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• 1. [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

• 2. [Article] 2011 Warner Sucker Investigations (Honey Creek) Progress Reports 2011

  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. Historically, this species ...

  Citation × Citation Citation Abstract Copy Title: 2011 Warner Sucker Investigations (Honey Creek) Progress Reports 2011 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. Historically, this species was abundant and its range included 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) (U.S. Fish and Wildlife Service 1985). 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 sucker inhabits the lakes and low gradient stream reaches of the Warner Valley. The Warner sucker metapopulation is comprised of both lake and stream life history morphs. The lake suckers are lacustrine adfluvial or potamodromous fish that normally spawn in the streams. However, upstream migration may be blocked by low stream flows during low water years or by irrigation diversion dams. When this happens, spawning may occur in nearshore areas of the lakes (White et al. 1990). Large lake-dwelling populations of introduced fishes likely reduce recruitment by preying on young suckers (U.S. Fish and Wildlife Service 1998). The stream suckers inhabit and spawn in Honey, Deep, and Twentymile Creeks. 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. To inform progress towards the first criteria, our objectives in 2011 were: 1) obtain a population estimate for suckers in the Honey Creek drainage and describe their current distribution and 2) describe the association between the distribution of suckers and habitat variables in Honey Creek. In addition, we obtained a population estimate of suckers at the Summer Lake Wildlife Management Area (WMA), where a self-sustaining population became established after a fish salvage from Hart Lake in 1991 when the lakes desiccated. Title: 2011 Warner Sucker Investigations (Honey Creek) Progress Reports 2011 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. Historically, this species was abundant and its range included 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) (U.S. Fish and Wildlife Service 1985). 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 sucker inhabits the lakes and low gradient stream reaches of the Warner Valley. The Warner sucker metapopulation is comprised of both lake and stream life history morphs. The lake suckers are lacustrine adfluvial or potamodromous fish that normally spawn in the streams. However, upstream migration may be blocked by low stream flows during low water years or by irrigation diversion dams. When this happens, spawning may occur in nearshore areas of the lakes (White et al. 1990). Large lake-dwelling populations of introduced fishes likely reduce recruitment by preying on young suckers (U.S. Fish and Wildlife Service 1998). The stream suckers inhabit and spawn in Honey, Deep, and Twentymile Creeks. 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. To inform progress towards the first criteria, our objectives in 2011 were: 1) obtain a population estimate for suckers in the Honey Creek drainage and describe their current distribution and 2) describe the association between the distribution of suckers and habitat variables in Honey Creek. In addition, we obtained a population estimate of suckers at the Summer Lake Wildlife Management Area (WMA), where a self-sustaining population became established after a fish salvage from Hart Lake in 1991 when the lakes desiccated. Close

• 3. [Article] Warner Sucker Investigations (2009)

  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. Historically, this species ...

