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101. [Article] Stock Assessment of Elk River Fall Chinook Salmon for Exploitation Rate Analysis Information Report 2004-02
Abstract -- Using various, research, and monitoring data from the Elk River, Curry County Oregon, estimates of the runsize of Fall Chinook Salmon were made for the period 1972-2001. These estimates could ...Citation Citation
- Title:
- Stock Assessment of Elk River Fall Chinook Salmon for Exploitation Rate Analysis Information Report 2004-02
Abstract -- Using various, research, and monitoring data from the Elk River, Curry County Oregon, estimates of the runsize of Fall Chinook Salmon were made for the period 1972-2001. These estimates could be allocated to either hatchery or wild origin fish and it was possible to construct the riverine harvest rates for each year. It is estimated that for large size Hatchery origin fish (>55cm), the run has varied from a low of 475 in 1981 to 10,821 in 2001. For wild reared Chinook the run has varied from a low of 1,166 in 1991 to 3,456 in 1999. Estimates of small sized Chinook (<55cm) are made but are believed t~ be less reliable than for large fish. This group of fish has been proposed as an Exploitation Rate Indicator Stock for use in the Coast Model as a representative of the harvest impact of ocean fisheries on wild Chinook populations from the Umpqua and Mid-South Gene Conservation (MOC) Groups composed of the Umpqua, Coos, Coquille, Sixes Rivers and Floras creek. To prepare this stock for this role it was necessary to integrate the Port Orford Terminal Ocean fishery into the Elk River as none of the other populations are subjected to terminal fisheries. Using the annual estimated riverine harvest rates the recovery of Elk River ERI-stock Chinook in the Port Orford fishery beginning in mid-October until the end of the year were simulated as return to river and apportioned to catch or escapement. This information will now be available to the Chinook Technical Committee of the Pacific Salmon Commission to include the MOC group in the annual exploitation rate analysis. Additionally, this information can be used in the FRAM model for domestic ocean fishery management, and by local area managers for operational planning and fishery regulations in-river.
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102. [Article] Sandy River Basin Fish Management Plan 1997 Draft
Abstract -- The Sandy River and its tributaries originate high on the west and south slopes of Mount Hood, flow approximately 55 miles in a northwesterly direction and enter the Columbia River near Troutdale ...Citation Citation
- Title:
- Sandy River Basin Fish Management Plan 1997 Draft
Abstract -- The Sandy River and its tributaries originate high on the west and south slopes of Mount Hood, flow approximately 55 miles in a northwesterly direction and enter the Columbia River near Troutdale (Columbia RM 120.5). The Sandy basin is situated in Multnomah and Clackamas counties (EPA reach 17080001), and drains approximately 508 square miles. The Sandy River basin is comprised of several subbasins, many of which are uniquely distinct hydrologically and geomorphologically. Principle tributaries include the Zigzag River, Still Creek, and the Salmon River in the upper basin and the Bull Run River, Gordon, Cedar, and Beaver creeks in the lower basin. Many other smaller tributaries located throughout the basin contribute significantly to stream flows and provide habitat for a wide array of fish and wildlife assemblages. The Sandy River is well known for its sport fishing. Winter steelhead, summer steelhead, and spring chinook are the most sought after species. Both winter and summer steelhead, coho, and spring chinook are supplemented with hatchery produced fish. Rainbow trout and fall chinook are no longer stocked in flowing waters of the Sandy River basin. In the late 1980's the Northwest Power Planning Council administered a planning process to create a management plan for the Columbia River basin. As a part of that process, a subbasin plan concerning management of steelhead and salmon was written for the Sandy River basin. This document, the draft "Sandy River Basin Fish Management Plan", significantly expands on the Northwest Power Planning Council document by adding resident fish species and new information on anadromous species and will ultimately produce the final plan used to guide fish resource management in the basin for the next 5 to 10 years.
