Information to Support Monitoring and Habitat Restoration on 

Ash Meadows National Wildlife Refuge

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2013-1022

Information to Support Monitoring and Habitat 

Restoration on Ash Meadows National Wildlife Refuge

By G. Gary Scoppettone, Editor

Open-File Report 2013-1022

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2013 

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Suggested citation:

Scoppettone, G.G., ed., 2013, Information to support to monitoring and habitat restoration on Ash 

Meadows National Wildlife Refuge: U.S. Geological Survey Open-File Report 2013-1022, 56 p. 

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iii

Prologue

The Ash Meadows National Wildlife Refuge staff focuses on improving habitat for the 

highest incidence of endemic species for an area of its size in the continental United States. 

Attempts are being made to restore habitat to some semblance of its pre-anthropogenic 

undisturbed condition, and to provide habitat conditions to which native plant and animal species 

have evolved. Unfortunately, restoring the Ash Meadows’ Oases to its pre-anthropogenic 

undisturbed condition is almost impossible. First, there are constraints on water manipulation 

because there are private holdings within the refuge boundary; second, there has been at least one 

species extinction—the Ash Meadows pool fish (Empetrichthys merriami). It is also quite 

possible that thermal endemic invertebrate species were lost before ever being described. 

Perhaps the primary obstacle to restoring Ash Meadows to its pre-anthropogenic undisturbed 

conditions is the presence of invasive species. However, invasive species, such as red swamp 

crayfish (Procambarus clarki) and western mosquitofish (Gambusia affinis), are a primary 

driving force in restoring Ash Meadows’ spring systems, because under certain habitat 

conditions they can all but replace native species. Returning Ash Meadows’ physical landscape 

to some semblance of its pre-anthropogenic undisturbed condition through natural processes may 

take decades. Meanwhile, the natural dissolution of concrete and earthen irrigation channels 

threatens to allow cattail marshes to flourish instead of spring-brooks immediately downstream 

of spring discharge. This successional stage favors non-native crayfish and mosquitofish over the 

native Amargosa pupfish (Cyprinodon nevadensis). Thus, restoration is needed to control nonnatives and to promote native species, and without such intervention the probability of native 

fish reduction or loss, is anticipated. 

The four studies in this report are intended to provide information for restoring native fish 

habitat and for monitoring native fish populations in relation to restoration efforts on the Ash 

Meadows National Wildlife Refuge. There are no precise records on conditions of each of the 

spring systems prior to anthropogenic alteration; however, fostering conditions that favor native 

over non-natives will be key to habitat restoration. Information regarding native species carbon 

source is needed to create habitat that favors native species, thus habitat restoration fostering 

food stuff consumed by native species should be considered in restoration efforts. In compiling 

data for the first part of this report, we tracked carbon source for native and non-native species at 

four stations along the Jackrabbit Spring system. Thus, we were able to contrast carbon source in 

warm- and cool-water habitats. Habitat in Jackrabbit Spring was improved for native fishes in 

2007. The second paper in this report focuses on native fish populations in Jackrabbit Spring 

system pre- and post-restoration. 

Much of the Ash Meadows Oases is marsh habitat where non-native red swamp crayfish 

and western mosquitofish are often abundant, to the detriment of non-natives. Because marsh 

habitat is broadly represented in the Ash Meadows landscape, establishing marsh habitat most 

conducive to the native fishes is important to the restoration effort, and the third paper addresses 

marsh habitat type with the relative abundance of fishes and crayfish. 

There are previous years of monitoring Ash Meadows’ native fish populations, but not all 

monitoring occurred at the same time of year. Desert-fish populations sometimes undergo 

seasonal fluctuation, so it might not be valid to compare population trends using different 

seasons. For report four, we tracked a closed population of Amargosa pupfish (Cyprinodon 

nevadensis) year round to track seasonal trends. Knowledge of seasonal trends is important in 

tracking changes of populations pre- and post-restoration. 
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v 

Contents

Prologue ........................................................................................................................................................iii

Carbon Source and Trophic Structure of Fishes and Crayfish along the Jackrabbit Spring System, 

and Implications for Habitat Restoration................................................................................................... 1

Background and Description of Area ......................................................................................................... 1

Methods ..................................................................................................................................................... 2

Collection Site and Processing Samples................................................................................................ 2

Gut Analysis to Determine Carbon Source and Trophic Position ........................................................... 3

δ13C and δ15N Analysis to Determine Carbon Source and Trophic Position........................................... 3

Results....................................................................................................................................................... 4

Warm- and Cool-Water Habitats ............................................................................................................ 4

Seasonal Gut Analysis ........................................................................................................................... 4

Stable Isotopes δ13C and δ15N ............................................................................................................... 6

Discussion.................................................................................................................................................. 7

Acknowledgments...................................................................................................................................... 9

References Cited ....................................................................................................................................... 9

Relative Abundance and Distribution of Ash Meadows Pupfish and Ash Meadows Speckled 

Dace in the Upper One-Third of the Jackrabbit Spring System: Post-Fire and Restoration............... 21

Methods ................................................................................................................................................... 21

Results..................................................................................................................................................... 21

Discussion................................................................................................................................................ 22

Acknowledgments.................................................................................................................................... 23

References Cited ..................................................................................................................................... 23

Shallow Marsh Habitat Use by Amargosa Ash Meadows and Amargosa Warm Springs Pupfish ..... 31

Background.............................................................................................................................................. 31

Materials and Methods............................................................................................................................. 32

Results..................................................................................................................................................... 32

Discussion................................................................................................................................................ 33

References Cited ..................................................................................................................................... 34

Population Dynamics of Amargosa Ash Meadows Pupfish in Five Springs, Ash Meadows, 

Nye County, Nevada.................................................................................................................................. 40

Description of Area .................................................................................................................................. 41

Materials and Methods............................................................................................................................. 42

Results..................................................................................................................................................... 42

Population Dynamics............................................................................................................................ 42

Discussion................................................................................................................................................ 43

Acknowledgments.................................................................................................................................... 44

References Cited ..................................................................................................................................... 44

Appendix...................................................................................................................................................... 53
vi

Figures

Figure 1.1. Location of four stations for carbon source and trophic position of Ash Meadows fishes and 

crayfish ........................................................................................................................................................ 12

Figure 1.2. Water temperatures taken from December 2009 through October 2010 at four stations 

along Jackrabbit Spring system................................................................................................................... 13

Figure 1.3. Relative δ13C in algae, C3 plants and crayfish at four stations along Jackrabbit Spring 

system ......................................................................................................................................................... 14

Figure 1.4. Relative δ13C in four Ash Meadows fishes at four stations along Jackrabbit Spring system..... 15

Figure 2.1. March 2006 distribution and relative abundance of Ash Meadow pupfish in the upper 

2.25 km of the Jackrabbit Spring system..................................................................................................... 25

Figure 2.2. March 2007 distribution and relative abundance of Ash Meadow pupfish in the upper

2.25 km of the Jackrabbit Spring system.................................................................................................... 26

Figure 2.3. March 2010 distribution and relative abundance of Ash Meadow pupfish in the upper 

2.25 km of the Jackrabbit Spring system..................................................................................................... 27

Figure 2.4. March 2006 distribution and relative abundance of Ash Meadow speckled dace in 

the upper 2.25 km of the Jackrabbit Spring system..................................................................................... 28

Figure 2.5. March 2007 distribution and relative abundance of Ash Meadow speckled dace in 

the upper 2.25 km of the Jackrabbit Spring system..................................................................................... 29

Figure 2.6. March 2010 distribution and relative abundance of Ash Meadow speckled dace in

the upper 2.25 km of the Jackrabbit Spring system.................................................................................... 30

Figure 3.1. Study sites at Northern and Southern spring systems at Ash Meadows National Wildlife 

Refuge......................................................................................................................................................... 36

Figure 3.2. Total number of Amargosa pupfish, western mosquitofish, and red swamp crayfish 

captured from Typha and Juncus marshes in four seasons, 2009 and 2010............................................... 38

Figure 4.1. Bimonthly population estimate (bar graph) and confidence interval of Ash Meadows 

pupfish in Five Springs from October 2009 to October 2010 ....................................................................... 46

Figure 4.2. Ash Meadows pupfish distribution and relative abundance within the Five Springs system; 

captures are a composite of bimonthly sampling from October 2009 to October 2010................................ 47

Figure 4.3. Daily HOBO temperature record at four locations within the Five Springs system.................... 48

