Bonneville Cutthroat Trout (Oncorhynchus clarki utah)

Data: Range-wide Status (May and Albeke 2005) - Updated in 2010 and 2015 Partners: Bureau of Land Management, Confederated Tribes of the Goshute Reservation, Idaho Game and Fish Department, National Park Service, Nevada Department of Wildlife, Trout Unlimited, Utah Division of Wildlife Resources, Wyoming Game and Fish Department, US Fish and Wildlife Service, US Forest Service, Utah Reclamation Mitigation and Conservation Commission ii | Western Native Trout Status Report - Updated January 2018

Species Status Review to catch, and most populations are managed through the use of fishing regulations that The Bonneville Cutthroat Trout (BCT) is protect population integrity and viability. In ad- listed as a “Tier I Conservation Species” by the dition, many BCT populations occur in remote State of Utah, as a “Sensitive Species” by the locations and receive limited fishing pressure US Forest Service, as a “Rangewide Imperiled making special regulations unnecessary. Due (Type 2) Species” by the Bureau of Land Man- to protective regulations and/or the occurrence agement, and as a “Vulnerable Species” by the of BCT in remote areas, over-fishing is not State of Idaho. This species has been petitioned considered to be a problem at this time. Short- for, but precluded for, listing as Threatened or term fishing closures are often imposed to Endangered by the US Fish and Wildlife Ser- promote the development of recently re-intro- vice several times in the past decade. The most duced populations of BCT. Spawning season recent determination, that the species does not closures are frequently used, particularly for warrant listing as a threatened or endangered brood populations. Other regulations requiring species under the Endangered Species Act was limited harvest, length restrictions (slot limits), released on September 9, 2008. catch-and-release, and terminal tackle restric- tions have demonstrated effectiveness in main- TheState of Utah Conservation Agreement and taining populations of BCT. Special regulations Strategy (CAS) for Bonneville Cutthroat Trout are very popular with some groups of anglers. was completed and signed by all parties in 1997 BCT (particularly the Bear Lake strain) are (Lentsch et al. 1997). The Range-wide Conser- cultured extensively in the State of Utah, and vation Agreement and Strategy was completed used widely in sport fish management pro- in 2000 (Lentch et al. 2000) and updated in grams. Angler support for BCT conservation 2018 (Oplinger et al. 2018). In 2004, the Utah management programs is strong in all four Conservation Team completed a Post Imple- states and is an important asset to conservation mentation Assessment to present progress and and management programs. accomplishments in BCT conservation in the State of Utah. Also during 2007, a comprehen- BCT Distribution sive Range-wide Status Review was published. A Management Plan for Conservation of Based on the 2015 Range- wide Status Update, BCT in Idaho was submitted during 2006. The At least 202 BCT populations collectively oc- Nevada Conservation Agreement and Strategy cupy about 2,728 miles of stream habitat in 21 was also finalized during 2006. watersheds in Utah, Idaho, Nevada, and Wyo- ming. These populations qualify as conservation BCT Sportfishing Status populations under standards developed by the States. Of the 202 conservation populations, 55 BCT are considered a game fish by all state, percent are considered core populations. federal, and tribal agencies that have manage- Conservation populations have at least 90 per- ment authority for this subspecies. Like other cent cutthroat trout genes and core populations cutthroat subspecies, BCT are generally easy have at least 99 percent cutthroat trout genes. BONNEVILLE CUTTHROAT TROUT (Oncorhynchus clarki utah) | iii

Of the 2,728 miles of occupied habitat, 1,160 Thirty-three of these populations representing miles (49%) are associated with lands adminis- 1,509 miles existed in drainages with strong or tered by the Federal Government. Almost 51% moderate connectivity. of BCT habitat occurs on land with non-fed- eral administration, including Goshute Tribal BCT Habitat Requirements lands (12 miles). Typical of most trout, BCT thrive in lotic habitats characterized by relatively cool, well Range and GMUs of the BCT oxygenated water; the presence of clean, well sorted gravels with minimal fine sediments for successful spawning; and habitat complexity composed of large woody debris and overhang- ing banks. However, BCT have been found to tolerate marginal habitat conditions as well (i.e., widely variable flows, high temperatures, poor instream structure, and high turbidity) due to the fact that they evolved in a desert environment. One study (Kershner 1995) found spawning substrate size to be proportional to body size. For example, large adfluvial BCT typically spawn in large gravels or cobbles, while smaller, stream resident BCT spawn over coarse sand or small gravels. Concerns and Issues Relative to the Conservation and Im- provement of BCT Primary threats include isolation of streams, BCT Range and GMUs habitat quality, oil and gas development, re- A total of 202 separate BCT populations cur- source extraction, grazing, water management, rently occupying 2,303 miles of habitat were and climate change. designated as “conservation populations” (84% of currently occupied habitat). These conser- vation populations were spread throughout the historical range, occurring in 19 of the 23 hydrologic units historically occupied by BCT. iv | Western Native Trout Status Report - Updated January 2018

