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NATIVE FISHES AND NATURAL AQUATIC HABITATS IN U. S. FISH AND WILDLIFE
SERVICE REGION II WEST OF THE CONTINENTAL DIVIDE
A Review of Population and Habitat Status and Evaluation of Survival Potentials for Native Freshwater Fishes, with Recommendations for Manaoement to Perpetuate the Indigenous Regional Fauna
by W. L. MinckiPs,'
Department of Zoolooy, Arizona State University, Tempe, Arizona 352S7
4 30 December 925 EXECUTIVE SUMMARY
Natural aquatic habitats are becoming scarce in the arid American Southwest due to man's expanding needs for water. Native fishes are in direct competition for this resource, and are rapidly losing in their struggle for existance. Judicious husbandry of existing habitats, reclamation of those which remain relatively natural, and an intensive program of management of native fishes can stop and reverse current trends toward faunal extinction. Recommendations are to treat these fishes as faunal complexes, and define, delineate, and acquire for management those habitats with attributes suitable to support groups of species in perpetuity. Already-protected and geographically remote habitats are of top priority, those used by man but still in a natural or semi-natural state are second, and others requiring increasing levels of reclamation are decreasingly emphasized. Big rivers and their fishes are most critically endangered, streams and fish species of intermediate and high elevations are least so, and special habitats and fishes are manageable through site acquisition and reintroduction programs. There is not =.uffirient time for in-depth research prior to artinnq to recover many of the imperiled species and populations. Collection of basic information on reproduction, species interactions, and population dispersion and dispersal, must occur concurrently with habitat and species recovery and management operations. Production and dissemination of carefully prepared reports will be necessary during the same time period so that application of new information can maximize successes of the program.
Recommended Citation:
NINCKLEY, W. L. 1985. Native fishes and natural aquatic habitats in U. S. Fish and Wildlife Service Reoion II west of the Continental Divide. Report to the U. S. Fish and Wildlife Service, Albuquerque, New Mexico. Deparment of Zoology', Arizona State University, Tempe, Arizona. Pp. ix + 1 5E, processed. TABLE OF CONTENTS
LIST OF TABLES vi LIST OF FIGURES vii LIST OF MAPS vii ACKNOWLEDGEMENTS ix INTRODUCTION 1 I: HISTORIC PERSPECTIVES 4 Summary of Ecoloaical Changes 4 Past and Present Aquatic Habitats 4 Fishes of the Reoion 5 Status of Regional Aquatic Habitats and Fishes 1 2 Patterns of Change in Aquatic Systems 12 Fishes Manaaement Needs, Potentials, and Plans 20 Classifications of Fishes and Available Habitats . . . 20 Management Plans .LL Needed Information 25 II: ACCOUNTS OF REGIONAL FISHES 29 Fishes of Mexican Watersheds 29 Longfin dace 29 Roundtail chub ( Yaqui form) 30 Sonoran chub 30 Yaqui chub :32 Beautiful shiner 33 Mexican stoneroller 36 Yaqui sucker 38 Yaqui cat-fish 38 Desert (Quitobaquito) pup-fish 41 Sonoran (Yaqui) topminnow 42 Fishes of the Lower Colorado River Basin 42.3 Marine Species 43 Machete ( Pacific tenpounder) 43 Striped mullet 45 Spotted sleeper 45 Big-river Fishes 45 Colorado squaw-fish 45 Bonytail 48 Humpback chub 51 Wound-fin 53 Razorback sucker 55 Flannelmouth sucker 58 Bluehead mountain-sucker 60 Big-river forms 62 Tributary stocks 62 Stream inhabitants 63 Lonafin dace 63 ▪ ▪
Fishes of the Lower Colorado River Basin (continued) Roundtail chub complex 65 Spikedace 68 Loach minnow ...... 7g Speckled dace complex ...... 72 Virgin spinedace ...... 74 Little Colorado spinedace ...... -76 Sonoran sucker ...... 77 Little Colorado sucker ...... 779 Desert mountain-sucker ...... 79 Bluehead mountain-sucker 81 Creek Fishes 82 Gila chub OZ. Las Vegas dace 84 White River spinedace 84 Pahranaoat spinedace 84 Apache trout 85 Gila trout 87 Sprinoicienecia Forms 87 Moapa dace 87 Desert pupfish 88 Monkey Sprino pupfish ag White River spingfish 91 Sonoran (Gila) topminnow 91 III: ACCOUNTS OF AQUATIC HABITATS 94 Closed Basins Laouna Salada and Salton Sink 94 Willcox Playa 98 Other Closed Basins in Arizona and New Mexico 99 Mexican Drainages 99 Rio Yaqui System 99 Rio Concepcion Watershed 100 Rio Sonoyta Basin 1 01 Lower Colorado River System 102 Rver 102 Reaches Downstream from Grand Canyon 103 Mainstream, and Tributaries in the Grand Canyon Reach 115 Gila River System 107 Mainstream Gila River 107 Downstream Reach, West of Coolidge Dam 107 Upper Gila River Mainstream .. 108 Hassayampa and Agua Fria drainages 110 Santa Cruz River Drainage 111 Lower Mainstream 112 Arivaca Creek 113 Rill ito Creek-Pantano Wash-Cienega Creek 113 Sonoita Creek 1 1 3 Uppermost Santa Cruz Watershed 114 Lower Colorado River System (continued) San Pedro River Watershed 1 L5 San Pedro Mainstream 115 Aravaipa Creek 116
Redfield Canyon and Hooker Hot Springs • • 117 Babocomari River System 117 San Carlos River Basin 118 Gila River Tributaries between San Carlos and San Francisco Rivers 119 Bylas Springs 119 Markham Creek 119 San Simon River 1 20 Bonita and Eagle creeks 120 San Francisco and Blue rivers 121 Salt River Basin 122 Lower Salt River Mainstream and tributaries 122 Upper Salt River Mainstream and Warmwater Tributaries 123 White Mountain Tributaries 1 25 Verde River and Tributaries 125 Pill Williamq Basin 1 '7 Virgin River Basin 1 28 Little Colorado River Basin 1 -)9 San Juan River Basin 1 31 ADDENDUM AND ERRATA 1 32 REFERENCES CITED 133
V LIST OF TABLES
Table 1. Common and scientific names and watersheds of occurrence of fishes in Mexican drainages
Table 2. Major patterns of ecological distributions of native fishes occupying Mexican drainages Table 3. Common and scientific names of -Fishes of the lower Colorado River basin 9 Table 4. Major patterns of distributions of native fishes o-F the l ower Colorado River basin 11
Table 5. Checklist of fishes of Fish and Wildlife Service Region II west oic the Continental Divide, with notes on occurrence, abundance, and listing status 16
Table 6. Partial listing of examples o+ Federal, State, and Private preserves that presently support native fishes and/or could be developed and managed to that end 23
Table 7. Drainages of U. S. Fish and Wildlife Service Region II discussed in text, arranged from down— to upstream 95 LIST OF FIGURES
Figure 1. Map of coterminous United States showing U. S. Fish and Wildlife Service Region II, the portion of that Region west of the Continental Divide dealt with in this report, and the collective geographic distributions of most species of fishes with which this report is concerned . . . . Figure 2. Estimated percentages of four categories of aquatic habitats at three levels of environmental quality for native fishes A Figure 3. Past and present conditions in aquatic habitats in U. S. Fish and Wildlife Service Region II west of the Continental Divide 13 Figure 4. Distribution of "high quality" aquatic habitats compared with present distributions of relatively intact, native fish communities in U.S. Fish and Wildlife Service Region II west of the Continental Divide 26 MAPS OF GEOGRAPHIC DISTRIBUTIONS
Nap 1. Sonoran and Yaqui chubs (Gila ditaenia, G. purpurea) • . . 31
Map 2. Beautiful shiner (Notropis formosus) 34 Nap 3. Mexican stoneroller (Campostoma ornatum) 37
Map 4. Yaqui sucker (Catostomus bernardini) 39
Nap 5. Yaqui catfish (Ictaluru pricep 40
Map 6. Machete and striped mullet (A ! Elops affinis; 8, Mugil cephalus) 44 Map 7. Colorado squawfish (Ptychocheilus l ucius) 46 Map 8. Bonytail (Gila elegan..7,) 49 Map 9. Humpback chub (Gila cypha) 52 Nap 10. Wo'undfin (Plagopterus argentissimuc.) 54 Map 11. Razorback sucker (Xyrauchen texanus) 56 Map 12. Flannelmouth sucker ( Catostomus l atipinnis) 59 Map 13. Bluehead mountain-sucker (Pantosteus discobolus) 61
Map 14. Longfin dace (Agosia. chrysogacfer) 64 Map 15. Roundtail chub (Gila robusta) complex 66 Nap 16. Spikedace and Moapa dace (Meda -F ulgida, Moa , a coriacea) 69
Map 17. Loach minnow (Tiaroga cobitiS) 71 Map 18. Speckled dace (Rhinichthys osculus) complex 73
Map 19. Virgin, Little Colorado, White River, and Pahranagat spinedaces (Lepidomeda mollispinis, L. vittata, L. albivall i s, L. altivelis) 75
Nap 20. Sonoran and Little Colorado River suckers (Catostomus insignis, Catostomus sp.) 78
Map 21. Desert mountain-sucker Pantosteus clarki) 80
Map 22. Gila chub (Gila intermedia) 83 Map 23. Apache and Gila trouts (A, Salmo aoache; 81 S. oilae) 86
Map 24. Desert and Monkey Springs pupfishes (Cy'prinodon macularius, Cyprinodon sp.) and White River springfish (Crenichthys bailevi) 89 Nap 25. Sonoran topminnow (Poeciliopsis occidentalis) 92 ACKNOWLEDGEMENTS
This report was researched and prepared while in residence at Dexter National Fish Hatchery, Dexter, New Mexico, on an Interagency Personnel Agreement between Arizona State University and Region II of the U. S. Fish and Wildlife Service (Albuquerque, New Mexico). George Divine and James E. Johnson of the l atter Agency arranged for and expedited that agreement. Buddy L. Jensen, Hatchery Manager at Dexter, made my tenure at the Station a memorable experience, and Sharon Coats assisted in manuscript preparation and in other ways too numerous to mention; support of other Station and Regional Office personnel also is acknowledged. Paul C. Marsh of Arizona State University assumed and performed many of my duties at that institution, assisted with literature for this report, and expedited other segments of the project. Divine, Johnson, Jensen, Coats, and Marsh read, criticized, and improved the manuscript at various stages in its long development, as did Pat L. H. Minckley in its final draft. I thank them all. Any errors or omissions remain solely my responsibility.
ix INTRODUCTION
of North America degradeO the technological development Settlement and streams, fish habitat. Since springs, quality and quantity of Continent's and i ndustrial uses, for domestic, agricultural, l akes provide water flow and and Watercourses cea....ed to dammed, diverted, and depleted. they were provided convenient dumping Aquatic systems also l evels declined. l ake for i ndustry, and many became energy and coolants sites for wastes, plus Mh.t were so that aquatic life suffered. or otherwise modified polluted fishes and other animals, introductions of non—native further changed by the original modified environments than seem tatter adapted to which often generally displaced native upon, competed with, and -f orms, and preyed species. American freshwater fishes and .subspecies of North At l east 25 species Ono et al. 1 := ?? between 1900 and 1 981 ( 933)(.. • suffe.red extinction Department of were listed by the U. S. Fifty—four United States fishes an additional 150 kinds threatened or endangered and .I nterior (192Fi) a. Federal jeopardy and probable candidates for the were believed to be in Nation's Endangered Species List. Almost four percent of the Threatened or disaopeared and another 30+ of freshwater fishes thus has 660 species populations so l ow the ess than a century to percent has declined in far l continued existance i s threatened. pressing - means i s ore t4 the most extinction thii ough unnatural !Species even more Losses of faunas are obviously biolodica problems of today. of principles involved in indioative of major misunderstandinos serious, contained in the natural resources. Information judioious uss of renewable in s far greater than that stored complement of a sinole species i genetic take human example, which if burned would our library repositories, for inchmpletely. r;enetic records l oat generafione. to recover, and then unique combination be extinction can never again in their through unnatural change. and selection to provide additional evolutionary acted on bx ohance extinction is forever. The lineage i s gone)since the Spec es Act n+ 1975 (P._. 93-204) With pas.-age of the Endangered 3ervioe ( USFWS) Government through its Fish ant United States those uf Lnt initiated action to pnesnt l ueeee in USFWS Region II extinction. With respect to fishes already fading Oklahoma, and Texas), about 40 kinds ( species, ( Arizona, New Mexico, and listed or afforded populations) have been i dentified subspecies, and protection of Recovery efforts have included candidate status or listing. species in f.rilitie. of the more critically endangered more than a third NF'7D in New Mexico. Efforts in Dexter National Fish Hatchery il, liXie have included propagation State and Fehieral adencie. chnjunrtion with othar or a number of severely i mperiled and reintrohuction hack into nature has, for one example, included springs, forms. Habitat acquisition the San southeastern Arionna to establish mar...hland.;, and artesian wells in i: NWR), principally dedicated to Bernardino National Wildlife Refuge United States. These and Rio Yaqui fish fauna in the perpetuation of the the trend po.sitiiities +hr reversal of ei tce.ieeq i nHihate other initial fish fauna of a few species, but the regional toward extinction of not just the American Southwest. The present document deals with the status of native fishes in USFWS Region II (hereafter Region) west of the Continental Divide (Fig. 1), one of the most critical areas of freshwater fish endangerment. Included are the vast lower Colorado River basin, plus headwater of three Mexican drainages that scarcely penetrate the United StatesTyet contribute a substantial portion of the Southwestern fish fauna. Some areas outside the Region, i.e., the White River drainage of eastern Nevada and the Salton Sea of California, are included in the conviction that geographic continuity is more important than political boundaries. This treatise provides a review of past, present, and projected distributions and population sizes of these animals, assesses reasons for changes in their status, and outlines measures that must be taken to insure their survival. Published papers, unpublished reports, and previously unrecorded information are summarized in three major Sections: I) a narrative with appropriate figures and tables dealing with the general status of Regional aquatic habitats and fishes; II) detailed accounts of species in each major geographic and ecological subfauna; and III) reviews of habitat conditions in each major watershed.
The first Section is in l arge part a summary of the following two, developed with a minimum of citations in text in an attempt to provide a readable overview of existing problems and recommended solutions. Section II cites details on historic, present, and projected status of species within the context of availability of required and/or preferred aquatic habitats. The third Section discusses the status of aquatic systems and habitats, and their suitability and potentials for management that should accomplish the goal of preventing extinction andin fact,result in faunal perpetuation in this rapidly developing Region. It is apparent that such an end may only be attained if we move quickly to protect and improve habitats to the point that native fish populations will increase to secure l evels, at which time listed species may be downlisted or delisted. Habitats and populations of unlisted species will be similarly maintained through association, or if depleted, increased sufficiently through direct action that listing will not be required. This report deals only with the kinds and bits of information judged to be required to perpetuate native fishes in the American Southwest. There was little or at most a secondary consideration of amenities required in modern-day politics of conservation, although awareness and acknowledgement of social, political, and economic ramifications implicit in statements of needs for conservation creep in from time to time. The reader should consider this rationale prior to spending time formulating arguments against (or perhaps for) proposed actions that may seem unreasonable or unrealistic when considered from the viewpoint of special interests other than mine. Figure I. Ma; cotermHsus United States showincl U. S. Fish and ',1ildli4e
3enk)ice Regicn II ( ta7k outline; ArHzona, Mexidc, Gklahoma, and Texas), ant the p:rtidh the i' eg:ch i,:est the :ch inente: DiHde ':, &.:tted line) deat wit`i t Hs h.eport, ahd .1::0-efricc 7 edtive geograch]c dHstr!dutions
,'„hat:hed a7sa 7iost spedies i shes 4ith !AJhich thHs -ep-_-,7t is dsnderned.
TI: HISTORIC PFRSPFCTIVFS
Summary of Ecological Changes
Past and Present Aquatic Habitats.
Much 04 the Regional area west o+ the Continental Divide is classed as desert (Brown 1 982). Evapotranspiration oreatly exceeds precipitation, so surface waters must depend either on subsur4ace sources or runo++ -from adjacent, higher—altitude and more mesic terrains. As might be expected, springs. streams, and lakes were rare in the past when compared to more mesir zones. Past aQL.tic habitats were nonetheless diverse, consisting of l arde, meandering, marsh—lined rivers in l owlands, +ed by canyon—bound river. and streams nf in elevation., which depended in turn on drainage -from mountain creeks (Minckley and Brown 1 922). Springs clustereC along 7nnes nf c;e l onir activity were more abundant than today, water tables were higher since vast basins +illed with coarse debris and rimmed by impervious stone were -filled to near the land surface, and streams and l akes were thus -far more reliable in discharge and levels (Miller 1 961; Cooke and Reeves 1976; Hendrickson and Minckley 1 96ff; Minckley at al. 1966). Floods were ameliorated by dense riparian vegetation and tinned alluvial plains (Hinckley and Brown 1 982). Fish +aunas consisted o+ a 4ew hidhly adapted species that occupied discrete niches in the system, and had done so -for miller ( Smith 1 172, 1 961a; Hinckley et al. 1 986). Direct anthroproenic mndi+irations tecoan.Q.4..:.--- with aboriginal diversions o+ l owland rivers and streams into extensive canal systems, both in the United States and Mexico. In central Arizona these supported agriculture su++icient to +eed more than 100,000 persons, even be-fore discovery of North America by European man. However, Indian dams l eaked and each -Flood removed them, negating _awl."' permanent impacts on the system.
Technolodical accomplishments in less than a century included -par more damaoino and permanent structures and alterations. Watercourses were changed into dry arroyos or arti+icialized delivery systems throug h csnatruction s+ water storage, hydroslectris, and +lood control dams, . channelization into canals or otherwise constrained watercourses, pumoade c+ water tables below levels of recharge, and curtailment o+ -flow or replacement o+ natural patterns o4 water pas...age by regulated discharge arid/or wastewaters ( Fradkin 1 961; Rea 1 98S). More subtle alterations resulted -F rom l rnd—term and severe overgrazind by domestic livestock, direct agricultural developments on +loodplains, and upstream watershed uses such as l umbering. A pattern o+ incision in river, stream, and arroyo channels in the late 1 800s occurred as a result o+ man's indirect in+luences, possibly augmented through sni+ts in redional climate ( Hastings 1959; Hastings and Turner 1966; Cooke and Reeves 1 976). Biolodical mogiiic.tions due to accidental and intentional introductions o+ exotic plants, Invertebrates, and -fishes orovids a 7i,7 1tVE,7 / new series o- changes in the system. Numbers is4 kinds s+ +ishes in many Western United States waters have tripled due to naturalidation o+ introduced -forms ( Minckley 1972; Ho:-le 177,.La, the s++ests o+ whirr are scarcely documented and poorly understood,
4 4 4 ( 4.4 os-td.‘,"( 6 410-4 - 1 4 t 44=rig) dii:di Ole de 44„Tek A Cted titot bet-d raieXad
Estimates of absolute amounts of habitat lost or degraded below useful levels are difficult to accurately project. However, Minckley (1979a) delineated modifications of the lowermost Colorado River, Brown et al. (1981) provided general information for Arizona watercourses, Hendrickson and Minckley (1985) assessed losses of cienega and intermediate-sized stream habitats between the 1700s and today, and Rinne and Minckley (1985) provided data on headwater streams in Arizona's White Mountains. Figure 2 summarizes those papers and adds some speculative estimates for other habitat types in the Region.
Fishes of the Region.
A total of 3? species is known from the portion of Region 11 west of / the Continental Divide (Minc l ey et al. 1986). Most are unique to the Region and drainagp basins in which the iur. 444 re 1. Of 6 :,-R•TIV 64,41/10441 Gabehh wt4oi am 04T.2 eA F, - . Ea.er of 1.4.4 predomi ately Mexican._,;.e.. ..tare restricted in the United Slag' States to the rios Son ta, Concepcion, JA.d YaquilErnage basins (Table AtiOlhtleS 1). The first suppor ed in the United States ilincendemic pupfisheA //MA \-.61 v,,./(Cyprinodon macular s subspp) and l ongfin dace (Agosia chrysogaster), the , %7 1 second only Sonora chub (Gila ditaenig5, iet.-.1 the 1 4444t;d an original fauna of eight sp cies including two chubs (G. robusta -Mbsp„ G. ir purpurea), l ongf n dace, beautiful shiner (Notropis formosus), Mexican stoneroller (C sostoma ornatum), Yaqui sucker (Catostomus bernardini'!7, Yaqui catfish (Ictalurus price , and Sonoran EYaqui1 topminnow (Poecilio s o. sonoriensif)Uable 1), N Although streams occupied by these r tishes in the United States are smaii in size, most species live in a far greater diversity of habitats in Mexico (Table 2). Of 31 species known from the lower Colorado River basin, 24 are endemic at the specific level and six are in endemic genera (Table 3). There are four geographic subgroups within this distinctive fish fauna (Rinne and Minckley 1986): 1) marine species, near the river's mouth; 2) big-river fishes that range widely throughout the mainstream Colorado River and its largest tributaries; 3) a special Gila River component (including the Bill Williams River); and 4) a "middle Colorado River subfauna" that is l ocalized in the Little Colorado, Virgin, and White rivers drainages. Marine fishes penetrate the l ower Colorado River scarcely farther than the most downstream dams. The other three subfaunas have more extensive and complicated distributions, which may be sorted out into smaller subsets of species (Table 4). Big-river fishes fall into two general groups, those such as Colorado squawfish (Ptychocheilus lucius), bonytail (Gila elegans), and razorback sucker (XYrauchen texanus) that ranged widely over many bottom types, but often most abundantly over soft (sandy) substrates, and others like humpback chub (Gila cypha) and bluehead mountain-sucker (Pantosteus discobolus) that seem restricted to areas of harder (boulder-gravel) bottoms. These fishes are generally at low elevations (less than 1,500 m). Gila River fishes include a few like longfin dace, Sonoran sucker (Catostomus insignis) and desert mountain-sucker (Pantosteus clarki) that occupy a broad spectrum of habitats, while most others segregate into
S.+ ;.1;.1:::::■,;*:,.:;;;:::;:■:;: LEGEND Unmodified Modified Destroyed
PERCENTAGE 20 40 60 80 100 1
SPRINGS/CIENEGAS
HIGH ELEVATION CREEKS
INTERMEDIATE ELEVATION STREAMS
Gila R. 'Ong:§M BIG RIVERS Colorado R. 1.ccPAMV
FIGURE 2. Estimated percentages of four categories of aquatic habitats at three levels of environmental quality for native fishes. 'Terms in the legend are relative: viz. "unmodified" refers to a resemblance to the natural state, such as Aravaipa Creek, Arizona, where seven native species persist in an apparently stable assemblage; "modified" denotes chemical, physical, and/or biological changes from the natural state that influence or appear to influence native populations, an example being the Colorado River in Grand Canyon where mainstream temperatures are too cold for reproduction by native species; and "destroyed" means actually de-watered or otherwise altered so that native fishes no long occupy the habitat, such as the lowermost Gila River now maintained by domestic and industrial wastewaters and inhabited only by introduced forms.
6 Table 1. Common and scientific names and watersheds of occurrence of fishes in Mexican drainages of Fish and Wildlife Service Region II; after Robins et al. (1980) unless otherwise noted.
River Basins Common Name Scientific Name Rio Sonoyta Rio Concepcion Rio Yaqui
Minnows Cyprinidae roundtail chub Gila robusta Baird & Girard1/ Yaqui roundtail chub G. robusta subspecies2/ X Sonora chub G. ditaenia Miller X Yaqui chub G. purpurea (Girard) X3/ X
longfin dace Oclosia chrysooaster Girard A X X beautiful shiner Notropis formosus (Girard)4/ X Mexican stoneroller Campostoma ornatum Girard5/ X
Suckers Catostomidae Yaqui sucker Catostomus bernardini Girard
North American catfishes Ictaluridae Yaqui catfish Ictalurus pricel (Rutter)6/ A
Pupfishes Cyprinodontidae Desert pufish Cyprinodon macularius Baird and Girard Quitobaquito pupfish C. macularius subspecies X
Livebearers Poeciliidae Sonoran topminnow Poeciliopsis occidentalis (Baird and Girard) Yaqui topminnow P. occidentalis sonoriensis Girard X7/ X
1/ See Section II for a discussion of taxonomy of roundtail chubs and of the occurrence of this i.pecies in the United States' seoment of the Rio Yaqui system'.
2/ Robins et 1,1. (193C) rec ended against formal common names for subspecies of fishes. Coined Fames are rsed here are for convenience and not intended for other than that purpose.
Yaqui chub may have been introduced in the Rio Concepcion drainage, where it has hybridized with Sonoran chub; see Section II.
II/ See Section II for a discussion of taxonomy of beautiful shiner.
5/ See Section II for a discussion of taxonomy of Mexican stoneroller.
6/ This species occurred in the Rio Yaqui basin immediately south of the San Bernardino National Oildlife Refuge in Mexico and almost certainly was native to the United States; see Section II.
7/ Occurrence of this species in the United States' portion of the Rio Concepcion has not yet been recorded; it is abundant downstream in Mexico.
7 Table 2. Major patterns of ecological distributions of native f'shes occupying Mexican drainages in Fish and Wildlife Service Region II; horizontal lines span the.Ainas of habitats utilized by each species. Note that habitats availaole for tnese fishes in the United States all are in upper parts of Mexican drainages, so that 'stream through 'marine' environments are not available for the species except far to the south ana west; compiled principally from - HenaricXson et al. / MI, i see l'so Section II).
Creegs Streams Big rivers
Springsicienedas elevations elevations bottom types Marine
higher I ower higher l ower harder softer
--- desert pupfish-
-- Sonoran topminnow -
Sonoran chub
ceautiful shiner
Mexican stoneroiler
longfin dace
suckr
roondtail chub
Yaoui catfish
8 Table 3. Common and scientific names of fishes of the lower Colorado River basin in Fish and Wildlife Service Region II; after Robins et al. <1980) unless otherwise noted.
Common Name Scientific Name
Tarpons and tenpounders Elopidae machete, Pacific tenpounder E s aff nis Regan Trouts, chars, salmons, graylings, and whitefishes Salmonidae Apache trout Salmi° apache Miller Gila trout Selma aLLIt Miller Minnows Cyprinidae l onofin dace A -osia chrysogaster Girard humpback chub Gila cypha Miller bonytail G. elegans Baird & Girard rounetail -hut Q. rebucta Baird & Girard Colorado roundtail chub G. r. rocusta Baird & Girarcil/ Moapa roundtail chut G. rotusta subspecies= Pahranagat roundtail chub G. r. , ortani Tanner Virein "tunetati chub G. r. semiruoa Cope 3 chubs '; 4 uncertain status G. robLisfa, i rrerfe cemis / Gila chub Gila i rtermedia 0Girard,' White River spinecace Lepidome:a altivallis Miller & Hubbs Pahranagat spine:ace L. altivelis Miller & Hubbs Virgin spinedace L. mollispinis Miller & Hubbs Meadow Valley spinedace L. m. oratensis Miller & Hubbs Virgin River sptnedace L. m. mol'ispinis Miller & Hubbs Little Colorado spinedace Lepidomeda vittata Cope spikedace Meda fulqida Girard Moapa dace Moapa cortacea Hubbs & Miller woundfin Plaqopterus aroentissimus Cope Colorado squawfish Ptychocheilus lucius Girard Las .'egas dace Rhinichthys deaconi Miller speckled dace Rhinichthys osculus (Girard) Colorado speckled dace R. o. iarrowi (Jordan & Evermann) Meadow Valley speckled dace R. osculus subspecies Moapa speckled dace R. o. moapae Williams Pahranaqat speckled dace R. o. velifer Gilbert Preston Spring speckled dace R. osculus subspecies southern speckled dace R. o. osculus (Girard) dace of uncertain status R. osculus. i ncerte cedis.2( l oach minnow Tiaroqa cobitis Girard Suckers Catostomidae Sonoran sucker Catostomus insignis Baird & Girard flannelmouth sucker Catostomus l atiptrinis Baird & Girard Little Colorado sucker Catostomus species' Desert mountain sucker Pantosteus clarki (Baird & Girard)2/ Gila mountain sucker P. c. clarki (Baird & Girard) White River sucker P. c. i ntermedia Tanner suckers of uncertain status P. clarki, incerte cedis2( bluehead mountain sucker Pantosteus discoboius (Evermann) Colorado bluehead sucker P. d. discobolus ( Evermann) Zuni bluehead sucker P. d. jarnowt Cope and Yarrow
9 Table 3. Concluded.
Common name(.s! Scientific Name
suckers of uncertain status P. discobolus, incerte cedis2/ razorback sucker (syraucrien texanus ,:Abbott) Pupfishes Cyprinodontidae desert puptish Cyprincoon macularius Baird & Girard Salton Sea pupfish C. m. calitorniens!s Girard Sonoran :esert pup-fish C. m. mac-Jlarius Baird & Girard Nonkex Spring pupfich Ciorincdon speciesil/ No common name GoodeidaeiL l White River sprinof sn Crenichthys baileYi Gilbert great springtisn C. b. randis Williams & Wilde Noaoa sprinofish C. b. moa ae Williams & Wilde northern sprinofish C. b. albivallis Williams & Wilde Pahranagat spring-fish C. b. baile , i Gilbert thermal soringfish C. b. thermophilus Williams & Wilde Livebearers Poeciliidae Sonoran topminnow Poeciliopsis occidentalis Bard & Girard) 3ila topminnow P. o. occ dentalis (Brd. Gir.) Mullets Mugilidae striped mullet Nuoil cephalus Linnaeus Sleepers Eleotridae sootted sleeper Eleotfls picta Knerr and 2te!ndachneri2=f
h/ Robins et al. (1980) recommended aoainst formal common names for subspecies of fishes. Coined Eames are irieThere for convenience and are not intended for other than that purpose. 2/ This distinctive form may be worthy of subspecific rank, but remains under study.
3/ Included here are most populations referred by Rinne (1969, 1976) to Gila robusta Qrahami Girard, problematic fishes that are currently under study by Bruce 2..DeMarais oT-WiT51177.7a.a '.niversitY; iri Sx:t.on - s taxon was raised to specific rank by Rinne (1969, 1 976). an action that has been followed by Many western workers (Rinne and Minckley 1970. Hinckley 1973, Hinckley gl 11. 1985). It was not, however, recbgnized other than as a form of G. rctusta by Rooms et al. (Ina).
5/ Numerous distinctive kinds of speckled dace occur in the lower Colorado River basin, especially. as Tbig-river" forms in most major streams and also as isolated populations in headwaters and sprincs. Status of these may never be determined because of complexities of their variation; see Section II.
6/ The Little Colorado sucker, proposed as an undescribed species related to Catostomus latioinnis, by Minckley (1973, 1981), is yet to be formally described. 7/ Minckley (1973) provided reasoning for retaining Pantosteus as a valid genus (see Smith 1966 for The alternative view)
0/ Certain Pantosteus of the Bill Williams and Virgin rivers are distinctive and may well represent valid specii;7-777is especially so in the former stream, where P. clarki typical of the Gila River system co-occur with another form (Hinckley 1973).
9/ As with P. clarki, this highly variable taxon may include a number of unrecognized species; see section II TorT717IFer discussion of its morphological variation.
10/ The Monkey Spring pupfish, proposed as an undescribed species related to Cyprinodon macularius by Maley (1973), is yet to be formally described.
11/ Parenti (1981) demostrated that the United States genera Crenichthres and Empetrichthys belong to Tfiis otherwise live-bearing, central Mexican family. 12/ Minckley (1979) excluded Electris picta from the regional fauna.as an incidental occurrence of a Tingle individual; see Section U. Table 4. Major patterns of ecolooical distributions of native fishes of the lower Colorado River basin in Fisn and Wiibilfe Service icn 11: horizontal lines an tne kinds of habitats utilized by eacn ipecies. Complied principally fro-. 'Inckley q973, 1979a), Lee et al. (1980), and Rinne and Minckley (1986).
Creeks Streams Big rivers
Springsicienegas elevations elevations bottom types Marine
higher lower higher lower harder softer
- Moapa dace –
— desert pupfish
Monkey Spring pupfish
--Sonoran topminnow
White River springfisn
Apacne trout —
--Gila trcut ----
—Gila chub —
---- Pahranagat spinedace
— White River spinedace
Las Vegas dace
Little Colo. spinecace
---- Little Colo. sucker ----
loach minnow
speckled dace
spikedace
Virgin spinedace
desert mtn. sucker
iongfin dace
Sonoran sucker
roundtail chub
bluehead mtn. sucker-
- flanneimouth sucker
-----humpback chub
bonytail-----
Colorado squawfish —
razorback sucker —
woundfin —
machete
spotted sleeper
striped mullet elevational groups. Species most common at low el tions (less than 1,000 m) in desert tend to be ubiquitous forms, plus a few specialists like roundtail chub (Gila r. robusta) and flannelmouth sucker (Catostomus latipinnis) that inhabited larger rivers and streams along with big-river forms. Fishes such as spikedace (Meda fuloida), l oach minnow (Tiarooa cobitis), and speckled daces (Rhinichthys osculus subsp.), occupying habitats intermediate in elevation (1,000-2,000 m), live in canyon-bound streams and creeks, or in cienegas, the last consisting of complex marshlands associated with stable streams or springs (Hendrickson and Minckley 1985). Some species (desert pup-fish ECyprinodon m. macularius], Sonoran [Gila] topminnow Poeciliopsis o. occidental is]) not only occupied springs and cienegas at intermediate to relatively high elevations, but also predominated in oxbows-, marshes, and along quiet shorelines of the larger rivers (Table 4). Headwater brooks are occupied by Apache and Gila trouts (Salmo apache, S. oilae), along with only a few penetrants from lower lands. Apache trout also live in headwater creeks of the Little Colorado River. The middle Colorado River system is distinctive and far more complex, including in addition to streams a diversified mixture of warm and cool springs in the White River subbasin. These springs and their outflow streams and marshlands have special fishes. Thermal endemics are in hot springs and their outflows (Moapa dace EMoapa coriacea3) and various forms of spring-fishes (Crenichthys bailey( subsp.). Pahranagat chub (Gila robusta jordani), spinedaces (Lepidomeda spp.), speckled daces, and White River mountain-sucker ( Pantiosteus clarki intermedius) inhabit intervening - waters. Large, lowland aquatic habitats are few and occupied by such species as woundfin (Plaqopterus aroentissimus), Virgin River chub (Gila robusta seminuda), and local forms of mountain-sucker and speckled dace. Intermediate-elevation, cool-water streams of the Virgin and Little Colorado rivers basins support spinedaces, speckled dace, forms of desert and/or bluehead mountain-sucker, and Little Colorado River sucker (Catostomus sp.).