Figure 4.4. Western mosquitofish distribution and relative abundance within the Five Springs system; 

captures are a composite of bimonthly sampling from October 2009 to October 2010................................ 49

Figure 4.5. Red swamp crayfish distribution and relative abundance within the Five Springs system; 

captures are a composite of bimonthly sampling from October 2009 to October 2010................................ 50

Figure 4. 6. Bimonthly length frequency distribution of Ash Meadows pupfish captured from 

Five Springs from October 2009 to October 2010. ..................................................................................... 51
vii

Tables

Table 1.1. Gut content mean percent by volume and standard deviation of Ash Meadows fishes and 

crayfish for all seasons at four stations. In parenthesis is number of fish or crayfish with empty guts......... 16

Table1. 2. Analysis of variance of difference in δ13C between spring-pool and 700-m in algae, C3 plants, 

fishes and crayfish....................................................................................................................................... 18

Table 1.3. Descriptive statistics for 13C in algae, aquatic invertebrates, terrestial invertebrates, fishes 

and crayfish of all four stations and two seasons in the Jackrabbit Spring system...................................... 18

Table 1.4. Mann-Whitney V test to determine if there is a significant difference in δ13C signal among 

potential prey items and potential prey item and of fishes and crayfish vs. potential prey. .......................... 19

Table 1.5. Calculated trophic position for four stations along the Jackrabbit Spring system. ...................... 20

Table 3.1. Values of the Akaike's information criterion corrected for small sample size used to select 

the best model from 53 candidate models of marsh occupancy during 2009-2010 (the top 17 models

are shown)................................................................................................................................................... 39
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1 

Information to Support Monitoring and Habitat 

Restoration on Ash Meadows National Wildlife Refuge

By G. Gary Scoppettone, Editor

Carbon Source and Trophic Structure of Fishes and Crayfish along the 

Jackrabbit Spring System, and Implications for Habitat Restoration

By G. Gary Scoppettone, Danielle Johnson, J. Antonio Salgado, Peter H. Rissler, and Mark Hereford, U.S. 

Geological Survey; and Michael S. Parker, Southern Oregon University

Restoration of Ash Meadows Spring systems aimed at enhancing habitat for native fishes 

requires understanding the spring ecosystems’ primary energy source, because habitat 

manipulation should target enhancement of energy flow to the native fishes. In thermal springs, 

such as those in Ash Meadows, water cools in a downstream direction (Garside and Schilling, 

1979); how the flow of energy may differ for native and non-native species in the warmer stream 

reach compared to the cooler reach is unknown. How native fishes overlap in food resources 

with non-native species in warm-water as opposed to cool-water habitats also is unknown. 

Investigation of carbon sources and trophic position of fishes and crayfish in the 

Jackrabbit Spring system can provide useful information for future Ash Meadows restoration 

projects and the ongoing management of the restored systems. In this study, we compare carbon 

source and trophic position in warm-water habitat with cool-water habitats for native fish and 

non-native fish and crayfish. We also compare trophic positions among species. 

Background and Description of Area 

The Jackrabbit Spring system is located in the southeastern part of the Ash Meadows 

National Wildlife Refuge (AMNWR) (fig. 1.1). Its discharge in 1962 was 0.04 m3

/s (Walker and 

Eakin, 1963). Typical for thermal springs, Jackrabbit Spring outflow cools in a downstream 

direction (Garside and Schilling, 1979). Water temperature in the spring-pool and discharge 

temperature at Jackrabbit Spring is about 26.9o C (± 1o C); water temperature 3.75 km 

downstream of the spring’s origin can range well over 20o C (Scoppettone and others, 1995). 

The Jackrabbit Spring system’s biotic community has undergone substantial 

anthropogenic disruption. Pumping the spring system dry was the most disruptive event (Soltz 

and Naiman, 1978; Deacon and Williams, 1991)—both Ash Meadows pupfish (Cyprinodon 

nevadensis mionectes) and Ash Meadows speckled dace (Rhinichthys osculus nevadensis) were 

extirpated from the system (and later restocked) (Williams and Sada, 1985). Presumably, these 

species also entered the system from the Big Spring system to which Jackrabbit Spring was 

connected. Non-native sailfin molly (Poecilia latipinna) and western mosquitofish (Gambusia 

affinis) also reinvaded the Big Spring system. Non-native red swamp crayfish (Procambarus 
2 

clarkii) are documented to have arrived in Ash Meadows by at least the late 1930s (Miller, 

1948), and may have survived the pumping events because of its ability to burrow into muddy 

substrate for extended periods (Hobbs and others, 1989). Bullfrogs (Lithobates catesbeiana) 

have occupied Ash Meadows spring systems since at least the late 1930s (Miller, 1948), and may 

have reinvaded the Jackrabbit Spring system from the Big Spring system or another proximal 

spring system. Red-rim malania (Melonoides tuberculata) probably was introduced to Ash 

Meadows in the early 1960s with the introduction and rearing of aquaria fish in an Ash 

Meadows’ spring (Soltz and Naiman, 1978); when they established in the Jackrabbit Spring 

system is unknown, but they could have survived the pumping of the system in 1970 (Mitchell 

and Hobbs, 2007). Presumably, the Jackrabbit Spring system harbored a suite of thermophilic 

invertebrates (some of which may have been endemic), but these perished when the system 

dried. 

Since Miller’s (1948) description of pupfish in Ash Meadows, the Jackrabbit Spring 

outflow has been redirected from a westerly to a southerly direction. In order to improve 

irrigation, the channel apparently had been diverted with a small impoundment constructed about 

2 km from the spring source. By the late 1990s, a segment of the spring outflow became 

overgrown with invasive salt cedar (Tamarix ramosissima), which hid the impounded stretch of 

stream from view. In March 2005, a fire along the Jackrabbit Spring outflow burned through the 

dense stand of salt cedar, exposing the impounded reaches of its outflow, and providing the 

opportunity to rehabilitate the channel into habitat more conducive to the native fishes 

(Scoppettone and others, 2005). In summer 2006, impoundments were removed and water 

diverted to an excavated channel; in summer 2007, property acquired by ANWR in 1996 was 

rehabilitated from marsh-like habitat to a well-defined channel.

Methods 

Collection Site and Processing Samples

We investigated carbon flow and trophic positioning using gut content and stable isotope 

(δ13C and δ15N) analysis of plant and animal tissue. Samples for this study were taken in 2009 at 

four sites and in four seasons along the Jackrabbit Spring system (fig. 1.1). Sites were selected to 

represent warm-water habitat (spring-pool and 700 m from spring-pool) and cool-water habitat 

(1,800 and 3,600 m from spring-pool). These selected sites were thermally characterized by 

placing a HOBO® onset temperature logger at each station in February 2009. HOBOs® were 

retrieved in October 2009; the 700-m station HOBO® was lost. Because of the importance of 

comparing temperature synchronously, we installed the HOBOs again in December 2009 and 

recovered them in October 2010. 

We set five 3.3 mm mesh, standard Gee minnow traps at approximately 1 m apart to 

capture fishes and crayfish for stable isotope and gut analysis at each outflow station; in the 

spring-pool, we spaced five minnow traps equidistant within the pools. Minnow traps were 

baited with dog food that was wrapped in gauze to prevent food from being ingested by collected 

fishes and crayfish. Because sailfin molly and mosquitofish are difficult to capture with a 

benthically situated minnow trap, we used dip-nets proximal to the minnow traps to secure 

additional specimens. Captured fish were weighed and measured. Fish guts were then removed 

and placed in 10 percent formalin. The remainder of the fish was placed on dry ice until it could 

be transferred to a freezer. Up to 8 pupfish and 4 speckled dace were taken at each station, while 

up to 9 mosquitofish, molly, and crayfish also were collected. Benthic invertebrates were 
3 

captured by stirring the stream bottom with a rebar post and capturing displaced invertebrates 

with a dip-net. Four samples were taken at 1-m intervals from each of the four sites. We used a 

600-μm mesh plankton net to sample for free-swimming organisms in Jackrabbit Spring outflow. 

A 600-μm mesh plankton net was dragged across the spring-pool 10 times each season. At each 

station, terrestrial invertebrates were collected using dip-nets to sweep vegetation within 2 m of 

the outflow and stream-pool. Clips of vascular plants (aquatic and terrestrial) were taken within 

the same area from which terrestrial invertebrates were sampled. All items collected were labeled 

as to date and station, and assigned an identification number. Each sample was placed in plastic 

bags, put on dry ice, and transferred to a freezer. 