Genetic Considerations Habitat Concerns

Most of the western states that have manage- Continued habitat degradation is one of the ment and conservation authority for cutthroat major threats to the abundance and improve- trout participated in the development of a posi- ment of BCT. Loss of habitat quality has been tion paper on genetic management (Lentsch et recognized as one of the two major human- al. 2000). This position paper describes a hier- induced influences in the loss of BCT popula- archical classification for conserving cutthroat tions. Major habitat concerns: trout that includes: • Modification and fragmentation of habi- 1) a core component of genetically unaltered tat from barriers to fish passage, entrain- populations or individuals; ment, and thermal barriers due to dams and water diversions. 2) designated conservation populations that may be either genetically unaltered or slightly • Aquatic habitat degradation and altera- introgressed and have attributes worthy of tion from mining, forestry and agricul- conservation; and tural land use practices that result in sediment loading, elevated temperatures, 3) populations that are managed primarily for changes to stream structure and mor- their recreational fishery value. phometry, and changes in water quality. Core populations are recognized as having im- • Flow depletion and water quality degra- portant genetic value and could serve as donor dation due to water diversions for hydro- sources for developing either captive or wild power, municipal and agricultural uses, broods or for re-founding additional popula- and groundwater pumping for urban, tions from existing BCT populations. mining, and power production. Management of conservation populations will • Secondary impacts of dams from res- emphasize conservation, including potential ervoir pools in large river systems (i.e., conservation populations. The Range-wide hydro-power entrainment, gas super- BCT Status Report provided a generalized saturation, modification of flow patterns, population health assessment for each conser- creation of nonnative fish habitat, and vation population based on population de- changes in tailwater water temperatures). mographics/productivity, temporal variability, connectivity, and size. Seventy-one BCT popu- • Climate change influences, such as lations (46%) were rated as having either high warmer water, changes in stream flow, general health (11 populations) or moderately and the increasing frequency and intensi- high general health (60 populations). Fifty-six ty of disturbances (Williams et al. 2008). populations (37%) were rated as having mod- The accumulation of these detrimental influ- erately low general health and 26 populations ences through time has led to isolation and (17%) were rated as having low general health. fragmentation of habitat and reductions in range, which adversely impact the stability and viability of BCT populations. BONNEVILLE CUTTHROAT TROUT (Oncorhynchus clarki utah) | v

Disease Concerns tamination. Thirty-four populations (17%) were rated as being at high genetic risk. A disease risk assessment was made for each conservation population using a ranking of 1 to Population Viability Concerns 5 based on the level of risk with a ranking of 1 being the lowest level and 5 being the highest For the purposes of conservation and recovery, level. BCT populations in the four states have been partitioned into a hierarchical classification Population isolation and security were impor- system. A sub‐basin or basin where a group of tant considerations, but they were not viewed genetically pure local populations may share as absolutes. Diseases of concern included, but common foraging, spawning, migrating, or were not limited to, whirling disease, furuncu- over‐wintering habitat and function as a meta‐ losis and infectious pancreatic necrosis virus. population are termed “Core populations”. Other concerns are invasive species such as New Zealand mud snails and parasites such as Populations were also designated as “conser- plestophera and epitheliocystis. A new and very vation populations” based on whether they serious invasive threat is the quagga mussel, a represent a core conservation population having close relative of the zebra mussel that appears no genetic alteration, or there were identified to have no elevational limit. With regard to unique attributes such as expression of unique risks associated with catastrophic diseases, 121 or multiple life-history strategies, adaptation (60%) of the conservation populations were to specific environmental habitat conditions, considered to be at limited risk, 25 (12%) were and geographic location. These populations at moderate risk, and 24 (12%) were already in- can be further aggregated into “Geographical fected with significant disease. No un-infected Management Units” –GMU’s that may cross populations were considered at high present jurisdictional boundaries. risk for disease. BCT are widely distributed over a large geo- graphic area. Increased habitat fragmentation Introduced Species Threats from dams, diversions, land and water manage- ment practices, and human development has Competition, predation, and hybridization reduced the amount of available well connected from introduced salmonids including rainbow, habitat. Increased isolation of local populations brook and brown trout, as well as genetically and the occurrence of non‐native salmonids compromised cutthroat trout, continue to pose increase the risk of losing genetically pure a threat to the expansion and conservation of populations. Although the effects of human BCT. Genetic risk is defined by the nature of activities over the past century have reduced the potential for future introgression of a non- their overall distribution and abundance, BCT native genome into a conservation population. are recovering. The 2015 Range-Wide Status Review provided a genetic risk assessment for BCT conservation populations. A total of 117 populations (58%) were ranked as being at low risk of genetic con- vi | Western Native Trout Status Report - Updated January 2018