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103. [Article] Status and Distribution of Native Fishes in the Goose Lake Basin Information Reports number 2008-02
Abstract -- This study describes the current distribution of the nine native fish species in the Oregon portion of the Goose Lake basin (Lake County): Goose Lake redband trout Oncorhynchus mykiss ssp., ...Citation Citation
- Title:
- Status and Distribution of Native Fishes in the Goose Lake Basin Information Reports number 2008-02
Abstract -- This study describes the current distribution of the nine native fish species in the Oregon portion of the Goose Lake basin (Lake County): Goose Lake redband trout Oncorhynchus mykiss ssp., Goose Lake lamprey Entosphenus sp., Goose Lake tui chub Siphateles bicolor thalassinus, Goose Lake sucker Catostomus occidentalis lacusanserinus, Modoc sucker Catostomus microps, Pit-Klamath brook lamprey Entosphenus lethophagus, speckled dace Rhinichthys osculus, Pit roach Lavinia symmetricus mitrulus, and Pit sculpin Cottus pitensis. The Goose Lake basin is an endorheic, or topographically closed basin located in south central Oregon and northeastern California. The basin is within the usually closed northeastern extremity of the adjoining Sacramento River basin, astride the Oregon-California boundary. Although most of the lake lies in California, most of its valley and nearly two-thirds of the total drainage area (~722 sq. mi.) are in Oregon. The largest streams in the basin are Drews, Cottonwood, and Thomas Creeks. Annual precipitation averages about 36 cm per year (Phillips and van Denburgh 1971). Goose Lake overflowed briefly into the North Fork Pit River in 1868 and 1881, but storage and diversion of irrigation water has substantially reduced the inflow and future overflow is unlikely (USGS 1971). The lakebed was dry in the summers of 1926, 1929- 1934, and 1992. About half the basin is forestland, 20% is hay fields and pastureland, and 16% is shrub and rangeland. Currently, almost 35% of the inflow is diverted for irrigation (OWRD 1989). The Goose Lake basin is home to four endemic fish taxa: the Goose Lake redband trout, lamprey, sucker, and tui chub. Endemic fishes of the Goose Lake basin split their life histories between Goose Lake and its tributaries, as opposed to the five native but non-endemic species that primarily occupy stream habitats. Pit roach and all endemic fishes except Goose Lake tui chub are listed as a “species of concern” by the USFWS, a designation that implies there is concern about species viability, but not enough information is known to initiate a listing review for threatened or endangered status. The Modoc sucker was listed as a federally endangered species in 1985 (USFWS 1985). No formal recovery plan was required due to an existing “Action Plan for the Recovery of the Modoc Sucker” (USFWS 1984). Most of the recovery actions outlined in the action plan were either completed or are no longer relevant (Stewart Reid, Western Fishes, personal communication). However, actions 26 and 27 pertaining to range expansion remain incomplete. Action 26 suggests reclassification to threatened upon establishment of safe populations (for 3-5 years) throughout the Rush and Turner Creek watersheds in the Pit River basin. Action 27 suggests delisting upon establishing safe populations in two other historic streams. At the time of listing, the historic range of Modoc sucker was thought to have included only two small tributaries of the Pit River in Modoc and Lassen Counties, Ash and Turner Creeks (USFWS 1985). Therefore, a major recovery goal was to expand the species’ range with additional populations (USFWS 1984). In 2001, reexamination of historical documents and museum specimens established that Modoc suckers had also historically occupied Thomas Creek in the Goose Lake basin. Field collections in 2001, with subsequent morphological and genetic analysis, confirmed that the population was still present in Thomas Creek (Stewart Reid, Western Fishes, personal communication); however, the broader range of Modoc sucker in the Goose Lake watershed was not known. In 1995, the Goose Lake Fishes Working Group drafted a conservation plan for “prelisting” recovery