Gut Analysis to Determine Carbon Source and Trophic Position 

None of the Ash Meadows fishes and crayfish we examined has a true stomach, so we 

examined the anterior one-third of their guts. Gut contents were identified using a dissection 

microscope and placed into one of the following categories: filamentous algae; detritus; vascular 

plant; fish; aquatic invertebrate; terrestrial invertebrate; unidentified invertebrate; and substrate 

(dirt, sand, and gravel). Food items consumed were quantified by mean percent by volume 

(Windell, 1971). We used a Kruskal Wallis test to determine whether there was a difference in 

food items consumed by fish species and crayfish among stations. The Kruskal Wallis also was 

used to test for a propensity for fish or crayfish to prey upon aquatic invertebrates more often 

than terrestrial invertebrates. Because of small sample sizes, seasons were grouped together by 

species for analysis . 

Following Vander Zanden and Rasmussen (1996), the trophic position of prey items was 

used to calculate the trophic position for each fish using the following formula: 

Ta = ∑ (ViTi) + 1, 

where Ta = mean trophic position of the subject fish, 

Vi = volumetric contribution of the ith prey item, and 

Ti = trophic position of the ith food item. 

Food item trophic positions were as follows: primary producers (algae, vascular plants, and 

detritus) were first trophic level and assigned a value of 1; aquatic invertebrates were considered 

to be a mixture of primary consumers (2) and secondary consumers (3), and thus given a trophic 

value of 2.5; and terrestrial invertebrates were a mixture of primary (2), secondary (3), and 

tertiary consumers (4), and assigned a trophic value of 3. Fish also were assigned a trophic value 

of 3. 

δ13C and δ15N Analysis to Determine Carbon Source and Trophic Position

 Stable isotopes (δ15N and δ13C) have become a popular tool to assess trophic positioning 

and energy flow within an ecosystem (Peterson and Fry, 1987; Vander Zanden and Rasmussen, 

1999; Post, 2002). An advantage of stable isotopes is that they give a time-integrated analysis of 

source of carbon input (Fry and Arnold, 1982). Primary producers typically have a distinctive 

δ13C signature and contribute relatively minor trophic enrichment (about 0.8 percent), making 

their signal useful in assessing carbon source (Vander Zanden and Rasmussen, 1999). The 

nitrogen isotope δ15N enriches 3.4 percent at each trophic level, and this magnitude is useful in 

calculating trophic position (Minagawa and Wada, 1984; Peterson and Fry, 1987). 
4 

We used δ13C to determine if carbon source for fishes and crayfish came primarily from 

the stream (algae, bacteria, aquatic invertebrates) or from more of a terrestrial origin (C3 plants, 

terrestrial invertebrates). Two methods were used to determine potential carbon source: (1) 

tracking δ13C enrichment in a downstream direction, and (2) testing whether there was a 

significant affiliation in carbon signal among organisms. If algae are enriched in a downstream 

direction, it follows that organisms feeding directly or indirectly upon algae also would 

experience δ13C enrichment. We used analysis of variance to test if there was downstream δ13C 

enrichment for algae, C3 plants, fishes, and crayfish between the spring-pool and the 700-m 

station. We restricted our analysis to the two stations from which we were successful in securing 

the algae δ13C signal. We also used analysis of variance to test if organisms had similar δ13C 

affiliations.

To determine trophic levels among fishes and crayfish we used the following formula 

from Post (2002): 

Tcon = Tbase + (δ15Ncon - δ15Nbase)/∆N,

where Tcon is the trophic position of the subject consumer, Tbase is the trophic position of the 

organism used to estimate δ15Nbase, δ15Ncon and δ15Nbase were measured directly, and ∆N is 3.4 

percent (mean enrichment per trophic level). Tbase was 1 for primary producer and 2 for primary 

consumer. We used filamentous algae Tbase 1, but only for the spring-pool and 700-m stations, 

because these were the only stations from which the δ15N signature was available for algae. 

Crayfish were used for Tbase 2 and at all stations because it was collected at all four stations in 

winter and summer. 

For stable isotope analysis, we used our January and July collections; these two seasons 

represented the environmental extremes for water temperature, day length, and food availability. 

Samples for stable isotope analysis were sent to the UC Davis Stable Isotope Facilities. Prior to 

sending samples they were rinsed in deionized water, oven dried, and pulverized. 

Results

Warm- and Cool-Water Habitats

The spring-pool and 700-m stations were considered warm-water habitats. Water 

temperatures at these two stations are fairly constant, with daily and seasonal temperature 

fluctuation not exceeding 3o C, and mean daily temperature was equal to or greater than 25o C 

(fig. 1.2). For the cool-water stations (1,800-m and 3,600-m), mean daily average temperature 

fluctuation exceeded 4o C and seasonal temperature was less than 25o C for much of the year. 

Water temperature at the spring-pool, 1,800-m and 3,600-m station is shown in figure 1.2. 

Seasonal Gut Analysis

In the thermal habitats (spring-pool station and 700-m station), filamentous algae was the 

predominant food item in the guts of Ash Meadows pupfish in all four seasons. Gut contents in 

the spring-pool station averaged 92.7% ± 14.4 by volume (table 1.1) and a seasonal range from 

82.7 to 100% (table A.1). At the 700-m station, average gut content was 86.2% ± 26.7 by 

volume, and a seasonal range of 57.0–96.4%. Although pupfish at the two warm-water stations 

consumed primarily filamentous algae, the spring-pool pupfish consumed a significantly greater 

(df = 1, χ2

 = 4.393, p = 0.036) proportion of algae than did pupfish at the 700-m station. 
5 

At the cool-water stations, the 3,600-m station algae comprised 22.2% ± 40.0 of pupfish 

gut contents by volume with a range of 0.0–65.2 percent among seasons (table A.1). The 

proportion of algae taken at the 700-m station was significantly (df = 1, χ

2

 = 21.612, p = 0.001) 

greater than the proportion of algae taken at 3,600-m station. Only a small portion of the pupfish 

diet consisted of invertebrates, and most of the consumed invertebrates were aquatic (table 1.1). 

There was a significantly (df = 1, χ2

 = 7.010, p = 0.008) greater proportion of aquatic 

invertebrates taken at the 700-m station (high of 10 percent by volume taken in winter) than the 

spring-pool and 3,600-m stations, which only represented a high of 3.3 percent in spring-time at 

the spring-pool station (table 1.1). There was no significant difference (df = 2, χ2 = 0.010, p = 

0.995) in terrestrial invertebrates taken among stations. Although pupfish fed upon a very 

meager amount of invertebrates (x̅= 1.7% ± 9.0 aquatic, x̅= 0.7% ± 5.3 terrestrial), the volume 

of aquatic invertebrates was significantly greater (df = 1, χ

2

 = 4.817, p = 0.028) than terrestrial 

invertebrates. The relative proportion of detritus consumed by pupfish increased in a downstream 

direction. However, there was little difference between the spring-pool station (x̅= 1.7%) and 

700-m station (x̅= 2.9%); the difference was statistically significant (df = 1, χ

2

 = 5.539, p = 

0.019), but probably not biologically significant. Detritus was the primary food item (x̅= 45.3%) 

consumed at the 3,600-m station, and this was significantly greater (df = 1, χ

2

 = 9.533, p = 0.001) 

than the detritus consumed at the 700-m station. There was relatively little vascular vegetation 

consumed by pupfish, and there was no significant difference (df = 1, χ

2 = 0.009, p = 0.924) 

between the spring-pool and 700-m station. There was significant difference (df = 1, χ2

 = 4.937, 

p = 0.026) in the relative proportion of vascular plants taken at the 700-m and 3,600-m stations. 

Seven of eight pupfish taken in the fall had bottom substrate (sand and pebbles) in their guts. The 

1,800-m station was not included in our analysis because it was represented by only one pupfish 

in all four seasons. 

Invertebrates were the predominant food items taken by speckled dace at three of the four 

stations, with aquatic invertebrates occupying a greater volume of the speckled dace’s gut at 

three of the stations (table 1.1). However, there was no significant difference in relative amount 

by volume of aquatic (df = 3, χ2 = 6.176, p = 0.103) or terrestrial invertebrates (df = 3, χ2= 

2.572, p = 0.666) taken among stations. This was true of all other food categories; there was no 

difference among stations. In all four seasons and all four stations, dace took a greater proportion 

of aquatic invertebrates (x̅= 29.4%) than terrestrial invertebrates (x̅= 13.8%), and this difference 

was significant (df = 1, χ2 = 4.442, p = 0.035). 

