Conservation Assessment for Inland Cutthroat Trout
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USDA Forest Service February 1995 General Technical Report RM-GTR-256 Conservation Assessment for Inland Cutthroat Trout Technical Editor: Michael K. Young, Fisheries Scientist Rocky Mountain Forest and Range Experiment Stationl I Headquarters is in Fort Collins, Colorado, in cooperation with Colorado State University. -m■- 4 Contents Preface ........................................................................................................................ ii Acknowledgments ................................................................................................ iii Names of Fishes .................................................................................................... iv Chapter 1 Westslope Cutthroat Trout .................................................................................. 1 John D. McIntyre and Bruce E. Rieman Chapter 2 Colorado River Cutthroat Trout .......................................................................... 16 Michael K. Young Chapter 3 Rio Grande Cutthroat Trout ................................................................................ 24 John N. Rinne Chapter 4 Bonneville Cutthroat Trout .................................................................................. 28 Jeffrey L. Kershner Chapter 5 Yellowstone Cutthroat Trout .............................................................................. 36 Robert E. Gresswell Chapter 6 Synthesis of Management and Research Considerations ............................ 55 Michael K. Young i Preface This conservation assessment for inland cutthroat ment that identifies the current distribution and char- trout focuses on five subspecies found largely on acteristics of all known populations of each subspe- public lands in the Rocky Mountain and Intermoun- cies is in preparation. tain West. Though derived from a common ancestor, A second goal of the assessment is to help manag- these subspecies have diverged at different rates to ers to make informed choices about the consequences the extent that one was proposed for elevation to full of land management for these subspecies. For some species status (Allendorf and Leary 1988) and another populations of certain subspecies, some of the data may be composed of up to three genetically distin- are available, but the habitats and life history strate- guishable groups (Shiozawa and Evans 1994). The gies of most populations are unstudied. Inventories five subspecies herein were selected because they of fish behaviors, life histories, and distribution, have become rare, they occupy lands under a vari- coupled with genetic analyses, are necessary to iden- ety of jurisdictions, and coordinated, progressive tify the total phenotypic and genotypic variability of management could halt a further decline to extinc- each subspecies, to recognize evolutionarily unique tion. Secure subspecies, those already listed under stocks, and to predict their response to management. the Endangered Species Act, and those of uncertain Future research must center on these information taxonomic status were not considered. As the ability gaps. to recognize taxonomic differences between subspe- An implicit assumption in each chapter is that these cies improves, consideration of new or existing sub- native fishes are worth saving, and that we have an species is merited. ethical and legal obligation to prevent them from The primary goal of the assessment is to identify going extinct. Though many readers may share that the state of the science for each subspecies. Recent vision, the choice of tactics to achieve it will not be treatises (Gresswel11988; Behnke 1992) summarized unanimous. Individuals, interest groups, states, and portions of this knowledge, but this assessment at- federal agencies will differ in their desire to see fed- tempts to be more comprehensive. Throughout this eral listing of these subspecies under the Endangered document, the authors sought to refrain from using Species Act or in their willingness to forfeit some information from one subspecies to interpret the bi- opportunities (to harvest fish, to angle for non- ology of another. In some instances this has been un- native fish, or to manage public lands for conflicting avoidable, because we are completely ignorant about purposes). Because these fish are vulnerable to ex- certain life history characteristics (or entire life his- tinction, we encourage the open, honest involvement tories) of subspecies. Also, the variability in length of everyone interested. A shared vision is the only among these chapters reflects the variability in our insurance for a future for these subspecies. knowledge; not surprisingly, the most abundant sub- species are also the best studied. A companion docu- Michael K. Young Literature Cited Allendorf, F.W., and R.F. Leary. 