Overutilization Concerns populations of BCT across the diverse habitats of their native range as well as preserve the There are numerous federal and state regulatory diversity of their life‐history strategies. Specific mechanisms that, if properly administered and conservation measures to improve the status of implemented, protect BCT and their habitats BCT can be grouped into several major catego- throughout the range of the subspecies, such ries, including: as 404 and water quality discharge permit- ting. However, effective implementation of • fish population manipulation (non-native these regulatory mechanisms depends largely removal, re-introduction, supplemental upon the appropriation of adequate funding stocking, spawn-taking, etc.) and, ultimately, commitment on the part of the • habitat manipulation (barrier placement management or regulatory agencies to fulfill or removal, in-stream structure, flow their respective responsibilities. enhancement, increasing connectivity, Adequate angling regulations are in place to isolation of fragments, etc.) protect BCT populations from impacts due • regulatory actions (fishing regulations, to fishing by recreational anglers, minimizing water use, land management, etc. concerns that recreational harvest is a problem. In addition, controls governing collections for BCT Restoration Potential scientific purposes and genetic testing have helped to reduce the risk that monitoring and The 2015 status update evaluated the potential sampling programs may result in a reduction of of restoration or expansion of BCT and found BCT populations. that 3,983 miles of historical habitat did not support conservation populations of BCT. Oil and Gas Development Threats The reestablishment of population connectivity There may be increased pressure on BCT habi- will be a primary focus of future restoration if tats from energy exploration in the near future. the risks to BCT are to be minimized over the The potential for development is most likely long-term. Conservation population designa- to occur in Utah and Wyoming, with habitat tions suggest that two different conservation degradation and loss of water constituting the strategies are needed to conserve BCT. One greatest concerns. strategy concentrates on preventing introgres- sion, disease and competition from other sal- Opportunities to Improve the monids; the second concentrates on preserving local population networks of various sizes that Status of BCT maintain meta- population function, multiple life-history strategies and expand the amount The objective of BCT conservation and resto- of occupied habitat by increasing the amount of ration is to ensure the long‐term persistence of connected habitat. self‐sustaining populations across the species native range. To meet this objective, managers will need to maintain multiple inter‐connected BONNEVILLE CUTTHROAT TROUT (Oncorhynchus clarki utah) | vii