The primary food item consumed by mosquitofish was invertebrates, with a greater 

volume of terrestrial invertebrates taken at each of the four stations. As with speckled dace, there 

was no significant difference between aquatic (df = 3, χ2

 = 5.514, p = 0.138) or terrestrial 

invertebrates (df = 3, χ2 = 2.372, p = 0.499) taken among stations. Also, as with speckled dace, 

there was no difference in any other food category among stations. Mosquitofish did take a 

significantly greater (df = 1, χ2

 = 4.479, p = 0.034) percent by volume of terrestrial invertebrates 

(x̅= 27% ± 32.4) than aquatic invertebrates (x̅= 18.6% ± 28.4). 

Sailfin molly were captured primarily in the spring-pool and 700-m stations where they 

fed almost exclusively upon filamentous algae and detritus. There was a significantly greater (df 

= 1, χ2

 = 5.375, p = 0.020) amount of algae taken by percent volume from the spring-pool, and a 

significantly greater (df = 1, χ2

 = 5.375, p = 0.020) amount of detritus by percent volume taken 

from the 700-m station.
6 

Detritus was the predominant item consumed by crayfish at three of the four stations, but 

there was no significant difference (df = 3, χ

2

 = 3.939, p = 0.268) in the amount taken among 

stations. Crayfish consumed few invertebrates, but fish and vascular plant material was found in 

their guts at each of the four stations. The only statistical difference (df = 1, χ2

 = 7.442, p = 

0.006) in food items taken among stations was vascular plant material between the spring-pool 

and 700-m station.

Trophic position using gut contents indicated pupfish and sailfin molly are the primary 

consumers at stations in which they occur (table 1.2). Mosquitofish were second-order 

consumers at all stations, while speckled dace were second-order consumers in warm-water 

stations and were slightly more omnivorous in cool-water stations. Trophic position of crayfish 

indicated omnivory, but tending toward herbivory at most stations; their trophic position was 

slightly higher in cool-water stations.

Stable Isotopes δ13C and δ15N

The δ13C and δ15N isotopes contributed further to carbon contribution and trophic 

positioning as related to warm-water and cool-water habitats. We harvested algae for stable 

isotope in sufficient quantity in the warm-water region of the Jackrabbit Spring system (Springpool and 700-m stations), which appeared to be the primary carbon source for fish species 

captured in the thermal upper reaches of the Jackrabbit Spring system. This conclusion was 

derived using Kennedy’s (2002) observation that there is δ13C enrichment of algae in a 

downstream direction, and consequently the organisms depending directly and indirectly on 

algae as a carbon source experience δ13C enrichment in a downstream direction. The enrichment 

from the spring-pool station to the 700-m station for algae in this study was significant (df = 1, χ2

= 6.61, p = 0.042), but (probably due to our small sample size) did not meet the test for normality 

(table 1.2, fig. 1.3). There was a significant difference in C3 plants in terms of δ13C between the 

spring-pool and 700-m station, but this was due to δ13C reduction in a downstream direction. All 

fishes and crayfish in our samples experienced δ13C enrichment from the spring-pool to the 700-

m station, and this increase was significant for all species except mosquitofish (table 1.2, fig. 1.3, 

1.4). For animal species, δ13C enrichment continued downstream to the 1,800-m station for all 

but the sailfin molly, which had very suspect δ13C and δ15N (discussed below). We did not use 

the 1,800-m station in our analysis because there were few pupfish (n = 1), and molly (n = 3) 

captured there.

The δ13C signature was useful in assessing potential carbon connections amongst 

Jackrabbit Spring system organisms, including potential predator/prey and competitive 

interactions. Among potential fish and crayfish prey items, terrestrial invertebrates had a mean 

δ13C -22.6 ± 3.8, compared to -28.2 ± 4.0 for aquatic invertebrates (table 1.3), and this difference 

was significant (table 1.4). Aquatic insects were not significantly different than algae, but 

terrestrial invertebrates had a significantly greater δ13C signal than algae. Among fishes, pupfish 

had the lowest mean δ13C at -27.7 (table 1.3), and this value was not significantly different from 

filamentous algae (-28.9) and aquatic invertebrates (-28.2) (table 1.4), suggesting that both may 

be a food source for pupfish. The mean δ13C of C3 plants was the same as pupfish, but the low 

δ15N signal (3.1) from C3 and C4 plants all but precluded these plants as a direct carbon source of 
7 

pupfish. Pupfish δ13C signature was significantly different than that for terrestrial invertebrates 

(table 1.3). There was significant difference between the δ13C signature between speckled dace 

and aquatic invertebrates, but not between dace and terrestrial invertebrates. Similarly, there was 

a significant difference between mosquitofish and aquatic invertebrates, but no difference 

between mosquitofish and terrestrial invertebrates. 

Analysis of δ15N among organisms for each of our stations in winter and summer adds 

more information as to items consumed over time. For example, trophic position of pupfish in 

January and July at the spring-pool ranged from 2.4 to 2.6 using algae as the producer base, and 

2.5 using crayfish as the primary consumer base suggesting pupfish are more omnivorous than 

portrayed by gut analysis (table 1.5). Speckled dace held the highest trophic position for each 

station for each season. Mosquitofish had a trophic position similar to pupfish at most stations in 

January and July (table 1.5). Crayfish were always lowest in δ15N and, hence, lowest in trophic 

order relative to fishes.

Pupfish, speckled dace, and mosquitofish generally had higher trophic position in winter 

than summer, suggesting invertebrates were a more important food source in winter. Trophic 

position for pupfish (3.0 using algae base and crayfish base) in January at the upper station was 

exceedingly high for a species for which filamentous algae is a primary contributor to the diet. 

The value of sailfin molly (2.7), which is primarily herbivorous, also is unexpectedly high. 

Discussion 

Gut analysis indicated that filamentous algae were the predominant food item consumed 

by pupfish in warm water for all four seasons. The warm, open water of the upper reaches of the 

Jackrabbit Spring system was particularly favorable to pupfish because it promotes year-round 

growth of filamentous algae (Kennedy and Hobbie, 2004; Kennedy and others, 2006). The δ13C 

signature of Ash Meadows pupfish also suggested an algal affiliation, as did the enrichment of 

δ13C in both algae and Ash Meadows pupfish in warm-water habitat.

Although filamentous algae appears to be important food stuff (Naiman, 1975; Kennedy 

and others, 2006), there are questions about its digestibility (Naiman, 1979). Microbial 

organisms associated with filamentous algae may be sufficiently small to be rapidly digested and 

hence not readily detected in gut analysis; however, they may contribute to pupfish diet and 

enhance the δ15N signal. Analysis of pupfish trophic position using δ15N indicated primary 

consumers contribute substantially to their nutriment, especially in winter, and more so than 

inferred from our gut analysis. Our trophic positioning for Ash Meadows pupfish was slightly 

higher than that observed by Kennedy and others (2006). Plausible explanations are habitat 

changes (fire and restoration) and the substantial temporal and spatial variation in δ13C and δ15N 

within an aquatic system (Boon and Bunn, 1994; Vander Zanden and others, 1997).

Among Ash Meadow fishes, pupfish exhibited the most dramatic change in gut contents 

between the warm- and cool-water stations. At the 3,600-m station, pupfish consumed detritus, 

algae, and substrate. Substrate (sand, gravel) was found in the guts of all eight pupfish collected 

in the fall (November). Whether substrate is associated with acquiring some food stuff from the 

stream bottom is unknown, but substrate also has been taken in substantial amounts from the guts 

of Devils Hole pupfish (Cyprinodon diabolis) (Minckley and Deacon, 1975; Wilson and Blinn, 

2007) and desert pupfish (Cyprinodon macularius) (Naiman, 1979). 
8 

Speckled dace also are bottom oriented, but in the spring-brooks of Ash Meadows, they 

feed primarily on drift, working the entire water column (Scoppettone and others, 1995); stable 

isotope analysis indicates they rely primarily upon terrestrial invertebrates. Perhaps a reason for 

reliance on terrestrial invertebrates is that the Jackrabbit Spring system harbored few native 

aquatic invertebrates, especially in its upper reaches (Andrews and others, unpub. data, 2006). 

Mosquitofish generally are surface oriented and have a body form adapted to taking prey from 

the water surface–the head is flattened and mouth dorsally situated (Swanson and others, 1996), 

thus they are perfectly suited for preying upon terrestrial insects that fall or land on the water 

surface. Speckled dace δ13C value was not significantly different from that of terrestrial insects. 

