THE TOPMINNOW 0. OCCIDENTALIS, AN OVERVIEW OF ITS HISTORY, ECOLOGY, AND CURRENT STATUS Bio. 520, Dan Kuhl Introduction:

I chose this topic because of my continuing interest in fisheries biology and conservation biology. The search for information about desert topics actually began with the idea of doing something out of my area of interest, like the Creosote Bush or the Joshua Tree. But, my investigation at the library lead me to a current issue of Great Basin Naturalist which contained an article about the current status of the , written by W. L. Minckley. The article was so interesting I decided to stay with this topic. This topic offered a good chance to learn about one of the lesser known endangered species in America.

History:

It is hypothesized the Gila topminnow Poeciliopsis o. occidentalis entered Arizona via the Yaqui

River (Figure la) that flow from southeastern Arizona into Mexico (Miller, 1958). It is also believed that a tributary of the system and Yaqui River flowed from a common lake in the area of the Wilcox Playa west of the Chiricahua Mountains. Once in the river system

Poeciliopsis occidental is spread (Figure lb) into the , as far north into the Verde

River, and downstream to Yuma (Minckley, 1973). Another endangered , the Yaqui topminnow Peociliopsis o. sonorensis, is found in the headwaters of the Rio Yaqui. It also came to Arizona from Central America (Figure 1 c, Meffe, 1983).

After establishing a stronghold in the Gila River system, Gila topminnow populations began to suffer from the presence of human development. Prior to the 1800's habitat alteration began with grazing and timber harvest: the loss of natural vegetation resulted in increased runoff,

1 erosion, and sedimentation. The loss of vegetation cover was followed by arroyo cutting, incision of stream channels by fast moving flood waters (Figure 2). During the 1800's damming, diversion and groundwater pumping was initiated for irrigation purposes. This development continues even today. In 1926 the Gambusia affinis was introduced to control . Introduction of nonnative species continued over the next 30 years, resulting in the restructuring of aquatic communities and further decline in Topminnow populations (Figures 3,

4, and 5) (Minckley, 1990,1999).

Habitat:

The Gila topminnow did occupy aquatic habitats having variable environmental conditions below 1600 meters throughout the Gila basin. It could be found along stream margins, and in springs and marshes. Today, as a result of the previously described disturbances and introduced species, Poeciliopsis occidentalis occupies a few springs, artesian wells ,or stream segments protected by barriers such as falls or stretches of long dry stream bed (Table 1, Meffe, 1985)

(Table 2, Weedman, 1997). They are greatly different from higher order streams exhibiting minimal variability. The water is usually clear, stenothermal, and flows at a constant rate.

Typically, the water temperature is close to the average annual temperature for the region, not varying more than 1 degree Centigrade. Springs are usually occupied by endemic species. In contrast, first order streams and higher are murky, eurythermal, and vary in flow due to flooding.

Gambusia affinis is readily found in these lower streams of this region. Because the quality and quantity of water flow from a spring is affected by activities occurring on the spring's recharge zone, the size and location of a population is greatly affected and speciation can occur (Hubbs, 1995).

2 Taxonomic Classification, Morphology, and Life History:

The Gila topminnow and its arch rival the mosquitofish are classified in the Teleostei Division, the ray-finned fish. This Division contains the most advanced and the greatest number of species (Figure 6 and 7). The teleosts have been so successful because numerous adaptions have allowed them to adapt to unusual aquatic habitats (Moyle, 1993), as exemplified by the Family

Poeciliidae (livebearers), which contains the Gila topminnow and mosquitofish (livebearers).

The next 3 sections are very academic, but are necessary for an understanding of the ecology and problems confronting future existence of the Gila topminnow in Arizona.

Section 1: (Characteristics of the Family )

-190 species of small livebearing (viviparous) fishes;

-Most have anal fin modified into a copulatory organ called a gonopodium which delivers the sperm to the female in small packets;

-Found in warm, fresh, and brackish water at low elevations;

-Most numerous in Central America. It is hypothesized they are most common here because the region is so unstable geologically and that Poeciliid are well suited to maintaining populations in such areas because they:

1. Have a broad tolerance of extremes in water chemistry;

2. Are small in size, large population can live in a small area;

3. Upturned mouth for feeding on available food near or on the surface;

4. Are livebearing, freeing them from the need for a surface substrate for spawning;

and

5. Are quick to mature, resulting in a high reproduction rate and rapid population

3 expansion under favorable conditions (Moyle, 1996) .