Status of Regional Aquatic Habitats and Fishes
Patterns of Chanoe in Aquatic Habitats
The greatest alterations in Regional aquatic systems are evident where dams beheaded natural rivers and waters were diverted into artificial delivery channels (Fig. 3), as in the Gila River and its major tributaries (Rea 1983). The Salt River was first impounded in 1913 by Roosevelt Dam (Roosevelt Lake), and its lower course progressively modified by three additional dams. The Verde River is similarly impounded in its lower course by Horseshoe and Bartlett dams and reservoirs. Granite Reef Diversion directs surface water from both these rivers into canals, where it is augmented by extensive groundwater pumping to supply agricultural and domestic needs for the Phoenix Metropolitan area and beyond. The Salt River channel is typically dry below Granite Reef. The l ower Gila River mainstream is similarly dewatered by Coolidge Dam (San Carlos Reservoir.) southeast of Globe, Arizona. Its waters are diverted to canals for agricultural developments in basins south and east of Phoenix. Water Fig. 3. Past (A) and present (B) conditions in aquatic habitats in U. S. Fish and Wildlife Service Region II west of the Cont- inental Divide. Past estimates of extent of aquatic habitats based on historic data and inference from early accounts cited in text, and present estimates based on personal observation. Present data are for "prime" habitats, relative or actually unmod- ified from a quasi- natural state, e.c., regulated stream reaches are excluded. The illustration is diagramatic, with many minor habitats ignored.
13 tables in this vast region also have been lowered by pumping, and infiltration is so great that runoff passes down the natural channel only during major floods. Floodwaters from both the Salt and Gila rivers are captured by Painted Rock Dam and Reservoir downstream from Gila Bend, Arizona, then slowly released to the Colorado River.
Dewatering also prevails in smaller streams due to watershed changes such as incision and destruction of cienegas, arroyo cutting, and groundwater pumping. Three such systems are the Santa Cruz River that now scarcely flows downstream from the U. S. and Mexican Boundary, the San Pedro, which is intermittent through much of its course (Hendrickson and Minckley 1985), and a large section of the lower Little Colorado that now is dry except in flood (Colton 1937). Historic evidence documents former occurrences of fishes that demanded permanent reaches of reliable habitat in all three streams. The Region's Mexican drainages have been impacted by these same factors, but all still have permanent springs or stream reaches in their watersheds. The mainstream Colorado River is perhaps second in severity of modification (Minckley 1979a; Fradkin 1981), although it still flows strongly. Storage and hydroelectric reservoirs 14 Incision of cienegas, drying of springs, and resulting reductions in water tables have substantially reduced the amount of fish habitat in the uppermost Santa Cruz, San Pedro, and San Simon basins, and headwaters of streams that flow into Mexico (Hendrickson and Minckley 1985). Introduction of mosquitofish (Gambusia affinis) in remnant habitats further reduced populations of Sonoran [Gila] topminnow through direct predation (Meffe 1983a, 1985; Meffe et al. 1983). Stocking of rainbow trout (Salmo gairdneri) for sports fisheries similarly reduced the range of native Apache and Gila trouts due to hybridization or other interactions (Rinne and irf:kley 1985). Direct changes H-1.;-'ngli and headwaters also include development of water supplies for domestic livestock. Especially damaging are containment or diversion of spring flows into concrete tanks or other structures. Such modifications for irrigation and other water supplies in White River Valley, Nevada, are documented to have reduced native fish populations in that region (Courtenay et al. 1985). Construction of farm ponds and other small impoundments associated with springs, surface streams, or even ephemeral channels in headwaters not only change flow regimes, but further provide habitat suitable for introduced fishes. Such habitats then act as sources for invasion of watersheds from upstream down, spreading non-native fishes and other organisms into otherwise isolated or inhospitable places, and supplying stocks for repopulation of natural streams after flood. Most reliably-flowing natural streams in the Region now may be placed in the classification of intermediate elevation (Fig. 3), and tend to show less faunal damage than either headwater or lowland habitats because of a number of factors. These systems are typically bound by canyons and isolated by impervious dikes of bedrock that lift subsurface, interstitial waters to the surface to insure permanency in bedrock pools. They are shaded by canyon walls and riparian gallery forests, and tend to have lower temperatures, evaporation, and salinization rates. Such streams also have substantial watersheds that insure collection of precipitation, resulting in reliable water supplies. Canyons also concentrate the impacts of high discharges, so that flood scour is pronounced and effects on introduced fishes are exaggerated. Most non-native fishes and other organisms have had little success in unregulated Southwestern streams. Floods decimate their populations, while those of native species are scarcely if at all impacted (Minckley and Meffe 1986). Intermediate-elevation streams are furthermore often too small to be considered sites for introduction of non-native, warm-water game fishes, and too warm for trouts, so fisheries development has been minimal. Their location in precipitous terrain impedes access and further minimizes man's modifications. Perhaps as importantly, they provide natural and efficient water delivery channels from highlands to densely populated lowlands where water is at a premium, so protection is advantageous not only to native fishes, but also to man. Fishes Among 57 taxa (species and subspecies) and four additional problematic populations or groups of fishes in the Region west of the Continental Divide (Table 5), at least 50 have experienced reductions in range of 50% or more since settlement by Western man (see maps in Section II). Three of 15 Tat 1e 5. TheckHst f:shes of Fish and Wildlife Service Region 11 west of the Continental Divide, with notes on occurrence, atunaance, and listing status; symools: 4 = principal annotation, a = secondary, ? = scanty data, T = orcdosed threatened, ana E = orcoosec endangered. Estimates of abundance are based on data accumulated or inferred from reports or;or to 1950, and may. be cruaely luantifiea as 4 o s: Abundant = widespread and commonly noted bY sc:ert i sts and laymen a!:.e: common = local', or seasonally abundant; scarce = noted as regular in occurrence, but considered neither ccmmonplace nor an oddity; nare = considered an oddity; and incidental = known to be unusual in a given area, but carincl elEewhere (.t/oi:ally referred t: mar:ne fisnes moving into freshwaters:). Histor c Hacites Historic Abundance Status listing pop. Ta- ,... w 1 ..L V. -7 0 '..) ; 0 0 0 .A g 1.., cu •-/ :••■ > > ow -..; w 0 m sw U status 1.4 ..... _... i-i o. 0 ..i, m Incidental. P 4 No Candidate Estuarine --) ox <4 - .1 C.11 !A - Pop, due machete Salmon. dae Apache trout 5.ila trout - x :,or:nidae.. lcnofin lace 4 - - - x X X .- numpoack :tu a 4 _ _ _ 4 X _ _ _ a _ _ - X tonytail 4 4 X - 4 - - - X rounota: chub 2cloraao roundtail cnub - X x X X x X Moapa roundta:1 :hut - - X - X x X - X x - - Pahranagat roundtai l :hut - 4 - - X x - X x X - - - X Uirgin roundta:1 chuD X - x - - X - - X x - E Yaqui roundtai! :hut X X a a A' - - x a X chubs of uncertain status. - - 4 - x X x X: x - X a X Gila chub x X - X - X - X Sonoran :nub - - X - a 4 - - X - - I Yaqui chub 4 x X - x ' X - - X White River spineaace - - X x - a X X - - - - E Oahranagat spinedace 4 - - % X Extinct - Viroin soindace Meadow Valley soinedace - - X x - - X - X - - Virgin River spinedace - - x X - X X - - X x - X - . Little Colorado spinedace - - X a X - - x A a - 4 x - - T 16 • 7ab:e f. Cont , nueC. Pistoric 114oitat Historic Abundance Status Ilsting Tax a t..11 I N 7". •1 -..:: --: = - ien - ... -: -4 • ..: 3 ': " : h -.-.. ,... .., ,3 ..... 71 ..--f I Cand -.., in . u"': :L sp,recace _ y _ x . _ y - 4 'rc a :aze _ _ . .k. ,c-u-cf , n - X x x - - / / . x Cs'sradc s:sua.iisn X _ _ ; .,, _ .. X _ - - ...as ..egas :ace - X, - x _ scesx'ed dace :d!crad: scect:e: :ace - - X x . x _ / meadow ,.4;!ek s,-...S. :ace - X - i - - : - , - "saca sceck:e: :ace ,e - _ Panranagat saez e: daze - - Y. _ x x x. Preston sor:::. sax!d. :ace - - X - - . t . southern speck!e: taze - - X - - X: - , - - aace of uncerti:n status - X X: X X A X X X X A X Coach minnow X X - X - E - beautiful shiner X X x X X - - X Mexican stonercner X: x X v - x ' x 'I, Catsstomidae Sonoran sucker . .x. X X x X X - X X flannelmouM. ace- -. X X x - X X - _ X X tt:e :olcrit: E::::F2r - - X X X X X - - X X X Yaqui sucker - - X X x - X - x 7 x 7 desert mountain-sucker southern des. at.-sucker - X x X x C X - X X White River mtn.-sucker - X X . - X X X suckers cf vicrto. status- - X X x X X - C x bluehead micunta:n sucxer Colo. blhd. mtn.-sucker - x X x 4 - x Zuni mounta , n-sucker X - - X - . X - - Y - sucke-s of uncrtn. status - X x X - X X x - ra:orback sucKer , x x x Table 5. Concluded. Historic Webi tat.> • • Hi;toric AbOndance Status I i s t i n g pap. on -,j v v .. G ..) •••3 W Taxa '.1. , 1) • W CU I -.0 G V Cl Cl -0 :i) w GO = 1 '-' W Cl'I ••-■ r-4 I) ,-, ..-, 0 0 C L' -; :J ../ 7.) --. ..0 w VI 'Cu C. V Cl 1.4 4-1 3, 1-, ".., 1... V Cu V C. 0 G. 'Cu 7: 1: C-. -J ,.) ..J ".: Cu 0 W Incidental - '4... :"‘.' VI ..-) VI Abundant '..T1 Cl) I.-4 I: C,,) C. r-; 3 Ictaluricae '7, .) ■ 1 T Yaqui catfish A C:Irincdontidae desert pupfish Falt:r :.ea pupi , sh ' ' X X - _ _ E S:ndran ClEert pupf:sh x X X g ',i X X X - X 'Siuitobaduito p_44sn - X - i' X _ X x *Monkey Spring p 4f.en - x - - X Y - - Codeidae l te Pliver springiist great springfish - X - - X X - X - - E Moapa springfish - - X - - X X X _ - X - ncrthern springfish - - X X X - _ X - - - c Pahranagat spr:ngf:sh - - X - - X X - - X - E thermal springish - - X - - - X X - - X - - X - Poeciliidae Sonoran topinnow S:la toominnow - - X x x X X X X - x '" - - X Yaqui topminnow - - X x x X X X x - - X tiugilidae striped mullet X x x X X X - - x X X - Eleotridae spotted sleeper X x x X - - X - X X 18 these species are extinct, eight are federally listed as endangered, another as threatened, 11 are proposed as either threatened or endangered, and 12 are included on a listing of candidate species. Of the Mexican forms (Tables 1, 2), all those of the rios Sonoyta and Concepcion persist, although l ongfin dace has disappeared from the United States' portion and desert pup-Fish is most abundant in a largely man-made refuge at Organ Pipe Cactus National Monument. The pup-fish is proposed as endangered (all subspecies). Sonoran chub of the Rio Concepcion basin is proposed as threatened. The Rio Yaqui fauna includes two endangered forms (Yaqui chub, Sonoran E Yaqui] topminnow), two threatened species (beautiful shiner, Yaqui catfish), and two candidate fishes (Mexican stoneroller, Yaqui sucker) (Table 5). Roundtail chub was rare and now is extirpated in the United States' portion of the Rio Yaqui, and l ongfin dace still live in a few remnant habitats. Big-river species 19 Management Needs, Potentials, and Plans Classifications of Fishes and Available Habitats Major objectives in recovery of native fishes must include identification of listed species restorable to population levels that will allow downlisting or del i sting, plus the identification of unlisted fishes that require action in insure their survival and thus preclude necessity for listing. These objectives can be realized only if habitats for the species concerned are identified, restored and restocked if necessary, then protected from factors that suppress population survival and growth. Three kinds of species can be identified in this fauna, which obviously correspond in general to subdivisions already used. Most endangered are those which are specialists in relatively large habitats. Included are the big-river fishes of the Colorado River that present special problems because of unique requirements within an otherwise l arge geographic range (Rinne and Minckley 1986). The l oach minnow is an example from smaller habitats, requiring special kinds of riffles in otherwise common types of streams (Propst et al. 1 985a). These fishes are especially difficult to manage because places they live are those which are also directly required by man for water exploitation, and modifications such as reduction of natural variability that accompanies reliable water delivery reduces or destroys their populations. Second are those species isolated in relatively small, special habitats (special because of unique and perhaps irreplacable ecology [e.g., temperature, chemistry], or location, or isolation, or anything else) (Courtenay et al. 1985). These animals must almost be maintained in place, so the most parsimonious approach is to purchase or otherwise set aside the habitat and insure continuation. Included here are trouts, many of the pup- and springfishes, many poeciliids, etc. The third group includes habitat generalists with relatively broad geographic ranges that maintain populations in the face of at least some modificiations, e.g., l ongfin and speckled dace, roundtail chub, and some suckers. Increasing rarity of some of these seems attributable to pressure from non-native fishes or other organisms, as does the ultimate disappearance of some species in the first two groups. 20 Restoration and management of all listed, proposed, and candidate forms of fishes from the Region presents an insurmountable task on a species-by-species basis. Numbers and diversities of fishes and habitats are great, distances are equally large, and expertise for such an effort is scarcely available. Co-occurrences between and among the various imperiled species, however, exist in definable geographic and ecologic patterns that allow simplification of the system. The most cost effective and biologically sound approaches to this endangered regional fauna are on the basis of these groupings. As an example, keys to restoration of both specialists of large habitats and maintenance of habitat generalists may lie in evaluation of their former common dispersion in diverse environments over broad geographic areas (Tables 2 and 4). Colorado squawfish, for instance, was undoubtedly most abundant in the mainstream Colorado River, but also penetrated far upstream in the Salt, Gila, and even San Pedro rivers. In these smaller streams they co-occurred with most species characteristic of intermediate-elevation waters. We may therefore assume that at least some habitat requirements of big-river species are met by such watercourses. Evaluation of these possibilities are critical to successful species restoration, and to pursue this goal habitats should first be delineated on a species-by-species basis as follows (in priority); I) within the natural range and relatively undisturbed - these probably will be places where the species naturally persists and should be given an "all cost" priority for maintenance; II) within the natural range and reasonable to reclaim, modify, or reconstruct; III) within the natural range, but highly modified, disturbed, or expensive in time and money to reclaim; IV) out of the natural range, but isolated in the same region and relatively undisturbed; kl) out of the native range, and otherwise as in III (above); and VI) artifical refugia. Once this exercise in compilation is completed, a beginning for which is presented in Section III, high priority habitats in each category may be sorted out by kinds of species they supported in historic time and those they support today. Those with highest probabilities of success for maintenance of greatest heterogeneity should be elevated in priority. Emphasis must be on habitat Categories I through IV for maintenance of ecological groupings of fishes. With some notable exceptions, probabilities of habitat Categories V and VI being developed for perpetuation of faunal complexes seem remote if supported by public funds, but should be feasible and encouraged through private foundations on a refugium basis. Category I habitats exist in two general states. First are those associated with a few places already recognized for some reason as valuable resources and set aside with some degree of protection by Governmental agencies or Private groups. Such places include designated and/or proposed Primitive and Wilderness areas, Research and Experimental areas, Federal Refuges, lands associated with State Parks, Private Preserves, essential habitats for threatened and endangered species, and habitats on restricted areas such as military installations (Table 6). A substantial number of these already exist, and an appropriate effort would be to identify, survey, and manage or participate in management of native fishes in these high-quality environments. The second state of Category I habitats includes stream and other aquatic habitats on Federal, State, or Indian l ands remote from development due to inaccessibility, distance from population centers, or other reasons. Indian lands are so extensive in the Region they must constitute a major storehouse of aquatic resources that has not yet been adequately assessed. Among Federal holdings, the upper Bill Williams River drainage in Arizona is relatively intact from both habitat and faunal perspectives, and recommendations for maintenance of native fishes was forwarded with recent reports of U. S. Bureau of Land Management (USBLM) survey results (Kepner 1981). Category II (and IV) habitats also exist on protected lands just discussed, but are perhaps more abundant on U. S. Forest Service (USFS), USBLM, State, and Private holdings. I mportance of water in the American Southwest is underlined by the extent of Private lands on watercourses. Early settlers claimed land on streams through necessity, and their claims descended to the present day so that distribution of Private lands parallels permanency of streams in the 1800s and before. For instance, most of the San Pedro Valley is in private ownership, whereas the lower San Simon Valley, with an historically dry or intermittent watercourse, was mostly passed over by settlers and is largely in Federal Trust. Some private holdings, e.g., upper Babocomari River and Cienega, Sonoita and Cienega creeks, upper Santa Cruz River Valley, large sections of the Verde River, and others, include important, actual or reclaimable fish habitats if they can be acquired or in some way placed under management easements. Some successes already have been achieved through acquisition of such places by Private organizations such as the Nature Conservancy (Canelo Cienega and Muleshoe Ranch [Redfield Canyon]) and Defenders of Wildlife (upper and lower Aravaipa Creek), USBLM (Aravaipa Gorge), and by the USFWS (San Bernardino, Moapa, and Ash Meadows NWRs). Compilation of information on Categories III and V is of lower priority, but such will automatically become available as data accumulates on other aquatic habitats. Refugia (Category VI) may be established at a number of levels, ranging from semi-natural artesian-fed ponds, streams, and cienegas propcsed or Federal holdings such as San Bernardino NWR (USFWS 1985a) and earthen ponds fed by pumped water at Dexter NFH to Public and Private Aquaria or Private Preserves. In the case of big-river fishes, semi-natural habitats on major USFWS Refuges along the Colorado River mainstream may be a more viable and inexpensive method of maintenance and propagation than now is available. This potential program is outlined by Minckley (1986; see also below). Management Plans Detailed management plans should be formulated on habitat, basin, and/or subbasin scales, within an overall commitment to perpetuation of the Regional fauna. Existing and potentially recoverable habitats should be Table 6. Partial listing of examples of Federal, State, and Private preserves that presently support native fishes and/or could be developed and managed to that end. Geographic Name and Available Information Location Ownership Habitats Source SE corner AZ .San Bernardino Nat- Springs, cienegas, USFWS 1985a, i onal Wildlife stream, artificial see text Refuge (NWR), USFWS ponds SE quadrant AZ Research Ranch Artificial pond, Smith n.d. (Elgin), private springs O'Donnell Cienega, Stear, ienege. private Roper Lake St. Pk. Warm springs, AGFD files Arizona St. Pks. artificial ponds Board Cluff Ranch Wildl. Pnnri.... springs Area, AGFD Kansas Settlement Ponds Wildl. Area, AGFD SW central NM Gila Wilderness Streams, springs USFS files, Area, USFS see text Gila River Reserve, Stream, backwaters Nature Cons- private ervancy files S central AZ Buenos Aires NWR, Springs, artifical USFWS files USFWS ponds It Goodding Res. Nat. Stream, springs USFS files, Area, US see text II Sonoita Creek Nat. Stream, sloughs Smith n.d., area, private MinckleY 1969d II Aravaipa Canyon Minckley Primitive Area, 1 981, Smith USBLM n.d. Aravaipa George Whittell Trust Area 23 Table 6. Concluded. Geographic Name and Available Information Location Ownership Habitats Source SW border AZ Organ Pipe Cactus Spring, artificial USNPS files, Nat. Mon., USNPS pond see text 94 AZ Imperial NWR, Colo. R., sloughs USFWS files, USFWS canals, backwaters see text H Mittry Lake Wildl. AGFD files ife Area, AGFD U Cibola NWR, USFWS USFWS files Havasu NWR, USFWS Central AZ Arlington Greenbelt Gila R., sloughs, AGFD files wildi. areas, AGFD pfLnds Sier7a 5 5 stream USFS files Area, USFS Montezuma Castle USNPS files Nat. Mon., USNPS West Fork flak Creek Stream Smith n.d. Canyon Nat. Area, USFS files USES N central AZ Sycamore Canyon Prim- Stream USFS files, itive Area, USFS see text Chevalon Creek Wildl. Stream A r, Area, AGFD N AZ Paria Canyon Prim. Stream US8LM files Area, USBLM NW AZ Lake Mead Nat. Rec. Backwaters, Color- USNPS files Area , USNPS ado River, springs see text Grand Canyon Nat. Colorado River and USNPS files, Pk., USNPS tributaries, springs see text SE Nevada Moapa NWR, USFWS Thermal springs and USFWS 1981 outflows 24 assessed from historical, contemporary, and projected standpoints as to their suitability for management of faunal complexes or species of i mperiled fishes, availability for such use within past, present, and potential patterns of water exploitation, and feasibility on biological, political, and economic grounds for maintenance of a native species fishery. Streams or other systems that are currently maintaining a native fauna should be of top priority since they will serve as models for restoration of other habitats. An illustration of probable distribution of high priority habitats is provided in Figure 4, which contrasts geographic ranges of selected taxa in various parts of the lower Colorado River basin at the time of settlement with those in the decade preceding 1985. It is apparent that fishes persist not only where natural waters are most abundant (compare Figs. 3 and 4), but also where stream channels and watersheds are least modified due to immediate or upstream protection by Indian Reservations (upper Salt River basin), wilderness or primitive areas (upper Gila River and Aravaipa Creek), or remote from human population centers (upper Bill Williams and southern Little Colorado River systems). Species complexes and subject habitats in the Region should be carefully selected and actively enhanced, when systematically followed to evaluate physical, biological, and political interactions that lead to success or failure in the management unit concerned. Expansion of these efforts to other areas and habitats requiring reclamation will thus be firmly based and far more likely to succeed. Management plans by habitats, drainage units, or subunits should be prepared and expedited by teams of Service, other Agency, and Academic personnel that include representatives of existing species' recovery teams, brought together at a common place for most efficient use of time and funds. Basin (or subbasin) wide teams should act as coordinating bodies for habitat identification, restoration, acquisition, and management, and could serve to develop species' recovery plans for those taxa yet to be so treated. Attempts should be made to focus expertise to consider all aquatic resources of selected watersheds, stream systems, or stream reaches, so that effort and monetary outlay will harvest a maximum of conservation benefit. Monitoring of natural and managed populations must be a major portion of the overall effort, and successes will be measured by establishment of numbers and qualities of populations dictated in species' recovery plans in association with self-perpetuating stocks of associated, non-listed fish species. Data acquisition on species successes or failures must further be accompanied by on-going production of carefully prepared and edited, high quality reports, to assure availability and dissemination of information and creation of the pattern of building on past experiences. Needed Information Despite substantial accumulation of data on Western freshwater fishes in the past two decades, major gaps exist in our knowledge of their basic life histories and ecological requirements (see Section II). Furthermore, aquatic systems in the American Southwest are unique, so that information Figure 4. Distribution of "high quality" aquatic habitats (outlined, from Fig. 3) compared with present distributions of relatively intact, native fish communities (darkened) in U. S. Fish and Wildlife Service Region 11 west of the Continental Divide. 26 developed elsewhere from limnology, fisheries management, and other phases of aquatic ecology often are inapplicable. Assuming adequate water quality and quantity, major habitat factors (Section III) seem to be "naturalness," reliability and predictability of discharge and discharge patterns, habitat diversity, and actual and potential biological interactions, especially with non-native fishes. Evaluation of survival potentials for fishes in the Region must be preceded or at least accompanied by a major review of existing information. Acquisition of basic data, not only on the species concerned but also on their habitats, must also comprise a major proportion of survey and monitoring activities. Faunal surveys should not only include data on occurrence and population sizes of fishes and other pertinent organisms, but also emphasize evaluations of critical biological features of subject taxa. With regard to these requirements, each major facility, e.g., Dexter NFH and San Marcos NFH and Technical Center, should be provided libraries dealing at a minimum with biological information on Regional fishes. Each should also consider acquisition, publication, and dissemination of information as major functions, with participation of technical personnel being a defined portion of their responsibilities. Basic biological information sorely needed for recovery efforts on Regional fishes include at a minimum assessments of patterns of success in reproduction and recruitment, patterns and results of species interactions, and population dispersion and dispersal in available habitats. Major functions of existing and anticipated facilities and personnel should be collection of information on these three critical areas, both in the field and under laboratory and/or hatchery conditions. Experimental studies could readily be designed, and such projects already have been accomplished at Dexter NFH (Inslee 1982; Marsh 1985; Hamman 1985b4 1986; Papoulias- Weisman 1986). Field investigations emphasized below should be paralleled by experimentation to document and confirm observations in nature. Short-lived species are far less of a problem to assess through direct field surveys than l ong-lived forms. If the former are simply present they likely represent a viable, self-perpetuatino population; failure of more than one or two year classes of a short-lived species is catastrophic. Monitoring of such fishes must be intensive, at least on a semi-annual basis, to insure that successful reproduction and recruitment are occurring. Reproducing stocks of adequate size and age strucutre must be maintained under hatchery conditions for critically endangered, short-lived forms, since a single event could lead to extinction in the wild. On the other hand, l ong-lived fishes such as razorback sucker may persist as large adults for longer than three decades (McCarthy 1986). If conditions for reproduction were (or are) such that recruitment occurred every few years (or even decades), razorback sucker, bonytail, and Colorado squaw-fish would likely be secure. If not, population declines might well occur over a relatively short period and at a time when senescence makes recovery of the species impossible. Long-term monitoring of such populations is thus i mportant, but annual production of year classes is not critical. Long-lived fishes can be perpetuated as brood stocks without production of young so long as genetic integrity is maintained, and thus remain available for propagation and reintroductions as conditions warrent. 27 Species interactions among native forms presumably were balanced and attuned over millenia of co-occurrence, and there is evidence that stream populations persist over long periods of time with little or no change despite vast fluctuations in physical environment. In one documented instance, fish populations were remarkably stable in Aravaipa Creek, Arizona, over more than 40 years of record. No native fish disappeared, nor did any invade the system (Meffe and Minckley 1986). Establishment of non-native fishes in other systems has been documented to disrupt natural p‘s terns and more often than not result in significant faunal changes Fishes of Mexican Watersheds Longfin dace, Agosia chrysogaster Girard, 1 857 (Map 14, p. 64) A general narrative and map of distribution for l ongfin dace in the Region's Mexican watersheds are included with discussion of Colorado River populations (p. 63). Three sub-populations of this ,species occur in Mexican drainages of the Region, one each in the Rios Yaqui, Concepcion, and Yaqui basins. A taxonomic evaluation throughout the geographic range of the genus is currently being completed by Dean A. Hendrickson of Arizona State University (ASU) (see Addendum). Longfin dace from the Rio Yaqui basin differ morphologically from other populations., and have been considered a distinctive form by some workers (Miller 1959; McNatt 1974); The fish formerly inhabited all permanent headwaters of the Rio Yaqui system near Douglas, Cochise County, Arizona, including artesian outflows and canals on what is now the San Bernardino NWR. It presently is restricted in that drainage to uppermost Whitewater Creek in Rucker Canyon, Leslie Creek, and the mainstream of San Bernardino Creek, a change in distribution and abundance generally attributable to reduced local streamflow. Maintenance of this form in the United States will require perpetuation and management of existing surface streams or creation of fl ing-water habitats, some of which already are planned at the San Bernardino National Wildlife Refuge (USFWS 1985a). Leslie Creek also is inhabited by two listed species (Yaqui chub and Sonoran [Yaqui] topminnow) and Rucker Canyon by the candidate Mexican stoneroller, so some protection is afforded l ongfin dace by association. Direct acquisition or achievement of a management easement for Leslie Creek, now in Private Ownership, should be explored. Permanent water in Rucker Canyon is mostly on USFS l ands (Coronado National Forest). Management plans for habitats of endangered and candidate forms that include consideration of l ongfin dace and other biotic elements of these systems should be developed and placed in operation. Longfin dace has not been recorded from the United States portion of Rio Concepcion, although it occurs in that drainage in Mexico (Minckley 1980a). A small population in Quitobaquito Spring, Organ Pipe Cactus National Monument (Rio Sonoyta basin) -)9 irolude l onofin dace aa tirP, faunal comp l e (including an undescribed species of hydrobiid snail Egenus desert pupfish, and an isolated population of Sonoran mud turtle EKinosternon sonoriense:) being perpetuated at that l ocality. A stock of 100 or more fish should i mmediately be obtained from Mexico and placed in Cluitobaquito Spring to establish a viable genetic pool. Proposed modifications for inflow of the spring should inr7!..ide shallow, flowing water, with sand.' bottoms to create spawning habitat for this indigenous Ipecies. Roundtail chub (Yaqui form), Gila robusta subsp. (Map 15, p. 66) A general narrative and map of distribution of roundtail chub in the Rio Yadui and more southern Mexican watersheds are included with di,..cu i on of Colorado !River populations (p. 65). The roundtail chub is not known from the small drainages between the Colorado River and Rio Yaqui syc.temc (Hoiden and Minckley 1 980b; Minckley et al. 1986). Subspecie.4 of this complicated group have furthermore scarcely been studied in Mexico. The only available name is Gila minacae Meek (1902), from the Rio Yaqui, which was referrer hy Miller (1976) to 0. robu..ta Baird and eirard. Roundtail phut as. tertatively recorded from what is now San Bernardino NWR by Hendrickson et al. (1981). Specimens l atled as being -From that l ocality were examined at the Univensity of Arizona, tut have not agair been found, The spec cc is abundant in Arroyo Cajon Sonito, Sonora, a few kilometers south of the U. S. and Msxioan Boundary '.. Hiendrickson st al. 1 981), and almost certainly occurred on San Bernardino NW? in the recent past. Its extirpation may be attributed to arroyo cutting and habitat destruction in San Bernardino Creek. Ponds and streams of the San B...i..acdino NWR comprise the only nstorio or potential habitat for this -F orm of roundtail chub in the United States. The fish should be readily accommodated within the faunal assemtlags ; either in constructed artificial systems that include ponds or other deep waters, or in the mainstream of San Bernardino Creek. The species recuiras relatively deep pools as adults, habitats now returning to San Bernardino Creek as.degradation reverses due to artificial gat i on installation and natural and augmented development of riparian vetetation. Brood .-torks must be arquired from Mexic o pr or to its propagation an: reintroduction, most desirably from the adjacent Arroyo Cajon Bonito. Propagation at Dexter NFH should include maintenance of genetic stocks at that station until a viable population is established at the NWR. Expertise for propagation of chubs of the genie 3i7a already is .e. ailable ( Hamman 1981, 1 982a, t). Sonoran chub, Ofla ditaenia Miller, 1 945 ( Map 1) Historic occurrence in United States: restricted, Sycamore ( Bear) Canyon, santa Cruz County, Arizona. Hi.trrir abundance : abundant to common. Geographic distribution: Rios Maotalena and Altar, co—tributaries forming the Ric Concepcion (= Asuncon), nf Sonora, Mexco („ Mi77er 0 1945; Minckley 1 9R0n). I i sting status: proposed as threatened. Reasons for decline or listing: habitat loss (likely influenced by reductions in flow due to overgrazing); listed due to potential endangerment through proposed mining development; hybridizing with introduced(?) Yaqui chub in Mexico, results of which are unpredictable. Sonoran chub is restricted in the United States to a single watershed, Sycamore (Bear) Canyon in Santa Cruz County, Arizona, on lands already set aside as a Natural Research Area administered by USES, (Coronado National Forest). Its distribution both in the United States and Mexico seems relatively intact, with the exception that Yaqui chub has appeared in the Rio Concepcion basin in Mexico (presumably intrnduced) and are hybridizing with Sonoran chub near Atascosa, Sonora (Hendrickson 1984). Restriction of the species to a single stream system in the United States and potentials for extensive-mining development in the watershed stimulated its listing. Distribution of Sonoran chub withir Sycamore Canyon has not been mapped in detail, but it appears mostly in the mainstream. This species is notorious for remaining in the largest, deepest, most permanent pools, even when flow conditions would allow -substantial expansion of its range (Minckley and Deacon 1 968; Minckley 1973). Principal dangers to the species, other than physiral modification of the watershed, are -prom introductions of non-native species, Bullfrog (Rana catesbeiana) already i s present and may have contributed to dieep , , earetnce of the native Tarahumara frog ( R. tarahumarae) from the system. Green sunfish 0 encmi., oyanellus) is present in cattle water n' tanks and the stream, but has yet to build significant populations in the latter due to violent seasonal floodino. Peniodic ( at l east annual) surveillance should be performed to monitor changes in Sonoran chub populations, detect introductions of non-native forms, and obtain baseline data on life ilistory of this i srlated species. Some additional security for Sonoran chub could be developed within its native range in the United States if seeps and springs in tributaries were developed as fish habitat through artificial creation of deep, permanent pools by means such as explosives on concrete oabions- The species also could be stocked in tanks in liu of non-native species, 555 TiflO fishes are desired ic:7 such things as pestiferous insect control, Other permanent water in the Rio Concepcion watershed, if such can be found, should also be managed for satellite stocks. Yaqui chub, Gila purpurea (Girard, 1 857) (Map 1) Historic occurrence in United States: highly restricted, upper San Bernardino Creek and artesian sprinos on San Bernardino Ranch, Cochise runty, and Ti..irkey Creek ( Morse Canyon), Giharam Cc;:rity, Arizona. Historic abundance: common to scarce. Geooraphic distribution: upper Rios Yaqui, Matape, and Sonora, Sonora, Mexico, and Willcox Playa basin in Arizona; presumably introduced in the Rio Concepcion basin, Sonora ( Minckley 1 930c, Hendrickson 1984). Listing status: endanciened. Reasons for decline sr listing: habitat loss (influenced by reductions in flow due to severe overorazing, incision of watercourses and tnainage of cieneoas, and tramp lino of habitats by cattle), 22 Astin Spring, comprising the headwaters of Black Draw (San Bernardino Creek), was the last natural locality where this species was abundant in the United States. The spring emerged from beneath a ledge of volcanic rock to fill a pool three to four meters wide and seasonally to more than 100 m l ong. Depths ranged to near 0.75 m. Just prior to its drying in 1969, thousands of Yaqui chub and topminnow were concentrated in a shallow two by 12 m pool that had been trampled to a quagmire by cattle. Approximately 200 of each were transported to Leslie Creek, Cochise County, Arizona, and introduced (Minckley 1973); those populations flourished (McNatt 1974; Silvey 1975). A few Yaqui chub persisted (McNatt 1974) (and may now persist) in artesian bores on what is now the San Bernardino NWR. Fish from Leslie Creek were transferred to Dexter NFH in 1976, where they produced thousands of offspring, some of which were stocked in 1 980 into North and House ponds on San Bernardino NWR. The former population still exists, the latter was destroyed during attempts to remove introduced mosquitofish from the House Pond system. The stock at Dexter NFH reproduced successfully for about five years, then failed for unknown reasons (Buddy L. Jensen, USFWS, pers. comm.). It was replenished in 1934 from North Pond. Failure of natural reproduction after a few years under hatchery conditions should be examined for its potential as a problem in pond propagation of the species. Yaqui chub were discovered in summer 1985 to have repopulated deep pools of San Bernardino Creek (David Galat, ASU, pers i comm), presumably from natural migrants. The l ocality -for Yaqui chub in Morse Canyon, Arizona (Map 1), is in the endorheic Willcox Playa basin, thus indicating faunal affinities of that system to the south. The only other native fish is l ongfin dace, plus unidentified minnows and suckers that were rotenoned from Grant Creek, Graham Mountains, Arizona, prior to trout introductions (Minckley 1973). Specimens from Norse Canyon were presumably lost in the San Francisco earthquake (Hendrickson et al. 1981), so the record cannot be confirmed. Hendrickson's (see Addendum) examination of l ongfin dace from the area should be able to document if their affinities are to the Yaqui or Gila system, which will provide inferential data on faunal relationships of the Willcox basin. Plans for San Bernardino NWR (USFWS 1985a) include substantial protection for Yaqui chub, and there are few additional habitats to be developed for the species in the United States. Leslie Creek, now in private ownership, should be set aside if possible as an excellent refuge for the faunal assemblage consisting of this species, Sonoran [Yaqui] topminnow, and the Rio Yaqui form of l ongfin dace. Private, State, and Federal lands in the Whitewater Draw area northwest of Douglas should be surveyed for possible habitats. If the Willcox area cannot be verified as comprising part of the native range for Yaqui chub, resulting Category IV l ocales in that isolated basin should also be considered as introduction sites. Beautiful shiner, Notropis formosus (Girard, 1857) (Map 2) Historic occurrence in United States: restricted, San Bernardino Creek and associated artesian wells and cienegas, Cochise County, Arizona, 33 MAP 2. Geographic distribution of beautiful shiner. Symbols: outlined area = known and probable former range; right hatched area = present distribution. 