It was therefore surprising that dace had a mean δ15N value identical to pupfish for all four 

stations and two seasons, and that they had close or identical trophic positions at co-occurring 

stations. Mosquitofish are opportunistic omnivores and may feed on algae and plants, along with 

terrestrial and aquatic invertebrates (Harrington and Harrington, 1961), and this may account, in 

part, for the similar δ15N. However, a more plausible explanation is that the δ15N we experienced 

in the Jackrabbit Spring system was fairly high (5.7), and close to the magnitude of terrestrial 

and aquatic invertebrates (6.6). Speckled dace held the highest trophic position at each station, 

indicating that this species secured more invertebrates than did mosquitofish. 

Sailfin molly tend toward herbivory (Meffe and Snelson, 1989), and our stable isotope 

analysis put them at the lowest trophic position among the fishes. From our data, we were unable 

to determine if the lower δ15N signal is the result of molly consuming greater amounts of 

vascular plant materials. Gut analysis indicated that molly compete with pupfish for algae and 

detritus. Western mosquitofish have been described as opportunistic omnivores, feeding on a 

broad array of food items (Swanson and others, 1996). In this study, gut analysis suggested that 

mosquitofish, along with speckled dace, held the highest trophic position among fishes and 

crayfish, but δ15N analysis put mosquitofish into a lower trophic position similar to pupfish. 

Because stable isotopes offer a time-integrated perspective of diet (Fry and Arnold, 1982), we 

concluded that in the newly restored Jackrabbit Spring system, mosquitofish were more 

herbivorous than speckled dace through much of the year. Our results differ from Kennedy and 

others (2006), who attributed a higher trophic position than this study. Western mosquitofish are 

specialized feeders, and the invertebrates they consume typically are terrestrial types (Moyle, 

2002) that probably were more available during the Kennedy and others (2006) study. Their 

study was pre-restoration, and focused on a densely covered reach of stream where terrestrial 

invertebrates were in much greater availability than the sparser riparian corridor present at the 

time of our study. 

Crayfish are known for their catholic diet, consuming vascular plant detritus, algae, and 

animal matter, thus exploiting all carbon sources in a system (Whitledge and Rabeni, 1997; 

Kennedy and others, 2006). Because of their dietary diversity, crayfish exert a major influence 

on the flow of energy; they are often predominant in bio-mass and compete with native and nonnative fishes (Momot, 1995). Although we did not compare relative bio-mass in this study, we 

observed that red swamp crayfish bio-mass far exceeds that of native fishes. Although crayfish 

consumed primarily vegetative material, they are sufficiently numerous that they may consume 

substantial amounts of aquatic invertebrates, fish eggs, and larvae. Judging from results of stable 

isotope analysis, crayfish benefited most from C3 vascular plant input, and this is consistent with 

other studies indicating vascular plants to be a substantial contribution to the crayfish diet 

(Kennedy and others, 2006). We suspect the crayfish population may grow with additional 

vascular plant contribution, including allochthonous materials. 
9 

Native fish diets observed in this study may be different than what occurred prior to 

manipulation of the Ash Meadows ecosystem. Anthropogenic changes to the landscape 

(including shifts in vegetation composition, extinction and extirpation of native aquatic 

organisms, and introduction of non-native aquatic species) have altered flow of energy in Ash 

Meadows Spring systems, including flow of energy to native fishes. Non-native species can 

cause a shift in diet and habitat use of native species, and without such a shift natives may face 

competitive exclusion. Our study suggests that, under current conditions, filamentous algae is 

important to the diet of Ash Meadows pupfish, and habitat conditions that foster algae growth 

should be considered in the rehabilitation and long-term management of spring systems. For 

speckled dace, invertebrate production and their availability for consumption should be target 

considerations in habitat rehabilitation.

Acknowledgments

We thank Ash Meadows National Wildlife Refuge for funding this study. Bryan Hobbs 

(U.S. Fish and Wildlife Service) assisted with fish collections. We also thank Tom Strekal and 

Mark Fabes (U.S. Geological Survey) for reviewing the manuscript. 

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(Cyprinidae): Southwestern Naturalist, v. 20, p. 105–111. 

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247–256. 

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data: Canadian Journal of Aquatic Sciences, v. 54, p. 1,142–1,158. 

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mionectes and Rhinichthys osculus nevadensis, from two springs in Ash Meadows, Nevada: 

Southwestern Naturalist, v. 30, p. 475–484. 

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allochthonous carbon in a desert cavernous limnocrene: Devils Hole, Nevada, v. 67, p. 185–

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12

Figure 1.1. Location of four stations for carbon source and trophic position of Ash Meadows fishes and 

crayfish. (Inset) Jackrabbit Spring system in relationship to Ash Meadows National Wildlife Refuge. 
13

Figure 1.2. Water temperatures taken from December 2009 through October 2010 at four stations along 

Jackrabbit Spring system.

0 

5 

10

15

20

25

30

35

Jackrabbit Spring-pool

Mean daily range ± SD = 1.33 ± 0.39

Sample mean ± SD = 27.46 ± 0.49

0 

5 

10

15

20

25

30

35

Jackrabbit 700-m 

(No Data)

0 

5 

10

15

20

25

30

35

Jackrabbit 1800-m 

Mean daily range ± SD = 4.38 ± 1.22

Sample mean ± SD = 24.01 ± 2.40

0 

5 

10

15

20

25

30

35

Jackrabbit 3600-m 

Mean daily range ± SD = 4.69 ± 1.27

Sample mean ± SD = 18.46 ± 4.96
14

Figure 1.3. Relative δ13C in algae, C3 plants, and crayfish at four stations along the Jackrabbit Spring 

system. 
15

Figure 1.4. Relative δ13C in four Ash Meadows fishes at four stations along the Jackrabbit Spring system.
16

Table 1.1. Gut content, mean percent by volume, and standard deviation of Ash Meadows fishes and crayfish for 

all seasons at four stations. 

[Number of fish or crayfish with empty guts is shown in parentheses ()]

pupfish

Spring-Pool 700-m 1800-m 3600-m

Algae 92.7 ± 14.4 86.2 ± 26.7 - 22.2 ± 40.0

Vegetation 0.2 ± 0.9 0.8 ± 0.9 - 4.7 ± 11.7

Detritus 1.6 ± 6.3 2.9 ± 4.4 - 45.3 ± 46.5

Substrate 3.7 ± 10.9 5.1 ± 20.1 - 25.7 ± 43.6

Fish 0.6 ± 3.5 1.1 ± 4.1 - 0.1 ± 0.4

Aquatic Invertebrate 0.8 ± 4.6 4.4 ± 15.3 - 0.2 ± 1.0

Terrestial Invertebrate 0.2 ± 0.9 0.2 ± 0.9 - 1.7 ± 9.1

Unknown Invertebrate 0.3 ± 1.8 0.0 ± 0.0 - 0.0 ± 0.0

N = 32 (0) N = 28 (0) N = 30 (0)

speckled dace

Spring-Pool 700-m 1800-m 3600-m

Algae 10.7 ± 28.3 21.8 ± 35.4 16.2 ± 35.5 2.5 ± 9.2

Vegetation 1.9 ± 4.9 1.0 ± 3.2 0.0 ± 0.0 0.0 ± 0.0

Detritus 14.3 ± 37.8 25.2 ± 46.6 59.0 ± 37.5 37.9 ± 45.9

Substrate 1.4 ± 3.8 0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0

Fish 1.7 ± 4.5 1.0 ± 3.2 0.2 ± 0.8 7.7 ± 27.7

Aquatic Invertebrate 45.0 ± 49.2 13.3 ± 31.4 12.7 ± 29.8 49.4 ± 47.5

Terrestial Invertebrate 25.0 ± 43.3 27.1 ± 44.3 8.8 ± 19.2 2.5 ± 8.9

Unknown Invertebrate 0.0 ± 0.0 10.6 ± 31.5 3.2 ± 11.4 0.0 ± 0.0

N = 7 (5) N = 10 (3) N = 13 (0) N = 13 (0)