Because the mosquitofish is instrumental in the decline of the Gila topminnow, comparison of both species follows

Section 2: (Gambusia affinis)

1. A male ranges from19-38 mm in length while the female is 32-57 mm (Figure 8).

2. It is native to northeast coast of Mexico and southeast coast of the United States

from New Mexico to Delaware.

3. It is not threatened in any state and has spread to populate almost all warm

waters in the Southwest.

4. Young develop in 24 days with brood size ranging from a few to 300.

5. During a breeding season of 2-4 months the female stores sperm in a pouch as

does the topminnow;

6. It is capable of bearing several broods from a single mating, and offspring born

early in season can reproduce by the end of the breeding season (Tomelleri, 1990).

7. Females continue to grow throughout their life, while males stop growing when

the gonopodium is fully developed.(Minckley, 1973).

8. The mosquitofish lives mainly in vegetated backwater pools within the top few

inches of the water surface, and lives a predatory existence, living on insect

larvae and immature fish, including its own young (Tomelleri, 1990)..

9. It can survive under conditions of extreme variability and spread quickly through

artificial and natural habitats (Minckley, 1999) .

4 Section 3: (Poeciliopsis o. occidentalis)

1 The male is rarely more than 25mm in length, while the female can be up to 50

mm in length (Figure 9).

2. Migrated to Arizona from Central America.

3. Distinct sexual dimorphism in size and coloration; the male becomes blackened

during the breeding season.

4. Because they lived alone in their native Arizona habitat, they are very easily

affected by introduced species.

5. In its habitat it concentrates in shallows in areas of aquatic vegetation and debris.

6. The brood size is 1-15, with a female having 2 broods developing at the same

time.

7. Currently found only in isolated springs and spring runs, living on vegetative

material, bottom debris, and amphipod .

8. It appears the topminnow's life span is not more than 1 year.

How Gambusia a. interacts with populations of Poeciliopsis o:

Because most researchers believe that this introduce fish is the primary cause for the decline in the distribution of the Gila topminnow, it is important to have an understanding of how a native species can be affected by an introduced species..

As previously noted, the geographic distribution of Poeciliopsis o. took a downturn when their habitat was impacted by human development. Meffe states in his research that changes in habitat has not contributed solely to the decline in topminnow populations. Because the

5 endemic species appears to have declined in geographic areas where the 2 species overlap,

Meffe goes on to hypothesize that the primary cause is predation. His research further demonstrated that:

1. Parasites and disease brought into the native areas have not impacted the endemic

species.

2. The native species has not been affected by hybridization with the introduced

species.

3. There is minimal competition between the 2 species. The introduced species is

an insectivore and a piscivore and the endemic species is feeds on detritus and

vegetation. Morphologically, the 2 species are quite different (Figure 10).

Gambusia a. has strong conical teeth firmly attached to the jaw, while its

counterpart has spatulate teeth weakly attached to the jaw. Gut length for the

former is 0.69 standard length while for the later the gut length is 1.5-2.0 standard

length. These differences are common of a carnivore and a herbivore/detritivore.

Also, there is no evidence that food is a limiting factor in highly productive desert

habitats.

4. The introduction of Gambusia a. has been correlated with population declines of

more than 20 species of fishes. Predation has been proven in the laboratory and

in the field by numerous researchers. Meffe demonstrated that juvenile

topminnows were the primary prey of mosquitofish. It is hypothesized that native

fish may be more susceptible to predation because of their lack of fear that is

gained living with a predatory species.

5. Physiological stress created by constant predatory pressure can affect populations

on a secondary level:

6 A. The shredding of adult fins by attacking mosquitofish allows disease to

enter the weakened individuals.

B. Adult females under predatory stress produce fewer embryos and mature

ova.

C. Predatory pressure causes cessation of normal feeding habits (Meffe,

1985).