Population Surveys, Genetic Analyses, and BCT Habitat Manipulations Fish Restoration Projects Restoration of BCT habitat will have to ad- Key actions include: dress both habitat quality issues and issues of spatial limitations. Current efforts to recover • Maintain and improve the connectivity BCT have been directed towards improving and genetic integrity of BCT popula- in-stream conditions, restoring limited stream tions in designated sub-basins (GMUs). fragments, and removing or placing in-stream • Maintain current distribution of BCT barriers to improve connectivity or protect within core areas as described in re- populations from intrusion by non-native covery conservation plans, and restore salmonids. distribution where recommended in Key habitat actions include: sub‐basins. • Restore and enhance water flow water • Characterize, conserve, and monitor quality, natural sediment regimes, and genetic diversity and gene flow among physical integrity of channels where local populations of BCT. feasible. • Control or eradicate nonnative species • Restore and improve altered channel and (i.e., rainbow, brook, non‐native strains riparian zone habitats. of cutthroat and hybrid BCT) where feasible and appropriate. • Expand small, isolated populations where possible, and maintain or enhance high • Develop and implement consistent quality habitats to prevent extirpation methods for fish population status and due to small population size or stochastic trend analyses. events. • Locate and assess BCT populations. • Monitor and evaluate natural catastroph- • Conduct standardized surveys and ic impacts, such as fire and drought. genetic analyses. • Identify and implement best manage- • Expand BCT populations through res- ment practices on US Forest Service, Bu- toration, reintroductions, and non-na- reau of Land Management, and private tive fish control in priority watersheds. lands to benefit BCT habitats. • Maintain BCT broodstock sources and adequate hatchery production to meet Regulatory Actions to enhance BCT status sport fish and conservation needs in Maintaining the sportfish status of the BCT each GMU. and utilizing regulations to control over- uti- lization will be an important component of maintaining the health of BCT populations. In addition, working with others to maintain ap- viii | Western Native Trout Status Report - Updated January 2018

propriate regulations for prevention of disease, regular rotation based on monitoring water quality impairment, and habitat distur- schedule. bance are important considerations • Conduct whirling disease (WD) moni- • Provide technical information, adminis- toring and public outreach to inform the trative assistance, and financial resources public and prevent the spread of WD. to assure compliance with the listed objectives and encourage conservation of • Continue surveys for potential new BCT BCT on private lands. populations and conduct genetic analysis to determine purity and/or assess any • Maintain and protect BCT habitat from possible introgression from non-native degradation by achieving compliance salmonids. with existing habitat protection laws, policies, and guidelines. • Identify habitat improvement oppor- • Enforce regulatory mechanisms that pre- tunities for BCT. Work with private vent impacts associated with recreational landowners and management agencies to angling. protect and improve habitat for BCT. • Enhance and maintain regulatory mech- • Pursue conservation easements to protect anisms that prevent diseases or illegal habitat from development and other introduction of nuisance species. impacts. • Work through the FERC re-licensing • Explore opportunities for treatment to process to require impoundment opera- remove non-native species for reintro- tors to operate dams to minimize impacts duction and/or expansion of BCT into where necessary to meet cooperative presently unoccupied historical habitat. agreement objectives. Conduct NEPA analysis as necessary. • Explore opportunities for removing or Recommended Actions to Im- installing barriers for fish passage issues, prove the Status of BCT and conduct barrier monitoring. • Expand the range of isolated populations Highest Priority Actions for BCT include the by increasing connectivity between head- following: water streams and river systems. Bear River GMU • Review current stocking of sportfish, and if necessary and feasible, change stock- (not necessarily in priority order) ing programs to protect current BCT populations. • Continue to monitor core and high priority conservation populations on a • Pursue appropriate BCT conservations outreach opportunities. BONNEVILLE CUTTHROAT TROUT (Oncorhynchus clarki utah) | ix

• Monitor oil and gas exploration, timber Northern GMU harvest, grazing, and recreation activities (not necessarily in priority order) on the Wasatch-Cache National Forest. • Continue to monitor core and high • Review and analyze all culverts on the priority conservation populations on a Wasatch-Cache National Forest for fish regular rotation based on monitoring passage. schedule. • Continue to promote harvest of non- na- • Conduct whirling disease (WD) moni- tive brook trout through liberal limits toring and public outreach to inform the and bait fishing. public and prevent the spread of WD. • Continue surveys for potential new BCT • Continue to explore ways to improve populations and conduct genetic analysis Bear Lake tributaries through habitat to determine purity and/or assess any manipulations designed to maximize possible introgression from non-native natural reproduction of BCT. salmonids. • Monitor the effectiveness of fish passage • Identify habitat improvement oppor- projects and reconnect tributaries on the tunities for BCT. Work with private Thomas Fork. landowners and management agencies to protect and improve habitat for BCT. • Monitor existing populations in First, Second and Third Creeks and evaluate • Pursue conservation easements to protect opportunities to enhance habitat. habitat from development and other impacts. • Complete BCT surveys of the Nounan reach of the Bear River. • Explore opportunities for treatment to remove non-native species for reintro- • Investigate fish passage opportunities on duction and/or expansion of BCT into FERC re-licensing of Bear River hydro- presently unoccupied historical habitat. electric facilities. Conduct NEPA analysis as necessary. • Renovate Deadman Creek. • Explore opportunities for removing or installing barriers for fish passage issues, • Minimize effects of domestic cattle and conduct barrier monitoring. and sheep grazing on Thomas Fork and • Expand the range of isolated populations Smiths Fork watersheds. by increasing connectivity between head- • Explore opportunities for restoring the water streams and river systems. South Fork of the Little Bear River. • Review current stocking of sportfish, and if necessary and feasible, change stock- ing programs to protect current BCT x | Western Native Trout Status Report - Updated January 2018