mosquitofish

Spring-Pool 700-m 1800-m 3600-m

Algae 17.5 ± 37.3 13.0 ± 24.4 3.4 ± 11.7 4.2 ± 20.4

Vegetation 0.0 ± 0.0 0.3 ± 1.8 5.7 ± 18.8 6.3 ± 17.0

Detritus 16.1 ± 28.1 33.1 ± 40.2 43.1 ± 42.3 27.8 ± 32.0

Substrate 0.0 ± 0.0 0.2 ± 0.9 0.0 ± 0.0 3.6 ± 17.8

Fish 2.3 ± 9.0 0.9 ± 4.9 0.0 ± 0.0 0.3 ± 1.4

Aquatic Invertebrate 23.1 ± 32.9 18.7 ± 28.4 11.0 ± 24.4 21.0 ± 28.4

Terrestial Invertebrate 37.0 ± 36.1 22.2 ± 29.6 26.1 ± 35.9 26.3 ± 29.6

Unknown Invertebrate 4.1 ± 15.2 11.5 ± 27.1 10.7 ± 21.3 10.6 ± 18.2

N = 20 (8) N = 30 (0) N = 22 (0) N = 24 (2)
17

Table 1.1. Gut content, mean percent by volume, and standard deviation of Ash Meadows fishes and crayfish for 

all seasons at four stations.—Continued

[Number of fish or crayfish with empty guts is shown in parentheses ()]

sailfin molly

Spring-Pool 700-m 1800-m 3600-m

Algae 84.1 ± 34.7 15.0 ± 24.0 - -

Vegetation 0.4 ± 2.1 0.0 ± 0.0 - -

Detritus 14.3 ± 34.5 54.5 ± 52.2 - -

Substrate 1.1 ± 5.2 30.5 ± 38.8 - -

Fish 0.0 ± 0.0 0.0 ± 0.0 - -

Aquatic Invertebrate 0.0 ± 0.0 0.0 ± 0.0 - -

Terrestial Invertebrate 0.0 ± 0.0 0.0 ± 0.0 - -

Unknown Invertebrate 0.0 ± 0.0 0.0 ± 0.0 - -

N = 23 (1) N = 11 (0)

crayfish

Spring-Pool 700-m 1800-m 3600-m

Algae 15.6 ± 32.3 11.1 ± 30.3 25.2 ± 42.1 0.0 ± 0.0

Vegetation 19.5 ± 26.7 4.1 ± 13.7 5.6 ± 16.7 30.0 ± 33.2

Detritus 55.0 ± 40.7 65.8 ± 43.5 47.4 ± 45.9 35.7 ± 47.6

Substrate 0.5 ± 0.2 4.3 ± 9.5 0.0 ± 0.0 14.1 ± 29.9

Fish 9.0 ± 21.1 7.0 ± 21.8 10.0 ± 30.0 20.0 ± 38.3

Aquatic Invertebrate 0.9 ± 3.4 0.2 ± 1.0 0.7 ± 1.7 0.1 ± 0.4

Terrestial Invertebrate 0.1 ± 0.4 4.3 ± 20.9 0.0 ± 0.0 0.0 ± 0.0

Unknown Invertebrate 0.0 ± 0.0 3.0 ± 14.6 11.1 ± 33.3 0.0 ± 0.0

N = 20 (1) N = 23 (4) N = 9 (8) N = 7 (15)
18

Table1.2. Analysis of variance of difference in δ13C between spring-pool and 700-

m in algae, C3 plants, fishes, and crayfish.

df F-ratio P-value

Plants

Algae 1(6) 6.610 0.042

C3 1(14) 5.607 *0.033

Fishes

pupfish 1(30) 6.939 0.013

dace 1(9) 19.081 0.002

mosquitofish 1(27) 2.240 0.146

sailfin molly 1(13) 9.043 0.010

Invertebrates

crayfish 1(28) 81.267 0.000

* Significant reduction in δ13C from Spring-pool station to 700-m station.

Table 1.3. Descriptive statistics for 13C in algae, aquatic invertebrates, terrestial invertebrates, 

fishes, and crayfish of all four stations and two seasons in the Jackrabbit Spring system.

Organism 13C SD 15N SD

Algae -28.9 3.2 5.7 1.3

Aquatic Invertebrates -28.2 4.0 6.6 1.9

Terrestial Invertebrates -22.6 3.8 6.6 2.7

pupfish -27.7 1.7 10.2 1.3

speckled dace -24.6 2.4 11.2 1.3

mosquitofish -23.4 1.6 10.2 1.6

sailfin molly -27.9 1.6 9.8 0.6

crayfish -24.8 1.7 8.0 1.1

C3 plants -27.7 1.6 3.1 2.8

C4 plants -14.2 0.7 2.1 3.3
19

Table 1.4. Mann-Whitney V test to determine if there is a significant difference in δ13C signal 

between potential prey items and potential prey item, and between fishes and crayfish and

potential prey.

Potential Prey Items

Organisms df χ2 P

Aquatic vs. Terrestial Invertebrates 1 11.84 0.001

Algae vs. Aquatic Invertebrates 1 *0.02 0.887

Algae vs. Terrestial Invertebrates 1 12.40 0.000

Fishes and Crayfish and Potential Food Items

pupfish vs. Aquatic Invertebrates 1 *0.92 0.337

speckled dace vs. Aquatic Invertebrates 1 9.35 0.002

mosquitofish vs. Aquatic Invertebrates 1 16.37 0.000

pupfish vs. Terrestial Invertebrates 1 34.46 0.000

speckled dace vs. Terrestial Invertebrates 1 *1.77 0.184

mosquitofish vs. Terrestial Invertebrates 1 *0.07 0.788

pupfish vs. Algae 1 *2.64 0.105

speckled dace vs. Algae 1 9.15 0.002

mosquitofish vs. Algae 1 15.43 0.000

sailfin molly vs. Algae 1 *0.44 0.505

crayfish vs. Algae 1 11.93 0.001

* Denotes no significant difference
20

Table 1.5. Calculated trophic position for four stations along the Jackrabbit Spring system.

Warm-Water Stations 

Spring-pool

δ

15N Producer base Primary consumer base

Species January July January July January July

pupfish 10.52 10.89 2.6 2.4 2.5 2.5

speckled dace 12.06 12.14 3.1 2.8 3.0 2.9

mosquitofish 10.36 10.36 2.6 2.2 2.5 2.4

sailfin molly 8.83 9.84 2.1 2.1 2.0 2.2

crayfish 8.79 9.14 2.1 1.9 2.0 2.0

700-m

δ

15N Producer base Primary consumer base

Species January July January July January July

pupfish 11.15 11.13 3.0 2.4 3.0 2.7

speckled dace 12.09 11.93 3.3 2.5 3.3 3.0

mosquitofish 11.16 11.76 3.0 2.5 3.0 2.9

sailfin molly 10.11 10.00 2.7 2.0 2.7 2.4

crayfish 7.82 8.64 2.0 1.6 2.0 2.0

Cool-Water Stations

1800-m

δ

15N Producer base Primary consumer base

Species January July January July January July

pupfish - - - - - -

speckled dace 11.27 11.28 - - 3.0 2.8

mosquitofish 10.91 10.55 - - 2.9 2.6

sailfin molly - 10.46 - - - -

crayfish 7.74 8.45 - - 2.0 2.0

3600-m

δ

15N Producer base Primary consumer base

Species January July January July January July

pupfish 9.04 8.00 - - 2.7 2.0

speckled dace 9.66 9.41 - - 2.9 2.6

mosquitofish 8.71 9.22 - - 2.6 2.6

sailfin molly - - - - - -

crayfish 6.65 7.32 - - 2.0 2.0
21

Relative Abundance and Distribution of Ash Meadows Pupfish and Ash 

Meadows Speckled Dace in the Upper One-Third of the Jackrabbit Spring 

System: Post-Fire and Restoration

By G. Gary Scoppettone, Mark Hereford, and Danielle Johnson, U.S. Geological Survey

Ash Meadows National Wildlife Refuge (AMNWR) in southern Nevada was established 

in 1984 to protect and perpetuate the highest occurrence of endemic species within the 

continental United States (Sada, 1990; Deacon and Williams, 1991). A particular area of concern 

was the protection of the Ash Meadows Native Fish assemblage that had been reduced in number 

due to habitat alteration and the introduction of non-native species. To improve the status of 

these fishes, AMNWR personnel have actively been restoring spring systems, including springpools and outflows; they also have eliminated non-native species from several spring systems 

(St. George, 1999; Weissenfluh, 2008, 2011). 