The importance of quality habitat can not be emphasized enough. Currently, the Southwest is suffering from drought conditions that effect spring and spring run aquatic habitats. The lack of flooding associated with the monsoon season does not promote dispersal and does not give the topminnow a hedge against extinction. It is important to remember that most terrestrial organisms are confronted with few barriers to dispersal and redistribution, while fishes are restricted to water in linear systems with varying connectedness. This becomes a significant factor affecting topminnow populations living under drought conditions. This fact is clearly evident in the Gila River watershed (Minckley, 1999).

Conclusion:

Poeciliopsis o. occidentalis has been listed by the USFWS as endangered since 1967. Plans for recovery are constantly being discussed and revised. Current plans should include the following approaches:

1. Because present-day and potential future connectedness are greatly reduced an increased effort must be made to translocate individuals to acceptable habitats.

2. Again, because of disrupted connectedness, existing refugia, both natural and

reestablished must be protected, and new artificial refugia and translocated

7 populations must be established and maintained.

3. Managers must become familiar with the natural ecological information in the

remaining refuges so that natural patterns of population fluctuation are recreated.

Topminnows have withstood, and continue to withstand, flooding as part of their

normal life histories. This must be coupled with maintenance of important

refugia, like Cienega Creek which supports the largest existing topminnow

population in the United States, that will be used as a source to repopulate the

areas affected by fluctuations in suitable aquatic habitats.

4. Elimination, exclusion, or effective management of Gambusia a. is essential so

that populations of Gila topminnow are safeguarded from predation and

introduction of them in areas currently free of their detrimental influence

(Minckley, 1999).

The overriding problem, in my opinion, is not biological; it is socioeconomic in nature.

Mosquito fish can be controlled But water cannot survive without water. There is a high value placed on clear, clean water in the American Southwest and elsewhere. High levels of pumping for human use have negatively impacted the aquatic habitats of the Gila topminnow. The people that live in these areas of the Southwest and put high demands on water resources must understand the uniqueness of the affected aquatic ecosystems and the danger they put systems in if their water usage continues to take precedence over the endanger species that inhabit them

Currently, the Arizona Game and Fish Department monitors the continued existence of the remaining populations of Gila topminnow. The 1994 recovery plan contains a strong emphasis on the genetic makeup of the individuals used in translocation and reintroduction of the

8 topminnow to suitable aquatic habitats. Genetic exchange between and among all population levels is of great concern. The plan requires that gene flow must occur so that all remaining natural populations are protected from the genetic influence of primary populations and that primary populations are protected from the genetic influence from secondary populations. Back in the early 90's it was determined that if 20 populations could be sustained for 3 years in their historic range, the Gila topminnow could be down listed from its endangered classification.

This goal has not been reached. (Weedrnan, 1997). In the recent past the Gila topminnow and the Yaqui topminnow in Mexico have not been as impacted as they have been in Arizona by changing abiotic and biotic factors. Are these speciespopulations still relatively unaffected today?

Other questions and comments that come to mind as a result of this research:

1. There appears to be a distinct difference in reproduction potential between the 2 species.

I did not see any discussion of this difference in my reading.

2. In Dr. Minckley's proposed management plan for the Sonora topminnow it is stated that

natural population fluctuations must be recreated, whereas the Weedman report states it

is important to keep the populations separate. These p[ans seem distinctly different.

Also, if the populations are kept separated in the springs, will not speciation occur?.

3. .I would have liked more history on the sites that failed and those sites that were

translocated between 1985 and 1997. Why did they fail and how were the new sites

determined?

4. How does one determine what a fish eats if it is listed as endangered?. Can specimens be

sacrificed to analyze gut contents?

9 BIBLIOGRAPHY

Hubbs, Clark. "Springs and Spring Runs as Unique Aquatic Systems." Copeia 1995(4): 989- 991.

Marsh, Paul C. and W.L. Minckley. "Management of Endangered Sonoran Topminnow at Bylas

Springs, Arizona: Description, Critique, and Recommendations." Great Basin Naturalist 1990: 265-272.