  Citation × Citation Citation Abstract Copy Title: Warner Sucker Investigations (2009) 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. Historically, this species was abundant and its range included 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) (U.S. Fish and Wildlife Service 1985). 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 sucker inhabits the lakes and low gradient stream reaches of the Warner Valley. The Warner sucker metapopulation is comprised of both lake and stream life history morphs. The lake suckers are lacustrine adfluvial or potamodromous fish that normally spawn in the streams. However, upstream migration may be blocked by low stream flows during low water years or by irrigation diversion dams. When this happens, spawning may occur in nearshore areas of the lakes (White et al. 1990). Large lake-dwelling populations of introduced fishes likely reduce recruitment by preying on young suckers (U.S. Fish and Wildlife Service 1998). The stream suckers inhabit and spawn in Honey, Deep, and Twentymile Creeks. 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. Objectives of our 2009 investigations included: 1) obtain a mark-recapture population estimate for suckers in the Twentymile Creek drainage and describe their current distribution, 2) describe associations between the distribution of suckers and habitat variables in Twentymile Creek, 3) evaluate a non-lethal ageing technique, 4) track radiotagged lake suckers (tagged in 2008) in Hart and Crump Lakes to assess spring movement patterns, 5) track spring spawning movements of lake suckers across a PIT-tag antenna installed at the mouth of Honey Creek, 6) test the feasibility of trapping larval suckers near the mouth of Honey Creek using larval drift nets and light traps to describe the relative abundance and timing of larval sucker movements, and 7) obtain a mark-recapture population estimate of suckers at the Summer Lake Wildlife Management Area (WMA), where a self-sustaining population became established after a fish salvage from Hart Lake during the 1991 drought. Title: Warner Sucker Investigations (2009) 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. Historically, this species was abundant and its range included 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) (U.S. Fish and Wildlife Service 1985). 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 sucker inhabits the lakes and low gradient stream reaches of the Warner Valley. The Warner sucker metapopulation is comprised of both lake and stream life history morphs. The lake suckers are lacustrine adfluvial or potamodromous fish that normally spawn in the streams. However, upstream migration may be blocked by low stream flows during low water years or by irrigation diversion dams. When this happens, spawning may occur in nearshore areas of the lakes (White et al. 1990). Large lake-dwelling populations of introduced fishes likely reduce recruitment by preying on young suckers (U.S. Fish and Wildlife Service 1998). The stream suckers inhabit and spawn in Honey, Deep, and Twentymile Creeks. 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. Objectives of our 2009 investigations included: 1) obtain a mark-recapture population estimate for suckers in the Twentymile Creek drainage and describe their current distribution, 2) describe associations between the distribution of suckers and habitat variables in Twentymile Creek, 3) evaluate a non-lethal ageing technique, 4) track radiotagged lake suckers (tagged in 2008) in Hart and Crump Lakes to assess spring movement patterns, 5) track spring spawning movements of lake suckers across a PIT-tag antenna installed at the mouth of Honey Creek, 6) test the feasibility of trapping larval suckers near the mouth of Honey Creek using larval drift nets and light traps to describe the relative abundance and timing of larval sucker movements, and 7) obtain a mark-recapture population estimate of suckers at the Summer Lake Wildlife Management Area (WMA), where a self-sustaining population became established after a fish salvage from Hart Lake during the 1991 drought. Close

• 4. [Article] Status, Distribution, and Life History Investigations of Warner Suckers, 2006-2010 Information Reports number 2011-02