34 and Mimbres River basin, New Mexico. Historic abundance: common to scarce. Geographic distribution: Rios del Carmen, Santa Maria, and Casas Grandes, Chihuahua, Mexico, and Mimbres River, New Mexico (basin of Lago de Guzman), and Rio Yaqui, Chihuahua and Sonora, Mexico, and extreme southeastern Arizona (Chernoff and Miller 1982). Listing status: threatened. Reasons for decline or listing: interactions with non-native fishes and habitat loss (influeried by reductions in flow due to severe overgrazing, incision of watercourses and drainage of cienegas, and trampling of habitats by cattle). Populations of beautiful shiner in the northern Rio Yaqui basin were formerly referred to N. mearnsi Snyder (1915) and those from the Lago de Guzman system (including Mimbres River; recorded from "Palomas Valley" by Koster [1957]) to N. formosus Girard (1857) and Moniana <= Notropis) santamariae Evermann and Goldsborough (1902) (Hubbs 1954; Minckley 1973; Hubbs and Miller 1978). Chernoff and Miller (1982) analysed variation in this droup and reduced all nominal forms to synonymy with N. formosus, with no recognized subspecies. Notropis mearnsi was described from San Bernardino Creek in Sonora Mexican stoneroller, Campostoma ornatum Girard, 1857 (Map 3) Historic occurrence in United States: restricted; tributaries to Rio Grande, Texas, in the vicinity of Big Bend National Park, and uppermost Rio Yaqui in Rucker Canyon, Arizona. Historic abundance: abundant to common. Geographic distribution: Big Bend region of Texas and extreme southeastern Arizona, west to the Rio Sonora, Sonora, and south to the Rio Aguanaval, Zacatecas, Mexico (Burr 1976, 1980). Listing status: candidate. Reasons for decline or listing: habitat loss (likely influenced by reductions in flow due to overgrazing); candidate status due to restricted distribution in the United States. Populations of Mexican stoneroller in the United States are obviously peripheral to its major distribution. The isolated population in Rucker Canyon, Chiricahua Mountains, Arizona (Coronado National Forest), was formerly known as Campostoma pricei Jordan and Thoburn (in Jordan and Evermann 1896). Minckley (1973) referred it to C. ornatum pricei. However, Burr's (1976) review of the species indicated no definable subspecies anywhere in its extensive range. Occurrence of two small specimens in collections from Leslie Creek, Arizona (McNatt 1974; Silvey 1975), must have resulted either from an unsuccessful transplant or contamination of a field collection. None has been taken in recent years nor does the habitat in that stream appear suitable for the species. Identification by Minckley (1973) of a putative hybrid between Mexican stoneroller and roundtail chub from Aravaipa Creek (Gila River drainage) indicates past transfers of this species. The Rucker Canyon stock has survived remarkable modifications of its habitat, including construction, maintenance, and operation of a headwater fishing i mpoundment, construction of campgrounds and access roads, periodic and sustained stockings of "catchable" rainbow and brook (Salvelinus fontinalis) trouts for a local sports fishery, and introduction and establishment of fathead minnow (Pimephales promelas) (Minckley 1973 and subsequent data). Perpetuation of this form in the Region west of the Continental Divide should include special management plans and consideration for the native stock in Rucker Canyon, examination of possiblities for introduction of new populations in fishless waters of the Chiricahua Mountains (e.R., in tributaries to the isolated Willcox Playa basin), and establishment of populations on the San Bernardino NWR, for which plans are already formulated (USFWS 1985a). Mexican stoneroller requires gravelly-bottomed riffles on which to spawn, a habitat that must be provided if a NWR population is to be self perpetuating. Adults occupy deeper pools when not in breeding condition. Stocking on the San Bernardino NWR should be directly from Rucker Canyon in early summer to take advantage of reproductive adults. Propagation of this species under hatchery conditions may be difficult due to its habitat requirements. :3 6 MAP 3. Geographic distribution of Mexican stoneroller. Symbols: outlined areas = present, disjunct and continuous range; dots occurrences of isolated populations. 37 Yaqui sucker, Catostomus bernardini Girard, 1 857 (Map 4) Historic occurrence in United States: highly restricted, uppermost Rio Yaqui in San Bernardino Creek, Arizona. Historic abundance: abundant to common. Geographic distribution: Rio Yaqui basin, Sonora and Chihuahua, Mexico, and extreme southeastern Arizona (Minckley 1980f, Minckley et al. 1986). Listing status: threatened. Reasons for decline or listing: habitat loss (influenced by reductions in flow due to severe overgrazing, incision of watercourses and drainage of cieneoas, and trampling of habitats by cattle); listed due to loss of populations within United States. This sucker is closely allied to, and possibly only subspecifically distinct from, certain nominal species of Catostomus in adjacent river basins: Sonoran sucker of the Gila River system: C. conchos Meek (1902) of the Rio Conchos system; and unstudied forms to the south (Miller 1976; Hendrickson et al. 1981; Hendrickson 1984; Minckley et al. 1986). Astin Spring, discusseLt above for Yaqui chub, was the only and also the last known locality to support Yaqui sucker in the United States (Minckley 1973). Habitat conditions apparently became too severe (too small or disturbed by cattle) for the species, which disappeared prior to final trampling to desiccation of that habitat by cattle in summer 1969. Yaqui sucker formerly must have also occupied the mainstream of San Bernardino Creek, although it was not taken there in 1941 (Miller and Simon 1943); it was originally described from Rio San Bernardino in Sonora and remains common in Arroyo Cajon Bonito a few kilometers south of the U. S. and Mexican Boundary. Yaqui sucker is wide ranging throughout the Rio Yaqui system in northeastern Mexico, where it occupies a diversity of habitats from l arge rivers to upland creeks. Based on this broad ecological tolerance, its planned re-establishment in artesian well - stream - pond complexes to be developed at San Bernardino NWR should be readily attained. Brood fish must be acquired from Mexico. Propagation at Dexter NFH and re-introduction to the NWR should be followed by maintenance of genetic stocks at the Dexter facility, until self-sustaining populations are established at San Bernardino. Other than possibilities of construction of ponds or discovery of suitable habitat on Private, State, and Federal lands of Whitewater Draw northeast of Douglas, Arizona, further expansion of the range of this species in the United States seems unrealistic. Yaqui catfish, Ictalurus price' (Rutter, 1896) (Map 5) Historic occurrence in United States: highly restricted, likely in the uppermost Rio Yaqui system in San Bernardino Creek, Arizona. Historic abundance: probably rare due to small habitat sizes. Geographic distribution: Rios Yaqui and Casas Grandes basins, Sonora and Chihuahua, Mexico, likely ranging south in Pacific coastal streams and north to extreme southeastern Arizona (Minckley and Gilbert 1980; Hendrickson 1984; Minckley et al. 1986; R. R. Miller, University of Michigan, pers. comm.). Listing status: threatened. Reasons for decline or listing: habitat loss (reductions in flow due to severe overgrazing, incision of Watercourses and :38 MAP 4. Geographic distribution of Yaqui sucker. Symbols; outlined area = present disjunct and continuous range; dot = locale of former occurrence. 39 MAP 5. Geographic distribution of Yaqui catfish. Symbols: outlined area = probable continuous range; dots = l ocales of former occurrence. 40 drainage of cienegas, and trampling of habitats by cattle); listed due to absence of a viable population within the United States. This species was described from San Bernardino Creek just south of the International Border in Sonora, Mexico, and almost certainly inhabited waters of that stream in the United States. An introduced population existed from 1899 to the late 1950s in a pond fed by Monkey Spring, upper Santa Cruz River basin, Arizona (Chamberlain 1904; Miller and Lowe 1964; Hinckley 1973). Its persistence for at least 50 years indicates a proclivity for lentic waters that may be exploitable in its proposed reintroduction into the United States (USFWS 1985a). Essentially nothing is known of the life history and ecology of this catfish. It inhabits large- to intermediate-sized streams in Mexico from elevations near sea level to 2,100 m. Brood stocks must be obtained from the Rio Yaqui basin in Mexico, preferably from the upper Rio de Bavispe drainage in Sonora, prior to propagation at Dexter NFH and re-establishment of the species in artesian well - stream - pond habitats under development at San Bernardino NWR. Care must be taken in selection of broodfish since recent introductions of related species (channel and blue catfishes EIctalurus punctatus, I. furcatus]) into Rio Yaqui (Hendrickson et al. 1981) may have resulted in hybridization. The long-term impacts of these introductions on Yaqui catfish populations should be monitored. As with the Yaqui sucker, genetic stocks of this catfish should be maintained at Dexter NFH until self- perpetuating populations are established at San Bernardino NWR. Yaqui catfish will likely be maintained in the United States only on San Bernardino NWR. Little opportunity seems available for expansion of populations within its native range in the United States due to habitat limitations. Introduction of this potential food and sport fish into other drainages, which almost certainly will be proposed as its presence becomes generally known, should be actively avoided. Desert (Quitobaquito) pupfish, Cyprinodon macularius subsp. (Map 24, p. 89) A map of distribution for this form of desert pup-Fish is included with discussion of Colorado River populations (p. 88). This pupfish, inhabiting wetlands fed by Ouitobaquito Spring, Organ Pipe Cactus National Monument, has long been recognized as a distinctive subspecies (Miller 1943; Hubbs and Miller 1948a), but has yet to be provided a formal scientific name. The name Cyorinodon macularius "sonovtae," used without description in "Endemic Fishes of the Colorado River, a Status Report" by the Colorado River Wildlife Council (Anonymous 1977), is inapplicable (Minckley and Brooks 1986). Robert R. Miller (pers. comm.) has concluded that pup-fish from the mainstream Rio Sonoyta differ substantially from those in Ouitobaquito Spring, although not at more than a subspecific level. Perpetuation of this form within its native range has been jeopordized mostly by agricultural developments in the immediately-adjacent Rio Sonoyta valley of Mexico. Extensive pumping appears to be influencing the local aquifer, and pesticide blowover also has been detected in the Ouitobaquito 41 area (Kynard 1979). The United States' population is relatively secure in Organ Pipe Cactus National Monument, yet unauthorized introduction of golden shiner (Notemigonus crysoleucus) by unknown persons in the late 1960s necessitated costly removal of the pup-Fish, habitat renovation, and re-introduction of the native form ( Minckley 1973). A native population of l ongfin dace was destroyed during that operation (see above). Populations maintained in artificial tanks on the Monument were recently removed to ASU, where they are being maintained. One introduced population is established at Bog Hole, upper Santa Cruz River, and a second exists in the Babocomari River watershed, San Pedro River drainage, both in Santa Cruz County, Arizona (Minckley and Brooks 1 986). Both originated through unauthorized transplants by unknown persons. A management plan currently being developed by the USNPS for Ouitobaquito Spring includes stabilization and concentration of spring discharge, construction of an inflow stream with semi-natural pool and run habitats, and maintenance of littoral habitat in the receiving pond. Intent is to maintain. desert pup-fish along with an unique assemblage including an undescribed hydrobiid snail, an isolated population of Sonoran mud turtle, and hopefully l ongfin dace (see p. 29). If deemed necessary and appropriate, potentials for development of additional habitat exist along the same fault line that gives rise to Ouitobaquito Spring, assuming the aquifer is adequate to maintain flow at more than one or a few points. USNPS should be provided all possible expertise and assistance in endeavoring to maintain this distinctive form and its associates. Sonoran (Yaqui) topminnow, Poeciliopsis occidental is sonoriensis (Girard, 1859b) ( Map 25, p. 92) A map of distribution for this subspecies of Sonoran topminnow is included with discussion of Colorado River populations (p. 91 ). The Yaqui topminnow was originally described as Girardinus sonoriensis Girard (1859b), from Rio San Bernardino, Sonora. Minckley (1973) first included it as a subspecies of P. occidentalis which is restricted to the Rio Yaqui and lowermost Rio Mayo basins ('rijenhoek et al. 1985). Its original range in the United States included essentially all lowland aquatic habitat-;- of the upper Rio Yaqui system (Minckley 1973). The Rio Yaqui subspecies now is restricted in the United States to San Bernardino Creek, a single natural spring, and a number of artesian outflows on San Bernardino NWR (Minckley and Brooks 1 986). A population noted before as introduced from Astin Spring to Leslie Creek, Arizona, also became established and remains viable ( Minckley 1973; McNatt 1 974; Silvey 1975; Minckley and Brooks 1 986). As to be detailed below (p. 91), the Gila River form of Sonoran topminnow has been extirpated from most o+ its native range by habitat alterations, but more importantly by interactions with introduced mosquitofish ( Meffe et al. 1 983). It was oenerally assumed that Yaqui topminnow would behave similarly and disappear soon after mosquito-Fish appeared. However, the Yaqui form appears to be far more aggressive and to have higher fecundity than the Gila River subspecies ( Minckley 1972; Schoenherr 1974, 1977, 1 981), and perhaps -f or these reasons, populations 42 forced into interaction with the introduced species appear to resist extirpation, at least in more diversified habitats. Mosquito-Fish are widely used for pest control by Municipal, County, and State Public Health Service agencies in Arizona, and this presents the single major problem in topminnow management. The non-native mosquitofish was not known to be present in the Rio Yaqui basin of Arizona until the early 1970s (Hendrickson et al. 1981), but it is now being disseminated and appears to be rapidly spreading in that system, both in the United States and downstream in Mexico. It infests waters of the San Bernardino NWR. Habitats on the San Bernardino NWR that are yet to be invaded by mosquitofish must remain uncontaminated at all costs. Mosquito-Fish eradication from the NWR should be of top priority, not only for maintenance of topminnow populations, but perhaps for other species as well (see Myers 1965 and Schoenherr 1981). An attempt should be made to persuade local Public Health agencies to use local Sonoran topminnow rather than mosquitofish for pest control. Alternatively, the area should be closed to use of fishes for such purposes. Expansion of the range of this form in the upper Rio Yaqui is desirable and feasible if additional habitats can be found, secured (such as existing farm ponds), or created in the San Bernardino and Whitewater creeks watersheds. The species has remarkable capabilities for colonization in a diversity of habitats. As for other Rio Yaqui species, Private, State, and Federal lands of the Whitewater Creek valley northwest of Douglas should be explored for potential re-introduction sites. Possibilities for acquisition or management easement for Leslie Creek also should be explored, since that stream supports a large, healthy population of Yaqui topminnow, Yaqui chub, and the local form of longfin dace. Fishes of the Lower Colorado River Basin Marine Species Machete (Pacific tenpounder), El ops affinis Regan, 1909 (Map 6a) Historic occurrence in United States: sporadic in the lower Colorado River. Historic abundance: incidental. Geographic distributiori: eastern Pacific Ocean from northern Peru to Ventura County, California (Miller and Lea 1976). Listing status: none. Reasons for declines or listing: not applicable. Machete formerly penetrated to the Salton Sea, California, where they appeared in the 1940s then disappeared, apparently without reproducing (Dill and Woodhull 1942; Walker et al. 1961). They still move upstream in the mainstream Colorado River to immediately below Imperial Dam (Minckley 1973, 1979a). There are no evidences for changes in abundance of this species in historic or recent time. Its appearance is and has been sporadic, presumably relating to access and proclivity to ascend into freshwaters from the Sea of Cortez. 43 A MAP 6. Geographic distribution of (A) machete (Pacific tenpounder) and (B) striped mullet in the American Southwest. Symbols: solid dots = records since 1975; clear outlined areas = probable 1985 ranges; right-hatched areas = former, sporadic, or seasonal ranges. 44 Striped mullet, Mugil cephalus Linnaeus, 1 753 (Map 6b) Historic occurrence in United States: sporadic, related to season in the lower Colorado River. Historic abundance: abundant to common. Geographic distribution: circumequatorial in warmer seas, entering estuaries and mouths of larger rivers throughout its range (Burgess 1980). Listing status: none. Reasons for declines or listing: not applicable. Striped mullet is common throughout the reach of Colorado River and deltaic distributaries in Mexico and occur upstream to just below Imperial Dam, Arizona. A few have been recorded as large adults (greater than 50 cm total length ETL]) as far upstream as Palo Verde Irrigation Diversion near Blythe, California (Minckley 1979a). It also enters the lowermost few kilometers of the Gila River (unpubl. data). As with machete, occurrences and abundance of this species presumably relate to suitability of connections between the Colorado River and Sea of Cortez. Populations in the Salton Sea were once large enough to support a commercial fishery, but apparently failed to reproduce and dwindled to extinction (Hendricks 1961). Early residents of the Yuma, Arizona, area claimed that mullet became abundant only after construction of extensive canals and drains in that area (Dill 1944). Young—of—the—year mullet congregate in and near the mouth of the Colorado River in autumn, then move into deltaic habitats to feed and grow (Follett 1961; Hendricks 1961). Both juveniles and adults enter freshwaters to feed on plankton and detrital materials, the adults returning to the sea in spring and summer to reproduce (Dill 1944; Johnson 1 969; Minckley 1973). There is some evidence for reproduction of mullet in the lower Colorado River (Johnson and McClendon 1 970), presumably in brackish or saline backwaters of the Delta. Minckley (1979)a hypothesized - -at Colorado squawfish may have moved onto the Delta to feed on an abundance of young mullet in winter, then migrated upstream when the marine species moved back to sea in spring and summer. Spotted sleeper, Eleotris picta Knerr and StPindachner, 1 863 Historic occurrence: sporadic or incidental. Historic abundance: rare. Geographic distribution: Pacific coastal, estuarine, and l owermost freshwaters from Peru to northern Gulf of California '.. Lindquist 1 980). Listing status: none. Reasons for declines or listing: not applicable. No map is provided since a single specimen of spotted sleeper from a canal at Winterhaven, California, is the only record for the United States (Hubbs 1953). Minckley (1979a) excluded this species from the Regional fauna on the basis of no additional material. Big—river Fishes Colorado squawfish, Ptychocheilus lucius Girard, 1 857 (Map 7) Historic occurrence in United States: widespread. Historic abundance: abundant to common. Geographic distribution: endemic to 45 MAP 7. Geographic distribution of Colorado squawfish. Symbols: outlined area = past distribution; right-hatched area = present distribution; solid dots = i solated records since 1975; open circles = archaeological records. 46 l arger streams of the Colorado River basin (Holden 1980b). Listing status: endangered. Reasons for decline or listing: basically unknown - habitat loss (dewatering of lower portions of major streams in lower basin); habitat modification (direct and indirect effects of impoundment, channel ization, diversion, and regulation of discharges); and possible interactions with non-native species. This large (to more than 1.3 m TL), piscivorous species ranged throughout much of the Colorado River Delta (Snyder 1915; Follett 1961) and the Salton Sea Basin (Walker et al. 1961), northward throughout the mainstream Colorado, San Juan, and Green rivers and their major tributaries to Colorado, Utah, and Wyoming (Evermann and Rutter 1895; Ellis 1914; Dill 1944; Simon 1946; Wallis 1951; Jonez et al. 1951; Koster 1960; Jonez and Sumner 1954; Seethaler 1978; many others). It was common in the Gila River at Yuma (Dill 1944; Miller 1961), and penetrated upstream in that basin to PerKinsville, Arizona, on the Verde (Minckley and Alger 1968), from Tempe (Gilbert and Scofield 1898), the mouth of Cibeque Creek, to the crossing of the present U. S. Highway 60 on the Salt River (Chamberlain 1904; Miller 1961; Dammann in Minckley 1965), to near Tombstone on the San Pedro (Miller 1955), and to the vicinity of Safford (presumably near the mouth of Bonita Creek) on the mainstream Gila River (Chamberlain 1904). The last documented specimens from the mainstream Colorado River below Lake Mead were taken or observed in the early. 1950s (Jonez et al. 1951; Miller 1961) and from Lake Mead between 1962 and 1967 (Minckley and Deacon 1968). A few were taken from below and within Lake Powell in the 1970s, and the species still persists in that reservoir (Miller et al. 1 982; Persons et al. 1982; unpubl. data) and in the lower San Juan River (Minckley and Carothers 1980). The last documented records from the Gila River are from Salt River Canyon in 1950 (Miller 1961). The report by Branson et al. (1966) of seven squaw-fish taken at the U. S. Highway 60 bridge in Salt River Canyon was based on misidentification of roundtail chub (R. R. Miller, University of Michigan Museum of Zoology CUMMZ], pers. comm.). Reasons for decline of this and other big-river fishes remain speculative. There is no doubt in the lower Colorado River basin that dewatering of the Salt and Gila rivers reduced available habitat, and that dams not only reduced or curtailed downstream flows but also created barriers to movement of squawfish that may (or may not) be necessary for completion of the life cycle. Habitat modifications reduced diversity and created cold temperature conditions that have been documented to reduce populations of squawfish and other big-river fishes in reaches below dams (Vanicek 1967; Van icek et al. 1970; Holden and Stahlnaker 1975a, b), but such adversity does not exist throughout all parts of the system. It is apparent, however, that reproducing Colorado squawfish populations remain only in the most natural segments of the Green and Colorado rivers and some of their less modified tributaries (Tyus et al. 1982; Valdez et al. 1982a, b; Colorado River Biological Subcommittee CCRBSC] 1984), but that none of its remaining habitat can be considered as more than marginally Category I (p. 21). Introduced predators and potential competitors are abundant, but their influence on Colorado Squawfish has yet to be demonstrated. Colorado squawfish have been successfully propagated at Willow Beach and Dexter NFHs and are being reintroduced into their native range in the 47 upper Colorado River basin (Valentine 1983). Tyus (1985) expressed concern that these stockings may result in disruption of natural homing or other behavioral features of the species in that area. Reintroductions into presumably suitable habitats in the lower basin have been delayed by political concerns, but were commenced in summer 1985 on an experimental basis in the Verde and Salt rivers, Arizona. Other habitats under consideration include the lower Colorado River mainstream (Category II or III) and upper Gila River (Category I, but of relatively small size). A conservative approach is recommended to reintroduction and re-establishment of this native predator in natural streams. Large habitats for this and other big-river species are at a premium in the lower basin, and presence of squaw-fish may be counterproductive to recovery efforts for other fishes such as bonytail or wound-Fin. Preliminary data on razorback sucker already indicate substantial predation by non-native fishes such as green sunfish (Lepomis cyanellus) and flathead catfish (Pylodictis olivaris), channel catfish, and others, on newly introduced stocks (Brooks et al. 1986). Heavy predation on newly-stocked squaw-fish by non-native species may also be anticipated, so stocking sites for fry, fingerling, and/or Juveniles should be carefully selected or prepared prior to reintroduction attempts. Perhaps only juvenile stocking should be attempted in order to avoid at least some of this predation pressure. Post-stocking mnvementc, by razorback sucker are furthermore predominately downstream, so recommendations were to introduce that species high in the selected watersheds (Brooks et al. 1986). This may also be true -f or Colorado squawfish. If relatively large squawfish are available for stocking, radiotaggino would be a valuable adjunct to subsequent monitoring and study of the species. Consideration of habitats other than natural streams that are or may be made available for management of big-river fishes of the lower Colorado River system are provided by Minckley (1986) and summarized in Sectisr (pp. 102-103). Bonytail, Gila eleoans Baird and Girard, 1 853a (Map 3) Historic 'occurrence: widespread. Abundance: common to scarce. Geographic distribution: endemic to larger streams of Colorado River basin (Smith et al. 1979; Holden 1980a). Status: endangered. Reasons for decline or listing: basically unknown - habitat loss ( dewatering of lower portions of major streams in lower basin); habitat modification (direct and indirect effects of impoundment, channelization, diversion, and regulation of discharges); hybridization with humpback and roundtail chubs, due in part to factors just given and to increasing rarity in the system ( Hubbs 1955, Smith et al. 1979); and possible interactions with non-native species. A major difficulty in dealing with historical data on this species is l ocal use of the name " bonytail" +or almost any Gila in the lower Colorado River basin. One is hard pressed to separate roundtail and true bonytail records, especially since they were broadly sympatric in the system. Distributinn of bonytail in the l ower Colorado River basin nonetheless 4P MAP .S. Geographic distribution of bonytail. Symbols: outlined zone = original range; l eft-hatched area = present distribution; dots = i solated records; open circles = archaeological records. 49 seems to have resembled that of Colorado sguawfish (citations above) except it did not penetrate as far into tributaries of the Gila River. The most upstream records were Salt River at Tempe. (Gilbert and Scofield 1898) and Gila River at Ft. Thomas (Kirsch 1889); it was not definitely recorded in the San Pedro mainstream. This is likely the most endangered species in the Region. Only a few adults and no recognized young have been taken in the intensive Colorado River Fisheries Project in the upper basin (Miller et al. 1 982; Keading et al. 1986) and the last locality of occurrence in the lower basin is Lake Mohave, Arizona-Nevada, where only 24 l arge adults (all greater than 40 cm TL) have been taken in extensive trammel-netting operations since 1975 (in part Minckley 1983). Reasons for decline of this species are as obscure and speculative as for Colorado sguawfish. As already demonstrated for razorback sucker (Minckley 1983; McCarthy 1986) bonytail in that reservoir seem to be persisting without successful recruitment. Three specimens from Lake Mohave aged by otolith examination ranged from 34 to 49 years of age. There may have been little if any reproductive success since at least the early 1950s, which may have resulted from habitat modifications, interactions with introduced species, or both. No solid data have been accumulated, and the fish is now so rare that no natural populations remain for study and evaluation. Requirements for maintaining natural stocks of this species in Category I or II habitats are as yet unknown. A brood stock of hatchery produced first generation fish derived from 14 wild-caught adults from Lake Mohave is currently at Dexter NFH. The species has been artificially propagated and reared to adulthood both in concrete raceways and earthen ponds (Hamman 1981, 1982a, b). Bonytail also surprisingly produce substantial year classes under pond conditions at Dexter NFH (unpubl. data). Furthermore, young placed in a small urban lake in Blythe, California, and allowed to grow to advanced fingerling stages in isolation, later grew to average more than 25 cm TL despite an expanding population of non-native mosquitofish and African cichlids ( Oreochromis spp.) (Linda Ulmer, California Department of Fish and Game ECDFG3, pers. comm.) This provides supporting data for possible maintenance of the species and perhaps other big-river forms in semi-natural habitats (Category VI) of USFWS Refuges or other protected lands along the Colorado River (Minckley 1986) (pp. 102-103). The only reintroduction attempts have been to augment existing stocks in Lake Mohave and a single stocking in an isolated backwater, which failed. Those placed in the main body of the lake were later recorded as an individual gill-netted a few weeks after stocking (Arizona Game and Fish Department EAGFD1, unpubl. data). Loss of the backwater fish was assumed to result from predation by introduced species that survived an attempted renovation (unpubl. data). However, no direct evidence of predation was collected even in this semi-natural situation. As with Colorado sguawfish, projected reintroductions of bonytail into the lower Colorado River basin have been delayed by political disputes, but are anticipated in the near future on an experimental basis. Stocking of this form in the upper basin may be ill advised because of already-apparent problems of hybridization in the genus Gila, which involves bonytail, 50 humpback, and roundtail chubs, and may be a major factor in disappearance of the first species and decline of the second (Joseph et al. 1977; Smith et al. 1979; Valdez 1 980; Valdez et al. 1982). The same potentials for hybridization between bonytail and roundtail chub exist in the lower basin, and must be considered a possible result of any reintroduction program. The Gila River mainstream in eastern Arizona seems the most logical place to attempt re-establishment of this species. Roundtail chub is extirpated or rare in that area and chubs in New Mexico segments of the Gila River tend to be in smaller habitats far upstream from historical records or probable penetration by stocked bonytail. Humpback chub, Gila cypha Miller, 1946 (Map 9) Historic occurrence in United States: probably widespread in canyon-bound segments of the Colorado River. Historic abundance: abundant to common. Geographic distribution: endemic to larger streams of the Colorado River basin (Holden and Minckley 1980a). Status: endangered. Reasons for decline or listing: basically unknown - habitat loss (dewatering of lower portions of major streams in lower basin); habitat modification (direct and indirect effects of impoundment, channelization, diversion, and regulation of discharges); hybridization with bonytail and roundtail chubs due in part to -f actors just given and to increasing rarity in the system; and possible interactions with non-native species. The late discovery and description of humpback chub in 1946 and its proclivity for inaccessible canyons of the Colorado River system precluded collection of data on its ecology, abundance, and distribution until after major modifications had occurred. The bizzare species remains common in the lower Colorado River basin only in the lowermost few kilometers of the Little Colorado River, Arizona (Minckley 1977, 1979; Suttkus and Clemmer 1977; Minckley et al. 1981; Keading and Zimmermann 1983). It infrequently occurs in the adjacent Colorado River mainstream, which presumably is avoided due to persistently cold waters (10-15 0 C) from the hypolimnion of Lake Powell. The river warms only a few degrees in its entire passage through Grand Canyon National Park from Glen Canyon Dam to Lake Mead, even in mid-summer (Kubly and Cole 1 979). Similar exclusion of native fishes downstream from Flaming Gorge Dam on the Green River, Wyoming-Utah, was documented by Vanicek (1967) and Vanicek et al. 1970). Colorado squawfish, bonytail, humpback chub, and razorback sucker may have suffered the same fate in the Grand Canyon region. Concentrations of humpback chub in the upper basin are in the most natural habitats, the lower Yampa River, Gray Canyon of Green River, and Westwater and Black Rocks reaches of the mainstream Colorado (Valdez 1980; Tyus et al. 1982; Valdez et al. 1 982; CR8SC 1984). I nterspecific hybridization, already mentioned with reference to bonytail, seems a major factor influencing humpback chub populations in the upper Colorado River basin. Despite ample evidence of a major and perhaps l ong-term problem (Holden and Stalnaker 1970; Smith et al. 1 979, VaLdez 1980; Valdez et al. 1982), the extent and significance of hybrid influence on any or all Gila of the upper basin remains to be thoroughly documented. The reader is referred to discussions of Colorado squawfish, bonytail, and razorback sucker for considerations of other factors relating to declines of big-river fishes, including humpback chub. =: 1 MAP 9. Geographic distribution of humpback chub. Symbols: outlined area = former distribution; left—hatched zone = sporadic and/or seasonal occurrences; darkened areas = zones ci-F concentration; open circles archaeological records. 52 Annual reproduction and recruitment occur in the Little Colorado River population (Carothers and Minckley 1981; Keading and Zimmerman 1983), a Category I habitat isolated from human influences except those of recreational river-running parties. Dangers to that population consist of water fluctuations in either or both rivers, pollutional conditions that could enter the system from the vast Little Colorado River watershed, or establishment of significant numbers of predatory or competing, non-native fishes. The last is a distinct possibility, since warmwater fishes tend to congregate in the Little Colorado inflow to avoid cold waters of the mainstream. Substantial numbers of large channel catfish are at least sporadically present and are known to feed on juvenile humpback chub ( James' E. Brooks, AGFD, pers. comm.). Striped bass (Morone saxatilis) is abundant in both lakes Mead and Powell, respectively below and above the Grand Canyon, and their appearance and colonization of the lowermost Little Colorado may be anticipated. The confluence area of the Little Colorado and Colorado rivers is closed by USNPS to fishing. Regulated and limited sports fishing for large species and individuals of catfish or striped bass could, however, be used to reduce predator populations, especially if such become an actual or potential threat to the chubs. Introduced trouts ( mostly rainbow) enter the habitat during cooler parts of the year. Humpback chub was successfully propagated at Willow Beach NFH Woundfin, Plagopterus argentissimus Cope, 1874 (Map 10) Historic occurrence in United States: widespread, based on scattered records from Salt, Gila, and Virgin rivers. Historic abundance: common to scarce: Geographic distribution: endemic to middle Colorado River basin (monotypic genus) (Minckley 1980d). Status: endangered. Reasons for ZPcline or li ,t. ting: basically unknown - habitat l oss ( dewatering n+ lower portions of major streams in lower basin) and early habitat modification ( direct and indirect effects of impoundment, channel ization, diversion, and regulation of discharges), Woundfin were taken in the lowermost Colorado River basin only from the Salt River at Tempe (Gilbert and Scofield 1898) and the Gila River near Yuma 53 MAP 10. Geographic distribution of woundfin. Symbols; outlined zone = reaches of almost certain former occurrence; cross-hatched area = present range; right-hatched area = zone of sporadic or seasonal occurrence; open dots = former records. Attemped introduction sites (Minckley 1970, 1973; USFWS 1985b; Minckley and Brooks 1986) are not plotted. 