Restoration of the Jackrabbit Spring system was important because it was the stronghold 

for the Ash Meadows speckled dace (Rhinichthys osculus nevadensis) and supported a sizeable 

population of Ash Meadows pupfish (Cyprinodon nevadensis mionectes) (Scoppettone and 

others, 2011). Ash Meadows pupfish density declined in the Jackrabbit Spring outflow in the 

early 1990s (Scoppettone and others, 1995). Within that time period, the reaches of the outflow 

channel became increasingly clogged with Phragmites and Scirpus, and there was increased 

canopy formation in other reaches created by Tamarix and Phragmites. Reduction of sunlight, 

especially caused by Tamarix, has been demonstrated to reduce Ash Meadows’ native fish 

populations (Kennedy and others, 2006). Another vegetative change to the Jackrabbit Spring 

systems occurred in March 2005 when a fire swept through the upper reach and denuded the 

streambanks. The fire presented the opportunity to rehabilitate the stream outflow, and create 

habitat favoring native fishes over invasive species (Scoppettone and others, 2005). 

The purpose of this survey was to document native fish distribution and relative 

abundance in a rehabilitated spring system as baseline information for evaluating future changes.

Methods

We used masks and snorkels to count speckled dace and pupfish in the upper 2.25 km of 

the Jackrabbit Spring system, which included the restoration area. Counts were conducted in 

spring 2007 and spring 2010, and were compared to a count made in spring 2006 (post-fire and 

pre-stream rehabilitation). Snorkel counts began 2.25 km from the spring-head, with the 

snorkeler crawling upstream. When pupfish or speckled dace were sighted, the number was 

vocalized to a data recorder who used a GarminTM GPS to mark the location of each sighting. 

Results

In 2006, only 378 pupfish were counted along the study reach, compared to 655 in 2007 

and 1,066 in 2010 (figs. 2.1, 2.2, and 2.3). In 2006, more than 95 percent of the pupfish counted 

were in the spring-pool and upstream of the rehabilitation site (fig. 2.1). By spring 2010, almost 

25 percent of the pupfish counted were within the rehabilitation reach. In 2006, more than 1,067 

pupfish were counted even though dense vegetation kept us from snorkeling the entire 2.25 km 
22

reach. Most dace (n = 511) were sighted in the upper 800 m, and immediately upstream of the 

reach of stream to be rehabilitated (fig. 2.4). In 2007, there was a slight decrease in total number 

of dace (n = 971), and the greatest number (n = 440) was along the rehabilitated reach (fig. 2.5). 

However, by 2010 only 437 dace were counted, but more than 40 percent of these were along the 

rehabilitation site (fig. 2.6). 

Discussion

The March 2005 fire and subsequent rehabilitation of the Jackrabbit outflow appears to 

have had a positive effect on the Ash Meadows pupfish population, presumably by increasing 

foraging and reproductive opportunities and reducing invasive fishes and crayfish. The fire’s 

elimination of a localized, dense canopy of salt cedar not only facilitated stream rehabilitation 

but also exposed the system to increased sunlight, which presumably stimulated algal growth. 

Filamentous algae is the Amargosa pupfish’s primary food item (Naiman, 1975; Soltz and 

Naiman, 1978; Moyle, 2002). 

There was a substantial shift in the abundance and distribution of native fish pre- and 

post- rehabilitation of Jackrabbit Spring. Ash Meadows pupfish increased in number from 2006 

to 2010, while speckled dace numbers decreased. Habitat rehabilitation is suspected to have 

expanded pupfish reproductive habitat. Jackrabbit Spring is a fairly cool thermal spring with 

spring-pool temperature about 26.4o C. Minimum water temperature for Amargosa pupfish 

reproduction is between 25 and 26o C (Soltz and Naiman, 1978), and thermal springs generally 

cool as they flow downstream (Garside and Schilling, 1979). Reverting marsh-like habitat to a 

flowing stream sustained the minimum water temperature required for reproduction farther 

downstream; it also served to reduce habitat for sailfin molly, mosquitofish, and crayfish 

(Scoppettone and others, 2005). Our food-habitat analysis indicated that sailfin molly compete 

for algae, and because they have been documented to be cannibalistic (Meffe and Snelson, 

1989), they also may prey on larvae of other fishes, as found for shortfin molly (Pecilia 

Mexicana) (Scoppettone, 1993). Mosquitofish are voracious predators of fish larvae (Meffe, 

1985), and diet analysis indicated there is resource competition, especially with speckled dace. 

Speckled dace numbers were highest in 2006 when pupfish numbers were near their 

lowest, and were lowest in 2010 when pupfish numbers were highest. As a result of outflow 

manipulation, the stream maintains a warmer water temperature over a longer stream reach, 

which may lead to male pupfish dispersing over a wider range. Male pupfish establish 

reproductive territories, and aggressively chase other fishes from their respective territory 

including speckled dace (Lema and Nevitt, 2004). An alternate hypothesis as to why speckled 

dace numbers were highest several months post-fire is that they were the most successful species 

to pioneer the habitat after a major perturbation. Presumably, the fire reduced the number of 

crayfish, mosquitofish, and molly, thus improving habitat conditions for speckled dace, which 

are quite mobile and fairly abundant downstream of the stream reach impacted by the fire. 

The snorkel surveys of Jackrabbit Spring outflow were conducted before and after a 

period of system disturbance, fire followed by outflow manipulation. These perturbations 

influence fish community structure (Moyle and Baltz, 1985); thus, the relative abundance and 

distribution when the stream reaches climax condition may be substantially different from what 

we observed in our surveys. Perhaps the most influential component to aquatic community 

structure is the vegetative climax, which may have a profound effect on native fish distribution 

and abundance (Kennedy and others, 2006; Scoppettone and others, 2011). 
23

Acknowledgments

We thank the Ash Meadows National Wildlife Refuge for funding this study. We thank 

Tom Strekal (Bureau of Indian Affairs, retired) and Mark Fabes (U.S. Geological Survey) for 

their critical review.

References Cited

Deacon, J.E., and Williams, C.D., 1991, Ash Meadows and the legacy of the Devils Hole 

pupfish, in Minckley, W.L., and Deacon, J.E., eds,. Battle against extinction—Native fish 

management in the American West: Tucson, The University of Arizona Press, p. 69–87. 

Garside, L.I., and Schilling, J.H., 1979, Thermal Waters of Nevada: Reno, University of Nevada, 

Nevada Bureau of Mines and Geology, Mackay School of Mines, Bulletin 91. 

Kennedy, T.A., Finlay, J.C., and Hobbie, S.E., 2006, Eradication on invasive Tamarix 

ramosissima along a desert stream increases native fish density: Ecological Application, v. 15, 

p. 2,072–2,083. 

Lema, S.C., and Nevitt, G.A., 2004, Exogenous vasotocin alters aggression during agonistic 

exchanges in male Amargosa River pupfish (Cyprinodon nevadensis amargosae): Hormones 

and Behavior, v. 46, p. 628–637. 

Meffe, G.K., 1985, Predation and species replacement in American southwestern states—A case 

study: Southwestern Naturalist, v. 30, p. 173–187. 

Meffe, G.K., and Snelson, F.F., Jr., 1989, An Ecological Overview of Poeciliid Fishes, in Meffe, 

G.K., and Snelson, F.F., Jr., eds., Ecology and evolution of livebearing fishes (Poeciliidae): 

Englewood Cliffs, New Jersey, Prentice Hall, p. 13–31. 

Moyle, P.B., 2002, Inland fishes of California, revised and expanded: Berkeley, California, 

University of California Press, 517 p. 

Moyle, P.B., and Baltz, D.M., 1985, Microhabitat use by an assemblage of California stream 

fishes; Developing criteria for instream flow determination: Transactions of the American 

Fisheries Society, v. 114, p. 695–704. 

Naiman, R.J., 1975, Food habits of the Amargosa pupfish in a thermal stream: Transactions of 

the American Fisheries Society, v. 104, p. 536–538. 

Sada, D.W., 1990, Recovery plan for the endangered and threatened species of Ash Meadows, 

Nevada: Reno, Nevada, U.S. Fish and Wildlife Service. 

Scoppettone, G.G., 1993, Interactions between native and nonnative fishes of upper Muddy 

River, Nevada: Transactions of the American Fisheries Society, v. 122, p. 599–608. 

Scoppettone, G.G., Hereford, M.E., Rissler, P.H., Johnson, D.M., and Salgado, J.A., 2011, 

Relative abundance and distribution of fishes within an Established Area of Critical 

Environmental Concern, of the Amargosa Canyon and Willow Creek, Inyo and San 

Bernardino Counties, California: U.S. Geological Survey Open-File Report 2011-1061, 32 p. 

Scoppettone, G.G., Rissler, P.H., Gourley, C., and Martinez, C., 2005, Habitat restoration as a 

means of controlling non-native fish in a Mojave Desert Oasis: Restoration Ecology, v. 13, p. 