Meffe, Gary K., et al.. "Factors resulting in Decline of the Endangered Sonoran Topminnow

Poeciliopsis occidentalis (Atheriniformes Poeciliidae) in the United States." Biological Conservation 25(1983): 135-159.

Meffe, Gary K. "Predation and Species Replacement in American Southwest Fishes: A Case Study." The Southwestern Naturalist May 1985: 173-187. Miller, R.R. "Origin and Affinities of the Freshwater Fish Fauna of Western North America."

Pages 187-222 in C.L. Hubbs, ed. Zoogeography. Washington D.C.: AAAS.

Minckley, W.L. Fishes of Arizona. Phoenix: Arizona Game and Fish Department, 1973.

Minckley, W.L. "Ecological Review and Management Recommendations For Recovery of the

Endangered Gila Topminnow." Great Basin Naturalist 1999: 230-244.

Moyle, Peter B. Fish an Enthusiast's Guide. Berkeley: University of California Press, 1993.

Moyle, Peter B., Joseph J. Cech, Jr. Fishes, Introduction to Ichthyology. Saddle River, New Jersey: Prentice Hall, 1996.

Tomelleri, Joseph R. and Mark E. Eberle. Fishes of the Central United States. Lawrence, Kansas: University Press of Kansas, 1990.

Weedman, David A. and Kirk L. Young. Status of the Gila Topminnow and Desert Pupfish in

Arizona. Phoenix: Arizona Game and Fish Department, 1997.

10 REPORT FIGURES AND TABLES

Figure 1 a. - Rio Yaqui

Figure lb.. - System

Figure 1 c. - Headwaters of Rio Yaqui

Figure 2. - Arroyo cutting

Figure 3., 4., and 5. - Changing demographics of mosquitofish and Gila topminnow

Figure 6. - Fish evolution

Figure 7. - Taxonomic classification

Figure 8, - Picture of Gambusia affinis

Figure 9. - Picture of Poeciliopsis o. occidentalis

Figure 10. - Jaw/teeth comparison

Table 1. - Location of known populations in 1985 (Meffe)

Table 2. - Location of known populations in 1997 (Weedman) , 1802 a Cochise He 2468 f-1 _ 7095 Sahuarit, 11 Pearce t IOUEENAC:ION I. 7 ua TrrijCION OE /

Sam

• Vearriz, 948 Desemboque

Al defeT

resi de Carlos A 739 I FIL 6 inn

ripa Natora Tiburon Ora PM. Las Animas acupeto

c 54cC3 San Jose k,. San Sebastian migis de Dima Tecon onichi San Lorenzo . arm - Moren S. Marc Onava Pta. San Gabriel a Dur Sua Bahia Sebastian C)" Gra Santo Domin Vizcalno Cue 3d u a genia _Pt6.- Naiizon - Tortuga A • • Ciud ta Rosalia Lobos Pta. San Pablo Sa n Lucas CDLan Marcos Pta. Chtvato 0 L56°600 En • Pta. ulege San Hipoli Mag4aIen. Pta. Concepcion L/7:flack, Huataba Pu ta Abreo t;) • IX Pta. Abreojos• / M. H .- ." A anirole r .17341 Pta. Peilpito ornillos o josv rota /in CALIFORNIA

7-1 Colorado River system. Map by R. D. Ono.

140 Gary K. Meffe, Dean A. Hendrickson, W. L. Minckley, John N. Rinne Decline of

Although P. a. sonariensis throughout its range in Mexi , occidentalis is restricted in di: 0 1.-1X 31,N M abundance. It now occurs in ti rkiozitp:- 1 springs, segments of creeks, or sn classed as endangered (US Depa 0 from '... one of the commonest fi . --I 9 , i:RIZONA gm, River drainage basin . ( Hubbs u 9 LtI z t.„ less than four decades has bee • cc oi •01 z destruction (hypothesis 1) ( Mi' ' `J) 4_ troduction of non-native fishe mosquitofish Gambusia affinis - Schoenherr, 1981). Mosquitofisl 1926 (Miller & Lowe, 1964), °fie) \ _ 0 introduction ( Miller, 1961; Mine It EI a 1981), although cases of longer-t

1 \ known (Minckley et al., 1977; Is _ A., I \ I The disappearance of Sono , • reported for a number of years (1 - I 1968; McNatt, 1974, 1979; Scl 1977), with State and Federal Tx • lations to ensure perpetuation c declines of topminnows based c years, assess the current status of use in future management of the s hypotheses.