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

  Citation × Citation Citation Abstract Copy Title: Status, Distribution, and Life History Investigations of Warner Suckers, 2006-2010 Information Reports number 2011-02 Abstract -- The Warner sucker Catostomus warnerensis is endemic to the Warner Valley, a subbasin of the Great Basin in southeastern Oregon and northwestern Nevada. This species was historically abundant (Snyder 1908) 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 that 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 1974). 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). The Warner sucker inhabits the lakes and low gradient stream reaches of the Warner Valley. The metapopulation of Warner suckers is comprised of two life history forms: lake and stream morphs. The lake suckers display a lacustrine-adfluvial pattern in which they spend most of the year in the lake and spawn in the streams. However, when upstream migration is hindered by low stream flows during drought years or by irrigation diversion dams, lake suckers may spawn in nearshore areas of the lakes (White et al. 1990). 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). Periodic lake desiccation also threatens the lake suckers. The stream suckers display a fluvial life-history pattern and spawn in the three major tributary drainages (Honey, Deep, and Twentymile Creeks). Threats specific to the stream form include water withdrawals for irrigation and impacts from grazing. Stream suckers recolonized the lakes after past drying events (mid-1930’s and early-1990’s). 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 three recovery criteria for delisting the species. These criteria require that: (1) a self-sustaining metapopulation is distributed throughout the drainages of Twentymile Creek, Honey Creek, and below the falls on Deep Creek, and in Pelican, Crump, and Hart Lakes; (2) passage is restored within and among these drainages so that 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. The Oregon Department of Fish and Wildlife’s (ODFW’s) Native Fish Investigations Project conducted investigations from 2006 through 2010 to describe the conservation (recovery) status of Warner suckers. The objectives of our investigations were to: 1) describe the current distribution of suckers in the Warner subbasin, 2) estimate their abundance in the lakes and streams, 3) collect life history information, and 4) describe the primary factors that currently limit the sucker’s ability to maintain a functioning metapopulation, including connectivity/fragmentation of habitats and factors affecting successful recruitment in the lake and stream environments. Previous similar studies were conducted in 1990, 1991, 1994, 1995, 1996, 1997, and 2001 (White et al. 1990; White et al. 1991; Allen et al. 1994; Allen et al. 1995; Allen et al. 1996; Bosse et al. 1997; Hartzell et al. 2001). We addressed these objectives by implementing the following tasks: 1) conducting surveys in Hart and Crump Lakes to describe the distribution and quantify the abundance of Warner suckers, search for evidence of recent recruitment, estimate sucker abundance relative to nonnative fish abundance, and describe certain life history characteristics, 2) tagging suckers with Passive Integrated Transponder (PIT) tags in the lakes and tributaries to estimate growth rates and describe seasonal movements, 3) radio tracking suckers in the lakes and tributaries to describe seasonal movements, 4) fishing screw traps in Warner basin tributaries to monitor downstream movements, 5) operating a trap at a fish ladder on a Warner tributary to assess upstream passage success, 6) conducting surveys in Warner basin tributaries to describe the current distribution of stream resident populations of Warner suckers and to quantify their abundance, 7) describing associations between the distribution of suckers and habitat variables in Twentymile Creek, 8) trapping larval suckers in the tributaries to describe the relative abundance and timing of larval movements, 9) describing life history parameters including growth rates, length frequency distributions, length at maturity, and weight-length relationships, 10) evaluating a nonlethal ageing technique, 11) describing the distribution and abundance of the Warner suckers at Summer Lake Wildlife Management area, where a self-sustaining population became established after fish salvage from Hart Lake during the 1992 drought, and 12) collecting tissue samples for future genetic analyses. This report compiles the results of this work, synthesizes and interprets findings relative to the conservation status of the species, and recommends future studies. Title: Status, Distribution, and Life History Investigations of Warner Suckers, 2006-2010 Information Reports number 2011-02 Abstract -- The Warner sucker Catostomus warnerensis is endemic to the Warner Valley, a subbasin of the Great Basin in southeastern Oregon and northwestern Nevada. This species was historically abundant (Snyder 1908) 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 that 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 1974). 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). The Warner sucker inhabits the lakes and low gradient stream reaches of the Warner Valley. The metapopulation of Warner suckers is comprised of two life history forms: lake and stream morphs. The lake suckers display a lacustrine-adfluvial pattern in which they spend most of the year in the lake and spawn in the streams. However, when upstream migration is hindered by low stream flows during drought years or by irrigation diversion dams, lake suckers may spawn in nearshore areas of the lakes (White et al. 1990). 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). Periodic lake desiccation also threatens the lake suckers. The stream suckers display a fluvial life-history pattern and spawn in the three major tributary drainages (Honey, Deep, and Twentymile Creeks). Threats specific to the stream form include water withdrawals for irrigation and impacts from grazing. Stream suckers recolonized the lakes after past drying events (mid-1930’s and early-1990’s). 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 three recovery criteria for delisting the species. These criteria require that: (1) a self-sustaining metapopulation is distributed throughout the drainages of Twentymile Creek, Honey Creek, and below the falls on Deep Creek, and in Pelican, Crump, and Hart Lakes; (2) passage is restored within and among these drainages so that 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. The Oregon Department of Fish and Wildlife’s (ODFW’s) Native Fish Investigations Project conducted investigations from 2006 through 2010 to describe the conservation (recovery) status of Warner suckers. The objectives of our investigations were to: 1) describe the current distribution of suckers in the Warner subbasin, 2) estimate their abundance in the lakes and streams, 3) collect life history information, and 4) describe the primary factors that currently limit the sucker’s ability to maintain a functioning metapopulation, including connectivity/fragmentation of habitats and factors affecting successful recruitment in the lake and stream environments. Previous similar studies were conducted in 1990, 1991, 1994, 1995, 1996, 1997, and 2001 (White et al. 1990; White et al. 1991; Allen et al. 1994; Allen et al. 1995; Allen et al. 1996; Bosse et al. 1997; Hartzell et al. 2001). We addressed these objectives by implementing the following tasks: 1) conducting surveys in Hart and Crump Lakes to describe the distribution and quantify the abundance of Warner suckers, search for evidence of recent recruitment, estimate sucker abundance relative to nonnative fish abundance, and describe certain life history characteristics, 2) tagging suckers with Passive Integrated Transponder (PIT) tags in the lakes and tributaries to estimate growth rates and describe seasonal movements, 3) radio tracking suckers in the lakes and tributaries to describe seasonal movements, 4) fishing screw traps in Warner basin tributaries to monitor downstream movements, 5) operating a trap at a fish ladder on a Warner tributary to assess upstream passage success, 6) conducting surveys in Warner basin tributaries to describe the current distribution of stream resident populations of Warner suckers and to quantify their abundance, 7) describing associations between the distribution of suckers and habitat variables in Twentymile Creek, 8) trapping larval suckers in the tributaries to describe the relative abundance and timing of larval movements, 9) describing life history parameters including growth rates, length frequency distributions, length at maturity, and weight-length relationships, 10) evaluating a nonlethal ageing technique, 11) describing the distribution and abundance of the Warner suckers at Summer Lake Wildlife Management area, where a self-sustaining population became established after fish salvage from Hart Lake during the 1992 drought, and 12) collecting tissue samples for future genetic analyses. This report compiles the results of this work, synthesizes and interprets findings relative to the conservation status of the species, and recommends future studies. Close