54 fishes that likely interact with woundfin, and its decline may have been related more to arroyo cutting and following years of drought rather than to direct influences of man. Woundfin co-occur with endemic Virgin River spinedace and roundtail chub, flannelmouth sucker, and desert mountain-sucker in patterns of distribution and abundance that closely resemble the original state (Miller and Hubbs 1960; Cross 1975). The habitat is severe, hot in summer and cold in winter, relatively saline, and violent in flood, so only a few non-native fishes have invaded and become established in unmodified reaches of the stream. Present and proposed alterations of the Virgin River watershed pose continuing threats to this assemblage of Western fishes due to increasing demands for domestic and agricultural water. Maintenance of sufficient quantities of water (Deacon and Hardy 1982; Hardy and Deacon 1 984), natural conditions that include unregulated flooding (Minckley and Meffe 1986), and perpetuation of present water quality should allow them to persist (Cross 1975; Lockhart 1979; USFWS 1985b). Woundfin has reproduced in an outdoor, artificial stream in Nevada (Greger and Deacon 1982). It also has spawned on gravel in current from inflowing pumped water in ponds, and has been artificially propagated at Dexter NFH (Buddy L. Jensen, USFWS, pers. comm.). The species is projected to be introduced on an experimental basis into the upper Hassayampa, Verde, and Gila rivers mainstreams, Arizona, in the near future. The last system in extreme eastern Arizona seems the most likely habitat for the species to become re-established. Its flow regimes, habitat, and associated species are similar to those in the Virgin River, except for a greater predator load in the form of flathead and channel catfishes. Introductions of small numbers of wild-caught fish into a number of other Arizona streams a decade cr sc ago f ailed for '1 • 7:2=Cey and Brooks 1986). Razorback sucker, Xyrauchen texanus (Abbott, 1861) (Map 11) Historic occurrence in United States: widespread. Historic abundance: abundant to common. Geographic distribution: endemic to l arger streams of Colorado River basin (monotypic genus) (Holden 1980c; Minckley 1983). Listino status: candidate. Reasons for decline or listing: basically unknown - habitat loss (dewatering of lower portions of major streams in lower basin); habitat modification (direct and indirect effects of impoundment, channelization, diversion, and regulation of discharges); and interactions with non-native species. McAda and Wydoski (1980) and Minckley (1983) documented the status of razorback sucker in the upper and lower Colorado River basin, respectively, and should be consulted for details on this unique fish (see also McAda 1977). This large, planktivorous and detritivorous species formerly occupied a range comparable to that of Colorado squawfish (citations in that account) from the Colorado River Delta eastward almost to New Mexico, south in San Pedro River nearly to Mexico, north in Verde River to near its headwaters, and throughout the mainstream Colorado River. Populations of l arge adults (maximum TL 73 cm), with no evidence of successful recruitment of young, are in Senator Wash Reservoir, California, and Lake Mohave, =.R MAP 11. Geographic distribution of razorback sucker. Symbols: outlined area = former distribution; left-hatched zone = present range; solid dots and zone = records since 1975 of isolated individuals or stocks; open circles = archaeological records. Introduction sites (Minckley 1983; Brooks et al. 1986) are not plotted. 56 Arizona-Nevada. Only isolated individuals have been captured elsewhere in the past decade (Coachella and Palo Verde valleys, California; Paria River, Arizona; Minckley and Carothers 1980; Minckley 1983; Ulmer, CDFG, pers. comm.), and these have included only a few individuals smaller than 35 cm long. Ages of Lake Mohave specimens, determined from otoliths collected in 1980 through 1982, ranged between 25 and 43 years (McCarthy 1986). Explanations for decline of this species parallel those given for Colorado squawfish and bonytail. As with the l atter, there is little evidence for reproductive success in the lower basin since at least the 1 950s; the few juveniles that have been taken were widely scattered and often of single occurrence (Minckley 1983). Reproduction and production of l arvae has been recorded in Senator Wash Reservoir, California (Ulmer 1981), and occurs annually in Lake Mohave, Arizona-Nevada (Paul C. Marsh and Minckley unpubl. data), but reasons for absence of recruitment past the larval state are yet to be determined. A predation hypothesis (Ulmer 1 981; Minckley 1983; Loudermilk 1985) has been variably borne out. On some occasions, stomach contents of potential predators collected directly from spawning aggregations indicate minimal consumption of razorback eggs and/or larvae. Other samples indicate significant levels of predation by a diversity of non-native species. Caged larvae and those in an isolated backwater from which non-native fishes had been eradicated grew far past the size where their siblings disappeared in the open lake. When wind action breached the backwater barrier, predatory non-native fishes destroyed the larval stock in a few days (Daniel R. Langhorst, ASU, pers. comm.). Studies are designed for 1986 to evaluate predation as a factor in survival under experimental conditions in hatchery ponds at Dexter NFH. Data for a series of experiments testing possibilities of food limitation on larval survival are at present being analysed by Paloulias-Weisman (1986). Concern that morphological variation in razorback sucker from Lake Mohave might reflect extensive introgressive hybridization with flannelmouth sucker was dispelled by genetic analysis (Buth and Murphy 1984). Alien genes were present at a percentage no greater than found in comparable populations of other sucker species. Razorback suckers are the subject of an intensive, 10-year reintroduction effort commenced in 1981 on the part of the USFWS and AGFD (Brooks et al. 1986). A memorandum of understanding between those Agencies deferred listing of the species until evaluation of attempts at re-establishment (Johnson 1985). If the program fails, listing may proceed. If it succeeds, the species will presumably be recovered and listing will be unnecessary. Stocking is being carried out within the former native range in the Verde, Salt, and Gila rivers (Minckley 1983; Hamman I985a; Brooks et al. 1986). Brood stocks from Lake Mohave ( wild-caught and hatchery produced) have high fecundity and produce great numbers of viable eggs and larvae (Inslee 1982; Hamman 1985b). Reintroductions are of fry, fingerlings, and juveniles, as available, with production of larger-sized fish being a function of available pond space. Brooks et al. (1986) reported on post-stocking behavior and monitoring studies of hatchery-reared razorback s:.::ker. Resident, non-native fishes such as green sunfish and channel and flathead catfishes respond to the 57 new and concentrated food source with rapid and substantial predation. Smaller native fishes such as l ongfin dace also feed heavily on newly-stocked fry. Juvenile razorback remain near the stocking site for a time, usually until d..-kness, then move downstream. It was assumed that juveniles moving to downstream reservoirs would mature and become susceptible to capture when in spawning aggregations similar to those in Lake Mohave four to six years after introduction. Sampling of mainstream reservoirs in 1985 did not obtain the species (Brooks et al. 1986), The only recoveries of stocked fish have been from irrigation diversions down-flow from an introduction site reflecting the pattern of downstream movement. Recommendations for alterations in the recovery program included changes in stocking sites to as far upstream as feasible, both to avoid concentrations of l arger predators and provide more linear kilometers of stream in which the razorback may settle and remain. Removal of predators in reaches to be stocked also was recommended. Monitoring efforts were thought to have been too widely spread to be effective, emphasis placed on one of the three rivers should maximize information acquisition at lesser cost and effort (Brooks et al. 1986). Razorback sucker recovery possibilities in habitats other than natural streams are further discussed in Section III ( Minckley 1986). Flannelmouth sucker Catostomus latipinnis Baird and Girard, 1854 ( Map 1 2) Historic occurrence in United States; widespread'. Historic abundance: abundant to common. Geographic distribution: endemic to larger streams of Colorado River basin (Minckley and Holden 1 980). Status: none. Reasons for decline or listing: basically unknown - habitat l oss (dewatering of lower portions of major streams in lower basin); habitat modification (direct and indirect effects of impoundment, channelization, diversion, and regulation of discharoes); and possible interactions-with non-native species. Minckley (1980k) reviewed the taxonomic status of lower Colorado River populations of this l arge sucker (to 75 cm TL) and concluded that specimens 4rom uiroin River and upstream from Lake Powell most closely resembled the type description. Material from Grand Canyon National Park differed substantially. One hypothesis was that cold waters from Lake Powell favored invasion of a Little Colorado River form, resulting in hybridization and modification of the typical flannelmouth phenotype. This proposal has not yet been tested on other than morphological grounds, but Suth and Murphy (1984) demonstrated statistically significant indications of restricted gene flow among four samples (three of C. l atioinnis and one of Catostomus sp., the latter from the upper Little Colorado River basin). Populations from the Little Colorado River basin were earlier referred to an undescribed species (Minckley 1973), and there is some evidence that sucker,: from tributaries of the i)iron River also represent the last form (Minckley et al. 1986), possibly reported by Smith (1978) as C. insignis. Flannelmouth sucker remains relatively abundant in the mainstream Colorado River in and above Grand Canyon National Park ( McAda 1977; Carothers and Minckley 1981; Miller et al. 1 982). It also may persist in 56 MAP 12. Geographic distribution of flannelmouth sucker. Symbols: outlined area = former distribution; left-hatched zone = present range; cross-hatched areas = reaches of concentration. 59 the Salt River Canyon, Arizona, where it was taken in the late 1 940s. If so, this represents the last locality of natural occurrence south of the Qirgin River system. Special attention should be given to searching for this fish during monitoring operations for razorback sucker reintroductions in that area. Flannelmouth sucker in the Grand Canyon area apparently spawn in mouths of tributaries; they may be excluded from reproductive activities in the mainstream becasue of continuously cold, hypolimnic water from Lake Powell. Suttkus and Clemmer (1979) reported flannelmouth in the Paria River remaining there so long as temperature remained higher than that of the Colorado River mainstream, then moving into the larger watercourse as winter temperatures declined in the tributary. An introduction of adult flannelmouth suckers from Paria River to the mainstream Colorado River belo 7. !.1 Dam :774 (Minckley and Brooks 1 986) may have had limited success. A small individual caught in 1935 near Blythe, California (Ulmer, CFGD, pers. comm.), very likely represents reproduction from that stocking, since no other populations of reproductive adults have been known from that region for a long period of time. Flannelmouth sucker in the lower Colorado River basin should be considered a candidate for listing. Extirpation in the lower basin could easil- be a prelude to their decline upstream, as has occurred in a number of other big-river forms. H Minckley (1980k) is correct in his interpretation of Grand Canyon specimens showino hybrid influence from invasion of Little Colorado sucker, flannelmouth in that area may further be altered by -f oreign genetic influence. A project d..e..ing, the taxonomic status of lower Colorado River suckers of this group will be a necessity. Furthermore, little is known of the life history of this species (or complex), and collection of basic biologic data would be desirable before any action toward listing (see, however, McAda 1977 and Minckley and Carothers 1981). Refer to accounts of other big-river fishes +or discussion of factors likely contributing to declines of thi. species. Bluehead mountain-sucker, Pantosteus discobolus Cope, 1 872 (Map 1 2) Historic occurrence in United States: widespread. Historic abundance: abundant to common. Geographic distribution: l arger streams of Colorado River watersheo, Bear and Weber rivers of Bonneville Basin, and upper Snake River system (Smith 1766, Holden and Minckley 1980c). Listing status: mostly none, one isolated subspecies considered a candidate. Reasons for decline or listing: range reduced to an extent due to dewatering and habitat modification, but still substantial. Smith (1966) clarified nomenclature o-F this complex that was formerly known as Pantosteus delphinus (Cope) in the Colorado River system, combining a number of nominal forms from adjacent basins under the name Catostomus (Pantosteus) discobolus. Minckley (1973) gave reasons for retaining Pantosteus as a full genus rather than a subgenus of Catostomus. This species consists of a number of phenotypes, some syntopic in the mainstream Colorado and others isolated in tributaries and other drainage basins. Comments are provided separately for: 1) onpulations in the mainstream Colorado and its l aroest tributaries; and 2) sub-populations occupxino smaller streams at i ntermediate cleat i ons. MAP 13. Geographic distribution of bluehead mountain-sucker. Symbols - mainstream populations: outlined zone = present range. Tributary populations in lower Colorado River basin: dark dots = present populations; outlined zone = former distribution; ZMS = Zuni mountain-sucker. 61 Big-river forms. - Two morphological types of bluehead mountain- sucker co-occur in the mainstream Colorado River, one with a long, pencil- thin caudal peduncle and the other with that structure relatively short, thick, and stubby (Smith 1966; Minckley 1973). Development and taxonomic significance of this polymorphism is neither known nor well studied. Both forms become large in size (to 40 cm TL) and remain relatively abundant and reproducing (McAda 1977; Carothers and Minckley 1981). Detectable reductions in range are attributable to dewatering, extreme regulation, or other physical modifications of streams. As with flannelmouth sucker, little information has appeared on the life history of big-river populations of bluehead mountain-sucker. McAda (1977) presented data for the species in the upper basin and Carothers and Minckley (1981) studied it in the Grand Canyon area. This is one of the few species of Southwestern fishes persisting in substantial numbers in modified systems such as the Colorado River downstream from Glen Canyon Dam, and there are few indications as yet of population declines in that reach or elsewhere. Reproduction seems most common in tributaries (Minckley 1978), but the species is distributed throughout the Grand Canyon area. Studies of extinction-resistant species such as this may be equally as important as those on endangered or threatened species. In some way, bluehead mountain-sucker and a few other native forms are able to cope with physical, chemical, and biological changes that have occurred in Western aquatic systems, and have remained relatively common. Knowing how this is being accomplished may provide a key to the reverse situation. Tributary Stocks. - A population in remnant headwaters of the Zuni River, New Mexico, was demonstrated by Smith and Koehn (1979) and Smith et al. (1983) to comprise an introgressed hybrid smarm between the Little Colorado River form of bluehead mountain-sucker and the Rio Grande mountain-sucker (Pantosteus plebeius) that resulted from natural stream capture over the narrow divide between the Little Colorado River and Rio Grande basins. They considered it a distinct taxon of hybrid origin, the Zuni mountain-sucker (Pantosteus discobolus jarrowi, [Cope, 1874]). Hybrid influence was further demonstrated to progressively extend downstream in tributary populations of the Little Colorado River. Specimens from northeast-flowing tributaries of that stream grade in morphology to resemble thick-caudal-peduncled forms in tributaries to the mainstream Colorado River in Grand Canyon National Park. Isolated stocks in l argely-ephemeral creeks of the southern San Juan River basin, Arizona-New Mexico, resemble those in San Juan headwaters in Utah and Colorado, but are dissimilar to Little Colorado River specimens. Problems of management are amplified by such a complicated array of fishes. Each subpopulation presumably has distinctive attributes, so when conservation plans are formulated, decisions must be made as to which stocks are to be emphasized for preservation and maintenance. Populations of relatively widespread forms like bluehead mountain-sucker appear relatively secure so long as natural or semi-natural flowing waters (Categories I and II) persist in remote areas. Small, isolated waters are subject to rapid and unannounced development that can be catastrophic for such fish populations, and if possible should be set aside and earmarked as 62. natural refuoia. Fisheries management activities in Nev Mexico already have influenced populations of Zuni mountain-sucker (Merkel 1 979). A program of surveillance of selected habitats should be developed for this species complex, as for other relatively common native forms. Such periodic monitoring will allow managers to avoid late detection of population changes leading toward extirpation. Basic information may be collected on these unknown fishes dun no survey operation;. Population.. of Zuni mountain-sucker are of far more restricted range thAn most other stocks (Hanson 1 979) and thus sould be kept under a program of annual monitoring. Stream Inhabitants Longfin dace, Aoosia chrysogaster 9ir.=trri, 1657 (Map 1'7) Historic occurrence in United States: widespread. Historic abundance: abundant. Geographic distribution: Bill Williams and Gila riven; south to Rio Sinaloa, Mexico (monotypic oenus) (Minckley 1 980a, Hendrickson 1 984). Listing status: none. Reasons -f or decline or listind: rare substantial, but reduced to an extent de to ded.,letering, habitat mndifiratinn, and int4rartinn= with nnn-native c:fleries. , Longfin dace remain widespread and abundant :r the l ower 3:] nrad,r River basin, occupyino habitats ranning from intermittent, watercourses, through moderate-sized streams such as 9alt and ',:erHe to some mountain creeks. Its success is largely because n-F hahitat versatHitx, resistance to environmenta7 extremes, and a caoatflity tn reproduce throughout much of the year. This fish remarkably capable of persisting in hot, intermittent, low-desert streams where it ac ,r.. umec. the role of an omnivore. Spawning is throughout the year, but most inten,..e in Eggs spring in summer. are deposited in bottoms and sides of depressions. duo by swirlinin antivitiec, of adult'. in rlear, sanriy aspects of the ecology of . this species have teen discussed ty Koster (1757), Mincklex and Barter (197C). Mincke/ 9- 73, Lewis Schreiber and Minckley (19'22), Fisher at al. '..19S1), and (19S2: Dean A. Hendrickson (ASU) is currentl/ completino a systematic study of the genus throughout its extensive ranoe. Long-fin dace has been introduced into the C)irgin, Hualapai, Zuni, Nimbres, and Rio Grande watershed'.., andis established at least in the Hualapai and Nimbres baAin. ,.. (Koster, 1957; M:rickley 1973, 1980a; Hendrickson unpubl. data). Imminent extirpation of the speries in the Rio Sonoyta and its decline in the Yacui 'basin Y]E-79 disoussed above (p. Notwithe ..anding its persistence, Deacon ant Minckley (1974) presented evidence that the range longfin dace in the Sila River basin has retreated upslope in the past century; lowland populations hae disappeared , , or constricted in range and the species has moved higher in the „., atershed A population in Aravaipa Creek, Arizona, one of the few low-desert streams set aside through Private and Federal efforts, spreads into cccl en waters of canyon segments. and becomes more abundant there d'.Jrinc drbucht, then MAP 14. Geographic distribution of l ongfin dace. Symbols: outlined area = present range, including areas now characterized by sporadic, local, or seasonal populations; dots = introduced populations. 64 dPclines t o relatively l ow population in periodc, of high, onn.Ai ,... tent discharde ( Minckley 1921). Such expansion of populations, especiallY upstream or into typically cooler stream reaches, seems an indication of major environmental change toward a hotter, more desert-like aquatic habitat, which may bode ill other fisnes in the system. Long-Fin dace are in no immediate danger of significant decline or extirpation in the Gila and Bill William.z rivers basins, except locally. The species should be included in management plans as a major component of the Sonoran Desert fish fauna, and certainly not i gnor;id because of its current abundance and widespread distribution, Roundtail chub complex, Gila robil..ta Baird and Girard, 1 9F3b ( Map 1 5) Historic occurrence in United States: widespread in the Colorado River basin. Historic abundance: abundant to rare, dependino on subspecies. .lil eographic distribution: Colorado River basin southward through Rio Yaqui basin, Chihuahua and Sonora, Mexico, to Rio Culiacan, Sinaloa, Mexico ( Minckley et al. 1986). Listino status: variable, depending on the taxon (see below). Reasons for decline or listing: variable, depending on subspecies; includes habitat l oss (dewatenino of l ower portions of major streams in lower basin): habitat modification (direct and indirect effects of impoundment, ohannelization, diversion, and reduction and renulation of di..nharo4,4): and interatinn... with non-native species. This complex s curnently under stud/ by Bruce D. DeMarais of ASU. :t has for years been considered one of the more taxonomically difficult groups in Western North America. Rinne 1 969, 1 9:7 ) elevated one nominal form to specific rank as Gila intermedia (Gila chub) and considered most problematic populations of the Gila River basin as a distinctive subspecies of roundtail chub that he referred to Gila rotusta nranami :Baird and Gi7ard (1853b), R. R. Miller (pers. comm.) examined the types of " crahami" and considers them indistinguishable from G. r. robusta. DeMarais ( pers. comm.) considers the problematic roundtail :hut popi.ilations to represent hybrids involvino and Colored: roundtal :nuts, and has documented , trat th'7_ ration either '1="adC event over mil:enia. Problematic populations Therefore cahno: be uci.isidered intergrades between subspecies in the classical sense. DeMara:si thesis will be available by spring 1986. Roundtail chub is a potentially l aroe species, achievino total l end"- of more than 40 cm in major rivers and streams. As with many Western fishes, smaller habitats tend to be i nhabited by small individuals ( Smith 1781b). They can re:Produce in their second or third year of life. Fnon`e. consist of a hioh proportion of filamentous algae, which i s surnrisino since they also feed on l aroe and small invertebrates and smaller vertebrates i ncluding other fishes (Neve 1 97,6: Schreiber and Minnkiey 1 9S2). Feedin a -from: the curfane to bottom. ern', l arce advlts Are pnone to attack artificial lures such as spinners and we and dry flies. ':'ouro frequent maroin,-; of flnwino water anri adlt= onefer =.haried, oipp,ssr especially those with overhanginc .. egetaton and undercut MAP 15. Geographic distribution of roundtail chub complex. Symbols; outlined areas = former distribution of roundtail chub; right-hatched area = present distribution; VRRC = Virgin River roundtaii chub 66 banks, boulders, or debris. Large adults often occupy eddying currents below boulders or at the downstream end of riffles (Vanicek and Kramer 1970; Minckley 1973; Neve 1976). Isolated, spring or spring-outflow populations of roundtail chub, such as those of the White and Moapa rivers, Nevada (G. r. jordani Tanner [1950] and G. robusta subspecies, respectively) are subject to declines due to reductions in discharge, modifications of aquatic habitats, and pressures from a horde of introduced fishes as discussed for endemic spinedaces (p. 84), White River mountain-sucker (p. 80), and Moapa dace and White River springfishes (p. 87 and 91, respectively) (Deacon and Bradley 1972, Cross 1976, Hardy 1982). Virgin River roundtail is similarly influenced by potential and actual physical, chemical, and biological changes in the Virgin River mainstream, to which it is essentially restricted (Cross 1 875, 1978; see also wound-fin, p. 53). The form of roundtail chub in the Rio Yaqui basin no longer occurs in the United States (p. 30), but is proposed for reintroduction to the San Bernardino NWR (USFWS 1985a); it remains relatively common in Mexico. Widespread populations of roundtail and problematic forms in the Gila River basin also have suffered progressive declines in numbers and distributions. Upper Salt River populations of roundtail chub are under severe predation pressure from introduced smallmouth bass (Micropterus dolomieui) and likely flathead catfish, with the former having been observed feeding directly on schools of fry in spring (Minckley 1973). Problematic populations of the upper Gila River in New Mexico have markedly decreased in abundance, so much so that LaSo7_inty and Minckley (1973) tentatively recorded them as extirpated. They now are known to persist in a few stream segments in that region ( Propst et al. 1985a; David E. Propst, New Mexico Department of Game and Fish ENMDGF3 pers. comm.). Substantial reaches of stream formerly occupied by roundtail, e.2. the San Pedro, middle and lower Gila, lower Salt, and much of the lower Verde rivers, either are dewatered, impounded, or adversely influenced by upstream dams. No specimen of roundtail chub has been taken from the Little Colorado River basin since 1965, when a single individual was recovered during attempted eradication of golden shiner from Chevalon Creek, Arizona, by rotenone renovation (Rinne 1969, 1976; Minckley 1 973). Populations of typical roundtail chub in the Bill Williams River maintain relatively large and stable populations (Kepner 1980, 1981), but are under increasing pressures from introduced sun- and catfishes, especially since construction of Alamo Lake, which acts as a reservoir not only for water, but for non-native fishes as well. Kepner's (1981) recommendation that the upper Bill Williams River be set aside as a native fish refuge should be expedited. If this complex of fishes had not been so widespread it would have suffered substantial population extirpation in the last two 'icades. Conservation of the roundtail chub complex of the Gila River basin, as with bluehead mountain-sucker (p. 60), speckled dace (p. 72), and other widespread and variable species (or complexes), will be a major challenge, likely accomplished only by maintenance of natural conditions in as many intermediate-elevation streams as possible. Perhaps it is best approached along with recovery efforts for species of more limited and definable distribution and ecology, a distinct possibility because of the relatively broad ecological tolerances of this evolutonary lineage. Of Spikedace, MAra fulriida 1 977 (map 1 A) Historic occurrence in United States: moderately restricted. Historic abundance: abundant to common. Geographic distribution: endemic to upper Gila River basin, Arizona-New Mexico (monotypic genus) (Rohde 1930b). Listing status: proposed endangered. Reasons for decline or - listing: habitat l oss ( dewatering of portions of major and intermediate elevation streams); habitat modification ( direct and indirect effects hf i mpoundment, channelization, diversion, and regulation of discharges); and in with non-native species. The spikedace is characteristic of streams with relatively l ow , oradiAnt and I ower velocities, with eddyino onol A And A.annforavel bottoms ( Barber et al. 1 970; Prnpst et al. 1 985a, b), It i s an Artive, viqual, mid-water feeder, mbstly on drifting benthic and terre-Atrial invertebrates (Schreiber and Minckley 1 982; Barter and Minckley 1933). Spawnino i A in spring and early summer in shallow flowino water over coarse sand or fine gravel bottoms ( Barter et al. 1970). The species formerly occupied moderate- to small-sized streams and l ower ends of creeks upstream from the Salt-Gila rivers confluence. I ts rante has been reduced complementary t o the spread of introduced red , - shiner, Amallmouth bass, and other nor-native fiA.hes in the .= y.-Atem (Minckley and Deacon 1 962, Minckley 1973), ant with dewaterino of the uppermost San Pedro River ( Minckley 1 973, Deacon ant Minckley 1 974). it persists in relatively oreat numbers only in a 20-km-lsno seoment of Arai!aipa Creek, Arizona ( Minrkley 1781), arH the upper Gila River, New Nexics (Propst at al, 1 985a, b). It seems likely that spikedace also remainA on the White Mountain Apache ReAervatinn, Ari7nnA, but it was not taken in a recent survey in that area (Propst et al. 1 985b). However, Reservation streams are now i nhabited by smallmouth bass, which may have excluded the native minnow. The only place spikedace, red shiner, and smalimouth bass have co-occurred for any period of time (at least 1972 to present) i s in the uppermost Verde River ( Barrett et al. 1 985); those communities have yet to be studied in detail, interactions amono these species that have proven detrimental to spike-bate are unknown, but the shiner is ecolooically similar i r sire, tehaHor end foot habits so it may compete +or resources in short subtly, and the bass i s a specialized, stream-adapted piscivore that may -find mid-water spikedade a hiohlx vulnerable prey item. - Maintenance n-F this species will likel / require manaoement tf unregulated streams in which it may remain i solated from introduced species such as red shiner. Research a coral y 7:seder on the interactive ernlooy of this native species with introduced fishes. Red shiner i s at present invadino the upper 0;la River of New Mexico, and spikedace is proorassively disappear r: (PrrpAt et Si. Studies and downstream frnm the area of interaction, and intensive work in that zone, should provide information on comparative ecology of the ti....: species both specifically and broadly oermane to problems of species replacement. The Aravaipa Creek population of spikedace has been intensively studied (Barber and Minckle/ 1966; Barter et al. :970, Schreiber and :932; Mincll,le/ 1931), thus provldind a baseline of information. The Verde River population has persLIted -F or more than a decade in the aca -edatoi- and MAP 16. Geographic distribution of spikedace and Moapa Dace. Symbols (Gila River basin for spikedace): outlined areas = former distribution; right-hatched zone = present range; open circles = introduced populations (now extirpated). MD = past and present range of Moapa dace. 69 potential competitors ( Ninckley 1973; Barrett et al. 1935), and prnvides a possibility for studies of rare co-existance. A ban on bait fishes already is in effect in most of Arizona, which may have been effective in slowing the spread of red shiner, yet illegal use of the latter as bait and its aggrassive dispersal from points of original introduction are resulting in continuing dispersal throughout the Region (unpubl. data). A similar ban on use of live bait in the Gila River in Ni.w Mexico should be encouraged. Reoulatory structures such as the proposed Conner and Hooker Dams should be disallowed since impoundments encouraoe piscivorous sports fishes that feed directly on native minnows and are further snught by fishermen throuoh the use of live haits. Modified streams in Arizona are furthermore widely occupied by red shiner, which is enhanced by moderation of extremes in flooding (Minckley and Meffe 1966). The species also succeeds in populating shorelines of reservoirs, in wh t ; s prL:,tatz-o, from devastating floods and from where is spreads both and HnwnstrsiPm. Loath minnow, Tiarora cobitis Girard, (Map 17) Historic occurrence in United States: moderately restricted. Historic abundance: common to scarce. Geooraphic distribution: endemio to upper Gila River basin, Arizona-New (m:not,- p : genus) ,:Minciif.ley 1930a). Listino status: proposed threatened. Reasons for decline or lieting: habitat loss ( dewataring of some intermediate-elevation streams); habitat modification ( direct and indirect effects of i mpoundment, charnel:cation, diversion, nd reoulation of discharges); and interactions with non-native species. Loath minnow formerly occupied moderate to small streams and r.'.!.,ser ends n-F creeks upstream from the -•= alt-qila rivers rnnfluence. It prefers imoderate oradient streams with turbulent riffles with medium- to high-velocity current and cobble-rubble substrate e.edia,oilially covered by filamentous aloae ( Propst et al, 1 985a). The species is tenthic in habit, and feeds or simuliid dipteranS and max-Fl:es ( Schreiber and Minckley 1 967). Spawning is beneath stones on or lateral to swift riffles ir sprino and early summer. Li:Ron minnow and red shiner are not '-: nown i:jid • Deacon 1968 and subsequent data. As with soikedace, its range has beer reduced complementary to the spread of the introduced shiner and with dewatering of the uppermost San Pedro River ( Deacon and Minckley 1 974; 1973). It remains in relatively great numbers only in Aravaipa Creek, Arizona ( Minckley 1961), and the upper Gila and San Francisco H vers, New Mexico ( Propst at al. 1 985b), and is rare in the Slue and White rivers systems of Arizona (Pilvey et al. "i 9Pi4; Prrpt et a:. 1 96Fia). Any study of interactive ecology of spikedace and red shiner (p. 85) should include loath minnow to provide a maximum of information from research funding. Interactions hetween shiner and l oach minnow that appear to prove detrimental to the native species, as with spikedace, are _.:nknown and should be studied immediatelx, The shiner i s ecologically similar in size and food habits to both l oacn minnow and spikedace, so it max compete for resources that are im short suppl>- , but the shiner scoupies MAP 17. Geographic distribution of l oach minnow. Symbols: outlined areas = former distribution; right-hatched zone = present range; open circles = introduced populations (now extirpated). 71 shallow, turbulent, aloae-covered niffles to which l oach minnow is essentially restricted) only sporadically ( Cross 1967; Matthews and Hill 1 979). it i s possible that other species, such as the young of in ofien inhabit riffle areas, are the major interference. A substantial backlog of information exists on l oach minnow in Aravaipa Creek (Barber and Minckley 1966; Schreiber and Minckley 1 932; Minckley 1 961 and ninpubl data) and the Gila River in New Mexic o (Prnost et al. 1985b) that may be applied to such a project. Damming or other regulation or modification that results in the destruction of n1-1:flee must be avoided. Construction of Conner or Hooker darns will clearly extirpate l oach minnow in the Lpper Gila River mainstream. and should be vigorously opposed. As with spikedace, maintenance of this species may further require management of unregulated streams in which it may remain isolated -From introduced species such as red shiner. Bans or the use of that species as live bait may aid in curtail in spread of introduced cyprinids ( see p. 70 ). Speckled dace complex, Rhinichthys osculus (Girard, 1 857) (Map 1 8) Historic occurrence in United States: widespread. Historic abundance: abundant to rare, depending on subspecies. Gecoraphi: dietnitution: Western North America - M Columbia 7iver basin south thnouoh Gila River basin ( Wallace 1 780). Lilting status: t'Fi'oids 7 7ii' hone, but variable, deoendino on subspeciee. Reasons -f or decline or listino: variable, depending on subspecies; includes hatitat l oss ( dewatenin,o of springs, headwaters, and middle portions of major streams in lower basin); habitat modification (direct and indirect effects of impoundment, channelization, diversion, and reoulation of discharoes): and interactions with non-native species. Morpholooical variation in speckled dace of Western North America has generally defied systematic . i nterpretation, and this plus the wide distribution and l oisal abundance of some members of the complex have tented to cause fisheries workers to i onore their population status. Williams (1976), Deacon and Williams (1964) and Mi717' (1964) have recently clarified the i dentities and distnibutione '7 4 some endemic forms in the Region. Evaluations of many others await detailed taxnnnmin studies, but the process of extinction obviously occurs whether or not a form is technically recnonizeH. Stream-inhabitino populations of speckled dace live in or adjacent t o riffiee and runs or in flowing pools. Larger adults tend to move into quieter areas where cover is available in the form of cut tanks or debris. All sizes remain on or near the bottom most of the time, feenlino principally on benthic invertebrates (Schreiber and Minckley Spawnino i s on riffle areas in spring, and there is some evidence that disturbance by summer spates can induce a second s awn by l arger adult; (Koster 1957; John 1962; Mueller 1 924). iiJi despread forms of speckled dace in the Gila River system have tended to move upt.i.n,fam, toward headwaters, over the past century (Deacon and MAP 18. Geographic distribution of speckled dace complex and Las Vegas dace. Symbols: solid dots south of Gila River = present populations, southern speckled dace (no status); open zones = former populations of adjacent forms; cross-hatched zones (Gila and Bill Williams rivers) = present distributions of populations trending toward southern speckled dace and (in Little Colorado River) those trending toward Colorado speckled dace (the Salt River mainstream in Salt River Canyon, Grand Canyon National Park, and Paria River, included within this zone, -support differentiated, "bid-river" populations); vertical hatch = San Juan, Virgin, and upper Colorado river's stocks of Colorado speckled dace (or relatives. none has status); left-hatched areas = zones of sporadic or former occurrence for adjacent forms; MSD = Moapa speckled dace (candidate); MVSD = Meadow Valley speeXled dace (candidate); PSSD = Preston Spring speckled dace (candidate); LVD = Las Veoas dace; inset = over-all geographic range of the speckled .clace complex. - 73 Minckley 1974), presumably as a reflection of changes in climatic conditions or some other factors in lowlands. This has been accompanied by a similar upstream penetration by longfin dace (p. 63). Interactions between the two native species may be involved in speckled dace displacement, but this possibility has not been studied. Forms of speckled dace in the southern part of Arizona have, however, been forced upstream into more ephemeral headwater systems (John 1964), and have largely disappeared. As proposed above for longfin dace, changes in dispersion of speckled dace populations as well may be usable as a index to environmental change in Southwestern stream habitats. Populations of this species in intermediate-elevation streams remain relatively intact, as do forms occupying mainstreams and tributaries of l arger unregulated rivers and in some regulated ones. These populations are under increasing predation pressure from introduced trouts in the cold Colorado River mainstream and by non-native flathead catfish in the Salt River basin. Those stocks depending on cienegas have become rare, along with reductions in that habitat type (Hendrickson and Minckley 1985). Spring-inhabiting forms in southeastern Nevada also are declining due to modifications of habitat and interactions with introduced species (Courtenay et al. 1985). Speckled dace and their derivatives have been able to maintain themselves through millenia in habitats ranging from springs of Death Valley to high mountain brooks. The complex is the most widespread group in Western North America (Miller 1959; Smith 1973). Extinction resistance of some populations is in itself in need of documentation and quantification, since information may exist in such populations that will allow interpretation of different responses by other, less successful species. Basic taxonomic and ecological work and evaluation will further be critical to maintenance of this complex of fishes and recovery of depleted populations. Management to maintain Regional diversity in speckled dace must be on both place-by-place and_general bases. Spring-inhabiting forms may be perpetuated by management of single habitats or relatively small stream segments, while those of intermediate-elevation streams and large rivers will most readily be maintained along with efforts to preserve other, more critical forms such as spikedace or Colorado squaw-fish. Compilation of U on distribution and atundarica of spsc!;led dacs max gc hand !n hand with data acquisition on other native species, and a status report should periodically be prepared to document any changes that occur. Detected fluctuations in population status may thus be used to thwart development of critical situations. Virgin spinedace, Lepidomeda mollispinis Miller and Hubbs, 1960 (Map 19) Historic occurrence in United States: restricted. Historic abundance: common to scarce. Geographic distribution: Virgin river system, Arizona-Utah-Nevada ( W. Rinne 1980c). Listing status: variable, depending on subspecies. Reasons for decline or listing: habitat loss (actual or potential dewatering of intermediate-elevation streams); habitat MAP 19. Geographic distribution of spinedaces. Sxmbols: outlined zones = former ranges; hatched areas = major populations; MVS = Meadow Valley spinedace; VRS = Virgin River spinedace; LCSD = Little Colorado spinedace; WRS = White River spinedace; PSD = Pahranagat spinedace. 