MATERIAL;

• All known United States' popu visited one to ten times between A o by 3 mm-mesh dip nets. 3.2 mm-r

RIO YAQUI DRAINAGE IN ARIZONA seines. Small voucher samples we

(a)

(b) Fig. 4. (a) Cienega Creek, Pima County, Arizona, a section which has not experienced the heavy incision characteristic of many Arizona streams (photograph by Minckley); and (b)Cienega Creek section illustrating recent ( <100 years) arroyo cutting which drastically altered topminnow habitats (photograph by Rinne). Despite these extensive abiotic changes, topminnows are abundant in this and other systems which have not received introduced fishes.

Extirpation of topminnows by mosquitofish is further documented by circumstances at Sheehy Spring (3), and House Pond, at San Bernardino Ranch (13). Upper Sheehy Spring was free of mosquitofish in March 1977 (Minckley et al., 1977), and topminnows were abundant; the lower section of spring was inhabited exclusively by mosquitofish. By December 1979, mosquitofish had invaded the upper reach, and topminnows 0 50 100 Arizona umicl scale, km

Verde New California Mexico

Colorado K. Salt K.

Gila K. Santa \ Crat ° San Simon R.00 San Pedro K. R. See Fig_ 3 for boxed area DETAILX ._1 Sonora Chihuahua

Fig. 1. Distribution ni all known collection kicalities tor natural populations of Cila topiiiinnows in the Gila River basin, United States and Nle.cico, basest on ittuselun pecimens and literature recorcis. Open circles are hit- extirpated oiintilations and dots indic-ate vollection sites lietu'eell 19V17 and 19117; in NOIlle instances chrseiy adjacent sites are cated Iw a stogie syinhoi. Existing populations in the United States (Table 1), with wax-wain of liylas Springs (intlieattsil by the numeral I I), are hosed and shown in detail lit 1ig,iire:1 Open triangles surround are:-as where piiplislies also were taken in times Fast. Fig. L Distribution of collection kxadities for nommtive inosquitofich in the Gib River biiiin. United States and Nies- k11, bused cm ASU specimens and litemture records. Fig. 3. L ast (opeil (Art-lest and prUSI.nli ((ION. rel11111 Site!: 19h7-1997) distribution of etoilirdiuu iIitie b r C:ila top- in the upper Santa Cruz !liver kciii. N .....liers arc (or initieutday kyealities of natural I = milk!) populations (See also locality ( in Figure I). MAJOR FISH GROUPS GEOLOGIC TIME (number of species) YEARS AGO Superclass Agnalha Class Chondrichthyes Class Osteichthyes (millions) ERA PERIOD Lampreys Hagfish Elasmobranchs Chimeras Sturgeon Gars Bowfin Teleosts Coelacanth Lungfish (40) (30) (700) 24) (25) (9) (1) (21.000) (1) (5) - Present Quaternary 0 o z - ur 0 0 NJ Tertiary

,--- 100 — Cretaceous Illd •1';' •.--'.-: • ! Jurassic MESOZOIC — 200 Cliondrostei L Triassic

AV" 1

Permian Acanthodii to let rapods

— 300 —

LATE Carboniferous 4SC:lairk' ,...,...... ,,, b Placoderms C?' ,.: Ostracoderms .„ „ Devonian \ 1110200, —400 — r PALEOZOIC

MIDDLE 111 Silurian liffler eo ‘‘e Ilkiiiik...... _ ,...rj -- - \ -J Ordovician cc a 500 — Lli Cambrian

Figure 1-3. An evolutionary tree for fish and agnathans.