of all native fish in response to severe drought and habitat degradation (GLFWG 1995). The Aquatic Inventories Project of the Oregon Department of Fish and Wildlife (ODFW) conducted habitat and fish distribution surveys (1991-1995) to obtain baseline information to help inform recovery efforts (ODFW, unpublished data). Since then, field work to monitor the distribution and abundance of Goose Lake fishes has been limited and sporadic, targeting only Goose Lake redband trout and Modoc sucker (Dambacher 2001; Reid 2007). No comprehensive follow up work has been conducted to evaluate fish response to climatic conditions, habitat restoration projects, and continued irrigation activities. ODFW recently drafted a status review of native fish of Oregon (ODFW 2005). Except for redband trout, Goose Lake fishes were not included in the status review due to a lack of new information since the previous status review in 1995 (Kostow et al. 1995). Further, the review of Goose Lake redband trout was limited by a lack of long-term data series. The first objective of this study was to document the current distribution of native fishes in Oregon’s portion of the Goose Lake basin and assess changes in distribution that may have occurred since the last surveys were conducted 12 years ago. The second objective was to provide new information about the distribution of Modoc suckers within the basin. The third objective was to determine relative abundance and age-class diversity of native fishes at randomly selected sample sites. All objectives were addressed throughout the potential riverine distribution of fish in the Oregon portion of the Goose Lake basin. Information gathered in this study is critical to effective conservation and management of each species and its habitat. In addition, this report describes the distribution and relative abundance of nonnative fishes (fathead minnow (Pimephales promelas), brown bullhead (Ameiurus nebulosus), white crappie (Pomoxis annularis), yellow perch (Perca flavescens), pumpkinseed (Lepomis gibbosus), and brook trout (Salvelinus fontinalis)) in the basin. Unlike prior efforts, this study used a statisticallybased design to select sample points with the aim of achieving a representative sample across the Oregon portion of the Goose Lake watershed. Additionally, a wide array of fish sampling gear was employed to maximize our ability to capture all fish species present across the diversity of habitat types encountered.
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104. [Article] Vector Control - Wetlands of Concern
Abstract -- The Wetlands of Concern dataset represents one type of “sensitive area” for the purpose of reviewing and approving Pesticide Use Plans per ODFW's obligations under ORS 452.140 and ORS 452.245. ...Citation Citation
- Title:
- Vector Control - Wetlands of Concern
Abstract -- The Wetlands of Concern dataset represents one type of “sensitive area” for the purpose of reviewing and approving Pesticide Use Plans per ODFW's obligations under ORS 452.140 and ORS 452.245. ODFW will only make recommendations for mosquito control treatment protocols on sensitive areas, as identified in ODFW's Vector Control Guidance for Sensitive Areas (http://www.dfw.state.or.us/fish/water/docs/Sensitive_Area_Guidance.pdf) or confirmed by the local fish and wildlife biologists utilizing the guidelines in the document. In general, a sensitive area is any area where fish and wildlife and their habitats are rare or of local importance due to their special nature or role in the ecosystem. Species-specific and location-specific details are not maintained in this dataset. This dataset is derived from the Oregon Wetlands Cover. The Oregon Wetlands Cover is a key component of the Oregon Wetland Explorer data portal (http://oregonexplorer.info/wetlands), and is intended to (1) serve as a framework for storing and disseminating information on the state's wetlands, and (2) promote comprehensive monitoring, assessment, conservation, and restoration of Oregon's wetlands. Wetlands with a Total Conservation Significance score of 70 and above were included in this dataset for the purpose of identifying wetlands of concern for vector control purposes.