populations. West Desert GMU (not necessarily in priority order) • Pursue appropriate BCT conservations outreach opportunities. • Continue to monitor core and high • Monitor streams in Tooele, Davis and priority conservation populations on a Salt Lake Counties on the Wasatch- regular rotation based on monitoring Cache National Forest. schedule. • Review and analyze all culverts on the • Conduct whirling disease (WD) moni- Wasatch-Cache National Forest for fish toring and public outreach to inform the passage. public and prevent the spread of WD. • Maintain a brood source for re-establish- • Continue surveys for potential new BCT ment and maintenance of other North- populations and conduct genetic analysis ern BCT populations. Conduct annual to determine purity and/or assess any egg taking operations. possible introgression from non-native salmonids. • Stock mountain lakes on the GMU with fish derived from brood stock. • Identify habitat improvement oppor- tunities for BCT. Work with private • Conduct fish population surveys in Tie landowners and management agencies to Fork, Little Deer Creek, North Fork protect and improve habitat for BCT. American Fork, Dairy Fork, and Spencer Fork. • Explore opportunities for treatment to remove non-native species for reintro- • Monitor existing BCT populations in duction and/or expansion of BCT into Red Butte Reservoir and City Creek. presently unoccupied historical habitat. • Evaluate the restoration potential of Conduct NEPA analysis as necessary. Little South Fork Provo River below • Explore opportunities for removing or Deer Creek Reservoir. installing barriers for fish passage issues, • Conduct fish population surveys in Lost and conduct barrier monitoring. Creek and East Canyon Creek Drainage. • Expand the range of isolated populations • Monitor existing BCT populations in by increasing connectivity between head- Strawberry Creek, Gordon Creek, Hard- water streams and river systems. scrabble Creek, Arthur Creek, and Lost • Pursue appropriate BCT conservations Creek. outreach opportunities.

• Accomplish genetic verification for BCT populations on Goshute Tribal Lands. • Monitor restored populations of BCT to evaluate needs for supplemental stocking BONNEVILLE CUTTHROAT TROUT (Oncorhynchus clarki utah) | xi

on Goshute Tribal Lands. Southern GMU (not necessarily in priority order) • Survey BCT restored reaches to deter- mine genetic risks and install barriers as • Continue to monitor core and high necessary on Goshute Tribal Lands. priority conservation populations on a • Protect and maintain stream habitat con- regular rotation based on monitoring ditions, with a focus on flow maintenance schedule. on Goshute Tribal Lands. • Conduct whirling disease (WD) moni- • Enhance and restore habitat where fea- toring and public outreach to inform the sible on Goshute Tribal Lands including public and prevent the spread of WD. fencing and instream habitat improve- • Continue surveys for potential new BCT ments. populations and conduct genetic analysis • Monitor and evaluate habitat/water qual- to determine purity and/or assess any ity conditions due to drought, ground- possible introgression from non-native water extraction, and fire in Deep Creek salmonids. Range (UT), North and South Snake • Identify habitat improvement oppor- Range (NV), Cherry Creek Range (NV), tunities for BCT. Work with private and Quinn Range (NV). landowners and management agencies to • Accomplish non-native fish eradication, protect and improve habitat for BCT. barrier placement, and re-establishment • Pursue conservation easements to protect of BCT in Silver Creek on the North habitat from development and other Snake Range (NV). (Silver Creek is impacts. the last remaining stream on the North Snake Range to be restored). • Explore opportunities for treatment to remove non-native species for reintro- • Monitor BCT populations in Basin duction and/or expansion of BCT into Creek, Birch Creek, Trout Creek, Toms presently unoccupied historical habitat. Creek, Red Cedar Creek, Indian Farms Conduct NEPA analysis as necessary. Creek, and Granite Creek. Accom- plish supplemental stocking of BCT as • Explore opportunities for removing or needed. installing barriers for fish passage issues, and conduct barrier monitoring. • Work towards meeting persistence crite- ria in five populations within GMU. • Expand the range of isolated populations by increasing connectivity between head- • Complete restorations of Snake Creek water streams and river systems. and Strawberry Creek. • Pursue appropriate BCT conservations • Develop at broodstock at Big Wash. outreach opportunities.

