In this report we summarize results of eight years (2007-2014) of habitat surveys for 18 independent Oregon coast coho salmon populations across four monitoring strata (North Coast, Mid Coast, MidSouth Coast, and Umpqua) in the Oregon Coast Coho Salmon Evolutionary Significant Unit (ESU). We also sampled dependent population blocks across three monitoring strata (North Coast, Mid Coast, and Mid-South Coast). Using a spatially balanced site selection process (Generalized Random Tessellation Stratification; GRTS) we surveyed 451 unique sites within the range of coho salmon spawning or rearing. With the exception of the 2014 survey year, habitat data were collected during winter conditions (February – March). Habitat sampled in 2014 occurred within the summer field season (June – September). We used a Habitat Limiting Factors Model (HLFM) to estimate habitat capacity for winter coho parr and the HabRate model to assess habitat quality for each surveyed stream reach. HLFM estimates were expanded based on the total coho distribution in each population. Based on the habitat data the HLFM predicted the Floras population could support the highest density of juvenile coho (1568 parr/km), while the streams in the Siltcoos watershed could support the least (290 parr/km). At the ESU-level, there was no detectable change of high quality rearing habitat (= 1850 parr/km) when compared to previous studies, but changes were observed among populations over the course of these survey years. We compared individual habitat metrics across populations, land use, geology, and between independent and dependent populations. While no significant differences were observed between independent and dependent populations, differences in habitat metrics were detected among individual populations, land use types, and geologies. In addition, we detected a difference in reproductive habitat quality (spawning and emergence) between both populations and land use types. Title: Information Report 2018-01; Winter Habitat Condition of Oregon Coast Coho Salmon Populations, 2007-2014 Abstract -- In this report we summarize results of eight years (2007-2014) of habitat surveys for 18 independent Oregon coast coho salmon populations across four monitoring strata (North Coast, Mid Coast, MidSouth Coast, and Umpqua) in the Oregon Coast Coho Salmon Evolutionary Significant Unit (ESU). We also sampled dependent population blocks across three monitoring strata (North Coast, Mid Coast, and Mid-South Coast). Using a spatially balanced site selection process (Generalized Random Tessellation Stratification; GRTS) we surveyed 451 unique sites within the range of coho salmon spawning or rearing. With the exception of the 2014 survey year, habitat data were collected during winter conditions (February – March). Habitat sampled in 2014 occurred within the summer field season (June – September). We used a Habitat Limiting Factors Model (HLFM) to estimate habitat capacity for winter coho parr and the HabRate model to assess habitat quality for each surveyed stream reach. HLFM estimates were expanded based on the total coho distribution in each population. Based on the habitat data the HLFM predicted the Floras population could support the highest density of juvenile coho (1568 parr/km), while the streams in the Siltcoos watershed could support the least (290 parr/km). At the ESU-level, there was no detectable change of high quality rearing habitat (= 1850 parr/km) when compared to previous studies, but changes were observed among populations over the course of these survey years. We compared individual habitat metrics across populations, land use, geology, and between independent and dependent populations. While no significant differences were observed between independent and dependent populations, differences in habitat metrics were detected among individual populations, land use types, and geologies. In addition, we detected a difference in reproductive habitat quality (spawning and emergence) between both populations and land use types. Close

• 8660. [Article] Information Report 2018-04, Smolt Abundance Estimates for the Oregon Coast Coho Evolutionarily Significant Unit

  Abstract -- Analysis of Coho Salmon (Oncorhynchus kisutch) smolt abundance can provide insight on freshwater habitat capacity and factors affecting salmonid persistence. To explore these relationships ...

  Citation × Citation Citation Abstract Copy Title: Information Report 2018-04, Smolt Abundance Estimates for the Oregon Coast Coho Evolutionarily Significant Unit Abstract -- Analysis of Coho Salmon (Oncorhynchus kisutch) smolt abundance can provide insight on freshwater habitat capacity and factors affecting salmonid persistence. To explore these relationships we linked multi-year data sets of overwinter survival rates from three streams within the Oregon Coast Coho Evolutionarily Significant Unit (OCC) to summer parr abundance estimates from calibrated OCC-wide snorkel survey counts to estimate annual Coho Salmon smolt abundance from 2000-2017. Smolt abundance estimates ranged from a low of 0.9 million in 2000 to a high of 4.1 million in 2013 within the OCC. Accuracy of the smolt abundance estimates was tested using two datasets: (i) adult abundance modeled from the corresponding smolt abundance estimate was compared with adult abundance derived empirically from spawning ground surveys and (ii) our smolt abundance estimates were compared with smolt abundance estimates from trapping efforts in select basins within the OCC. Adult abundance modeled from smolt abundance estimates was highly correlated with adult abundance from spawning ground surveys (r = 0.88, p < 0.001) and smolt abundance estimates correlated with abundance from smolt trapping efforts (r = 0.81, p <0.001). Graphical relationships between smolt abundance and parental abundance suggest that freshwater productivity may be limited in the OCC by density dependent processes at spawner levels observed since 1998. Additionally, smolt abundance estimates have potential use as a variable in adult forecast models and could be used to assess trends in freshwater productivity and to probe factors of density dependence. Title: Information Report 2018-04, Smolt Abundance Estimates for the Oregon Coast Coho Evolutionarily Significant Unit Abstract -- Analysis of Coho Salmon (Oncorhynchus kisutch) smolt abundance can provide insight on freshwater habitat capacity and factors affecting salmonid persistence. To explore these relationships we linked multi-year data sets of overwinter survival rates from three streams within the Oregon Coast Coho Evolutionarily Significant Unit (OCC) to summer parr abundance estimates from calibrated OCC-wide snorkel survey counts to estimate annual Coho Salmon smolt abundance from 2000-2017. Smolt abundance estimates ranged from a low of 0.9 million in 2000 to a high of 4.1 million in 2013 within the OCC. Accuracy of the smolt abundance estimates was tested using two datasets: (i) adult abundance modeled from the corresponding smolt abundance estimate was compared with adult abundance derived empirically from spawning ground surveys and (ii) our smolt abundance estimates were compared with smolt abundance estimates from trapping efforts in select basins within the OCC. Adult abundance modeled from smolt abundance estimates was highly correlated with adult abundance from spawning ground surveys (r = 0.88, p < 0.001) and smolt abundance estimates correlated with abundance from smolt trapping efforts (r = 0.81, p <0.001). Graphical relationships between smolt abundance and parental abundance suggest that freshwater productivity may be limited in the OCC by density dependent processes at spawner levels observed since 1998. Additionally, smolt abundance estimates have potential use as a variable in adult forecast models and could be used to assess trends in freshwater productivity and to probe factors of density dependence. Close