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105. [Article] 2009 Borax Lake Chub Investigations Progress Reports 2009
Abstract -- The Borax Lake chub (Gila boraxobius) is a small minnow endemic to Borax Lake and adjacent wetlands in the Alvord Basin in Harney County, Oregon (Williams and Bond 1980). Borax Lake chub are ...Citation Citation
- Title:
- 2009 Borax Lake Chub Investigations Progress Reports 2009
Abstract -- The Borax Lake chub (Gila boraxobius) is a small minnow endemic to Borax Lake and adjacent wetlands in the Alvord Basin in Harney County, Oregon (Williams and Bond 1980). Borax Lake chub are represented by a single population that inhabits a 4.1 hectare geothermally-heated alkaline lake. Borax Lake is a natural lake perched 10 meters above the desert floor on sinter deposits, which is fed almost exclusively by thermal groundwater. The Borax Lake chub was listed as endangered under the federal Endangered Species Act in 1982 (U.S. Fish and Wildlife Service 1982). Population abundance estimates obtained since 1991 indicate a fluctuating population ranging between approximately 4,000 and 34,000 fish (Salzer 1997; Scheerer and Jacobs 2008). The basis for the Borax Lake chub’s listed status was not population size, but the security of a very limited, unique, isolated, and vulnerable habitat. Because Borax Lake is situated above salt deposits on the desert floor, alteration of the salt crust shoreline could reduce lake levels and the habitat quantity and quality available to Borax Lake chub. At the time of the listing, Borax Lake was threatened by habitat alteration caused by geothermal energy development and alteration of the lake shore crust to provide irrigation to surrounding pasture lands. The Borax Lake chub federal recovery plan, completed in 1987, advocated protection of the lake ecosystem through the acquisition of key private lands, protection of groundwater and surface waters, controls on access, and the removal of livestock grazing (U.S. Fish and Wildlife Service 1987). Recovery measures implemented since listing have improved the conservation status of Borax Lake chub and protection of its habitat (Williams and Macdonald 2003). When the species was listed, critical habitat was designated on 259 hectares of land surrounding the lake, including 129 hectares of public lands and two 65-hectare parcels of private land. In 1983, the U.S. Bureau of Land Management designated the public land as an Area of Critical Environmental Concern. The Nature Conservancy began leasing the private lands in 1983 and purchased them in 1993, bringing the entire critical habitat into public or conservation ownership. The Nature Conservancy ended water diversion from the lake for irrigation and livestock grazing within the critical habitat. Passage of the Steens Mountain Cooperative Management and Protection Act of 2000 removed the public BLM lands from mineral and geothermal development within a majority of the basin. These actions, combined with detailed studies of the chub and their habitat, have added substantially to our knowledge of the Borax Lake ecosystem (Scoppettone et al. 1995, Salzer 1992, Perkins et al. 1996). However, three primary threats remain. These include the threat to the fragile lake shoreline, wetlands, and soils from a recent increase in recreational use around the lake (particularly off-road vehicle usage), the threat of introduction of nonnative species, and potential negative impacts to the aquifer from geothermal groundwater withdrawal if groundwater pumping were to occur on private lands outside the protected areas (Williams and Macdonald 2003). A review of the conservation status of the Borax Lake chub by Williams and Macdonald (2003) cited the lack of recent and ongoing population and ecosystem monitoring as one argument against downlisting or delisting the species at that time. Although an increase in abundance is not a goal in the successful recovery of this species, monitoring trends in abundance over time is an important management tool to assess species status. The objectives of this study were to: 1) obtain a mark-recapture population estimate of Borax Lake chub and 2) to evaluate habitat conditions at Borax Lake, including the condition of the fragile lake shoreline and outflows. This report describes results from monitoring conducted by Oregon Department of Fish and Wildlife’s Native Fish Investigations Project in 2009.
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106. [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
- 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.
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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
- 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.