75 mndifiration ( direct and indirect effects of i mpoundment, channelization, diversion, and reculation of discharoes); and interactions with non-native species. The typical subspecies (...epidomeda m. mollisoini.. Miller) i s a candidate -for listing because o4 actual and potential developments in the Virgin River drainage. It lives in the mainstream Virgin River in association wit spring in-flows, but pre-fers and is most abundant in ridie 17-2 lower portions creeks in clear, cool waters and relatiely hard bottoms (Rinne 1971). It has not yet teen in+luenced by introduced spec:es - such a red shiner, reds ide shi ncr (Richardson us : -.a.lteatus), and/or channel cat+ish, all o+ which occur l ocally in the Virgin River system (Rinne 1571; Cross 1 975). Meadow Valley spinedace (L. moilissinis pratensis) was believed extinct (Miller and Hubbs 1 960) until rediscovered in 1977 (Allian 1 983; W. Rinne 1 580c); it i s now proposed as threatened. Maintenance of both these forms appears mi.:.st readily accomplished ty habitat protection from major modificatisns and avoidance of increased l oading by non-native species. Agricultural and urban development of some south -flowino tributaries to the Viroin River already have influenced the Virgin River spinedace, and such may be expected to intensify. Tributaries should be assessed as to ownership, and some Federal and State l ands should be set aside as a nefugium for the Virgin River tributary fauna. Annual monitsrino at selected tributary station; should be initiated to detect and document chances in native and non-native fishes that may indicate development of major problems in surHi:ai =:r-ma. Problems associated with continuino management of 77:4: mainstneam Fiver are discussed along with wound-fin (p. 53). Msnitsring i s already beino accomplished in conjunction with woundfin res.:very efforts ( USF15 Little Colorado spinedace, Lepidsmeda Httata Cope, 1 874 ( Map 1 9) Historic occurrence in United States; restricted. Historic abundance: common to rare. Oesgraphic distribution; upper Little Colorado River masin, Arizona ( Miller 1 563; Minckley and Carufel 1 567; Rshde 1980a), Listino status: orsposed threatened, Reassns fsr decline sr listino: considered fsr listino tesai..2se untei-tairties ovar status and psten;.ials fsr development in LJttC Colorado :asin, Status of this form has been remarkably difficult to assess. it abundance varies spectacularly, and sometimes on a short-term basis (Miller 1982; Minckley and Carufel 1 567; Minckley 1 573; Minckley 1 584:;. There are +ew evidences -for major contraction o+ its oerall range, but proposed water developments on East Clear Creek and amjasent stream basins will influence some of the l arger psoulatisns. E.itersive. stocHno of troiJts for sport fisheries, impoundment fsr fisting plus renovation of some streams have almost certainly reduced population sizes. Golden shiner and -f athead minnow both have been introduced as tait and are establ:shed. The -f ormer i s considered a major -:: i sheries maraoement protiami in the area (Minckley 1 573). No specific studies have teen done on the influence of these introducer^ fishes or the native soinedace. Little Colorado River spinedace are trout-lie in s;:.: tat preference oeneral SahaHor. T're fees mostly - rvertetrates. i s in early summer, with some evidence of a second, midsummer spawn by l arger females ( Minckley and Carufel 1967). The species becomes most abundant in l arger creeks and upper parts of streams, inhabiting deep pools, eddies, and runs below riffles. They also penetrate far into head,.aters, occurring sporadically in tiny tributaries flowing through montane meadows at elevations greater than 2,000 m. The species should be successfully maintained with careful husbandry of watersheds and prohibition of modification on a few selected streams. Its apparent tendency to invade and populate headwaters in wetter years should be exploited by avoiding construction of barriers on even typically-ephemeral tributaries. For example, culverts allowing floods or nominal perennial flows beneath logging or other access roads should not have vertical drops of more than a few centimeters to assure capability of passage by spinedace and other native species. Temporary colonization of ephemeral tributaries may be periodically interrupted by drought, but such cycles of invasion, extirpation or retreat, and reinvasion will insure maintenance of a pattern of population change that must have in the past been characteristic of many Western fishes. Another consideration is potential interaction of spinedace and non-native trouts, despite the fact it has coexisted with introduced saimonids including hatchery rainbow and brook trouts and resident brown trout (Salmo tnutta) for decades, and presumahly with native Apache trout in higher parts of its range for millenia. Predation by trouts should suppress spinedace and other native fish populations, and is a factor that should be evaluated. Sonoran sucker, Catostomus i nsirnis Saird and Girard, 1 854 ( Map 20) Historic occurrence in United States: moderately restricted. Historic abundance: abundant to common. Geographic distribution: endemic to Gil a River basin, Arizona-New Mexico (MinckiPy 1980h, Minrkley et al. 1 986). Listing status: none. Reasons -for decline or listing: habitat loss (dewatering of intermediate-elevation streams); habitat modification ( direct and indirect effects of i mpoundment, channelization, diversion, and regulation of discharges). Sonoran sucker is one of the more taxonomically stable forms in the l ower Colorado River basin. Populations in the Bill Williams and Gila rivers basins have relatively uniform morphology. Some individuals from the mainstream Salt River have unusually large, fleshy lips, and may represent an unrecognized variant (unpubl. data). This species is closely related to the Yaqui sucker and other forms in Mexico (Hendrickson et al. 1981 Ez.ee. p. 3P]). Smith (1978) recorded thi.a ...• pacieq from the Viroin Riven basin, but the occurrence has yet to be confirmed. He may have based the record on specimens that resemble the Little Colorado River sucker (see that account and Minckley et al. 1986). Sonoran sucker remains one of the most widspread native species in the Gila River basin, occupying small- to moderate-sized streams, smaller rivers, and even water-delivery canals in the Phoenix Metropolitan area Minckley 1973: Marsh and Minckley 1982). It disappears from reservoirs MAP 20. Geographic distribution of Sonoran and Little Colorado River suckers. Symbols: outlined zones = former, sporadic, or incidental distributions; left-hatched area = present occurrences of Sonoran sucker; cross-hatched area = zone of population concentrations for Sonoran sucker; vertical hatch = zone of population concentrations for Little Colorado River sucker. 78 after a few years of i mpoundment, except -for incidental individuals near the mouths of i nflowind stream. The species is principally insectivorous (Schreiber and Minckley 1 932). It spawns for an :e xtended period from late winter to summer (Minckley 1981). Adults achieve total l enoths exceeding 50 dm i n larger habitats. Perpetuation of this species seems assured so l ong as natural and semi -natural flowind waters exist in the area However, its populations should be watched for an apparent lack of recruitment. Such is i ndicated in cold water below dams in the Salt River, Arizona, where populations of l arde adults are rarely accompanied by Juveniles. Stocks in that area are presumably repleniqheri by movements 0+ yound from the Verde River system. Records or this still-abundant species should be maintained, as for other such forms, along with those for i mperiled t axa. Little Colorado sucker, flatostomus sp. (Mas 20) Historic occurrence in United States: restricted. Historic abundance: abundant to common. Geooraphic distribution: endemic to Little Colorado River basin, Arizona (Minckley 1 973, 1980k). Listing tatuie: none. Reasons for decline or listing: habitat l oss < dewaterino i ntemediate-elei)ation streams: habitat modification (direct ant indirect effectei of impoundment, channelization, diversion, and regulation of discharoes), The Little Colorado River C„..:Lu muei iocmerly considered a form of flannelmouth sucker, was proposed as a full species by Minckley <1973), but has yet ts receive formal recognition. Some specimens from tributaries hf the Virdir River, Utah, resemble this soecies recorded by Smith [19723 as Sonoran sucker, see above), as do certain i ndividual specimens from the Colorado Riven in Grand Canyon National Park (Minckley 1 980k). Little Colorado River sucker remains widespread in moderate-sized creeks and small streams, and develops l arge population and body sizes at l east 70 cm TL) when it becomes established i n artificial ponds or reservoirs. In streams it lives as adults in the deepest souls near , undercut tari.f.s, koulders, or 7_,th'er. cover , T17 f.Dd hac reproduction. and l arval or juvenii,e ecology have not been studied. Perpetuation of this species should be assured so long as natural and semi-natural +l owing waters are maintained in the area. Populations are now present and relatively l arge, and should persist in areas proposed for protection as habitat for Little Colorado spinedade. As with other large species, the Little Colorado sucker should be monitored for apparent lack of recruitment, althouoh all known necentlx -saTo7eC 5EfF07' viable at present. Records should be maintained, as for other relatively common forms, along with those +or imperiled taxa. Desert mountain-sucker, Panthieteus clarki ( Baird and Girard, 1 354) ( Map 21) HiStt!rIC SCCr7-i'7:CS i n United States elatively widespread. , Historic abi_indarcet abundant t'...: 7arS, kj rHri"; subspecies or population. MAP 21. Geographic distribution of desert mountain-sucker complex. Symbols: outlined areas = present and former distribution; solid dots = present isolated distribution of southern Gila River form (SGRMS); CGRMS = central Gila River form; BWMS = distribution of Bill Williams River form(s); VRMS = distribution of Virgin River form(s); WRMS = distribution of White River mountain-sucker. See text for further explanation. 80 Geographic distribution: White River of eastern Nevada, south throughout Gila River Basin, Arizona-New Mexico (Smith 1 966 ! Minckley 1980o). Listing status: none, with exception of the candidate White River mountain-sucker. Reasons for decline or listing: habitat l oss ( dewatering of intermediate- elevation streams throughout Region and springs in Nevada); and habitat modification (direct and indirect effects of impoundment, channelization, diversion, and regulation of discharges). Smith (1966) analysed morphological variation in mountain-suckers of Western North America and concluded that material from the White River, Nevada, south through the Gila River basin represented a single, polytypic species. Minckley (1973, 1980g) espoused the alternative that the complex consisted of a number of allopatric (and partially sympatric, in the Bill Williams and perhaps Virgin rivers) species. The problem has yet to be re-examined. Minckley (1 973) gave reasons for retention of Pantosteus as a genus rather than a subgenus of Catostomus. This species achieves its oreatest abundance in hard-bottomed streams intermediate elevation, although ascending as high as 1,800 m in mountain brooks and downstream into l ow-desert creeks and even canals of the Phoenix Metropolitan area ( Minckley 1973; Marsh and Minckley 1982). Shifting bottoms of the lowermost Gila River apparently formed a barrier to this species, and it was not historically recorded downstream from the Salt River inflow. Desert mountain-sucker, along with l ongfin dace desert pup-Fish, and Sonoran sucker and t opminnow comprise a distinctive, Sonoran Desert sub-Fauna, highly resistant to intermittency, hot summer water temperatures, and other low-desert adversities. Arizona populations feed mostly on diatoms and other algae (Schreiber and Minckley 1981; Fisher et al. 1 981: Clarkson 1 982) scraped from stones with their modified, cartilagenous jaws. Nevada populations live in spring runs and outflows over softer bottoms (Hardy 1 980, 1982). Southern populations of desert mountain-sucker (the typical form) are becoming rare due to general reductions in surface waters in that area, and might be considered as a candidate for listing. Most other populations in Arizona and New Mexico seem relatively stable and should persist in stream habitats protected for species such as spikedace, roundtail chub, and other fishes, Virgin River stocks are protected in association with woundfin, Vir3in soinedace, and Virgin River roundtail. The White River mountain-sucker has had its range substantially reduced through modifications of springs and their outflows, and perhaps due to interactions with non-native species (Hardy 1 980; Courtenay et al. 1 985), and will likely require direct protection through habitat acquisition in the near future. Bluehead mountain-sucker (tributary stocks) Pantosteus discobolus (Cope, 1 872) ( Map 1 3, p. 61) Discussions of the status, taxonomy, and distribution of tributary populations of this relatively widespread and abundant species are provided along with data on big-river forms (p. 62). Si Creek Fishes Gila chub, Gila intermedia (Girard, 1857) (Map 22) Historic occurrence in the United States: restricted. Historic abundance: common. Geographic distribution: upper Gila River basin, Arizona, New Mexico, and Sonora, Mexico (Rinne 1969, 1976; Minckley 1973). Listing status: candidate. Reasons for decline or listing: habitat loss (reductions of flow due to overgrazing, dewatering of springs and spring— fed habitats). The nominal Tig0Ma, intermedius Girard (1857) was elevated to speci4ic rank as Gila intermedia by Rinne (1969, 1976), a status generally accepted by Western workers (Rinne and Minckley 1 970; Minckley 1973; Hnokirk 1973; Smith et al. 1979; others). Robins et al. (1980) considered Gila chub a variant of G. robusta. Problematic populations exist, which trend toward Colorado roundtail chub in morphology and may represent ancient hybrids between the two species. Intergradation typical of subspecies or races has not been demonstrated (DeMarais, ASU, pers. comm.). This chubby—bodied, dark colored species persists only in isolated habitats, typically in springs or spring— or under-flow--fed stream segments separated from other watercourses by long reaches of typically—dry stream bed. Despite determined efforts, Gila and Colorado roundtail chub have never been taken syntopically, yet some populations of the two forms are separated by only a few tens of meters of strream through which e:ther could move into proximity with the other. Gila chub is hiohly secretive and presumably sedentary in deep pools with extensive cover such as undercut banks, overhanging vegetation, or debris. Little is known of its life history. It appears to be omnivorous, but has been recorded to harass and presumably feed on Sonoran topminnow (Minckley 1969a). Reproduction is over an extended period, perhaps as long as from early spring through summer and early autumn (unpubl. data). Two stocks of Gila chub are relatively secure on The Nature Conservancy's Caneln rieneoa and Muleshoe Ranch preserves in southe astern Arizona. Populations in the upper Verde River system are approaching extir2atinn, and those in eastern Arizona. with only a few exceptions, are under pressure from introduced green sunfish (San Carlos River). The taxonomic and population status of New Mexico populations have yet to be assessed; a stock originally inhabiting San Simon Cienega, Arizona—New Mexico (Rinne 1 976), is gone. Maintenance of this distinctive chub will likely require direct acquisition of or management easements on habitats in the form of headwater cienegas or spring—fed streams. The species seams to do well in spring—fed ponds so long as not subjected to predation or other pressures from non—native fishes, so refuge situations may be successful if necessary. Some populations of this form appear to have been extirpated after introduction of l argemough bass, bluegill, goldfish ( Carassius auratus), and/or other non—native species (Minckley 1973). Others have dissapeared as a result of habitat desiccation, the last especially due to loss of oienegas ( Hendrickson and Minckley 1985.) The species is restricted in occurrence and reduced in numbers; listinc; as threatened is appropr MAP 22. Geographic distribution of Gila chub complex. Symbols. solid dots = present distribution; open circles = extirpated populations; l eft-darkened circles = extant problematic populations, most closely resembling Gila chub; right-darkened circles = extant populations, most closely resembling roundtail chub. See text for further explanation. 83 Las Vegas dace, Rhinichthys deaconi Miller, 1984 (Map 18, p. 73) Historic occurrence in United States: highly restricted. Historic abundance: common to scarce. Geographic distribution: Las Vegas Valley, Clark County, Nevada (Miller 1984). Listing status: none (extinct). Reasons for decline or listing: dewatering of springs and spring-fed habitats by municipal development. This distinctive member of the speckled dace complex was lost prior to its formal description. It presumably evolved in isolation in the Las Vegas Valley, a large, intermontane basin historically tributary to Boulder Canyon of the Colorado River. Perennial springs in the valley fed an extensive spring - creek - marsh wetland that was dried by development of the aquifer for the domestic water supply of Las Vegas and associated municipalities (Miller 1984). White River spinedace, Lepidomeda albivallis Miller and Hubbs, 1960 (Map 19, p. 75) Historic occurrence in the United States: restricted. Historic abundance: abundant to scarce. Geographic distribution: upper White River Valley, eastern Nevada (W. Rinne 1980a). Listing status: proposed endangered. Reasons for decline or listing: habitat modifications (alteration of spring flow); and interactions with introduced species. White River spinedace was restricted to clear, cool springs and their outflows of the now-isolated White River system (Miller and Hubbs 1960). Almost nothing is known of its biology. Courtenay et al. (1985) reviewed problems of reductions in springflows, diversions of watercourses, and introductions of non-native species influencing this unique spinedace; it persists in only one spring system. As with much of the White River fauna, purchase or maintenance of habitat under management easements seems the most expedient means of perpetuating White River spinedace. Any physical acquisition almost certainly must be followed by exclusion of introduced competitors and predators if management is to be successful. Pahranagat spinedace, Lepidomeda altivelis Miller and Hubbs, 1960 (Map 1 9, p. 75) Historic occurrence in the United States: highly restricted. Historic abundance: rare. Geographic distribution: cool springs and their outflows, Pahranagat Valley, eastern Nevada (W. Rinne 1980b). Listing status: none (extinct). Reasons for decline or listing: unknown. This species was considered extinct prior to its formal description. It was last collected in 1938 from the outflow of Ash Spring and in upper Pahranagat Lake. Miller and Hubbs (1960) thoroughly searched for the species in 1959, to no avail, and attributed its extermination largely to an "increased abundance of carp [Cyprinus carpio] and to the establishment of the mosquito-Fish..." Courtenay et al. 1985) reviewed the status of the White River fauna, corroborating other workers' views of its continuing deterioration. 84 Apache trout, Salmo . apache. Miller, 1972 (Map 23) Historic occurrence in the United States: restricted. Historic abundance: common. Geographic distribution: headwaters of Salt, San Francisco, and Little Colorado rivers, Arizona (J. Rinne 1980a; Rinne and Minckley 1985); a problematic population in uppermost Eagle Creek, Arizona, has yet to be assessed. Listing status: threatened. Reasons for decline or listing: interactions with introduced species (hybridization with non-native rainbow trout); habitat loss (dewatering of headwater and high-elevation creeks); and habitat modifications (direct and indirect effects of impoundment, channelization, diversion, and regulation of headwater discharges, especially in Little Colorado River basin. Rinne and Minckley (1985) and Rinne (1985) reviewed the status of Apache trout and documented that most populations below 2,100 in elevation had been replaced or were genetically contaminated by hybridization with introduced rainbow trout. Some hatchery-produced populations both within and outside the native range also showed evidence of genetic contamination, presumably as a result of lack of success in removal of rainbow trout from streams, unauthorized stocking of other than the native species, or hatchery contamination. Competitive and other interactions with brook and brown trouts also have been documented to decrease population sizes of this endemic species (Harper 1978; Rinne et al. 1982). This species formerly occupied most streams higher than 1,800 m in the White Mountains of eastern Arizona, and possibly extreme western New Mexico. It formerly descended (at least seasonally) into the larger tributaries of the Salt and uppermost Little Colorado rivers, but now is characteristic of small, headwater brooks. As with most trouts, foods consist largely of aquatic invertebrates and terrestrial animals that fall into the water. Spawning is in early summer (Harper 1978). A recovery plan for Apache trout has been produced (USFWS 1979) and is being implemented, with the primary goal to re-establish and maintain 30 uncontaminated, self-sustaining populations prior to consideration for de-listing. Curtailed stocking of rainbow and other trouts in the native range of this species would be of apparent benefit (Rinne and Minckley 1985), and should be a major management effort. No non-native trouts should be stocked above 1,800 in elevation within its native range. A program is being developed to stock hatchery-produced Apache trout in lieu of non-native rainbow trout for White Mountain Apache Reservation sport fisheries (George Divine, USFWS, pers. comm.). Hatchery fish will not, however, be introduced into areas of wild Apache trout populations, thus avoiding genetic alteration of natural stocks by those possibly changed under domestication for propagation and production. This program is potentially of considerable public interest, and should be accompanied by an educational drive emphasizing endangered species in general and Apache trout in detail. Potential sport fishes like trouts should be used to "carry" other, less known species into the public eye. Assuming careful husbandry of watershed resources, this species should be relatively secure within its native range for the near future. On-going and systematic surveillance of natural and reintroduced populations will be OJ A ■-.'„ 1, ' I . / 0 , 1 . ' .; ) I ( ; , .1 4, J _." .16•••••■■••■••■••• !'l ap 2:— Geograpr distr but : : c cut': !red arse.E; areri = 7 ±;str:c t:o7 Apa.che (natu7a 2:: a t'r:= uppE.n = introduced popul a t i ons o che trout; dots = i ntroduced popC cns Gi 1 a trout ; and open cirri es = probl ematic popul at : ons Ksee required to avert habitat changes that will almost certainly occur now that exploitation of natural resources of the White Mountain Apache Reservation is being accelerated, e.g., increased timber harvest and intensity of grazing of pasturelands). Gila trout, Salmo gilae Miller, 1950 (Map 23) Historic occurrence in the United States: restricted. Historic abundance: unknown, likely common. Geographic distribution: headwaters of Verde River, Arizona, and Gila River, New Mexico (J. Rinne 1980b); a problematic population in uppermost Eagle Creek, Arizona, is yet to be assessed. Listing status: endangered. Reasons for decline or listing: interactions with introduced species (hybridization with non-native rainbow trout); and habitat loss (dewatering headwater and high-elevation creeks). A recovery plan for Gila trout (USFWS 1978) is being implemented, with the aim of re-establishing populations to replicate each of the five remaining natural stocks in the upper Gila River basin, New Mexico, prior to consideration for downlisting from endangered to threatened status. A reintroduced population is established in Gap Creek, Arizona, in the Verde River basin, and one stocking outside its native range is established in McKnight Creek, Mimbres River basin, New Mexico (J. Rinne 1980b). Gila trout is ecologically similar to Apache trout, spawning in early summer and feeding mostly on aquatic invertebrates. It is restricted to headwater streams (Regan 1966; Rinne 1981). Programs suggested and under implementation for Apache trout also would seem reasonable for this species. If Gila trout re-establish viable populations, natural protection afforded by isolation of their range in and adjacent to the Gila Wilderness, New Mexico, will preclude most if not all non-native salmonid introductions. Other than due to natural catastrophe such as general drought or remarkably large forest fire, the species should be secure. Management of re-established stocks should be relatively straightforward, consisting of population monitoring (that may involve considerable expense because of access) and routine modifications of habitat to enhance populations. Snrinn-cieneo=. Fnrm= Moapa dace Moapa coriacea Hubbs and Miller, 1948b (Map 16, p. 69) Historic occurrence in the United States: greatly restricted. Historic abundance: common to scarce. Geographic distribution: endemic to thermal springs of the uppermost Moapa River, Clark County, Nevada (monotypic genus) (Lee 1980). Listing status: endangered. Reasons for decline or listing: habitat loss (dewatering of critical middle and lower portions of spring runs); habitat modifications (direct and indirect effects of impoundment, channelization, and diversion of spring discharges); and interactions with non-native species. This species is a thermal endemic in moderately warm- to hot-spring pools and outflows (28.0-33.8° C) (Hubbs and Miller 1948b; USFWS 1981), 87 the upper limit of which approaches a thermal maximum for some introduced species, thus partially excluding them from dace habitat. The species is insectivorous, tends to move in small, loosely-organized schools, and has an extended spawning period (LaRivers 1962; Deacon and Bradley 1972; Cross 1976; USFWS 1981). Little is otherwise known of its biology. Potentials for extinction of Moapa dace were first pointed out by Wallis (1951). Unlike most situations, its decline was clearly a function of habitat modifications. Diversions, concrete lining, impoundment, and other physical alterations of headsprings and their outflows associated with resort development, domestic water supplies, and irrigation reduced available habitat to a critical level. Appearance of non-native fishes, shortfin molly (Poecilia mexicana) and mosquitofish (Minckley and Deacon 1968), and perhaps interactions with parasites introduced with the exotics (Wilson et al. 1966), must have contributed in concert to endangerment of this native species. Moapa dace is currently under management by the USFWS <1981). Key headsprings and their outflows have been purchased and are being developed as a refuge for this species and the associated Moapa springfish. Assuming maintenance of springs these fishes may be relatively secure. Desert pupfish, Cyprinodon macularius Baird and Girard, 1853b (Map 24) Historic occurrence in the United States: moderately widespread. Historic abundance: abundant to common. Geographic distribution: Gila River basin, Arizona, generally lower than 1,500 m, Salton Sea basin, California, and lower Colorado River and Delta, downstream from Gila River, Arizona, California, Sonora, and Baja California del Norte, Mexico (Minckley I980i; Miller 1981). Another distinct subspecies occupies the Rio Sonoyta basin, Arizona and Sonora (see p. 41). Listing status: proposed endangered (all subspecies). Reasons for decline or listing: variable, depending on subspecies; includes habitat loss (dewatering of springs, some headwaters, and lower portions of major streams and marshlands); habitat modification The typical subspecies of desert pupfish has been extirpated from the Gila River basin (Minckley 1973). It was originally described from the San Pedro River, Arizona, near the International Boundary (Baird and Girard 1853b; Girard 1859a). Populations from Santa Clara Slough, Sonora, Mexico, on the east side of the Colorado River Delta, most closely resemble the Gila River form (in part Turner 1983), and are under propagation at Dexter NFH and by AGFD for attempts at reintroduction within the native range (Minckley and Brooks 1986). The Salton Sea form also has been placed in artificial refugia by CDFG (Black 1980; Minckley 19800. The desert pupfish is a small (less than 3.0 cm), pugnaceous, omnivore that can resist almost any natural environmental extreme known in aquatic systems of the Sonoran Desert. Its disappearance from such a formerly wide geographic range can only be attributed to interactions with introduced fishes; dewaterino has been extensive, but not absolute, and many areas of 88 MAP 24. Geographic distribution of desert and Monkey Spr ng pupfishes and White River springi:sh. Symbols in Gila and l ower Colorado rivers basins: outlined area = former distribution, and cots = present pple.t.ons of desert pup-fish; open circle = -former locale for Monkey Spring pup-fish (MS). Symbol in White River basin: outlined area = present and past distribution o+ spring-fish (SF), including from north to south northern spring-fish (proposed endangered), Pahranagat springfish (proposed endangered), great spring-fish (proposed endangered), thermal springiish (no status), and Moapa springiish (candidate). 89 former occurrence still support substantial aquatic habitat. Early interactions between mosquitofish and desert pup-fish were noted in the Salton Sea (Evermann 1916), and those populations further declined toward extirpation when sail-fir molly ( Poecilia latipinna) and African cichlids (Oreochromis sp., Tilapia zilli, and perhaps others) became abundant (Black 1 930; Schoenherr 1979). Desert pup-fish do not require large, complex habitats, and as noted above often do well in enviroments so severe because of high salinities or temperatures that other fishes are excluded. The most expedient and effective technique for maintenance of subspecies of this unique fish is to acquire existing wetlands through purchase or management easements, or construct a diversity of isolated habitats, and reintroduce selected populations. The fish was naturally and widely syntopic with Sonoran [Gila] topminnow in the Gila River basin ( Minckley 1973), thus allowing multiple management attempts. It seems unnecessary to seek reintroduction sites outside the native ranges of unique forms of this species. Unauthorized stocking of the Guitobaquito form (p. 42) in the range of the typical subspecies already has occurred (Minckley and Brooks 1 986). These populations should be removed and replaced with the typical subspecies prior to realization of their potential spread into the upper Gila River system. The typical form also is stocked in the 3177 !Alill1ams River basin, oLts:O7 James E. Brooks, A277:, per.- comm.). Monkey Spring pupfish, CYprinodon sp. Historic occurrence in UnitedStates: greatly restricted. HISTCRC abundance: abundant. Geographic distribution: Monkey Spring pond, headwaters of Sonoita Creek, Santa Cruz County, Arizona (Minckley 1 973: Miller 1 981). List nnne, extinrt. Reasons -f or decline nr listing: interactions (direct predation) with largemouth bass. Monkey Spring pup-fish, which has yet to receive a -f ormal scientific name, is presumably extinct. The spec es must have evolved from desert pup-fish or its progenitor. Its only habitat and presumed place of origin was isolated upstream from a travertine dam formed by calciHm rarbnnate precipitation from waters issuing from Monkey Spring, Santa Cruz Court ----- Arizona. Tha dam was augmeritd in tha 12,30s ty f th- ill structurs, presumably to i nci.,edt.t. wetland volume and elevation. Water was diverted around a hill to another pond, constructed to allow irrigation of the adjacent Sonoita Creek. floodplain. Attempts to deepen the original marsh reportedly "broke the seal" of its bottom and it was drained (Chamberlain 1904; Minckley 1969a, 1973). The puofish had by that time -i sund its way to the irrigation pond, where it persisted until 1 969-70. Largemouth bass, introduced in 1 969, were successfully removed, but a second unauthorized stocking went undetected until after it has reproduced. A second attempt to remove the non-native bass in 1 970 was too late, and the Monkey Spring pup-fish had disappeared. Stocked maintained in artificial habitats in an attempt to perpetuate the species failed in 1971 (Minckley 1973). Searches of other aquatic systems in the region have failed to discover other than introduced stocks of the Guitobaquito form n-F desert White River springfish, Crenichthys bailey' Gilbert, 1893 (Map 24) Historic occurrence in United States: restricted. Historic abundance: abundant to scarce, depending on subspecies. Geographic distribution: springs and streams of White River basin, eastern Nevada (Williams and Wilde 1981.) Listing status: variable, depending on subspecies. Reasons for decline or listing: habitat loss (dewatering of springs); habitat modifications (direct and indirect effects of i mpoundment, channelization, diversion, and regulation of discharges); and interactions with non-native species. Williams and Wilde (1981) and Courtenay et al. (1985) respectively reviewed the springfishes and the White River fauna in general, and made recommendations for listing and candidacy, both of which are reflected here. Introductions of non-native fishes• ranging from guppy (Poecilia reticulata) and goldfish, through exotic cichlids (numerous genera), and l argemouth bass, have been documented to directly influence populations of various springfishes, either through direct predation or competition (Deacon et al. 1964; Deacon 1968! 1979). There are further evidences that parasites introduced with non-native fishes resulted in at least temporary declines in some spring-fish populations (Wilson et al. 1966; Deacon 1 979). Some forms, however, survive and flourish in dissolved oxygen concentrations so low or temperatures so high that exotic fishes are excluded (Hubbs and Hettler 1 964; Deacon and Minckley 1974). Concrete lining, hannelization, and diversion of spring flows -for development of resort facilities, domestic and agricultural water supplies, and so on, also have been demonstrated to effect reductions in populations (Williams and Wide 1981; USFWS 1781; Hardy 1982; fl.ourtenay et al. 1 985). Spring-fish are so specialized in ecology and restricted to spring-fed habitats that direct management of natural springs and their outflows may be the only feasible way to perpetuate some forms. The Moapa spring-fish will presumably persist in habitats purchased and being manacled by USFWS for Moapa dace (USFWS 1931), but others may reouire additional, similar acquisition of easements and/or property. Experimental propaoation of these fishes in anticipation for futre needs 40;.;:::: be an excellent investmant as facilities are or become available. Sonoran (Gila) topminnow, Poeciliopsis o. occidentalis (Baird and Girard, 1857b) (Map 25) Historic occurrence in United States: moderately restricted. Historic abundance: abundant to common. Geographic distribution: Gila River basin, Arizona-New Mexico, below ca. 1,500 m elevation, south to the Rio Mayo of northwestern Sonora, Mexico (Minckley 1 980j); Vrijenhoeck et al. 1 985). Listing status: endangered. Reasons -for declines or listino: habitat loss (dewatering of springs, some headwaters, and lower portions of major streams and marshlands); habitat modification (direct and indirect effects of impoundment, channelization, diversion, and regulation discharges); and interactions with non-nat :ye species f' direct predation by mosquito-Fish). C."1 MAP 25. Geographic distribution of Sonoran topminnow. Symbols. outlined area = former distribution; dots = extant populations in the United States (single dots may cover more than one isolated population); hatched area denotes range of Yaqui topminnow and other, undefined populations in Mexico. Numerous introduced populations (Minckley and Brooks 1986) in Arizona are not plotted. 