1988. Conservation interior stocks of cutthroat trout. American Fish- and distribution of genetic variation in a polytypic eries Society Symposium 4. species, the cutthroat trout. Conservation Biology Shiozawa, D.K., and R.P. Evans. 1994. Relationships 2:170-184. between cutthroat trout populations from thirteen Behnke, R.J. 1992. Native trout of western North Utah streams in the Colorado River and Bonneville America. American Fisheries Society Monograph 6. drainages. Utah Division of Wildlife Resources, Gresswell, R.E., ed. 1988. Status and management of Ogden. Final Report. Contract 92-2377. II Acknowledgments The authors thank the following people for reviewing portions of earlier ver- sions of this document: Robert Behnke Dan Mahony N. A. Binns Anita Martinez Michael Bozek Bruce May Dan Carty Tom Nesler Chris Clancy Bryce Nielson Jim Cooper Phil Pister Todd Crowl Dave Propst Don Duff Nick Schmal Lane Eskew Brad Shepard Kurt Fausch Clay Speas Mark Fowden Jerry Stefferud Chris Frissell Russ Thurow Jack Griffith Pat Van Eimeren Dale Hepworth Dan Vos Dave Langlois Robert White Names of Fishes Catostomidae Percidae Catostomus ardens Utah sucker Perca flavescens yellow perch Catostomus catostomus longnose sucker Catostomus commersoni white sucker Salmonidae Catostomus discobolus bluehead sucker Coregonus clupeaformis lake whitefish Catostomus latipinnis flannelmouth sucker Oncorhynchus aguabonita golden trout Catostomus platyrhynchus mountain sucker Oncorhynchus clarki Catostomus plebeius Rio Grande sucker bouvieri Yellowstone cutthroat Catostomus tahoensis Tahoe sucker trout Chasmistes liorus June sucker Oncorhynchus clarki clarki coastal cutthroat trout Oncorhynchus clarki Lahontan Centrarchidae henshawi cutthroat trout westslope cutthroat Micro pterus spp. bass Oncorhynchus clarki lewisi trout Oncorhynchus clarki Colorado River Cottidae cutthroat trout mottled sculpin pleuriticus Cottus bairdi fine-spotted Bonneville mottled Oncorhynchus clarki Cottus bairdi semiscaber subsp. cutthroat trout sculpin Bonneville cutthroat Bear Lake sculpin Oncorhynchus clarki utah Cottus extensus trout Oncorhynchus clarki Rio Grande Cyprinidae virginalis cutthroat trout Couesius plumbeus lake chub Oncorhynchus gilae Gila trout Gila atraria Utah chub Oncorhynchus gorbuscha pink salmon Gila bicolor tui chub Oncorhynchus kisutch coho salmon Gila copei leatherside chub Oncorhynchus mykiss rainbow trout, Gila pandora Rio Grande chub steelhead Gila robusta roundtail chub Oncorhynchus nerka kokanee Iotichthys phlegethontis least chub Oncorhynchus tshawytscha chinook salmon Phoxinus erythrogaster southern redbelly dace Prosopium abyssicola Bear Lake whitefish Ptychocheilus lucius Colorado squawfish Prosopium coulteri pygmy whitefish Ptychocheilus oregonensis northern squawfish Prosopium gemmiferum Bear Lake cisco Rhinichthys cataractae longnose dace Prosopium spilonotus Bonneville whitefish Rhinichthys osculus speckled dace Prosopium williamsoni mountain whitefish Richardsonius balteatus redside shiner Salmo trutta brown trout Semotilus atromaculatus creek chub Salvelinus confluentus bull trout Salvelinus fontinalis brook trout Esocidae Salvelinus namaycush lake trout Esox lucius northern pike Thymallus arcticus Arctic grayling iv Chapter 1 Westslope Cutthroat Trout John D. McIntyre and Bruce E. Rieman, USDA Forest Service, Intermountain Research Station, 316 E. Myrtle Street, Boise, Idaho 83702 Introduction Westslope cutthroat trout begin to mature at age 3 but usually spawn first at age 4 or 5 (table 2). Sexu- The westslope cutthroat trout inhabits streams on ally maturing adfluvial fish move into the vicinity of both sides of the Continental Divide. On the east side tributaries in fall and winter where they remain un- of the divide, they are distributed mostly in Mon- til they begin to migrate upstream in the spring tana but also occur in some headwaters in Wyoming (Liknes 1984). They spawn from March to July at and southern Alberta (Behnke 1992). They are in the water temperatures near 10°C (Roscoe 1974; Liknes Missouri Basin downstream to about 60 km below 1984; Shepard et al. 1984). A population of adult fish Great Falls and in the headwaters of the Judith, Milk, in the St. Joe River, Idaho, included 1.6 females for and Marias rivers. On the west side of the Continen- each male (Thurow and Bjornn 1978). Average length tal Divide the subspecies occurs in the upper was 334 mm for females and 366 mm for males. A Kootenai River; the Clark Fork drainage in Montana similar population in Big Creek, Montana, included and Idaho downstream to the falls on the Pend Oreille 4.1 females for each male (Huston et al. 1984), and River; the Spokane River above Spokane Falls; the the average length was 381 mm for females