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108. [Article] Oregon Fish Passage Barriers
Abstract -- The Oregon Fish Passage Barrier Data Standard (OFPBDS) dataset contains barriers to fish passage in Oregon watercourses. Barriers include the following types of natural or artificial structures: ...Citation Citation
- Title:
- Oregon Fish Passage Barriers
Abstract -- The Oregon Fish Passage Barrier Data Standard (OFPBDS) dataset contains barriers to fish passage in Oregon watercourses. Barriers include the following types of natural or artificial structures: bridges, cascades, culverts, dams, debris jams, fords, natural falls, tide gates, and weirs. The OFPBDS dataset does not include structures which are not associated with in-stream features (such as dikes, levees or berms). Barriers are structures which do, or potentially may, impede fish movement and migration. Barriers can be known to cause complete or partial blockage to fish passage, or they can be completely passable, or they may have an unknown passage status. This dataset complies with version 1.1 of the OFBPDS data standard. New optional attributes have been added to describe fish passage barrier feature modifications, to describe supplementary information (via a comments field) and also to linear reference the barrier features to the National Hydrography Dataset. The OFPBDS dataset now contains over 40,000 barrier features from 19 separate sources including: Oregon Department of Fish and Wildlife (ODFW), Oregon Department of Transportation (ODOT), Oregon Department of Water Resources (OWRD), Oregon Department of Forestry (ODF), Oregon Watershed Enhancement Board (OWEB), Oregon Department of Land Conservation and Development (DLCD) US Bureau of Land Management (BLM), US Forest Service, Nez Perce Tribe, Benton SWCD, Washington county, Lower Columbia River Estuary Partnership and watershed councils representing the Rogue, Umpqua, Siuslaw, Santiam, Calapooia, Clackamas and Scapoose basins. The Data Steward obtained fish passage barrier data from multiple data originators between 2008 and 2015, collaborated with them to develop inclusion / exclusion criteria and dataset specific crosswalks for converting data from its original data structure to the structure of the OFPBDS. The data were then converted into the OFPBDS format and analyzed for duplication with existing OFPBDS barrier features. Where duplicates were identified, depending upon the scenario, one feature was either chosen over the other or in some cases attributes from different sources are combined. Source information is retained for each feature. The data were then loaded into the OFPBDS database. Barrier features were linear referenced (Framework Hydro only which is outside of the standard) and the corresponding optional attribute elements were populated. The data conversion, duplication reconciliation and linear referencing protocols are documented in the Oregon Fish Passage Barrier Data Management Plan. A separate dataset containing fish passage barrier features that have been completely removed or replaced (e.g. dam removals and culvert replacements) is published simultaneously with the OFPBDS dataset. The OFPBDS database is the most comprehensive compilation of fish passage barrier information in Oregon however, it does NOT represent a complete and current record of every fish passage barrier within the state. Efforts to address deficiencies in data currency, completeness and accuracy are ongoing and are often limited by lack of sufficient resources. Attributes (including key attributes such as fish passage status) are often unknown or incomplete. Consistency in attribution also varies among data originators. Field verification of barrier features and their attributes will be an important component to making this dataset current, comprehensive and accurate. Fish passage status is a key attribute. Many barrier features have an unknown passage status. For other features, the passage status may have changed since it was originally documented. Note that this metadata file is best viewed in ArcCatalog. Documentation for the OFPBDS can be found online at http://www.oregon.gov/DAS/EISPD/GEO/docs/bioscience/OregonFishPassageBarrierDataStandardv1dot1.pdf.
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109. [Article] 2006 Borax Lake Chub Investigations Progress Reports 2006
Abstract -- Borax Lake chub (Gila boraxobius) is represented by a single population that inhabits a 4.1 hectare geothermally-heated alkaline lake in Harney County, Oregon. The Borax Lake chub is a small ...Citation Citation
- Title:
- 2006 Borax Lake Chub Investigations Progress Reports 2006