• 5. [Article] The Distribution and Abundance of Great Basin Redband Trout: An Application of Variable Probability Sampling in a 1999 Status Review

  Abstract -- Using a variable probability sampling design, streams throughout the entire range of Great Basin redband trout (Oncorhynchus mykiss ssp.) were randomly sampled use the EMAP sampling protocol, ...

  Citation × Citation Citation Abstract Copy Title: The Distribution and Abundance of Great Basin Redband Trout: An Application of Variable Probability Sampling in a 1999 Status Review Abstract -- Using a variable probability sampling design, streams throughout the entire range of Great Basin redband trout (Oncorhynchus mykiss ssp.) were randomly sampled use the EMAP sampling protocol, such that 35 sample sites were apportioned to each of six subbasins (Silver Lake, Lake Abert, Goose Lake, Warner Valley, Catlow Valley, and Malheur Lakes). A total of 185 sites (out of a target of 210) were visited by three-person crews that conducted habitat surveys and population estimates in sample reaches whose length were nearly 20 times their channel width. A minimal sampling intensity was based on previously encountered levels of between site variance in abundance estimates for the species. The population estimate for age 1+ redband trout was 948,852 fish (+/– 21%), with confidence limits ranging from 26% to 43% of individual subbasin estimates. Age 1+ fish abundance in terms of density (fish m-2) showed no significant differences between any subbasin, while there were significant differences in biomass (g m-2), where one subbasin had significantly higher (Catlow Valley) biomasses, and one significantly lower (Goose Lake). These comparisons were supported by like differences in mean weight (g fish-2). Analysis of stream habitat characteristics and fish abundance revealed no relationship, or model, that was generally consistent throughout the Great Basin, though interpretable patterns were evident within some stream systems where sampling intensity happened to be sufficiently high. Thus while a landscape level sampling design was well suited to address a regional estimate of abundance, useful interpretation of fish and habitat relationships appeared to be embedded within the stream level of organization, and could not be addressed by the variable probability sampling design set for a minimal sampling intensity. Title: The Distribution and Abundance of Great Basin Redband Trout: An Application of Variable Probability Sampling in a 1999 Status Review Abstract -- Using a variable probability sampling design, streams throughout the entire range of Great Basin redband trout (Oncorhynchus mykiss ssp.) were randomly sampled use the EMAP sampling protocol, such that 35 sample sites were apportioned to each of six subbasins (Silver Lake, Lake Abert, Goose Lake, Warner Valley, Catlow Valley, and Malheur Lakes). A total of 185 sites (out of a target of 210) were visited by three-person crews that conducted habitat surveys and population estimates in sample reaches whose length were nearly 20 times their channel width. A minimal sampling intensity was based on previously encountered levels of between site variance in abundance estimates for the species. The population estimate for age 1+ redband trout was 948,852 fish (+/– 21%), with confidence limits ranging from 26% to 43% of individual subbasin estimates. Age 1+ fish abundance in terms of density (fish m-2) showed no significant differences between any subbasin, while there were significant differences in biomass (g m-2), where one subbasin had significantly higher (Catlow Valley) biomasses, and one significantly lower (Goose Lake). These comparisons were supported by like differences in mean weight (g fish-2). Analysis of stream habitat characteristics and fish abundance revealed no relationship, or model, that was generally consistent throughout the Great Basin, though interpretable patterns were evident within some stream systems where sampling intensity happened to be sufficiently high. Thus while a landscape level sampling design was well suited to address a regional estimate of abundance, useful interpretation of fish and habitat relationships appeared to be embedded within the stream level of organization, and could not be addressed by the variable probability sampling design set for a minimal sampling intensity. Close