92 , Schoenherr (1974, 1977, 1 981), Constant: (1974a, 11 1112.), Minckley (1973), Minckley st al. (1777), Me-t+ e (1983a, et •ser.), and Meffe et al. (1983) should be consulted for details on the past and present ecolooy, distribution, and abundance of Sonoran topminnow. It is a small (less than 2.0 cm), omnivorous species that practices internal -fertilization and birth of living young. It formerly occupied a diversity of habitats ranging -from hi l ows and barkwaters of large river.. through small .and-bottomed nreek.s to marshlands and cienegas, mostly at elevations less than 1,000 m above mean sea level. It thus occupied severe environments of the low deserts, subjected to summer heat, salinization, and other vaoaries of those systems. As noted el.ewhere, l ong-fin dace, desert mountain-sucker, Sonoran sucker, desert pup-fish, and Sonoran tnpminnow -F ormed a distinctive assemblage in such places. The most upstream occurrence in the Gila River basin was in the vininity of Frisco Hot. Spring in New Mexico ( Roster 1977'). The species has been replaced throughout much of its natural range in the United States by mosquitofish, which prey,., directly on young and shreds fins of adults of the net form,Thesultinc in the l atter case in secondary i nfections and death ( Me-Ffe 1 92!). Replacement of topminnow by mosquitofish occurs rapidly in the 3ila River basin (Gila topminnow). The Rio Yaqui form seems more resistant to replacement (p. 42). A recovery plan has been produced ( USFWS 1 984) and i s being i mplemented in Arizona -for the Sonoran topminrow. The Gila River form is under propabatcn at Dexten NF Hi and by ASFD stcc'xing in an extensH}e recoverx e-F-fcrt 4thin its Rertnoductic jntc isclated habitats, maintenance the -F ew remaining natural populatisrs uncontaminated by mosquitc-Fish, and possible a u:siton o-F easements br proper..tx ccntaining su!table hat:tats are the most expeditious ways to p' erpetuate this +. Cr7 the Ha RH)er tae- n, San 2errardHc NWR alreadY has been charged with maintenance o4 Yaqui tccminnow as a major portion of i ts management program ( USFWS 1 98a; p. 42). III. ACCOUNTS OF AQUATIC HABITATS Silvey et al. (1984) produced a digital drainage hierarchy for identification of perennial lotic waters of Arizona, which is expanded here without numerical designations to include the White River of eastern Nevada, the Salton Sea region of southeastern California, and upper parts of the San Juan and Gila basins in New Mexico. Drainage systems mentioned in text and/or discussed in this Section are arranged from south to north and from down- to upstream in Table 7 (see also Figs. 1 and 2). Narratives which follow are general discussions of environmental and faunal conditions in each drainage basin and/or in selected stream systems or watersheds. Comprehensive coverage of the Region is neither claimed nor achieved, but I have drawn upon published and unpublished reports, personal experience, and information contributed by colleagues to assess historical, current, and future conditions in the aquatic habitats concerned. Specific discussions are intended in large part as examples of conditions past, present, and future, and of my ideas and hopes relative to perpetuation of parts of the native fauna. No major group of habitats is excluded, but some, such as small, headwater streams are scarcely covered. In many instances, proposals to remedy declines in faunal groups or hatitat=. broadly overlap for different drainages, and in such instances, cross-referencing is used to avoid undue repetition in narratives. Specific information on fishes has already been provided in Section II. Habitat Categories give before and discussed in text are applied throughout this section at least on theoretical ground to examples of actual or potential places where native fishes may be maintained. Repetition is in this instance warrented, as follows: I) within the natural range and relatively undisturbed - these probably will be places where the species naturally persist and should be given an "all cost" priority for maintenance; II) within the natural range and reasonable to reclaim, modify, or reconstruct; III) within the natural range, but hiohly modified, disturbed or expensive in time or money to reclaim; IV) out of the natural range, but isolated in the same region and relatively undisturbed; V) out of the native range, and otherwise as in IV (above); and VI) artificial refugia. Closed Basins Laguna Salada and Salton Sink Closed basins associated with the Delta of the Colorado River, specifically Laguna Salada in Baja California del Norte and the Salton Sink in California, have a history of desiccation and filling relating to vagaries of flooding and regional tectonism. Essentially nothing is known of the native fish fauna of Laguna Salada, if ... urh existed in such an ar:d Table 7. Drainages of U. S. Fish and Wildlife Service Region II discussed in text, arranged from down- to upstream. CLOSED BASINS Laguna Sal ada Salton Sink (Sea) Animas and Lordsburg basin Wilcox Playa Turkey, Grant, and Pinery creeks Croton Springs Hooker Cienega Mormon and Stoneman lakes Hualapai (Red) Lake Trux ton Wash Aubrey Valley MEXICAN DRAINAGES Rio Yaqui Whitewater Creek ( Rio Aqua Prieta) Leslie Creek Rucker Canyon Arroyo Cajon Bonito San Bernardino Creek (Black Draw) Astin Spring Guadalupe Canyon Rio Concepcion ( = Rio Asuncion) Sycamore (Bear) Canyon Hank's and Yank's Spring Rio Sonoyta Quitobaquito Spring LOWER COLORADO RIVER SYSTEM rolorP,,do River Gila River Hassayampa River Agua Fria River Tule Creek Cave Creek (7-Springs Wash) Santa Cruz River Arivaca Creek Rillito Creek Pantano Wash Cienega Creek Sonoita Creek Redrock Canyon Monkey Spring Cottonwood Spring 95 Table 7. Concluded. Santa Cruz River (continued) "Heron", Sharp, and Sheehy springs Potrero Creek Bog Hole Salt River Verde River Camp, Sycamore, West Clear, and Oak creek=. Wet Beaver Creek Dry Beaver Creek Gap Creek East Verde River Fossil Creek Tonto Creek Canyon, Cibique, Carrizo, and Cedar creek White and Black rivers San Pedro River Aravaipa Creek Redfield Canyon Bass Canyon Hooker Hot Spring Babocomari River and Cieneoa) Turkey and O'Donnell creeks (and cieneoas) San Carlos River Blue Spring Bylas Springs Markham Creek San Simon River East Turkey Creek San Simon Cienega Bonita and Eagle creeks San Francisco River Slue River Cailp1:,ell Blue Creek West, Middle, and East fork=. Gil; River Bill Williams River Big Sandy River Burro Creek Santa Maria River Las Vegas Wash Virgin River Moapa and (pluvial) White river Grand Canyon tributaries (Kanab, Tapaets, etc. creeks) Little Colorado River East Clear, Chevalon, Silver, and Nutrioso creeks Zuni River Paria River San Juan River region. Laguna Salada remained generally dry until development of agriculture in the Calexico-Mexicali area provided adequate irrigation and domestic wastewaters to begin to flood its basin. However, the system has from about 1977 to present received massive influxes of fresh water -From flooding in the Colorado River mainstream and now supports a large fauna of mostly introduced fishes (unpubl. data). It is included as an area in need of survey and evaluation as possible or potential native fish habitat. The Salton Sink last received water when floods of the Colorado River broke through irrigation works in the early 1 900s to flow long enough to establish the present inland sea. Ecology of that system has been reviewed by Evermann (1916), Coleman (1929), Dill (1944), Walker (1961), and Moyle (1976a). Fishes recorded in the Salton Sea immediately after fillino were the same as those of the lower Colorado River, including mostly freshwater species (bonytail, Colorado squawfish, razorback sucker, possibly flannelmouth sucker, desert pup-fish, and a trout) plus striped mullet. Most springs and seeps on the floor and along margins of the Salton Sink were flooded in the period 1904-07 so any fishes in those systems were undoubtedly forced into l acustrine environments. Of species present in early years, only desert pupfish was likely a preflood resident. Water levels of the Salton Sea were and are maintained by irrigation and domestic wastewaters of relatively high salinities and subjected to intense evaporation rates that further increase salt content. Salinities have predictably increased to near sr above tolerance levels of both native and introduced fishes. The fauna an prooressively through natural appearances and intentional stocking toward more salinity tolenant species, until only marine and se ryhaline species presently remained. Unli:. ,ss recharged, the Salton Sea is soon expected to become too saline to support vertebrate li=e. Introduced marine fishes all remain restricted to the body of the Salton Sea, accompanied by salinity tolerant thread-Fin shad (Dorosoma oetenense), Sail fin molly, mosquitofish, and tilapia. The l ast four plus common carp, red shiner, goldfish, porthole livebearer (Poeciliopsis gracilis), Mexican molly, and others smarm in in-Flowing springs, stream, canals, and drains. Desert pupfish i s apparently being displaced in -Fresher waters by these hordes of non-native species, and even has U;z*ppe.oed in highly-ealine watens alono manoins o= the Sea formerly had the advantage of its tolerance ( Barlow I 958a, b) to remarkable salinity and temperature variations that excluded most other fishes. Desert pup-Fish did well in the Salton Sea system despite increasino salinities, probable inputs of pesticides, fertilizers, and domestic wastes to the system, and fluctuatino water levels until subjected to non-native species. Biological interactions between pup-Fish and mosguitofish, which was introduced in the region in 1 922 and with which it coexisted for many years, and the more-recently-appearing sail-Fin molly and tilapia seem especially severe (vim part Moyle 1 976a and Schoenherr 1979). The last fish produces tremendous populations, and its young invade and occupy shallow, warm, saline, organic-bottomed areas that are prime habitat for pup-Fish. In addition to the Salton Sea area, African tilapias have spread and established dense populations throughout the Delta o-F the Colorado 7;;JE.7 to the Gul-f o-f Cali4ornia and up the Gila River system to the Phoenix Metropolitan area (Barrett 1 983), thus COVi'f' 7:; MiCh cfthE, natural reri e desert pl.ip i sh. 97 Despite proposed listing of this species, even more immediate action is necessary to perpetuate the Salton Sea form of desert pupfish. Alternatives seem limited to rapid acquisition and isolation of suitable Category I, II, and III habitats, eradication of non-native fishes, reintroduction of pupfish from local stocks or from existing artificial refugia (Minckley 1980 ) , then protection against reintroduction of non-native forms. Major problems associated with such an effort are mosaic patterns of land ownership and development in the area ( Ulmer, CDFG, pers. comm.), fluctuations in level of the Salton Sea that must be planned for in development of habitats, actual or potential variations in flow of incoming freshwaters (especially if drains or other artificial channels are used), and lack of public education and appreciation that results in transport of non-native fishes between and among waters of the region. The last is an especially difficult problem since many introduced species are so abundant they are readily caught, plus the fact many originated from aquarium stocks or are otherwise attractive to laymen as pets. If immediate security cannot be obtained, stocks of the pupfish should be maintained in refugia as insurance against its imminent extirpation. Willcox Playa This intermontane basin is located in southeastern Arizona between the San Pedro and San Simon rivers basins. A few thousand years ago the Willcox Playa supported a lake that covered about 200 km2 and was greAter than 1 4 m deep, as evidenced by remnant beach ridges and dunes (Schreiber et al. 1 972). Its central playa still occupies about 1 30 km2 , but holds water only in periods of heavy precipitation. Historic aquatic habitats included at least two major (Croton and Sulpher springs) and presumably a number of minor springs on the basin floor, cienegas associated with these springs and with alluvial fans of inflowino streams, and three perennial streams in surrounding mountains (Turkey, Grant, and Pinery creeks systems) (Silvey et al. 1 984; Hendrickson and Minckley 1985). Only a few cienega habitats and the three streams persist. Aquatic habitats on the basin floor have dried as a result of water mining for aoriculture. Meinzer and Kelton (1913) reported a 320 km 2 area with water l esc. than 5.0 m beneath the surface and Mann et al. (1978) mapped a similar area with the water table lying deeper than 20 m. Native fishes of this basin consisted of l ongfin dace in Croton Springs and the Turkey Creek system; the species persists only in the latter and the former is dry (Hendrickson and Minckley 1985). Yaqui chub were reported from Morse Canyon (Turkey Creek system), but no longer occur there. And, unidentified minnows and suckers were rotenoned from Grant Creek system in the 1960s prior to introduction of non-native trouts (see Section II). Non-native fishes are uncommon in the Willcox Playa system, consisting of bluegill, redear sunfish (Lepomis microlophus), largemouth bass, and goldfish restricted to artificial tanks, rainbow and brook trout stocked in Riggs Flat Lake (built on an ephemeral tributary in the Pinaleno Mountains) and Apache trout introduced and established in the Grant Creek system. The l ast population is one of the few self-perpetuating stocks of this 98 threatened species outside its native range. Grant Creek also has in the past supported brook, rainbow, and brown trout, Apache X rainbow trout hybrids, and speckled dace (Silvey et al. 1984; unpubl. data), all introduced. Turkey Creek system receives sporadic stocking of rainbow trout (unpubl. data); an early record of cutthroat trout from the system (Silvey et al. 1 984) is not supported by specimens. Assuming the Yaqui chub record is valid, faunal affinities of this large basin would be to the south Other Closed Basins in Arizona and New Mexico Hualapai ( Red) Lake, Aubrey Valley, Mormon Lake, and Stoneman Lake basins in Arizona, and Lordsburg and Animas basins in New Mexico, plus other (lesser) closed systems in both States were originally fishless (Hubbs and Miller 1948a). Truxton Wash system in Hualapai Lake basin now supports an introduced population of l ongfin dace (W. G. Kepner, pers. comm.; Silvey et al. 1984). Mormon and Stoneman lakes are managed for sport fisheries by AGFD (Minckley 1973) and support numerous non-native fishes undesirable both to that program and to native species management (golden shiner, green sunfish, yellow perch [ Perca flavescens], northern pike fEsox l ucius3, etc.). I know of no perennial waters in the other basins, but surveys of closed systems An the search for habitats are recommended. Mexican Drainages Rio Yaqui system Guadalupe Canyon in southwestern New Mexico and the San Bernardino and Douglas valleys of southeastern Arizona comprise the Rio Yaqui watershed in the United States. Guadalupe Canyon flows from the southern Peloncillo Mountains into Mexico. San Bernardino Valley makes up the southern part of the San Simon structural trough and is hydrographically and geologically related to the south-flowing, lower Douglas Valley. Drainage of the former originates on south and east slopes of the Chiricahua Mountains and southern end of the Peloncillo Mountains. Douglas Valley drains west slopes of the Chiricahuas, mostly through Rucker Canyon, which enters Whitewater Draw and flows around the north end of the Swisshelm Mountains to turn south and cross the U. S. and Mexic an Border just west of Dnuolas. Leslie Creek passAs through the Swisshelms to enter Whitewater Creek from the east, and drainages from the Mule Mountains enter from the west. All three watersheds join in Sonora and pass south to Rio de Bavispe, which flows to the Rio Yaqui (Hendrickson et al. 1981; Hendrickson and Minckley 1985; USFWS 1985a). The region was modified in early days of Spanish and Mexican settlement by extensive livestock ranching. Agriculture becian in the Douglas Valley in 1910 with drilling for the first wells (reviewed by Mann and English 1 980). Wells drilled in the San Bernardino Valley at about this same time produced reliable flows of artesian water from an aquifer distinct from that which produces natural springs in that area ( Wilson 1976). Guadalupe Canyon in Sonora had water permanent enough near the turn of the century to support beaver Declining water tables in Douglas Valley may be attributed to withdrawal for agricultural and industrial uses (Mann and English 198V. Those in the San Bernardino and Guadalupe watersheds are less readily explained except presumably as a result of grazing i mpacts and perhaps climatic change. Arroyo cutting ( Hastings 1 959; Hastings and Turner 1 965; Cooke and Reeves 1976) is severe on streams flowing through relatively deep alluvium. Such incision concentrates flow and accelerates additional erhsion, drains adjacent water tables, and generally decreases (or destroys) permanency of the system ( Hendrickson and Minckley 1 965). A l ong-needed hydrologic study of the San Bernardino aquifer has been commenced (USFWS 1 985a). Native fishes of the upper Rio Yaqui watershed comprise six to eight species, Yaqui chub, beautiful shiner, Mexican stoneroller, longfin dace, Yaqui sucker, Sonoran C Yaqui] topminnow, and likely roundtail chub and Yaqui catfish ( Section II). Introduced species include trouts in Rucker Canyon Rio Concepcion Watershed This drainage in the United States commences in and flows southward through the Atascosa Mountains to cross the International Boundary into Sonora about 30 km west of Nogales, Arizona. The small watershed is scarcely modified except by local and relatively old mining activities and heavy grazing by domestic livestock. Exploration for potentially increased mining activities has been going on for a number of years, but status of those projects are unknown. The stream is canyon bound and occupies an highly erosive channel throughout most of its course, with fish habitat consisting of scoured pools and undercuts in bends. Tributary canyons are gsilerally ephemeral except in periods of unusual runoff. Seeps and springs provide little fish habitat, with the exception of Hank's and Yank's Spring that is enclosed in concrete to create an artificial pool a few meters square. Sonoran chub is the only indigenous fish species recorded from this system in the United States. The drainage s!!pports native l ong-fin dacP, Sonoran topminnow, and presumably-intnoduced Yaqui chub in St.77 7- (Hendrickson 1984; Minckley et ai. 1986). The habitat in the United States is of Category I, and the species should remain secure barring' major environmental chanhe; possibilities for enhancing Sonoran chub populations are discussed in Section II (p. 30). Rio Sonoyta Basin This watershed is relatively extensive, but is in one of the most arid regions of the United States. Perennial, fish-supporting habitats exist only at Quitobaquito Spring, Organ Pipe Cactus National Mounument, Arizona, and in a short reach of the mainstream Rio Sonoyta in Sonora, Mexico. The system originates at its eastern margin on west-facing slopes of the Baboquivari Mountains and in the north at ill-defined divides between it and Growler and Santa Rosa valleys of the Gila River basin. The system drains westward until diverted south by the Pinacate Volcanic field to disappear in desert sands before any surface flow reaches the Gulf of Cali-Fornia (Hubbs and Miller 1 948a). 101 Grazing by domestic livestock and mining operations have been major influences on the watershed. Arroyo cutting has occurred along Rio Sonoyta and its ephemeral tributaries, resulting in lowered water tables and degraded floodplains. Agricultural developments in Mexico commenced in the 1970s, spurred by pumpage from the Rio Sonoyta aquifer, and presumably have resulted in further lowering of water tables in the area. This., plus pesticide blowover and leaching from fields and domestic wastewater inputs • have influenced -Fish populations in the Rio Sonoyta mainstream, and native l ongfin dace and desert pup-fish are becoming rare. Pesticides also have been noted at Quitobaquito Spring ( Kynard 1979). Quitobaquito Spring has been for years modified by man, and its original state will likely never be known. Amerinds presumably used it for water supply and irrigation, as did later settlers. Spring outflows were ditched and canalized and its down-Flow area was impounded to create a small pond. The original fauna also included long-fin dace and a distinctive -Form of desert pup-fish; the former has disappeared and the latter remains abundant. Introduction and establishment of golden shiner necessitated renovation of the system in the early 1 970s, pup-fish were removed, the pond drained, rotenoned, and deepened, and the pup-fish successfully reintroduced (Minckley 1973). However, the l ongfin dace population was destroyed at that time. The Quitobaquito form of desert pup-fish also was maintained in artificial habitats on the Monument for a number of years, but those have now teen removed to ASU (USNPS personnel, pers. comm.). The USNPF has an active program of management for the spring and its fauna (Section II, p. 29). Lower Colorado River System Mainstream Colorado River The Colorado River is one of the greatest desert rivers in the world, with a 632,000 km2 watershed and a total length of 2,334 km. This master stream originates at the Continental Divide in Rocky Mountain National Park, Colorado. It enters the Region at the Arizona—Utah border to flow west and south to exit the United State,-; near San Luis., Arizona, and enter the Gulf of California in Mexico. This is one of the most highly modified and controlled ,-.y..temc in North America and is now quite different from its original state (Minckley 1979a; Fradkin 1981). Prior to impoundments, spring snowmelt in the Rocky Mountains resulted in peak flows during May and June, followed by gradual declines through remainder of the year. Flash flooding frequently caused second peaks in late summer. Recorded discharges ranged from less than 1.0 m3/second (Dill 1 944) to more than 11,000 m3/second (USFWS 1980). High and l ow flow cycles 'resulted in cyclical erosion and deposition of sand and silt, with sediment loads varying from near 30,000 metric tons per day in flood to essentially none in periods of low flow. The stream thus ranged from the consistency of heavy cream in flood to crystal clear at low discharges (Fortier and Blaney 1928; Dill 1 944; Dolan et al. 1974). Seasonal water temperatures ranged from minima near 0° to maxima of more 0 than 30 C (Minckley 1979a). Today, 10 major dams and water manipulation 1 02 structures regulate the mainstream and others have been constructed on major tributaries. Flooding has been eliminated except in periods of unusual runoff, silt and sand are caught by quiet waters of reservoirs, and temperatures are ameliorated by hypolimnetic releases of water From hydroelectric dams (Dolan et al. 1974; Minckley 1979a; Turner and Karp i scak 1982). Biological characteristics of the lower Colorado River have been changed even more spectacularly (Dill 1 944; Miller 1 941; Minckley 1973, I979a, 1982; Nicola 1 979; Carothers and Minckley 1981; and others); the native fish fauna has been essentially replaced by introduced species. Reaches downstream from Grand Canyon Much of the watercourse downstream from Lake Mead is channelized, dredged, rip-rapped, diked, or otherwise directly altered from the original state. Harnessed water resources are used for irrigation, generation of hydroelectric power, municipal and domestic water supplies, and recreation, and impounding structures also function in flood control. Under average watershed conditions the entire volume of flow is withdrawn several times -f or use before all water is ultimately consumed. Progressively smaller downstream flows are maintained by return of agricultural and domestic wastewaters, seepage, and tributary inflow, until no surface flow reaches the Sea of Cortez in periods of average precipitation. Altered -flow regimes, increased water clarity, and creation of large re=servoirs en echulon alternating with cold tailwater reaches, are habitats heretofore unknown to the lowermost Colorado River downstream from Grand Canyon. These lakes and interconnecting streams provided suitable homes for a variety of introduced fishes such as trouts, common carp, a number of catfishes, mosquitofish and other poeciliids, sunfishes (including large- and smallmouth basses), striped bass, and tropical cichlids in warmer places. Concommitant with physical-chemical alterations and establishment of an exotic -fauna was a dramatic decline in abundances, diversities, and distributions o4 native fishes. Once plentiful species such as Colorado squaw4ish, bonytail, razorback sucker, and desert pup-fish are extirpated or reduced to tiny fractions of their former populations in only a few places. Other natives of lesser historic abundance, woundfin, roundtail chub, flannelmouth sucker, are gone. Only marine forms sporadically entering -from the Gulf of California crntinus to recirs-,,ent the former n7-,tive faun;i. at any level of abundance. Modifications of the lowermost Colorado River mainstream are so vast and the system is so large that most reaches now may be unsuitable for reclamation for management of native fishes. Only the lowermost portion of the reach below Parker, Arizona, has yet to be severely modified, and plans have long existed for channelization and installation of control structures in that area. On the other hand, we do not known why native big-river fishes disappeared, and if it resulted from an event or events now passed, they might well re-establish if available to colonize the area. Colorado squawfish from Willow Beach and Dexter NFHs stocked in the upper Colorado River basin have survived at least three years (Valentine 1983), and no preparati ere made prior to their re-introduction. Natural 1 03 spawning of bonytail in earthen ponds at Dexter, and their survival and growth with a mixed population of mosquitofish and African cichlids in ponds at Blythe, California (Section II, p. 48) indicate that species is perhaps more hardy than expected. And, success at pond culture of razorback sucker indicates a high survivability of that species under conditions quite different than those in the primeval riverine habitat. Most segments of the lowermost mainstream must be assigned to Category III since all but a few reaches would entail substantial effort and expense to maintain for big-river fishes, other than by stocking. There are, however, three viable possibilities for re-establishment of native fishes in the system (Minckley 1986): 1) stocking of selec. ted backwaters and river reaches, including those of delivery canals and perhaps drains, with big-river fishes, either as fry in segments from which non-native fishes have been removed or suppressed, or reared to sizes where reasonable chances of survival accrue; 2) creation of suitable habitat on the extensive USFWS NWR holdings or elsewhere along the Colorado River to be managed for perpetuation of the indigenous fauna; or 3) a combination of 1 and 2 above, involving use of suitable habitats on Refuge lands to rear indigenous fishes to sub-adult or adult size prior to release in the open river. Opportunistic stocking of naturally or artificially isolated backwaters along maroins of major reservoirs, or even canals and drains after repairs or winter drawdowns, may also be used to increase native fish populations. Such places should be used as "grow-out" habitats, especially if drawn down annually, with native fishes removed and introduced elsewhere in the winter of each annual cycle. If frx or fingerlings could be placed in such semi-natural or artificial habitats prior to reinvasion by non-native fishes, populations might be expected to establish and be maintained for considerable lengths of time. Successful natural reproduction and larval growth to more than 25 mm TL of razorback sucker occurred in such a backwater of Lake Mohave cleared of non-native fishes in 1985; larvae produced in the adjacent reservoir disappeared at about 12 mm "IL (Langhorst, ASU, pers. comm.). Broad, sand-bottomed areas in the reach of Colorado River mainstream below Parker, Arizona, are relatively devoid of l arger predators (Minckley 1 979a) and selected backwaters or shallow areas behind sandbars could be readily treated for removal of undesired species without widecpread or l ong-term imparts on snort fisheries. It seems advisable to anticipate problems of species interactions adverse to the native forms and rear native fishes to be stocked in the mainstream to fingerling or larger sizes prior to reintroduction, and local eradication or suppression of non-native fish stocks still likely be necessary. It is unlikely that reestablishment of of native fish populations would have discernible effects on the sports fishery in this or other parts of the l ower basin. Creation of habitat or reclamation of existing habitat on NWR holdings and other federal lands along the Colorado River seems the most highly viable and expeditious way to reestablish big-river components of the indigenous fauna (Valdez and Wick 1981; Minckley 1 926), especially since some of those species are now known to be capable of reproducing in lentic habitats (Section II, p. 48). Numerous cut-off habitats exist along The l ower Colorado River mainstream that could be reclaimed by ichthyntnxin 1 04 then stocked with native species. Dry cuts across oxbows are further a major method of channelization in the Region, and seepage through porous alluvium fills depressions excavated deeper than the local water table. Planning prior to river modifications would allow development of major habitats in this manner. Spoil from dredging operations could be used to produce berms to protect isolated water areas from potential flooding and escape of native fishes or invasion by non-native forms. Security already existing on many such lands would further assist in maintaining an uncontaminated native fauna. Water rights for indirect losses through evaporation could be negotiated or otherwise compensated for by removal of less desirable (for example shallower) habitats from use by NWR or other management entities. Direct costs for such operations could be recovered as mitigation for river modifications that effect changes in wildlife and fish habitats, and additional water areas would benefit waterfowl and other organisms already managed for by the Refuge system. Such habitats could be large and self-sustaining, or might be designed smaller and more amenable to direct management such as periodic eradication of undesirable fishes if they became established. Although these are obviously habitats of Category VI (artificial refugia), a strong case may be made for former occupation of oxbows and other cutoff aquatic habitats along the Colorado River by species now listed as endangered. The only differences between excavated and natural depressions are in the mode of formation. Relatively small ponds or other aquatic habitats constructed adjacent to the mainstream or isolated bays of reservoirs as discussed above could further double as grow-out systems to produce fingerling or l arger individuals of native species for periodic release into the river. Such a combination of semi-natural refuge and production facility would be no more expensive than the second possible alternative, and should be strongly considered. If a decision is made to maintain Desert pup-Fish along the lower Colorado River, alternatives 2 or 3 are highly applicable since that species reproduces prolifically in small habitats if no other species are present. Any attempts to re-establish native fishes should be accompanied by studies geared toward evaluation and documentation of introduction successes or failures. Experimental stockings should be made and studied to determine interactions of reintroduced natives and resident non-native species. Some important questions to be answered include the following. What is the pattern of dispersal and survivorship of young native species upon stocking and over a time period after introduction? What is the relative survivorship of introduced native fishes in the presence and absence of potential predators and competitors? What species prey on introduced young of native species and what are the predation rates and overall pressures? And, do competitive interactions such as red shiner and young of native species feeding on the same foods comprise a significant problem, or is food abundant enough for all? Mainstream and Tributaries in the Grand Canyon Reach Although still flowing in a natural channel, the reach of Colorado River .f rom Lake Powell through Grand Canyon National Park to headwaters of 105 Lake Mead flows reoulated, cold, and clear as a result of hypolimnetic relPv4Pc. n+ water from Glen Canyon Dam. Cold, regulated releases of water tend to exclude native fishes in the upper Colorado River basin ( Vanicek 1 967; Van icek et al. 1970), and seem also to be doing so in the Grand Canyon area (Carothers and Minckley 1981; Keadino and Zimmermann 1 983). Vast changes also are occurring as a result of curtailed sediment input to and transport through the canyon segment (Dolan et al. 1 974), the impacts of which on native fishes are unknown. The fauna of the reach is now l argely dominated by common carp and non-native trouts. Native fishes include speckled dace, flannelmouth sucker, and bluehead mountain-sucker that reproduce in tributaries and remain abundant as adults in the mainstream, humpback chub that almost certainly reproduces only the the lowermost Little Colorado River, and razorback sucker, which is exceedingly rare and nearing extirpation. Colorado squawfish, bonytail, and roundtail chub appear to be extirpated from the reach. Perpetuation of native fishes in the Grand Canyon segment of the lower Colorado River will perhaps be best assured by monitoring and active management of tributaries (see below). However, warming of the mainstream through installation of variable penstock intakes in Lake Powell, as has been done on Flaming Gorge Reservoir to the north (Joseph et al. 1977), may be an alternative. This would be remarkably expensive unless engineered along with other modifications of that system, and should be carefully assessed hefc".re `, einoaer i cusly ccrtempl ated. Cold water of the mainstream also suppresses reproduction by common carp, most of which were thought by Carothers and Minckley (1981) to move in the reach from Lake Mead, and warmer waters could furthermore enhance populations of other Temperate species like red shiner, redside shiner, channel catfish, mosquitofish, plains killifish (Fundulus zebrinus), diverse centrarchids, and striped bass, all of which are already present in low numbers. Increased predator l oading of the system is certainly not desirable if native fishes are to be perpetuated. Re-establishment of Colorado squaw-fish, razorback sucker, roundtail chub, and bonytail may be infeasible without warming of the river, and in the case of the last two species may be inadvisable unless problems associated with hybridization of Colorado River chubs can be resolved and circumvented. Habitat diversity required to allow ,zyntopic occurrence of bonytail, roundtail chub, and humpback chub (Smith et al. 1979) without hybridization and genetic swamping of one or all three species may not be possible in a regulated system. Attempts to reintroduce hatchery-produced squaw-fish and razorback sucker by placing them in appropriate nursery ..... such as backwaters or creek mouths are, however, encouraged. Tributaries to Grand Canyon are largely spring fed and most are relatively short and precipitous. Other than the larger systems such as Kanab Creek and Paria River that originate far from the mainsteam and are thus influencPd by settlements, agriculture, or grazing in their watersheds, most of these systems are relatively undisturbed. Native fishes using tributaries and tributary mouths include speckled dace, humpback chub, flannelmouth sucker, razorback sucker, and Oluehead mountain sucker (Minckley and Carothers 1980; Carothers and Minckley 1981). Colorado squaw-fish and bonytail, formerly present !ri the area, also must have utilized such habitats, at least for restino or -f eeding areas. 'Mouths of these minor streams are important and perhaps critical to reproduction and recruitment of native fishes that occupy the mainstream (Carothers and Minckley 1 981). The ma am Colorado River +1:-w3 clear from the hypolimnion of Glen Canyon Dam (Kubly and Cole 1979; see p. 51) and there is little evidence for successful reproduction of either native or non-native fishes other than trouts in that habitat. Spawning by speckled dace, flannelmouth sucker, and bluehead mountain-sucker appears to occur only in tributaries (Carothers and Minckley 1931), and juveniles of the last two species remain in these smaller streams for a time before venturing into the cold mainstream. Humpback chub also appear to depend on tributaries for reproduction and early growth (Keading and Zimmermann 1983; see Little Colorado River and p. 51). Sediment transport from the Grand Canyon reach has removed many barrier bars and other particulate substrates ( Dolan et al. 1974), so inputs of sand, gravel, and boulder from minor creeks may soon provide much of the available spawning substrate. Protection of these habitats should be relatively simple; they should be maintained in an unaltered state. However, rainbow trout stocked in the mainstream also use tributaries for spawning and significant competition for space, plus predation on young and adults of smaller native fishes has been reported (Minckley and Blinn 1976). If this is determined to be a significant problem, exclusion of spawning trouts might well be considered, at least from selected tributaries or tributary systems. Gila River System Mainstream Gila River The mainstream Gila River rises in the Mogollon Mountains of western New Mexico with union of its East, Middle, and West forks, flows south and west to enter and traverse southern Arizona, and flows into the Colorado River mainstream at Yuma. Prinr to alterations by man, the 3 a River flowed strongly through canyons in mountains and across small intermontane basins of New Mexico and eastern Arizona. Large imtermontane basins west of what is now Florence, Arizona, apparently had infiltration capacities sufficient to absorb most water from the stream at low flow. This was exaggarated by withdrawals for irrigation by agricultural Indians and dry reaches were commonly recorded in early literature. Impermeable bedrock near the defile between Sierra Estrella and South Mountain south of Phoenix, Arizona, forced water to the surface and inflow of the Salt River immediately downstream insured perennial flow from that point to the Colorado (Miller 1961; Rea 1983; Hendrickson and Minckley 1985). Downstream Reach, West of Coolidge Dam. - Modifications of the lower Gila River were far more straightforward than those on the mainstream Colorado River. The system was simply de-watered by construction of Coolidge Dam on its mainstream east of Globe, Arizona, and Roosevelt and other dams on its major tributary (Salt River) (Minckley and Brown 1982). The reach from Coolidge Dam to its former confluence with the Salt River remains dry except in periods of high runoff and affords no viable fish habitats except immediately below the dam and in delivery canals and 107 secondary desiltino and water-holding facilities like Picacho Reservoir. Down-flow from the Salt River, however, seepage, irrigation returns, and domestic and industrial wastewaters rise to form persistent and perennial reaches in the Gila from the Phoenix Metropolitan area to its mouth (Brown et al. 1981). Flood waters from the entire system are captured and retained by Painted Rock Reservoir near Gila Bend, Arizona, then slowly released to the Colorado River mainstream. With minor exceptions, the entire lower reach must be classified as Category III with respect to habitat development or potential. The lowermost Gila River, west of the Phoenix area, orioinally supported essentially the same fauna as the lower Colorado River, abundant Colorado squawfish, bonytail, razorback sucker, and desert pupfish, and scarcer roundtail chub, woundfin, and flannelmouth sucker. Sonoran ( Yaqui) topminnow also was abundant in the Gila to Yuma, but was never recorded from the mainstream Colorado River. Perennial wastewaters in this region now support a fauna largely of tropical derivation, African tilapias, sail-fin molly, and mosquito-Fish are remarkably abundant. Common carp, goldfish, red shiner, fathead minnow, bullhead catfishes, and sunfishes form more minor components of this totally non-native fann.:t ( Kepner, USFWS, pers. comm.). With the exceptions of desert pupfish and Sonoran (1-iila) topminnow, reestablishment of native fishes in the reach of Gila River downstream from Coolidge Dam seems unlikely without major and improbable changes in regional water use. However, pup fish and topminnow, as noted above, are readily maintained in relatively small habitats so as other fishes are excluded. They occurred syntopically under natural zonditions. A minimum effort of construction or renovation of smal I habitats such a.. sprinos and seepages along the Gila River mainstream ( Cateocry II) would perpetuate populations of both these species. A discussion of fishes- in tributaries to this stream section ( Hassayampa and Aoua Fria rivers) is below (p. 113). Upper Gila River Mainstream. - Grazing, l ogoing, minino and other practices undoubtedly caused early changes in the upper Gila River watershed that rnntrituted to arroyo and channel cytting in the entire drainaoe between ca. 1 880 and 1 917 ( Olmstead 1 919; Burkham 1970, at seq.; Turner 1 974). Another cycle of severe floodino and erosion has occurred since 1 9144 (Purkham 1 972; Minrkley 1 979b: Minci(ley and Clark 1 984; Hendrickson and Minckley 1 985). , Water uses consist of domestic supplies or a few small communities, plus agricultural irrigation from pumpage and direct diversion of the stream into earthen canals. Diversion dams generally are of alluvium and allow substantial underflow that maintains the stream. Floodplains are furthermore narrow, low, and porous so irrigaton water- returns directly to the system, a pattern that was almost certainly the same when agricultural Indians and later settlers -farmed the area. Habitats of Categories I through I V for rolorado River fiches thus persist in substantial amounts and diversities, although at l evels of flow reduced from those a century ago. Barring additional development of water resources or major chanoes in population sizes or species composition of the present non-native fish fauna, native fishes may be relatively secure in this reoion. However, major threats are authorized and/or proposed resercoirs in eastern Arizona ( Camelback damsite), and in New 7.1exico 1 cnner and Hcoker damsites). 