•-• . HIERARCHICAL CLASSIFICATION OF THE GILA TOPMINNOW

Phylum -

Class - Osteichthyes

Division - Teleostei

Order -

Family - Poeciliidae

Genus - Poeciliopsis

species - occidental is occidentalis Mosquitofish, female,

Gambusia affinis Mosquitofish, male Gambusia affinis MT 152 Gary K. Meffe, Dean A. Hendrickson, W. L. Hinckley, John N. Rinne

formerly acted specialised piscini may be 'naive'. fa that reduction of juveniles by intrc piscine predators ( be a major mecl Minckley. 1983). extinctions (plant species. 50 (70.4 extinctions (15.5 forms, while only . Eckhardt (1972) r Galapagos Island ponent of this was I toward man and 'fearlessness as a li; (a) important element Alternatively, it (hypothesis 1), sucl are largely respons of prolonged droul 1981) has contribu above, and has Channelisation, be water tables due t( habitats of all fiihes completely destroy( of desiccated chanr fishes when upstre induced catastroph some cases, then, c1( of topminnow popi of these changes b before major declini (b) effect on topminnot oceidenialis; and Fig. 5. Scanning electron micrographs of lower jaws of (a) Poeciliopsis of exotic fishes. at 85 x (photographs by J. Roth). (b) Gambusia affinis Flooding does nc the most extreme TABLE 2 Status of Sonoran Topminnow Populations in Arizona, with Brief Habitat Descriptions. (P. o. occidentalis = -8a, P. o. sonoriensis = 9-14

Map Site Ekration Temp. Habitat Physical Dominant Other Comments no. (m) regime type description aquatic fishes (see Fig.3) regetation (exotic')

(1) Monkey Spring 1 387 Constant. Oak woodland Hard water spring; Lihopsts recurrata: Stable isolated 27 1°C pool -40m by 1-3m. ludwigia natant: population leading to cement Nasturtium officinak flume (2) Cottonwood Spring -1 390 Constant, Oak woodland Hard water spring: Liliopsis recurrata: Stable isolated 26-31°C pool - 30 m by Ludifigia natans: population but with 05-3m Nasturtium officinale potential access to mosquitofish from Sonoita Creek (3) Sheehy Spring 1 432 Fluctuating. Oak grassland Spring run-50m: Lemma sp: Gila intermrdia Steadily declining 7- 27 °C 2 pools, extensive Lobelia cardinaks: 'Gamhusia uffinis population since cienega 'marshland) :Vasturttum olficinule: Gambusia invasion. habitat Polygonum sp.: 1977-1979 Near Pntomogrton sp. extinction Unnamed Spring I 445 Fluctuating. Oak grassland Spring run -600m. .4 :oil° lilac uloules: 'Gambusia Both pure topminnow 6- 25 'C 18 pools. extensive Bidrns sp.. and mixed popula- cienega habitat Lenin° sp.: tions. stable for past Navin-faun allicinale: two years Paromugrum sp. (4) Santa Cruz R. I 400 Fluctuating Oak grassland Intermittent stream. Chan, sp.: Ago= chrrsugasier Populations of both subject to flooding Mrruamrllum sp.; Gila intermetha topminnow and and drying Xmas guithalupensts: Paniustrus dark, mosquitofish are Si:start:um ullsonale: ▪ Gambusw allum patchy. and fluctuate Putumageum sp. ▪ LerMIMS cyanellus both spatially and temporally

_ (5) • Redrock Canyon 1 400- • fluctuating Mesquite Intermittent stream. Cladophora sp. Agosia chrysogaster Small topminnow 1 300 bosque subject to flash population in highly flooding fluctuating habitat (6) Cienega Creek 1310- Fluctuating Mesquite Permanent stream Bidens sp.: Gila tntermedia Large. locally I 200 bosque 12km long: pools. Hydrocatrie sp.: .4 coma eh,' Iwo zaster abundant populations riffles. springs Luau-mist natans: Nut:art:um offirinak (7) Cocio Wash 695 Fluctuating Lower Sonora Desert wash fed by Typha ungusttfUlia A gosia chrrsogastrr Topminnow rare in Desert: mine tailings ▪ Lepomis crane//us June 1980. not Tanwrtsk wash observed in September 1980; rare in August 1981