Abstract -- Borax Lake chub (Gila boraxobius) is represented by a single population that inhabits a 4.1 hectare geothermally-heated alkaline lake in Harney County, Oregon. The Borax Lake chub is a small minnow endemic to Borax Lake and adjacent wetlands in Oregon’s Alvord Basin (Williams and Bond 1980). Borax Lake is a natural lake, perched 10 meters above the desert floor on sinter deposits, which is fed almost exclusively by thermal groundwater. The Borax Lake chub was listed as endangered under the federal Endangered Species Act in 1982 (U.S. Fish and Wildlife Service 1982). Population abundance estimates obtained in 1991-1996 indicated a fluctuating population ranging from a low of 8,144 fish to a high of 34,634 fish (Salzer 1997). The basis for the Borax Lake chub’s listed status was not population size, but the security of a very limited, unique, isolated, and vulnerable habitat. Because Borax Lake is situated above salt deposits on the desert floor, alteration of the salt crust shoreline could reduce lake levels and the habitat quantity and quality available to Borax Lake chub. At the time of the listing, Borax Lake was threatened by habitat alteration caused by geothermal energy development and alteration of the lake shore crust to provide irrigation to surrounding pasture lands. The Borax Lake chub federal recovery plan, completed in 1987, advocated protection of the lake ecosystem through the acquisition of key private lands, protection of groundwater and surface waters, controls on access, and the removal of livestock grazing (U.S. Fish and Wildlife Service 1987). Numerous recovery measures implemented since listing have improved the conservation status of Borax Lake chub and protection of its habitat (Williams and Macdonald 2003). When the species was listed, critical habitat was designated on 259 hectares of land surrounding the lake, including 129 hectares of public lands and two 65- hectare parcels of private land. In 1983, the U.S. Bureau of Land Management designated the public land as an Area of Critical Environmental Concern. The Nature Conservancy began leasing the private lands in 1983 and purchased them in 1993, bringing the entire critical habitat into public or conservation ownership. The Nature Conservancy ended water diversion from the lake for irrigation and livestock grazing within the critical habitat. Passage of the Steens Mountain Cooperative Management and Protection Act of 2000 removed the public BLM lands from mineral and geothermal development within a majority of the basin. These actions, combined with detailed studies of the chub and their habitat have added substantially to our knowledge of the Borax Lake ecosystem (Scoppettone et al. 1995, Salzer 1992, Perkins et al. 1996). However, three primary threats remain. These include the threat to the fragile lake shoreline, wetlands, and soils from a recent increase in recreational use around the lake (particularly off-road vehicle usage), the threat of introduction of nonnative species, and potential negative impacts to the aquifer from geothermal groundwater withdrawal if groundwater pumping were to occur on private lands outside the protected areas (Williams and Macdonald 2003). Although an increase in abundance is not a goal in the successful recovery of this species, monitoring trends in abundance over time is an important management tool to assess species status. From 1998-2004, data describing the abundance of the Borax Lake chub population are not available. Abundance estimates were obtained from 1986- 1997 by The Nature Conservancy (Salzer 1997) (Figure 1). Abundance estimates for 1986-1990 are not comparable with those obtained in 1991-1997. Prior to 1991, estimates were obtained only from traps set around the perimeter of the lake. In 1991, estimates were obtained from traps set on a regularly spaced grid throughout the lake. A study comparing the methods suggests that prior to 1991 abundance was under estimated, perhaps by as much as 50 percent (Salzer 1992). A recent review of the conservation status of the Borax Lake chub by Williams and Macdonald (2003) cited the lack of recent and ongoing population and ecosystem monitoring as one argument against downlisting or delisting the species at this time. The chub population has experienced substantial fluctuations in abundance over the time period (1986-1997) when abundance data are available (Figure 1). At the time of the review, the most recent abundance estimates that were obtained in 1996 and 1997 were some of the lowest estimates since 1991. Borax Lake chub population abundance estimates from 1986 to 1997 and 2005 to 2006. Horizontal bars represent 95% confidence limits. In 1986-1990 (solid symbols), only the perimeter of the lake was trapped. After 1990 (open symbols) the entire lake was trapped. Estimates are not directly comparable across these time periods. There are limited data on population age structure that offer valuable insight into the productivity of Borax Lake chub. Williams and Bond (1983) examined lengthfrequency data and concluded that the population consisted primarily of age 1 fish, with few age 2 and age 3 fish present. Limited opercle bone aging of chub collected in 1992- 1993 also indicated that most Borax Lake were less than one year of age (67-79%), yet a few individuals were aged at 10+ years (Scoppettone 1995). Because Borax Lake chub are only found in one location and the population is apparently dominated by a single year-class of adults, the species has a high inherent risk of extinction. 3 The objectives of this study were to: 1) obtain a mark-recapture population estimate of Borax Lake chub, and 2) to evaluate ways to reduce handling of Borax Lake chub when monitoring population abundance both by modifying previous mark-recapture protocols and by developing snorkeling survey protocols to use as an alternative to mark-recapture estimates. In addition, we collected data regarding lake temperatures, chub size (age) structure, and the condition of the fragile lake shoreline and outflows.