• Brood stock maintenance and disease xii | Western Native Trout Status Report - Updated January 2018

certification at Manning Meadow. Native cutthroat restoration in the Middle Fork Sheep Creek drainage (UT) (2012) - $72,000 • Complete re-establishment of BCT in Upper Clear Creek (Sevier County). Clear Creek (UT) native Bonneville Cutthroat Trout restoration (2013) - $34,000 • Complete restoration of Mammoth Creek and Upper East Fork of the Sevier Mill Creek (UT) watershed restoration (2016) River - $41,000 Mill Creek (UT) watershed restoration (2017) WNTI Completed and Ongoing - $25,000 Jacobs Creek (UT) upper culvert fish passage Projects (2017) - $3,000 Transtrum Diversion fish passage restoration for Bonneville Cutthroat Trout in St. Charles Creek (ID) (2007) - $75,000 Bonneville Cutthroat Trout culvert renovation for 3 miles on South Fork Chalk Creek (UT) (2007) - $44,286 Georgetown Creek (ID) hydro headgate fish ladder (2008) - $15,000 Georgetown Road relocation project, Bear River Basin (ID) for Bonneville Cutthroat Trout (2009) - $15,750 East Fork Bear River (UT) fish screen design and placement for Bonneville Cutthroat Trout (2009) - $105,000 Streambank stabilization and fish screen in St. Charles Creek (ID) (2010) - $71,400 Chalk Creek (UT) fish passage and screening (2011) - $23,000 Weber River (UT) watershed improvements to enhance Bonneville Cutthroat Trout habitat beyond 3 restrictive barriers (2012) - $78,500 Bonneville Cuttthroat Trout telemetry survey, Upper Bear River (WY) (2012) - $2,250 BONNEVILLE CUTTHROAT TROUT (Oncorhynchus clarki utah) | xiii

References Kershner, J.L. 1995. Bonneville Cutthroat Trout. Pages 28-35 in M.K. Young, Tech. Ed. Conservation assessment for inland cutthroat trout. General Technical Report RM-256. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 61pp. Lentsch, L., Y. Converse, and J. Perkins. 1997. Conservation agreement and strategy for Bonneville Cutthroat Trout in the state of Utah. Utah Department of Natural Resources Publication 97-19. Salt Lake City, Utah. Lentsch, L.D., C.A. Toline, J. Kershner, J.M. Hudson, and J. Mizzi. 2000. Range-wide con- servation agreement and strategy for Bonn- eville Cutthroat Trout (Oncorhynchus clarki utah) in the state of Utah. Publication number 00-19. Utah Department of Natural Resources, Division of Wildlife Resources, Salt Lake City. 90pp.

May, B.E., and S.E. Albeke. 2005. Range-wide This publication was funded (or partially status of Bonneville Cutthroat Trout (On- funded) by Federal Aid to Sportfish Restora- corhynchus clarki utah): 2004. Printed agency tion Funds through the Multistate Conser- report. 139pp. vation Grant Program (Grant WY M-8-P), Oplinger, R. et al. 2018. Range-wide conser- a program supported with funds from the vatoin agreement and strategy for Bonneville Wildlife and Sport Fish Restoration Program Cutthroat Trout ((Oncorhynchus clarki utah) in of the U.S. Fish and Wildlife Service and the state of Utah. In press. jointly managed with the Association of Fish Teuscher, D., and J. Capurso. 2007. Manage- and Wildlife Agencies, 2006-9. ment Plan for Conservation of BCT in Idaho. 84pp. Williams, J.E., A.L. Haak, H.M. Neville, and W.T. Colyer. 2008. Potential consequences of climate change to persistence of cutthroat trout populations. N.A. Journal of Fisheries Mange- ment 29(3):533-548.