108 Numerous species formerly appeared or still persist upstream from soft-bottomed reaches of the mainstream Gila. Longfin and speckled daces, roundtail chub, Sonoran sucker, and desert mountain-sucker became abundant and spikedace and l oach minnow were common. Lower river species (Colorado squawfish, bonytail, flannelmouth and razorback suckers, desert pupfish, Sonoran [ Gila.1 topminnow, became increasingly rare as one ascended the system (Koster 1957; LaBounty and Minckley 1973; Minckley 1973; Minckley and Clarkson 1979). All seven of the first group of fishes persist, but spikedace, l oach minnow, and roundtail chub are markedly rarer at present than in the past, and the remainder have suffered reductions in range (Hatch 1979; Propst et al. 1985a; Propst, NMDGF, pers. comm.). Five of the six lower-river species are extirpated from the upper Gila River basin; topminnow persist as natural populations only in springs near Bylas, Arizona, on the San Carlos Apache Indian Reservation, Non-native fishes now occupying this region are largely riverine in habit. Lentic-adapted species find little suitable habitat in the channel since mainstream impoundments do not yet exist upstream from San Carlos Reservoir. Goldfish and common carp are especially abundant in the last impoundment, but only the latter penetrates far upstream. Red shiner has spread over the past decade from San Carlos Reservoir into New Mexico waters (Hatch 1979; Propst et al. 1985a). Mosquitofish is throughout the area in almost all kinds of habitats. Channel, flathead, bullhead catfishes (Ictalurus melas, I. natalis) also are abundant. Sunfishes, with the exception of smallmouth bass, are relatively uncommon (Koster 1 957; LaBounty and Minckley 1973; Minckley 1973; Minckley and Clarkson 1 979; Propc.t et al. 1 995a, b). Disallowing additional mainstream impoundments in the upper Gila River mainstream of eastern Arizona and western New Mexico is the major way to conserve remaining components the native fish fauna. Dams not only would directly destroy substantial amounts of habitat through inundation and downstream effects such as curtailment of flow or discharge regulation, but also would enhance existing populations and provide habitat for additional non-native fishes. Non-native predators such as catfishes and smallmouth bass should be evaluated as to their impacts on native fishes and if substantial could perhaps be sunpre ed by relaxed rectrictions on their capture by sport fishermen, i.e. legalizatinn n+ sPtlines in Arizona and liberalization of creel limits in both Arizona and New Mexico. Monitoring of the short-lived spikedace and l oach minnow should be on an annual or semi-annual basis and data on the remainder of the native fauna could be acquired along with those efforts. Status of roundtail chub in the upper Gila River basin should especially be evaluated and Federal listing of the population considered if they are in fact as low in numbers as they appear. Attempts to reestablish razorback sucker in the Arizona reach of the Gila River (Johnson and Rinne 1982; Minckley 1983; Brooks et al. 1986) should be expanded to include larger waters in New Mexico. The Arizona reach should further be stocked with woundfin and bonytail (as is already proposed) to attempt establishment of a second population of the former and a riverine population of the latter. Wound-Fin would be somewhat out of their historic range (Category Ik)), but the 3ile- River in eastern Arizona i s deemed as best of only a q.: ew habitats in which that species might be :U9 expected to establish. Stocking of bonytail is certainly justified by proximity of historic records at Ft. Thomas, Arizona ( Kirsch 1 839), and the absence or marked rarity of other chubs in the reach that should preclude hybridization problems recorded or possible elsewhere. Suggestions to introduce Colorado squaw-Fish, which was known from the Safford, Arizona, area (Chamberlain 1904), seem premature, but might be considered after populations of more critically imperiled species such as bonytail or razorback sucker have established. Canyon areas of the upper Gila River have in the past been proposed as "wild or primitive" rivers. Most if not all are in Federal ownership, and the USFWS should join with Private groups and/or other agencies in promoting preservation of these reaches under such a classification. Such action is not only desirable for endangered and threatened fishes, but also for substantial populations of raptors, songbirds, and other vertebrate species of special concern and sporting importance (especially waterfowl). Hassayampa and Aqua Fria Rivers systems Waters from these drainage basins rarely reach the mainstream Gila River as surface flow; most pass beneath sands of their broad, lowermost channel... They begin between the Bill Williams and Verde drainages in the montane transition zone that separates low-desert and the Colorado Plateau, and flow southward to join the Gila River just west of Phoenix, Arizona. Isolated headwaters of the Hassayampa River support native l ongfin dace and introduced fathead minnow, and include a short reach deemed suitable for attempted establishment of wound-Fin (USFWS 1985b). An earlier attempt to establish that species through transplant of a few adults into both the Hassayampa and Aoua Fria systems met with failure (Minckley 1973; Minckley and Brooks 1986). The Aqua Fria system formerly contained spikedace, and remains locally populated by longfin dace, speckled dace, desert mountain-sucker, and a headwater stock of enigmatic trout that may represent genetic remnants of Gila trout that in the past suffered introgressive hybridization with introduced rainbow. Spring-fed streams of the lower Aqua Fria basin have received transplants of Sonoran 4 1 C poorly known, and merits compilation of field and other information into a compendium to provide a baseline for future work. Identification, setting aside, and periodic monitoring o-f isolated habitats in upper parts of both these systems will assist in preservation of the remnant fauna. Gila chub and perhaps the trout are especially important in this regard because of their otherwise limited (and/or declining) distributions. Cave Creek (7—springs Wash) is a small, spring—fed tributary to the mainstream Gila River or lower Agua Fria River. This system heads in low mountains just north of Carefree, Arizona, flows north, then turns west and south. Its lower course has been so modified by urban development and diversion that the original direction of flow is no longer discernible. The source is a relatively large spring that produces perennial flow -for about two kilometers on USFS l ands. The stream was originally inhabited by Gila chub and speckled dace. Long-Fin dace were later introduced and became established, or invaded from downstream (Stout et al. 1970). ASU, AGED, and USFS biologists attempted in 1970 and 1971 to remove l ong-Fin dace, re—establish the original two species, and introduce l oach minnow and spikedace to develop research populations. Longfin dace removal did not succeed, the original species were apparently extirpated, and the introduction failed (Minckley 1973; Pinne 1975; Minckley and Brooks 1986). Speckled dace from the adjacent Camp Creek (Verde River system) were reintroduced, but apparently did not establish. Sonoran (Gila) topminnow also were introduced (Minckley 1969b; Minckley and Brooks 1 ) and became established, -f orming a viable population near the springs that exists today. This system is relatively isolated and it remains feasible that populations of at least the original native fishes can be re—established there with minimal additional effort. No introduced fishes other than l ongfin dace are krow;:,- but crayfish (Orconectes sp.) have been stocked and , drt. Private lands south of 7—springs Wash are being developed rapidly, but existing USFS picnic grounds near the stream have little influence on its headwaters and the system remains intact. Santa Cruz River System "Headwaters of the Rio Santa Cruz... drain the north, west, and south slopes of the Canelo Hills, and all sides of both the Patagonia and Santa Rita mountains... The mainstream flows south through the San Rafael Valley, receiving tributaries from the Huachuca Mountains to the east. Entering Sonora [Mexico7 it l oops around the south end of the Patagonia Mountains to again enter Arizona. It then receives discharge from the western Canelo Hills via Sonoita Creek, which passes between the Santa Rita and Patacionia mountains. The valley broadens as it passes between the Santa Rita and Serrita mountains and countinues north to Tucson. On the north side of Tucson, Rillito Creek enters from the east with drainage -From the north slope of Canelo Hills via Cienega Creek and Pantano Wash. Further downstream the broad Avra—Al tar Valley enters from the southwest, draining the area between the Soboquivari and Sierrita mountains. The Rio Santa Cruz historically disappeared into its bed, except in -flood, in the vicinity o+ Tucson,,. There is no evidence that the Rio Santa Cruz extended 111 as surface flow to its confuence with the Gila River in historic time [Hendrickson and Minckley 1 9851." Substantial historical data are available for the Santa Cruz basin because of the long and important role of Tucson as a base of operations in Spanish and later settlement and development of the Arizona Territories. Native fishes were studied early, and relatively thoroughly. Included in the fauna are l ongfin and speckled daces. Gila chub, Sonoran sucker, desert mountain-sucker, Sonoran (Gila) topminnow, and desert and Monkey Spring pup-fishes. Big-river fishes and some Gila River endemics ( spikedace and l oach minnow) are conspicuous in their absence, presumably being excluded by structural features that include a broad, delta-like land-plug as it approaches the Gila River that must have acted as an effective and l ong- term barrier. Desert pup-Fish are extirpated from the region and Monkey Spring pup-fish is believed extinct as a result of largemouth bass introduction in its isolated habitat. All other species perist at least as remanant populations. Historically, this area has been under intense agricultural development l onger than most other parts of Arizona. Early floodplain alterations were far more extensive than elsewhere (Cooke and Reeves 1 976). i vaatock nra7ing has been a major acfivH.y since about 1 700 ( BnItnn 1 926: Wagoner 1 952). No major impoundments have yet been constructed in the watershed, but pumpaoe for domestic, industrial, and irrigation supplies has been extensive and water tables have been lowered far beyond levels of recharge (White et al. 1 766; Babcock 1980), The Santa Cruz basin has sustained some o-F the most severe arroyo cutting in southern Arizona and dewatering rl.f l ower portions of streams is of general occurrence. Plans for further regional development, especially of additional communities in headwaters of the system, will likely result in major losses of aquatic habitats such as Cienega and Sonoita creeks due to increased groundwater pumpage ( Arizona Water Commission 1 972). Introduced fishes, with the exception of mosquito-fish, are relatively rare except in stock watering tanks and small fishing impoundments. Nosquitofish are widely used in control of pestiferous insects, and occur thrniiohoi!t the waterahed, Non-native trniit ere stocked at hiohar and sometimes low elevations in winter for put-and-take or seasonal fisheries. Common carp, fathead minnow, channel and bullhead catfishes, centrarchids (largemouth bass and various sunfishes), and tilapias also are present. Introduced bullfrogs may be a fishery management problem in some isolated habitats. Lower Mainstream. - The mainstream Santa Cruz i s essentially dry from Tubac, Arizona, to its mouth south of Phoenix, and may be classed only as Category III aquatic habitat. Local perennial flow in the Santa Cruz River from the U. S. and Mexican Border to "%bad, Arizona, now is ephemeral or unreliable, and the degraded, deeply incised stream is infested with mosquitofish and fathead minnow where permanent waters persist. Longfin dace persist as the only native species. Potrero Creek, which entera thi s reach from the west and supported topminnow and l ongfin dace is dewatered. Status of habitat and fishes in the southern loop of the Santa Cruz in Sonora is unknown as it has not been surveyed since about 1 974. A number of perennial streams tributary to these reaches, and recently described in detail by Hendrickson and Minckley (1985), support native fish populations (Minckley et al. 1977; Me-He 1983a; Me-He et al. 1982, 1983) that may yet be salvaged and perpetuated. Arivaca Creek. — Arivaca Creek drainage comprises the extreme headwaters of the Avra Valley, Arizona, where a stream and cienega system persists downstream from a fishing impoundment (Arivaca Lake). The area has long been subject to grazing, cultivation, and mining operations. Its original fish fauna consisted only of l ong-fin dace, but Sonoran (Gila) topminnow were introduced in the 1 940s, presumably for mosquito control, only to be replaced by mosquitofish in the late 1950s (Miller 1961). Other non—native forms include fathead minnow, channel and bullhead catfishes, l argemouth bass, and smaller centrarchids. Aquatic habitats of this system are considered as marginal Category II or Category III for native fishes. Rillito Creek—Pantano Wash—Cienega Creek. — This extensive watershed heads in grasslands of the Sonoita—Patagonia, Arizona, area and enters the Santa Cruz in northern Tucson. It historically supported abundant cienega and stream habitat that was heavily used by Indians, early explorers, and livestock ranchere. (Hendrickson and Minckley 19S::' Lower parts of the system are l argely dewatered and ephemeral as results of grazing pressures, pumpage and diversion, and arroyo cutting. Cienega Creek and its associated springs and marshes persist, however, as important aquatic habitats isolated by long reaches of ephemeral channel and a number of barrier falls on Private lands between the Empire and Whetstone mountains. No introduced fishes are known from that system, which supports abundant l ongfin dace, Gila chub, and Sonoran (Gila) topminnow. This Category I habitat may soon be threatened by development (see above) and should be placed as high priority for acquisition or easement toward native species management. Sonoita Creek. — The Sonoita Creek system originates in grasslands near headwaters of Cieneos Creek and flows to enter the Santa Cruz River between Nogales and Tubac, Arizona. The watershed is relatively intact, although heavily grazed for many years. Mining activities in surrounding mountains have influenced some headwater streams, most of which are ephemeral. Most natural aquatic habitats that persist are on Private lands, including Cottonwood and Monkey springs and a reach of mainstream Sonoita Creek downstream from the town of Patagonia, the latter fed in part by domestic wastewaters. The Nature Conservancy owns and manages the Sonoita Creek Sanctuary in the upper part of that reach, and is to be commended for its conservation of native fishes along with riparian plant and animal communities. Patagonia Lake, privately developed but later purchased and now managed as a fishing lake by AGFD, impounds a relatively l ong segment of this lower reach. Waters passina over and through the dam maintain habitat almost to the Santa Cruz River. Introduced fishes include thread-fin shad, trouts (seasonally), carp, goldfish, fathead minnow, channel and bullhead rat-Fish, and largemouth taee and smaller eunfiehes, most of which occupy Pataoonia Lake. An early introduction of Yaqui 11? catfish into this drainage became establi..,hed, but was extirpated in the 1 950s ( Minckley 1969a, 1973). Native fishes of this watershed included all species known from the Santa Cruz system (Minckley 1969a). Long-fin and speckled daces, desert mountain-sucker, and Sonoran (Gila) topminnow persist. Attempted introductions iDJ:; spikedace and l oach minnow in Sonoita Creek (Minckley 1973) were unsuccessful. Natural populations of Sonoran (Gila) topminnow and relatively unmodified habitats in headwaters of Monkey and Cottonwood springs and in Redrock Canyon (Rinne et al. 1980) and three species (longfin and speckled daces and desert mountain-sucker) in Sonoita Creek support their inclusion as Cateoory haOitats. Topminnow are sometimes also taken in Sonoita Creek (Minckley 1969a), where they co-occured with m osquito-fish downstream from Patagonia Lake in the 1 970s (Minckley et al. 1 977), in a segment that may be considered of Category II. The reach supporting co-occurring populations of the two poeciliids was sampled in 1985 and the situation surprisingly still persists. The system is long overdue for an in-depth survey todetermine status of its fauna and to search for other actual and potential habitats. Uppermost Santa Cruz Watershed. - The mainstream Santa Cruz River in San Rafael Valley, Arizona, from its source and before it enters Sonora, still supports Gila chub, longfin dace, Sonoran sucker, Gila mountain-sucker, and Sonoran (Gila) topminnow, along with i ntroduced fathead minnow, mosquitofish, desert ( Cuitobaquito) pupfish, and green ... unfich. Native -fish populations tend to decline in periods of low -Fl ow then resuroe after floodino decimates non-native fish populations ( MincXley et Si. 1977; Meffe et al 1963, MA-Ffe 1983A, 1934; Minckley and MPffe 1 986), a pattern that seems to have existed for more than 20 years. How l ong this can persist is unknown. A l ong and severe drought might well allow populations of non-natives to extirpate the indigenous fauna, or alternatively, near-final or actual desiccation could destroy the former and allow the latter to persist or reinvade from upstream springs. Renovation of the entire system, especially during drought, and reintroduction of natives, is not infeasible and perhaps should be considered. A barrier near the U. S. and Mexican Boundary could prevent or at least curtail upstream movement of undesirable fishes and create a manageable situation in this relatively small and remote area. Sheehy, Sharp, and "Heron" springs that enter the Santa Cruz River from the east on lands owned by the San Rafael Cattle Company all, flow strongly. Sheehy Spring is modified for irrigation, but its upper part i s unchanged. It supports Sonoran ( Gila) topminnow and Gila chub, but is infested with mosquitofish and both native species are in low numbers. Arrangements should be made for renovation of this system, which now is isolated from further invasion from downstream by irrigation works and could readily be managed for the native forms. Sharp spring is occupied by topminnow and invading mosquitofish and should be carefully monitored to insure perpetuation of the former. It may be necessary to renovate this system and create a mosquitofish barrier in the rear future. " Heron" SvMg was fishiess until 1982, when authorized transfer of Sharp Spring topminnow cnsatid Hat 7 e pov2lation. It flows into a small, fishiess i mpoundment and thus is isolated from other than i ntentional introducticon 114 of mosquitofish or other non—native species. Abundant bullfrogs are, however, spreading throughout the upper Santa Cruz system from this area and may be expected to have some impact. Bog Hole Tank in the uppermost portion of the drainage is fed by natural springs in extreme headwaters of the Santa Cruz River that were impounded by AGFD in 1 975 on USFS l ands in an attempt to enhance populations of Mexican Duck (Anas platyrhynchos diazi). A reservoir several meters deep was formed and almost immediately stocked by unauthorized persons with the Quitobaquito form of desert pup-fish (Section II, p. 41), which became established and has populated the Santa Cruz mainstream for at least a kilometer down-flow. The only -fish native to the Bog Hole was l ong-fin dace, which has now disappeared. A problematic, state—listed tiger salamander (Ambystoma ticrinum stebbinsi) breeds abundantly in the habitat. The pup-fish population should be removed and replaced by desert pup-fish genetically similar to original stocks (Santa Clara Slough form, now being propagated at Dexter NFH, p. 34). Mosouito+ish, l argemouth bass, green sunfish, and perhaps other non—native species in two or three upstream stock—watering tanks also should be removed and replaced with native fishes such as Gila chub, desert pup-fish, and Sonoran (Gila) topminnow. Designation as a refuoium area and active monitoring and management of this system would provide a qourc= of rat ye -Fi ,zhes that could move downstream with flood. San Pedro River Watershed This river flows approximately 40 km north from oak—grassland hill,... near Cananea, Sonora, to enter Arizona and flow ca. 200 km more over deep alluvial fills to enter the Gila River near Winkleman. The San Pedro system was large and complex enough in the past to support most of the Gila River fauna. It is historically important due to the -Fact that early collectors obtained a large percentage n+ the fish species known from the Gila River basin from this stream or its major tributary Babocomari River, and sent them to specialists in eastern United States where they were described. Type localities for spikedace, dace, l oach minnow, Sonoran sucker, flannelmouth sucker, and desert pupfish all are in this area. Woundfin did not occur so far upstream in the Gila basin, Sonoran (Gila) topminnow were only near its mouth, and bonytail was not recorded, although it occurred upstream from the San Pedro mouth in the mainsteam Gila River (Kirsch 1889). Razorback sucker were abundant enough to be sold commercially in Tombstone (Miller 1 961) and "salmon trout, up to three feet l ong" (Cooke 1 938; Eccleston 11950) were present. The last could only have been Colorado squawfish (Hendrickson and Minckley 1 985). San Pedro Mainstream. This watershed has long been grazed by domestic livestock, its floodplains farmed, and its surrounding mountains mined. Nevertheless, as recently as a century AL-40 the river was unincised and marshy along much of its lenth ( Hastings 1959; Hastings and Turner 1 965; Hendrickson and Minckley 1 985.) Permanent water now exists only where structural features of the channel force underflow to the surface. 115 :ndustrial pollution from ore reduction mills occurred early and dewatering from diversions and later pumpage from subsurface aquifers began to influence the ...;tream in the late 1 800s. Other than dewatering, the most important impact on the system now n. . ea major mining operations in Mexico, including water removal from the headwaters and uncontrolled or accidental releazes of pollutants that periodically decimate the mainctream biota inotn in Mexi:o and it:r con;iderabledi.. tanc==. into the United States. Introduced species include common carp, goldfish, fathead minnow, red shiner, catfishes (mostly bullheads), mosquito-Fish, largemouth bass, tluegill, and green sunfish, mostly in stoex-watering tanks, but also in some permanent tributaries (especially mosquito-Fish, bass, and green sunfish). Short segments of the San Pedro mainstream that persist now support only l ongfin dace, desert mountain-sucker, and introduced 4ishe the l ast mostly near its co--l uence with the Sila River: Conditions in the Mexican portion o4 the mainstream and its tributariel ceneraLy un _-n, but in 1971 that area supported only lrnd-Fin dare, desert mountain-sucker, and Sonoran sucker (Jnpubl. data). Desert pup-Fish, l oach minnow, and likely spikedace were there in the 1 950s (Miller and Winn 1 951). Tributaries to the system include a number of major Catecory I and 11 habitats in the United States, especially Aravaica Creek and Red-Field Canyon and with some exceptions in the Batocomari Rkier 9system. Aravaipa Creek, - This stream is one o4 the most pristihe 4:sh han,ii tats in rit.ona: The central corde o4 Aravaida Area ( scheduled -F or Wilderness designatior atmihisteret USELI, and the upper and l ower ends constitute the 2eorga Hh cc I ;.eserve owned ahd operated by the Dei=enders o4 Wild7i4e: This stream has been thoroughly studied and has provided many o4 the available data on li-Fe histories art ecolooy o4 Southwestern +ishiss ( Barber et al. 1 370; Minckiey and Barber 1 970; Deacon and Minckley 1974; Bruns and Minckley 1 980; Minckley 1 9E1; Clarkson 1 982; Siebert 1 980; Kepner 1 982; Schreiber and Minckley 1 922; Barber and Minckley 1 983; Me-F. 4e and Minckley 1986; Minckley and Me44.:E, 15'86). Seven native species persist in ravaioa 07?i< and its tributaries. l onc-Fin and speckled daces, l oach minnow, spikedsce, roundtail onut, Sonoran sucker, and desert mountain-sucker. There have been no statistically sidni-Ficant changes in community composition r 40 years record (Meffe and Minckley 1 926). 3onor SLa.. pminnow were native aionr the San Pedro near the moth D*F Area:pa Creek, but were never actually taken in that stream. Repeated attempts to establish the species have been unsurreec,4u1 (Minckley 1 9695, 1772; Minckley and Brooks 1286). Introduced -Fishes have never become established despite repeated records -F O7 greer: S;..1M i Sh a 4ew e>:amples o= l ardemiduth bass, and one collect:oh o= mosquitc-Fish. Severe -Flooding decimates or sup:: - their populatione ( Me-F.fe and Minckley 1936), which re-established through stock tanks in the watershed durind minor .=locds: introductions o-F any species but Sonoran ( 3 a• topminnow in the i- ravaipa Creek system should be avi:jec,,. 7-re stream now supports a richer :aura than iAias nistorically pr o-sent in most streams o-F its size and configuration in low deserts of Arizona. Removal of non-native fishes from tanks in the watershed would alleviate sporadic influxes of alien forms and preclude possiblities that one or more could establish and influence the native fauna. Remoteness of the watershed makes such a management effort feasible since few if any sportsmen travel to the region seeking game fishes. Establishment of Sonoran (Gila) topminnow in remote tanks would provide a supply of that species for the watershed and would negate any pestiferous insect problems that might arise. Protection of the Aravaipa Creek watershed from potential pumpage and channel modifications in Sulphur Springs Valley is mandatory if the system is to be perpetuated. If not yet established by USBLM, a monitoring program for water table conditions in Aravaipa Creek aquifer areas would seem a minimum effort toward this end. Minimum flow conditions for maintenance of the native fauna already have been estimated Redfield Canyon and Hooker Hot Springs. - These stream systems are far less known than Aravaipa Creek, and should be carefully and immediately surveyed. Both or in the remote and relatively inaccessible Galiuro Mountains so their watersheds should readily be protected. The streams collectively support only native fishes, Gila chub, l ongfin and speckled dace, and desert mountain-sucker. Attempted introduction of Sonoran ( Gila) topminnow in Redfield Canyon did not succeed (AGFD records), presumably because of flooding. Substantial amounts of Category I habitat are nevertheless present for perpetuation of native fishes. The Muleshoe Ranch Preserve of the Nature Conservancy is already established on Redfield Canyon, so that a substantial amount of protection already has been provided. Efforts of that organization should be commended and encouraged; offers of USFWS assistance in management of the non-native fishes are appropriate. Babocomari River System. - The Babocomari River originates in grasslands and oak-grasslands between the Canelo Hills and Mustang Mountains and enters the San Pedro River near Fairbank, Arizona. Hinton (1878) described the Babocomari River as "20 feet wide, 2 feet deep, and 25 miles long, flowing east through a fine valley, with water all the way and in places large cienegas." Three permanent reaches persist in the watershed, Turkey and O'Donnell creeks in Canelo Hills and a five to seven kilometer reach of the mainstream lying across. the Pima-Cochise counties line downstream from Elgin on the Babocomari Ranch (Hendrickson and Minckley 1985). Native fishes included l ong-Fin and speckled daces, Gila chub, Sonoran sucker, desert mountain-sucker, and oerhaps desert pup-Fish. Longfin dace, possibly Gila chub, and the two suckers remain. The mainstream Babocomari River is intermittent from Elgin, Arizona, well onto the Babocomari Ranch, where it flows through one of the largest and most intact cienega habitats remaining in the American Southwest. Arroyo cutting was curtailed by early construction of a concrete dam that protected the cienega and perpetuated the habitat. Downstream, the stream is deeply incised and soon again intermittent. Non-native fishes in the cienega include goldfish, yellow bullhead, green sunfish, bluegill, and largemouth bass. The cienega habitat and its potential for native 'fish management make this one of the more valuable Category II systems in southern Arizona. Easements for management of the area should be pursued and obtained, the dam should be thoroughly checked and repaired if HeLe dry, and plans to reclaim the cienega should be formulated and executed. Drainage would be possible by siphon or pumpage over the dam. Once drawn down, the area could be chemically treated then restocked with indigenous fishes retained from the habitat itself or obtained from other parts of the same basin. Speckled dace and desert pupfish of the original fauna are no longer present in the system and Gila chub may be extirpated from Babocomari Cienega proper. The first occurs in and is available from Sonoita Creek or East Turkey Creek of the Santa Cruz or San Simon system, respectively, the last is available as hatchery material from Dexter NFH, and Gila chub remain in adjacent tributaries (see below). Sonoran (Gila) topminnow also should be considered for introduction, althouoh Babocomari Cienega is technically a Cateoory I V habitat for that species. Tributaries to Babocomari River that support native fiches include Turkey and O'Donnell creeks and cienegas, which are inhabited by Gila chub, l ongfin dace, desert mountain-sucker, and perhaps others. No introduced fishes are known from these systems, both of which alternately flow through USFS (Coronado National Forest) and Private l ands. San Carlos River Basin This small river system orioina s in sprinos in a broad grassland between the Gila Mountains and Natanes Plateau and flows northwest, then south to enter the Gila River near San Carlos, Arizona. It is entirely on the San Carlos Apache Indian Reservation. Native fishes include Gila chub, l ong-Fin and speckled dace, Sonoran sucker, desert mountain-sucker, and Sonoran (Gila) topminnow. Only the l ast species has disappeared from the system. The watershed has been and is subjected to heavy livestock use. One small impoundment is located near the lower end of the system and the lowermost few kilometers are flooded when San Carlos Reservoir is at full pool. The lower portion of San Carlos River was thoroughly surveyed then treated with ichthyotoxin prior to closure of its small, mainstream reservoir. Few native species were present in that reach, which mostly supported common carp and green sunfish. Both impoundments now support l arge, non-native fish faunas, including thread-fin shad, common carp, ooldfish, red shiner, fathead minnow, channel, flathead, and bullhead catfishes, largemouth bass, black crappie, and smaller centrarchids. Unidentified tilapia (likely Oreochromis mossamticuc) were introduced years ago in a warm spring on the San Carlos River ( Minckley 1573), but disappeared. Other non-native fishes in the San Carlos RI von include common carp, fathead minnow, mosqitofish, and green sunfish, the last being l ocally abundant and sometimes dominant (Propst et al. 1 985b). No non—native fishes have been taken from Blue Spring, a major tributary entering San Carlos River from the west. This system has not yet been adequately surveyed. Available collections are from near the mouth and at two points upstream, Warm Spring and at a road crossing Blue Spring Wash (Minckley 1973; Propst et al. 1 985b). An in—depth survey is appropriate, as is protection of the system from additional introductions. If deemed appropriate by the San Carlos Tribe, Category I habitats should be set aside for native fishes and consideration should be given to renovation, construction of barriers to upstream movements of non—native species, and reintroduction of native fishes into Category II habitats such as the upper San Carlos River mainstream. Gila River tributaries between San Carlos and San Francisco rivers Bylas Springs and the Markham, Bonita, and Eagle creeks systems, all south—flowing tributaries to the mainstream Gila River, form Category I and II fish habitats of considerable importance to native fishes. San Simon River, entering from the south, innlude=. Category II, III, and VI habitat:. Bylas Springs. These tiny, Category II habitats emerge along limestone terraces on the San Carlos Apache Indian Reservation just north of Bylas, Arizona (Mee 1 983b; Meffe and Marsh 15 ), Prior to fl-coding in 1977 they were inhabited only ny Sonoran (I;i7a) topminnow (Johnson and Kobetich 1970; Minckley et al. 1 977). Flood waters rose high enough -from the mainstream Gila River to allow invasion of mnc.duitofi:t into all but one Of the three spring-flows and topminnow beoan to decline. Red shiner invaded one system, but disappeared. Topminnow became rare by 1 979; a stock was salvaged and moved to ASU, and an attempt to eradicate mosquitofish failed in 1 982 ( Meffe 1 783b). Barrier.... were constructed on all three systems in 1 984 1 topminnow was again secured and maintained, and mosquitofish eradication attempted. Topminnow was reintroduced into habitats apparently devoid of mosquitofish in Jul:' that xear; the system has not since been vi.:ted. Gradients are low; the spring runs flow through a mesquiteSsaltdedar bosque to disappear under normal conditions through seepage into floodplain alluvium. Existing barriers constrain only the immediate spring runs, so that floodwaters pass laterally to negate their effectiveness. Additional construction of berms lateral to concrete structures will preclude thi:. possibility. Bylas Springs are isolated and small, and should be excellent and secure habitats for topminnnw once mosquitofish are excluded. Markham Creek. — Markham Creek is an isolated, Category I habitat in the Gila Mountains north of Safford, Arizona. It supports speckled dace, serving as a refuge for a stock most similar to the southern form of that species. Periodic monitoring of population status is recommended. The habitat is likelx too small to consider for introductions of additional species. .;" . San Simon River. - This stream originates in the San Simon Cienega on the Arizona-New Mexico border north of Portal, Arizona, and its now-ephemeral channel passes north-northwest in a broad structural trough to join with the Gila River near Solomon, Arizona. Historically, the system consisted of watercourses flowing through heavily-vegetated, braided channels. Marshes were prevalent near the headwaters (Hendrickson and Minckley 1985) and near the mouth (Chamberlain 1904). Native fishes known from the system were Gila Chub and Sonoran (Gila) topminnow in lowlands and speckled dace in the Chiricahua Mountains. Only the last persists. Time of disappearance of the chub is unknown, but topminnow were replaced by mosquitofish in the early 1 960s (Minckley 1973; Minckley et al. 1977). Rapid change occurred after 1885, with disappearance of lush grasslands due to intense grazing and beginning of severe erosion and arroyo cutting (Cooke and Reeves 1976). Gullying resulted in dewatering. The San Simon Cienega was protected by a concrete dam and still exists, although artifically deepened and maintained by pumpage. It supports at least four non-native fishes, yellow bullhead, mosquito-Fish, largemouth bass, and bluegill, plus a dense population of bullfrog, and may considered as Category II or III habitat, depending on what would be necessary for renovation. Artificial and semi-natural, artesian-fed habitats persist in the valley, including thermal springs and spring-fed ponds and lakes in the vicinity of the Pinaleno Mountains and especially on Roper Lake State Park near Safford, Arizona. These systems are inhabited by introduced red shiner, yellow bullhead, channel catfish, mosquitofish, l argemouth bass, smaller sunfishes, and tipalias. Some isolated springs, at least, could be developed for use as Categories II through V habitats for pupfish and