• 6. [Article] Evaluation of a Sampling Approach to Monitor the Status of Great Basin Redband Trout in Southeastern Oregon (2007 – 2009) Information Reports number 2010-02

  Abstract -- The summer 2009 field season marked the completion of the third of a six year sampling effort to assess the distribution and abundance of redband trout (Oncorhynchus mykiss newberrii) in the ...

  Citation × Citation Citation Abstract Copy Title: Evaluation of a Sampling Approach to Monitor the Status of Great Basin Redband Trout in Southeastern Oregon (2007 – 2009) Information Reports number 2010-02 Abstract -- The summer 2009 field season marked the completion of the third of a six year sampling effort to assess the distribution and abundance of redband trout (Oncorhynchus mykiss newberrii) in the six interior basins of Oregon’s high desert: Catlow Valley, Chewaucan, Fort Rock, Goose Lake, Malheur Lakes, and Warner Valley Species Management Units (SMUs). Across all sampling years, sites were randomly selected using Generalized Random Tessellation Stratified (GRTS) design, which provides a random spatially balanced sample allowing for statistically rigorous evaluation of status, trend and distribution at multiple spatial scales. A total of 700 site surveys were conducted over the course of the study covering nearly 2% of the entire 2,420 km sampling frame. Abundance of age-1+ redband trout at the SMU level has remained relatively stable throughout the course of this study but has decreased since intensively sampled in 1999. Estimates of landscape-wide abundance of age-1+ redband trout were of similar magnitude and had comparable precision across all three study years, averaging 878,000 + 16%. However, abundance at the SMU and population (stratum) level showed substantial variation, both spatially and inter-annually. Fish densities (fish/m) sampled at sites visited annually (2007-2009) showed significant differences between years, specifically between 2007 and 2009 in the Chewaucan and Fort Rock SMUs. Target levels of relative precision were achieved twice at the SMU level, and in approximately half of the strata. Increasing the number of sites sampled to increase precision is not likely, given limited funding. Yet, the current study design falls short of providing precise information to develop conservation management plans. Alternative sampling designs that would maximize data acquisition at the population level, while allowing for estimates of yearly variation were explored and suggested. Title: Evaluation of a Sampling Approach to Monitor the Status of Great Basin Redband Trout in Southeastern Oregon (2007 – 2009) Information Reports number 2010-02 Abstract -- The summer 2009 field season marked the completion of the third of a six year sampling effort to assess the distribution and abundance of redband trout (Oncorhynchus mykiss newberrii) in the six interior basins of Oregon’s high desert: Catlow Valley, Chewaucan, Fort Rock, Goose Lake, Malheur Lakes, and Warner Valley Species Management Units (SMUs). Across all sampling years, sites were randomly selected using Generalized Random Tessellation Stratified (GRTS) design, which provides a random spatially balanced sample allowing for statistically rigorous evaluation of status, trend and distribution at multiple spatial scales. A total of 700 site surveys were conducted over the course of the study covering nearly 2% of the entire 2,420 km sampling frame. Abundance of age-1+ redband trout at the SMU level has remained relatively stable throughout the course of this study but has decreased since intensively sampled in 1999. Estimates of landscape-wide abundance of age-1+ redband trout were of similar magnitude and had comparable precision across all three study years, averaging 878,000 + 16%. However, abundance at the SMU and population (stratum) level showed substantial variation, both spatially and inter-annually. Fish densities (fish/m) sampled at sites visited annually (2007-2009) showed significant differences between years, specifically between 2007 and 2009 in the Chewaucan and Fort Rock SMUs. Target levels of relative precision were achieved twice at the SMU level, and in approximately half of the strata. Increasing the number of sites sampled to increase precision is not likely, given limited funding. Yet, the current study design falls short of providing precise information to develop conservation management plans. Alternative sampling designs that would maximize data acquisition at the population level, while allowing for estimates of yearly variation were explored and suggested. Close