(8) Bylas Springs 800 Fluctuating Mesquite Two spring runs fed Anemopsis calif:arnica: • Gambusia affinis One spring recently bosque by multiple spring Chara sp.: invaded by Gamhusw heads Newts guadalupensis (winter 1978-797): topminnow persist in low-moderate numbers. Other spring remains pure - (8a) Salt Creek 800 Fluctuating Mesquite Single spring head Anemopsis calif arnica: • Gambusia affinis Recently invaded bosque and run; low pH at Chara sp.: 'Notropis lutrensis by Gambusta and head Najas guadalupensis Notropis (winter 1978-79?). Top- persist in low numbers in head- spring (9) San Bernardino Creek -1 600 fluctuating Mesquite Intermittent stream/ Chara sp.: Agosia chrysogaster Gambusia first bosque arroyo Potamogeton foliosus: 'Gambusia affinis recorded here in June Typha sp.: 1980. Numbers have Zamichellia palustris steadily increased since then 236 GREAT BASIN NATURALIST [Volume 59

Table I. General description and status of natiwal f5 /011iailOOS Of Gila tOI ...... • in the United States. based on \Vet-din:in and Young (19971 and original data: localities are indicated by ..... hersii, Figures 1 and 3. The year in paren- theses is when liliOliinfillt.! was last areomplisheil: statements of e(nisemition status set in lioldfare type refer to that

1. Sharp Spring 11995): low-vol .... flow through 6. Sonoita Creek (1996): permanent read, in intermit- heavily vegetated channel. —0.5 km lime, isolated tent stream subject to flooding. Ixittoms sand/ from Santa Cniz River except in flood: top lll i l mow gravel. with sonic backwaters anti pool-like habitats greatly outnumbered by mos(1uitofish„ most near obstructions: topminnow abundant, occurring CO ...... extreme springhead. with native , (Paniosieta 2. Upper Santa Cniz River (1996. to, ...... last clarki I Baird and Girard))_ introduced - taken 1993): heavily vegetated stream channel. fish. and I or more species of introduced cyprinid, ...... lv intermittent. with ent Ivinks alternating centrarchid_ and ictalurid fishes. with vegetated shorelines: subject to flood scour: 7. Fresno Canyon (1996): stream smaller but similar to toputinnow occurs sporadically: consistently rare 6. above. toi ...... present along with introduced and often absent from collections (see also NI inckley centrarchids. et al. 1977). perhaps extirpated. S. Coalmine Canyon (1996): stream smaller but s ....lar 3. NIonkey Spring (1995r wann. constant-volume dis- to 6. alxwe: topminnow abundant along with charge changed little in past 30 yr Ism however. longfin dace and rare introduced centrarchid...... inaley et al. 19911. topn the only fish 9. Lower Santa Cruz River (1996): relatively swift present in headspring and outlet_ the former with channel over sand llottom: topminnow present and a livestock exclosure...... at 3 of 4 sites in a 5.0- to 6.0-km reach, 4. Cottonwtxxl Spring (1996r warm. constant-volume occurring with longfin dace and desert sucker; discharge inside livestock exclosure: flows through MOM witofish taken in 1994. short run into Somata Creek: toplll i ll now the only 10. Cienega Creek (1995): permanent stream similar to fish present in springhead and rim. slllll etimes locale 6. above: topminnow present along with occurring with native longfin dace (Aeosia chryso- longfin dace and (Gila itriennedia osier Girard) in creek, which is intermittent or IGirardl). sometimes dry: 11. Bylas Springs (19971:3 small springs (S-I, S-2. S-3). 5. Redrock Canyon_ separated for sampling into originallv flowing through narrow. heavily shaded_ Falls/Gate Spring (1995) and Cott Tank drainages vegetated channels into marsh or directly into Gila (1996): typically intermittent channels subject to River: S-3. from which all topmi llll ows were extir- flomling. with small pools and streamside ...... pated. recently re lified, and toi springs/seeps, toi • rare along with longfin now stock from S-I (retained in an artificial dace at former, abundant with mosquitofish at lat- refugium) reintroduced in 1995; S-2 renovated in ter; population sizes of both livebearers and pres- 1996 (mosquitofish successfully removed), ence of piscivorous central-chid fishes variable. modified, and original toplll i lll mw successfully reestablished.

ii„ ill