topminnow, and perhaps for Gila chub. Contacts should be made with the Arizona State Land Department and USBLM, agencies responsible for most of this area, to expedite recovery of native fishes in the San Simon system. USBLM in 1985 introduced Sonoran (Gila) topminnow at five localities in their Safford District, most of which were in the San Simon trough. Bonita and Eagle Creeks. - Both these streams originate on the San Carlos Apache Indian Reservation and flow southeast and south, respectively, to their confluences with the Gila River. Native fishes of these systems included problematic chubs resembling Gila chub, speckled and l ongfin daces, Sonoran sucker, and desert mountain-sucker in headwaters and all but Gila chub-like fish, plus roundtail chub, in downstream portions of both systems (Minckley and Clarkson 1979; Clarkson 1 982). Headwaters of the Eagle Creek system support a problematic native trout (Mulch and Gamble 1954; Lowe 1 960) possibly referable to Gila trout or a hybrid between that species and Apache trout. Minckley (1973) reported the population extinct, but there is more recent evidence they persist in the area (Kynard 1980). Introduced fishes, with the exception of non-native trout stocked in Eagle Creek, are absent from headwaters. Common carp, goldfish, red shiner, fathead minnow, black and yellow bullhead, channel and flathead catfish, mosquitofish, green sunfish, and bluegill are recorded from lower parts of one or both streams (Minckley 1973; Minckley and Clarkson 1979). Reservation and other lands in these watersheds have been heavily grazed. Most of Bonita Creek south of the Reservation is, however, under 1 20 USBLM jurisdiction, so regulation of grazing is possible. Upper Eagle Creek is on National Forest and San Carlos Indian lands and the lower portion is owned by Phelps Dodge Mining Corporation. Both streams are modified in their lower reaches, Bonita Creek by construction of an infiltration gallery and pipeline for delivery of domestic water to Safford, Arizona, and Eagle Creek by diversion of water via Willow Creek from Black River and a major pumping station that transports water to mining operations in the Clifton-Morenci area (Minckley 1 979b). Eagle Creek often becomes intermittent downstream from the pumping station during periods of little precipitation, but flows strongly throughout the year in its upper segments. If recent trends toward curtailment of mining operations in the Clifton-Morenci area are realized, lower Eagle Creek may be expected to become a major stream habitat in eastern Arizona. This should be anticipated by preliminary discussions with Phelps Dodge Corporation toward establishment of a non-native fishery in the system. Flathead and channel catfish are abundant in Eagle Creek except after major flooding in 1983-84, which essentially removed them (Minckley and Meffe 1986), and Phelps Dodge has recently constructed a major diversion that may act as a barrier to their reinvasion of the upper two-thirds of the system. Suppression of non-native fish populations by liberalized limits and means of taking legalization of setlines) would almost certainly benefit existing populations of native fishes. Upper Eagle Creek is in need of further, in-depth surveys, especially on the San Carlos Apache Indian Reservation. Propst et al (1985b) reported on its fishes, but it is a relatively l arge and inaccessible stream with extensive and diversified habitats that very likely support unrecorded stocks of imperiled fishes like spikedace and l oach minnow. Some spring-fed tributaries have habitat suitable for introductions of Sonoran (Gila) topminnow, especially those fed by warm springs and entering the mainstream from the west downstream from the Phelps Dodge pumping plant (Minckley 1979b). Bonita Creek is smaller, but also includes habitats that appear suitable for spikedace, l oach minnow, and topminnow, and should be seriously considered as a transplant site for those species. Recent re-establishment attempts for razorback sucker have already included substantial stockings in parts Lf both Bonita and Eagier creeks (Minckley 1983; Brooks et al. 1986). San Francisco and Blue Rivers This major system rises on the south and east sides of the White Mountains of Arizona and in the western Mogollon Mountains of New Mexico and enters the Gila River near Clifton, Arizona. Much of the watershed is remote and in Federal Stewardship, either under USFS or USBLM jurisdiction. Some of the lower portion of San Francisco River is owned by Phelps Dodge Corporation and flows through an area of intense mining development. The watershed has been heavily grazed by domestic livestock and subjected to substantial lumbering. No major dams exist, although a number of fishing impoundments have been constructed at higher elevations. Native fishes include(ed) local and limited populations of native trout, roundtail and Gila chubs (or problematic chubs similar to the l atter), longfin and speckled daces, spikedace, l oach minnow, Sonoran sucker, desert mountain-sucker, and Sonoran (Gila) topminnow. The last was known only from Frisco Hot Spring in New Mexico (Koster 1957; Hatch 1979; LaBounty and Minckley 1973). Native trout from the system have not yet been definitively assigned to a species, although Hatch (1979) suggested that Gila trout might be native. Introduced populations of Apache trout now are present in the watershed (Minckley 1973; J. Rinne 1980a, 1985). Roundtail, Gila chub-like chubs, and spikedace have disappeared from the San Francisco River in New Mexico (Hatch 1979; Propst et al. 1985a); both chubs persist in tributaries to the system in Arizona. Non-native fishes are widespread and abundant in the San Francisco system, with far more species occurring downstream than in headwaters. Mountain streams are widely stocked to support non-native trout fisheries, generally in larger habitats distant from Apache trout populations. Down-flow habitats support common carp, red shiner (in Arizona), mosquito-fish, channel, flathead, and bullhead catfishes, and smallmouth bass and smaller centrarchids (Minckley and Clarkson 1979). Most lowland habitats must be considered Category III, whereas Category I and II habitats are not uncommon upstream. This system is poorly known in Arizona, and merits an intensive search for available data and perhaps a major survey. Blue River is known to support l oach minnow in one of its major tributaries, Campbell Blue Creek, and surveys o+ that area to determine extent and size of populations of at least that species are certainly in order. NMDGF has accumulated many data for the San Francisco River in that State (Propst et al. 1985a). Salt River Basin This complicated system drains most of central and eastern Arizona through numerous south- and westerly-flowing tributaries to enter the Gila River near Avondale, just west of Phoenix, Arizona. Its major tributary is the Verde River, which originates in the broad Chino Valley to flow parallel and drain through west- and southwest--flowing tributaries the highly fragmented and dissected western margin of the Colorado Plateau (locally termed the Mogollon Rim). The Salt River mainstream arises with the confluence of White and Black rivers, two major streams that respectively drain the northwest and southern flanks of the White Mountains, eastern Arizona. Lower Salt River Mainstream and Tributaries. -- Canyonlands of approximately the downstream half of the Salt River are now inundated by reservoirs. Roosevelt Dam and Lake, the first reclamation project in western North America, was completed in 1913. Three additional reservoirs, up- to downstream Horse Mesa, Mormon Flat, and Stewart Mountain dams (respectively impounding Apache, Canyon, and Saguaro lakes) were constructed below Roosevelt, and Granite Reef Diversion moves water from both the Salt and Verde rivers into canals for delivery to the Phoenix Metropolitan area and beyond as the stream channel passes from mountains to a the desert floor. its lowermost part is dried except -for underflow that persists in excavated gravel pits, and during periods of unusual runoff. Most of the tributaries to this section of river are ephemeral, with a few having short perennial segments. The Salt River reservoirs support a l arge introduced fauna and essentially no native fishes (Minckley and Johnson 1968; Minckley 1973). Non-native species include thread-fin shad, trouts (seasonally or on a put-and-take basis in colder lakes), carp, goldfish, red and golden shiners, fathead minnows, bigmouth, black, and smallmouth buffalo-Fishes (Ictiobus cyprinellus, I. niger, I. bubalus), flathead, channel, and bullhead (yellow and black) catfishes, yellow bass ( Morone mississippiensis), largemouth and smalimouth bass, green, bluegill, and redear sunfishes and their hybrids, black craopie, yellow perch (rare), and walleye ( Stizo=.tedion vitreum). The stream section between Stewart Mountain Dam and Granite Reef Diversion is stocked with trouts in winter, plus essentially all species in the upstream lakes have been recorded at one time or another. That reach also supports a large, apparently non-reproducing population of native Sonoran sucker and desert mountain-sucker, and an occasional roundtail chub (Minckley 1973). All these natives are presumably derived from limited reproduction in the Verde River below Bartlett Reservoir. Canals in the Phoenix Metropolitan area and gravel pits excavated in the Salt River channel support many of the non-native fishes just recorded, plus Sonoran and desert mountain suckers, a few roundtail, and longfin dace ( Marsh and Minckle; 1992). With a few ml nor exceptions, habitats of the l ower Salt River car. Lnly be considered Category III, so highly modified that recovery would be remarkably expensive in time and money, A few small, seepage-fed habitats are managable for desert pupiish and Sonoran ( Gila) topminnow (see Gila River Mainstream, p. 107). Upper Salt River Mainstream and Warmwater Tributaries. - The Salt River mainstream above Roosevelt Lake remains undammPd and thus unreoulated. Its drainage is principally from the Fort Apache and San pxCarlos Apache Indian reservations, both of which are grazed and logged, but are otherwise comparatively undisturbed. The river flows through a spectacular, precipitous canyon at high gradient and is relatively inaccessible except at major highway crossinos. Tributaries are similarly unmodified except by lumbering and grazing activities, and with the exception of the Tonto Creek watershed, also are relatively Tonto Creek flows into the western end of Roosevelt Lake after originating in and receiving domestic wastewaters and other impacts from an area of moderate human population and land use adjacent to the Mogollon I ntroduced fishes include a substantial number of predators. Trouts are heavily stocked in the upper Tonto Creek system and to a lesser extent in other headwaters. Flathead and channel catfishes, smallmouth bass, and green sunfish are widespread in the upper Salt River, the first two in the lower portion of the reach and the last two upstream. Yellow bullhead., are sporadic in occurrence and most common in lower parts of major tributaries. Common carp, red shiner, fathead minnow, and mosquitofish are present, especially near Roo=.evelt 1:2 2 Habitats of Categories 1, 11, and IV nevertheless remain common in the upper mainstream and its warmer tributaries. Native fishes remain locally abundant to common, especially l ongfin and speckled daces, roundtail chub, Sonoran sucker, and desert mountain-sucker. Colorado squaw-fish was last taken in 1950, spikedace and l oach minnow have not been recorded since 1969, flannelmouth sucker occurred in the early 1960s, and razorback sucker disappeared about the same time as squaw-fish (see Section II). Sonoran (Gila) topminnow ascended only to lower Tonto Creek; its natural populations are extirpated. There are no historic records for bonytail, wound-Fin, or desert pupfish in the upper Salt River (Minckley 1973). As with the Gila River mainstream, the single most important protective measure for the upper Salt River is opposition to and prevention of further impoundments on its mainstream or major tributaries. Stabilization to a negotiated level of minimum nstream flow also should be avoided (Minckley and Meffe 1986). Headwater or upstream reservoirs would provide habitat for additional introduced fishes and enhance existing populations of non-natives, and cessation of flooding would likely spell doom for native fishes. Scouring floods are integral components of the ecology of this and similar rivers. Southwestern stream ecosystems are reset by such events and stream fishes indigenous to the region seem to have special (behavioral) adaptations allowing them to survive even the most severe floods. Non-native fishes are far less capable of resisting scourino flows (Meffe 1984; Minckley and Meffe 1986) and are typically decimated craven destroyed. Canyons of the Salt River thus provide refuoia -f or native species that are periodically cleared of non-native competitors and predators by natural events. Periods of low flow typically result in the l arger species of native fishes persistino as l arge adults. Small species and individuals of larger ones presumably are eaten by predators such as flathead catfish and smallmouth bass or succumb to more subtle pressures of competition for food or space. Floods are typically followed by substantial reproduction and recruitment of native forms, which allows at least the long-lived species to perpetuate their populations until the next scouring event. Short-lived species may or may not be capable of such cycling in recruitment success. New introductions of non-native species in the upper Salt River basin should be vigorously opposed. Existing legislation against use of live bait may already have assisted in arresting transfer of non-native fishes. Predator populations are large, at least locally, and flathead catfish seems to be extending its range. Such could perhaps be suppressed or held in check by increased harvest of catfishes through liberalized catch limits and legalization of setlines. Reintroductions of both razorback sucker and Sonoran (Gila) topminnow are underway (Brooks 1 985; Brooks et al. 1 986) and a proposal for reintroduction and re-establishment of Colorado squaw-fish has been approved and expedited (see Section II). Current monitoring with respect to razorback sucker, and that nPrP=Pary followino squawfish stockings should be expanded to include the entire fauna. I recommend against the proposed introduction of bonytail into the system until the status of roundtail chub (and its hybridization elsewhere with bonytail) have been evaluated. Wound-f i n introductions have been proposed and should be attempted, although habitats in the canyon do not appear optimal -FCP that species. 1 2-4 White Mountain Tributaries. - High altitude tributaries of the Salt River on the White Mountain Apache Indian Reservation have been disturbed mostly by lumbering, grazing, and introductions of non-native trouts. Other introduced species in headwater situations include northern pike, which has become abundant and stunted in some lentic habitats, golden shiner that has proven to be a problem in trout management in certain fishing lakes, and fathead minnow that is often stocked as forage for trout fisheries. Native fishes other than Apache trout are minor components of the fauna at elevations exceeding 2,000 m, but speckled dace and desert mountain-sucker penetrate that high where winter conditions are not too severe. Habitats of the last two species are relatively secure, even in areas where non-native trouts are abundant. Streams inhabited by uncontaminated populations of Apache trout already are under protection by the White ourutain Apache Tribe. Rinne (1985) and Rinne and Minckley ( reviewed status of the native trout and should be consulted for ----- etails on its status and available habitats (Categories I and II) in the area. Their major recommendation was to terminate stocking of rainbow trout, with which Apache trout hybridize, in areas of actual or potential contact. A Regional program to propagate Apache trout for replacement of rainbow trout in at least some White Mountain fishing waters (Davies 1985; Divine, USFWS, pers. comm.) is presently underway. Verde River and Tributaries. -- This drainage presents a mosaic of habitats ranging from ephemeral to perennial creeks and streams fed by montane runoff to large, limestone springs that may directly form or indirectly feed other flowing systems. There are numerous small- and moderate-sized reservoirs in upper parts of the watershed and two major dams (Horseshoe and Bartlett) impound its lower mainstream and are sometimes closed long enough to prevent flow through the lowermost reach. Pumpage for agricultural use is relatively extensive in the extreme headwaters in Chino Valley and substantial withdrawals also are made for domestic, light industrial, and floodplain irrigation uses in its middle sections. Domestic wastewaters are passed into the system from Prescott, Sedona, Cottonwood, and lesser communities. Plans for a major dam (Cliff damsite) on the lower Verde River will flood additional reaches of the l ower river. Proposed withdrawals of water from its upper sections for use by cities of Prescott and Flagstaff bodes further ill for the system. Native fishes of the Verde River system include all those recorded for the Gila River basin with exception of Gila trout, bonytail, woundfin, flannelmouth sucker, desert pupfish, and Sonoran (Gila) topminnow. Flannelmouth sucker and Sonoran (Gila) topminnow historically occurred both up- and downstream in the Salt River (Minckley 1973) and both must also have entered at least the lowermost Verde. Attempts to establish Sonoran (Gila) topminnow and wound-Fin in the system have largely failed (Minckley 1969b; Brooks 1985; Minckley and Brooks 1986). Native fishes definitely recorded, but now absent from the Verde system, include Colorado squaw-Fish and l oach minnow. However, it would not be surprising if the last were found through an intensive survey. As noted above, Gila trout were native in tributaries, but were extirpated by hybridization with introduced rainbow trout, perhaps prior to 1900 (Miller 1972). A population has been 125 reintroduced and has become established in Gap Creek (USFS lands; see Section II, p. 85). Diverse non-native fishes are widespread. Trouts of various species are commonly stocked in tributaries. Northern pike are present in oxbows in the upper reaches (unpubl. data). Common carp are widespread, goldfish are rare, red shiner are throughout the mainstream and in lower parts of some tributaries, and fathead minnows and golden shiner occur sporadically. Channel, flathead, and bullhead catfishes are especially abundant in reservoirs, deeper pools of the mainstream, and mouths of some larger tributaries. Mosquitofish is throughout the basin and sail-fin molly live in the lowermost reaches. amallmouth and spotted bass (Micropterus punctulatus), rock bass (Ambloplites rupestris), smaller sunfishes, black crappie, and largemouth bass are in reservoirs, tributaries, and the mainstream, with the first species and green sunfish being prevalent (Minckley 1973). Spotted and rock bass are rare and may have disappeared from the system. African cichl ids (Tilapia zilli) have been recorded from as far upstream as Cornville, Arizona (Barrett 1983), but will probably disappear in cold winters at that elevation. Despite physical and chemical'changes and obvious loading by non-native species, substantial amounts of Category I, II, and IV habitat remain in the Verde River mainstream and tributaries for a number of reasons: 1) the mainstream remains relatively unregulated in its upper portion; 2) large springs feeding many tributaries have persistent and perennial discharge, so water developments have not yet affected them or have influenced only their lower courses; 3) many tributary streams have dry reaches near their mouths or barrier rapids or falls that have precluded invasion of non-native fishes; and 4) the watershed is characterized in part by precipitous, canyon-bound channels that exaggerate scour effects in flood, effects that have little impact on native fishes, but tend to decimate population of most introduced forms (Meffe 1984; Minckley and Meffe 1986). Discussion of the mainstream Gila and Salt rivers (pp. 107 and 122, respectively) apply in this regard as well to the Verde River upstream from mainstream reservoirs. With respect to Verde River tributaries, maintenance of springheads and a few kilometers downstream in a natural state Will Q0 far toward perpetuation of part of the fauna of this system. As an example, one such system (Fossil Creek) was isolated naturally by barrier falls and now is diverted into a flume for power generation ca. 1.5 km downstream from its source. Its highly protected headwaters on USFS lands support a population of problematic chubs, speckled dace, and desert mountain-sucker. Sonoran (Gila) topminnow introduced to the headspring persisted for a number of years, then disappeared (Minckley 1969b). Natural barriers also exist on a number of other tributaries, West Clear, Oak, Wet and Dry Beaver creeks, perhaps the East Verde River, Sycamore Creek, and others. Most originate in relatively remote areas and are inaccessible except at a few places. Oak Creek and the East Verde River are the most accessible and both are managed in part for non-native trout fisheries. Oak Creek furthermore receives substantial domestic wastewater from the community of Sedona and from private cabin sites along its course. Status of the fauna of these tributaries is poorly known. 126 Pis:: barriers provide opportunities for renovation of upstream are and reasonable expect or; of re-establishing native species and having them remain uncontaminated for at least a while. However, the presence of stock tanks and upstream impoundments. precludes possibilities for eradication of non-native fishes from other than the smallest watersheds. Maintenance of natural, unregulated conditions in major tributaries, as in the mainstream, will go far toward perpetuation of native fishes. General comments given earlier with respect to in-stream flow analyses and projections for maintenance of native fishes are again applicable for most warm-water tributary habitats. Reoulation enhances non-native fishes and works against populations of natives, even in relatively small systems. Perpetuation of cycles of flood, "normal conditions", and even drought seem the most 1-aaunable way to maintain an indigenous fauna. Bill Williams River System This watershed drains south and west from its origin along the western margin of the Colorado Plateau to enter the Colorado River just upstream from Parker Dam (Lake Havasu), Arizona-California. Its basin is arid and of rugged terrain, and perennial stream segments tend to be isolated in canyons separated by l ong dry reaches in periods of drought. Headwater streams are canyon bound and l ower-elevation watercourses flow alternate .i y through canyons and broad valleys that represent small i ntermontarie basins. The recorded native fish fauna is 7'elatYvely small, speckled and l ongfin daces, roundtail chub, Sonoran sucker and desert mountain-sucker. Mountain-suckers f.:! 4 the drainage may also include an unrecognized taxon ( o. 79). Although restricted in distribution as a result of relatively small amounts of perennial water, native fishes remain abundant and communities are relatively intact (Kepner 1 981). The region is sparsely populated .:, nd influenced principally by mining and livestook orazino. Few communities exist and agriculture is limited to a few individual ranches that pump or divert water from surface streams for irrigation of pasturage. One mainstream i mpoucidment. l a Lake that was constructed principally -; Cr flood oontrol and desiltation of thi Sill Williams Arm of Lake Havasu the point of intake for the Central Arizona Project), exists on the mainstream, Introduced fishes are relativel'y few in flowing-water habitats. Green sunfish is throughout the system, common carp penetrate into larger streams, rsd shiner is widespread at lower elevations, and fathead minnow and mosquito-Fish are locally common. Channel catfish are greatly outnumbered by abundant yellow bullhead. Unidentified tilapias odour in a thermal spring ar its outflow near :.6i ckiup, 4!rizone. Alamo Reseroir supports i ntrndrrer4 threadfin shad, carp, charnel and bullhead rat-fishes, mosquitofish, centrarchids (largemouth bass, redear, bluegill, and green sunfish), and a richilid best referred to blue tilapia (Orsornromis aurea: (Minckley 197S, unpubl. data; Barrett 1 3S2; Kepner The Sill Williams system supports all of its historic fauna and thus max be considered mostly of Category : in hatitat quality. Kepner 's (1721) - survex was and ttasHa 71snit.:7 : ng th:s watershed to insure its integrity. Introduced fishes and pollutional conditions near the Bagdad Mine (Kepner 1981) create some Category II habitat that should be rectified to increase values of the system for maintenance of native fishes. Possibilities exist that some species from the Gila River basin, perhaps spikedace or l oach minnow, could be placed in habitats of the Bill Williams if absolutely necessary, but this should be preceded by long and careful assessment of other possibilities. Desert pupfish already have been introduced in the Bill Williams watershed (Kepner, USFWS, pers. comm.); severe endangerment of that species may, however, have warrented the action. Virgin River System This river system heads in Kane County, Utah, flows west and southwest crossing the tip of northwestern Arizona to end its course by flowing into the Colorado River mainstream (Lake Mead) in Nevada. Its former major tributary, the presently-discontinuous White River system of eastern Nevada, consists of two major forks. White River is on the west, and can be traced as discernible channels from its headwaters to the Virgin, but now consists of isolated reaches fed by springs. Moapa River in southern Nevada occupies the lowermost portion of this ancient system. The other fork, Meadow Valley Wash on the east that enters Moapa River near Glendale, Nevada, has a substantial reach of permanent flow in its middle course ( LaRivers 1962). Each major segment of this highly disjunct system has its own fish fauna. The Virgin River supports Virgin River spinedace, woundfin, Virgin River roundtail chub, Virgin River speckled dace, flannelmouth sucker, and desert mountain-sucker (or perhaps more than a single species of mountain-sucker; p. 79). White River proper is occupied by Pahranagat roundtail chub, three subspecies of speckled dace, White River and Pahranagat spinedace, White River mountain-sucker, and four subspecies of White River spring-fish. Moapa River provides habitat for Moapa roundtail chub, Moapa dace, Moapa speckled dace, and an additional subspecies of spring-fish. Meadow Valley Wash supports Meadow Valley speckled dace and Big Spring (Meadow Valley) spinedace. 0+ these, Pahranagat spinedace is believed extinct. A substantial literature exists on this local and unique fauna, most of which was reviewed by Hubbs and Miller (1948a), LaRivers (1962), Deacon and Minckley (1974), Deacon (1979), Hardy (1980), Williams and Wilde (1981), USFWS 1981; Courtenay et al. (1935), and Minckley et al. (1986). Springs and other waters of this arid region are heavily exploited for water supplies, both for domestic uses and for stock watering and irrigation. Habitats are severely to moderately damaged, and some have been destroyed (Williams and Wilde 1981; Courtenay et al. 1985). Introduced fishes are abundant and diverse (Deacon and Williams 1984) and have been demonstrated to adversely influence this native fauna (directly) through predation, displacement, or (indirectly) by carrying or providing abundant hosts -for detrimental parasites (Deacon et al. 1964; Wilson et al. 1966; Courtenay et al. 1985). Typical non-native species such as common carp, goldfish, channel and bullhead catfishes, mosquitofish, and 128 l aroemouth bass and smaller sunfishes are wideeeed. Spottail shiner ( Notropis venustus), recorded once from Viroin River ( Pranson 1563), has not again been taken. In addition to these temperate -F orms, presence of thermal springs in the White River segment has allowed tropical fishes such as sailfin and Mexican mollies, guppies, platy-fishes and swordtails (Xiphophorus spp.), and a remarkable variety of African and South American cichlids to survive and become established (Hubbs and Deacon 1 944; Courtenay and Deacon 1 922; Courtemay et al. 1 985). A large percentage of this native fauna i s listed, proposed for listing, or currently of candidate status (Table 5, p. 1e). Other than these actions, part of Moapa River (headwaters) i s be n' developed as a refuge +or Moapa dace and Moapa springfish (USFWS 1981), Virgin River has been thoroughly studied in anticipation of modifications for water developments (Cross 1975), and the plight of aquatic habitats and fishes of the entire region has been documented. Development is expanding, however, and groundwater demands are or will soon increase exponentially. If this happens, many of the aquatic systems and their fle.heia that depend or eprino flows will disappear. Most of the fishes are so specialized, adapted to special conditions in their unique habitata, that establishment elsewhere will be difficult, if possible. Dee,pite af-releratino :robl e s substant ci amounts of Cateonry : through III habitats. remain. Sprinos and water rights ts insure the - continuation must be directly acquired or easements must be obtained for their maraoement, and streams must be protected from i mpoundment, regulation, dewaterino, or pollution if this major assemblaoe of Western -Fieihes is to be perpetueted. Little Colorado Riyer System Little Colorado River receives most of its water -F 7OM tributaries draining northward from the uplifted maroin of the Colorado Plateau and -F rom the White i'lountains of eastern Arizona. Extensive trainaos exists, hnwever, frnm arid l andia to the east in New Mexico, and headwater streams ni the Zuni River system include perennial waters, The native fish fauna of the upper Little Colorado River i s relatkiely small, but diverse. Apache trout is in high—elevation tributaries, Speckled dace is widespread, Little Colorado River spinedase occupy tributaries and the upper mainstream, and roundtail chub i s apparently extirpated. Sluehead mountain—sucker includes a distinct subspecies, the Zuni sucker, in New Mexico, a heterogenous array of forms as one passes downstream, and mainstream Colorado River forms in the mouth. Zuni sucker apparently arose through nytridization after natural stream capture between biuehead and Rio Grande moLintain—SUCkirE extreme headwai:ers of the system ( Smith et al. 1 ?82). Little Colorado River sucker remains relatively widespread, and was considered a d:etinct, endemic species by . . Minckley (1972,1R20 ). Bonytail was orHoirail e described from the Zuni River ( Saird and Sirard 1 353a), Cut this was dsuoted by Emith et al. (1979), who proposed that the type l ocality was rear 'Grand Falls on the , - 1 014.5., 7 portion of the syetem. uppi7 Little '77 Colorado basin ( Hemphill 1 954) almost certainly resulted from application of the common name to roundtail chub, a common practice in Arizona then and now. Native fishes downstream from Grand Falls include Colorado squawfish, =peckled dace, humpback chub, bonytail, roundtail chub, bluehead mountain-sucker, and flannelmouth sucker. Bonytail and roundtail are apparently extirpated. Razorback sucker almost certainly wa= in the Little Colorado River mouth, but no actual records are known. Intensive livestock grazino in lowlands of the drainage, l umbering in the highlands, and widely scattered, sometimes extensive mining operations have influenced the watershed for many years. Widespread application of ichthyocide= in the 1950s and 1 9A0s had unas=e==ed i mpacts on native fie.nee. ( Hemphill 1 954). A large area in Arizona was cleared for agriculture and modified by construction of a remarkable number of small reservoirs early in settlement of the region ( Rinne and Minckley 1985). Headwater - development of fishing l akes, communities, expanded mining operations, and proposed water diversions +or use in cities like Flagstaff are present or projected imparts on the system. Small fishing l akes in Arizona have i mposed some regulation on variations in discharges of streams such as East Clear and Chevalon creeks. Such Impoundments act as refuoia +or non-native fishes that then spread downstream, but tn the other hand also provide a reservoir that maintains flow in formerly-eohemeral reaches due to aeepaoa throuoh dams uroubi. data introduced fishes include non-native trouts that have influent..ad. populations of Apache trout through hybridization (rainbow trout) ant other interactions (cutthroat, brown, and brook trouts), common carp, goldfish, fathead minnow, redside and golden shiners, channel and bullhead catfishes, Plain= killifiet, l argemouth ba=s, smaller sun-fishes, and tilapia=, the l ast in water heated by operation of a generating station. Sand shiner (Notropis stramineus) recorded from the system by Miller and Lrwe (1964) has not again been taken (Minckley 1 973). Golden shiner caused major trout management problems in the area i mmediately upon its introduction and establishment. Dependence on natural fertility for growth of fingerlings was neoated due to otlden shiner competitirn, and the program was through necessity shift-ed to more expensive produotitn and stockint of Matchable' trouts (Minckley 1 973). The population of endangered humpback chub in and in the vicinity of the Little Colorado River mouth seems relatively large and viable ( MinckleY 15'775 1 979 5 1 9'95: flarother= and Minrkley 1 981 ; Minckley et al, 1 991: Kaeding and Zimmermann 1 983). Problems associated with conservation of this population are discussed in Section II (p. 51) and in this Section on the Grard Canyon Rearh of the Colorado River mainstream ( p. 1 05). Frotettion of existino Cataoory I ard II habitats is test accomplished by resistance to damming and water diversion, policies that prohibit removal of timber from precipitous slopes of canyons and other high- altitude water oour=es, and active prohitition of further i ntrodurtiors Of non-native fishes into the system. Monitorino procirams should be established for more important habitats as East Clear Creek, the iJ opir mainstream Little Colorado, and C7i"?'X, not snly for the Little Colorado River spinedace ;: which props-act f iirc; 7atle f, o. but for the entire fauna. Status of the Little Colorado River sucker should be clarified and the species described. Chevalon Creek, treated with ichthyotoxin in an attempt to remove golden shiner in the 1960s, should be thoroughly resurveyed and native fishes absent from that system reintroduced. A determined effort should further be made to discover populations of roundtail chub, and if found it should be reestablished (taxonomic status of the Little Colorado River form remains somewhat in doubt; DeMarais, ASU, pers. comm.). San Juan River System This extensive watershed lies mostly in New Mexico and Utah, originating on western flanks of the southern Rocky Mountains of New Mexico and southern Colorado and flowing to enter Lake Powell upstream from the Arizona-Utah boundary. Tributaries in arid parts of the drainage in Arizona support only speckled dace and local forms of bluehead mountain-sucker. The mainstream in Utah, New Mexico, and into Colorado was occupied by a big-river fauna, Colorado squawfish, bonytail, roundtail chub, a mainstream form of speckled dace, flannelmouth sucker, and bluehead mountain-sucker. With the exception of bonytail, all these species still occupy the area, at least in its lower reaches (in part Minckley and Carothers 1981). Razorback sucker was never recorded, but almost certainly was present in this system along with other big-river species. Headwaters support speckled dace and mottled sculpin (Cottus bairdi). I known of no records for native trout in the San Juan system. Major impacts on this watershed include grazing, lumbering, agricultural developments, extensive mining operations, a major (Navajo Reservoir) and numerous minor impoundments, and water diversion to the Rio Grande basin (Koster 1957; Anonymnous 1976 [in part], Hatch 1979). Upper parts of the system are intensively managed for non-native trout fisheries; rainbow, cutthroat, brown, and brook trouts are present. Other introduced species include fathead minnow, white sucker (Catostomus commersoni), black bullhead, channel catfish, largemouth bass, and smaller sunfishes. Introduced fishes in the lower river might be expected to include striped bass or other species entering from Lake Powell Persistance of a major portion of the indigenous fauna in lower San Juan River underlines the presence of Category II habitats, at least. Upper parts support a relatively small number of introduced species and are remote, both indicating habitats of Categories I and II. If data are not available from conservation agencies of New Mexico and Colorado, or elsewhere, an in-depth survey of the San Juan system is in order. Introduction of razorback sucker and augmentation of existing stocks of Colorado squawfish seem appropriate, especially above Navaho Reservoir where predatory species likely ascending from Lake Powell would not be a -f actor. Introductions of additional non-native species in the system should be vigorously opposed, especially of striped bass in Navaho Reservoir, from which it could move upstream. Hybridization between non-native white sucker and native suckers (Anonymous 1976) should be assessed; extensive, the non-native and hybrids should be eradicated. 121 ADDENDUM AND ERRATA Dean A. Hendrickson has completed examination of specimens of l onafin dace, Aoosia chrysocaster, from throughout its range and is finalizing -his Ph.D. dissertation on systematics of the species. His conclusions include determination that two subspecies exist, one inhabiting the Gila and Bill Williams River basins in the United States and the Rios Sonoyta and Sonora in Mexico, and the other living in the Rio Yaqui basin, United States and Mexico, and southern basins in Mexico. Fish from the Willcox Playa basin, the Rio Yaqui n both morphological and elsctrophoretic characteristics. Genetic (electrophoretic) differences are of a magnitude similar to that demonstrated in other intraspecific cyprinid comparisons. This provides direct evidence that the Willcox Playa basin derived its fauna from the Rio Yaqui system, as was indicated by the early (and now lost) specimens of Gila purpurea from "Morse Canyon" (Hendrickson et al. 1981; see p. 32). Fishes of the Mimbres River basin, New Mexico, technically west of the Continental Divide, were inadvertently excluded (with one exception, a brief account of Notropis f. formosus, p. 35). These include Gila nicirescens (Girard) and Pantosteus plebeius (Baird and Girard) as natives, and an introduced population of Aoosia chrysoclaster, which will be dealt with in a future report on the remainino fishes of Region II east of the Rocky Mountain Axis. Typographical and other oversights noted after preparation of final copy are as follows: TABLE 3, p. 10, Footnote 4 -" Minckley et al. 1985 = Minckley et. al. 1986. Footnote 7 -- Minckley 1981 = Minckley 1980k. Footnote 12 - Minckley 1970 = Minckley 1979a.