247–256. 

Scoppettone, G.G., Rissler, P.H., Byers, S., Shea, S., Nielsen, B., and Sjoberg, J., 1995, 

Information on the status and ecology of Ash Meadows Fishes and Ambrysus: National 

Biological Service, Reno Field Station, 111 p. 

Scoppettone, G.G., Rissler, P.H., Johnson, D., and Hereford, M., 2011, Relative abundance and 

distribution of fishes and crayfish at Ash Meadows National Wildlife Refuge, Nye County, 

Nevada, 2007–08: U.S. Geological Survey Open-File Report 2011-1017, 56 p. 
24

Soltz, K.L., and Naiman, R.J., 1978, The natural history of native fishes in the Death Valley 

system: Natural History Museum of Los Angeles County, California, Science Series, v. 30, 76 

p. 

St. George, D., 1999, Ash Meadows National Wildlife Refuge nonnative fishes eradication 

report 1998: Ash Meadows National Wildlife Refuge, Nevada, 4 p. 

Weissenfluh, D., 2008, Ash Meadows NWR aquatic exotic control activities summary 

accomplish report (FY 2008): U.S. Fish and Wildlife Service, 9 p. 

Weissenfluh, D., 2011, Eradication of sailfin molly (Poecilia latipinna) from the Longstreet 

Spring System, Ash Meadows National Wildlife Refuge, Nevada Report: U.S. Fish and 

Wildlife Service, 10 p. 
25

Figure 2.1. March 2006 distribution and relative abundance of Ash Meadow pupfish in the upper 2.25 km 

of the Jackrabbit Spring system. The stream image is divided into three equidistant strata, with number (n) 

of fish in each strata and in the spring-pool.
26

Figure 2.2. March 2007 distribution and relative abundance of Ash Meadow pupfish in the upper 2.25 km 

of the Jackrabbit Spring system. The stream image is divided into three equidistant strata, with number (n) 

of fish in each strata and in the spring-pool.
27

Figure 2.3. March 2010 distribution and relative abundance of Ash Meadow pupfish in the upper 2.25 km 

of the Jackrabbit Spring system. The stream image is divided into three equidistant strata with number (n) 

of fish in each strata and in the spring-pool.
28

Figure 2.4. March 2006 distribution and relative abundance of Ash Meadow speckled dace in the upper 

2.25 km of the Jackrabbit Spring system. The stream image is divided into three equidistant strata, with 

number (n) of fish in each strata and in the spring-pool.
29

Figure 2.5. March 2007 distribution and relative abundance of Ash Meadow speckled dace in the upper 

2.25 km of the Jackrabbit Spring system. The stream image is divided into three equidistant strata, with 

number (n) of fish in each strata and in the spring-pool.
30

Figure 2.6. March 2010 distribution and relative abundance of Ash Meadow speckled dace in the upper 

2.25 km of the Jackrabbit Spring system. The stream image is divided into three equidistant strata, with 

number (n) of fish in each strata and in the spring-pool.
31

Shallow Marsh Habitat Use by Amargosa Ash Meadows and Amargosa 

Warm Springs Pupfish

By Danielle M. Johnson, Mark E. Hereford, Peter H. Rissler, and G. Gary Scoppettone, U.S. Geological 

Survey

Ash Meadows National Wildlife Refuge (AMNWR) harbors two of the five extant 

subspecies of Amargosa pupfish (Miller, 1948), the Ash Meadows Amargosa pupfish 

(Cyprinodon nevadensis mionectes), and the Warm Springs Amargosa pupfish (Cyprinodon 

nevadensis pectoralis), both of which are federally listed as endangered (U.S. Fish and Wildlife 

Service, 1983). To improve the status of these fishes, the spring systems they inhabit are being 

restored. Ash Meadows spring systems typically include a spring-pool from which the spring 

emanates; a spring-brook discharging from the spring-pool, and marsh habitat at the springsystem terminus. Habitat conducive to Amargosa pupfish has been studied for spring-pools and 

spring-brooks (Scoppettone and others, 1995, 2005), while less information exists for marshes. 

A comprehensive survey suggested Amargosa pupfish were widespread throughout Ash 

Meadows (Scoppettone and others, 2011), but that their number was substantially greater in 

specific habitat types. In marsh habitat, the largest number of pupfish were captured in more 

open-water marshes with sparse vegetative growth, while substantially fewer captures of pupfish 

typically occurred in dense stands of cattails (Typha spp.). Determining which habitat is 

conducive to native fishes is important when planning and executing habitat restoration. In this 

study, we test pupfish abundance in terms of marsh habitat type. 

Marsh habitat occupies more than 50 percent of Ash Meadows surface water, and is 

primarily comprised of two vegetative communities (Typha or Juncus spp.). Our focus in this 

study was shallow water (less than 500 mm) marshes, because they are easier to control and 

manipulate than an expansive deep water marsh. The deep-water, marsh-like habitats of Ash 

Meadows also are occupied by non-native largemouth bass (Micropterus salmoides) and green 

sunfish (Lepomis cyanellus), predators incompatible to pupfish persistence. 

Background

Historically, Ash Meadows’ larger spring systems discharged into a common channel 

(Carson Slough) and thence the Amargosa River (Miller, 1948). Major alteration in the 1960s 

and 1970s associated with the development of Ash Meadows and its spring system for 

agriculture led to spring-system alteration and fragmentation (Pister, 1974; Soltz and Naiman, 

1978; Sada, 1990; Deacon and Williams, 1991). Water was conveyed in earthen and concretelined ditches, or pumped from the spring-source (Pister, 1974). 

Ash Meadows also has had a long history of non-native species introductions. Non-native 

western mosquitofish (Gambusia affinis), American bullfrog (Lethobates catesbeiana), and redswamp crayfish (Procambarus clarki) inhabited Ash Meadows spring systems when spring 

systems were sampled in the 1930s (Miller, 1948). An endeavor to rear tropical freshwater fishes 

commercially in an Ash Meadows spring system released several fish invaders into Ash 

Meadows aquatic habitats in the 1960s (Soltz and Naiman, 1978), but only the sailfin molly 

(Poecilia lapinna) successfully established itself during that early enterprise and still persisted at 

the time of this study.
32

Materials and Methods

Twenty sampling sites were established in marsh habitat throughout Ash Meadows; 10 

sites in Typha and 10 in Juncus marsh (fig. 3.1). Sites were sampled seasonally from July 2009 

through April 2010 using standard Gee minnow traps (3.3 mm mesh). At sites with water equal 

to or less than 120 mm in depth, we used fabricated traps, described by Scoppettone and others 

(2011), 90 mm in width and also having a 3.3 mm mesh. Traps were baited with dry dog food 

and fished overnight. Captured fish were identified by species and enumerated, and 10 

individuals were randomly selected for fork-length measurements. Vegetation and substrate 

surveys were conducted at each station. We used analysis of variance to test for a difference in 

number of pupfish captured between Typha and Juncus marshes. To satisfy conditions of 

normality and homogeneity, data were subjected to square root transformation. We also tested 

vegetation cover, water depth, and temperature between the two types of vegetative marshes. 

Vegetative cover was estimated by judging what percentage of the sample site was occupied by 

vegetation. Depth measurements were from water surface to marsh bottom, and water 

temperature was taken with a pocket thermometer. We used analysis of variance to test 

differences for each of the habitat conditions. Relative percent cover among sites was arc sin 

transformed, and depth was natural log transformed to improve normality and homogeneity. 

We used a single-season, multi-state occupancy model in Program Mark (White and 

Burnham, 1999; Hewitt and others, 2008) to determine if there were differences between pupfish 

densities in Typha and Juncus marshes. We counted the number of fish captured by species for 

each site. Pupfish captures were divided into three abundance categories as follows: absent (no 

pupfish captured); low density (1-9 pupfish captured); and high density (equal to or greater than 

10 pupfish captured). We also measured water depth, water temperature, dissolved oxygen, 

conductivity, pH, and estimated percentage of vegetation cover at each site. We ranked results 

from candidate models using Akaike’s information criterion adjusted for small sample size 

(AICc), and used model averaging to obtain parameter estimates (Burnham and Anderson, 2002). 

Results

Pupfish were captured from Juncus marshes in greater frequency than Typha marshes 

(fig. 3.2); there was a mean of 28 pupfish captured per site, while Typha had a mean of 4 pupfish 

captured per site, and this difference was significant (df = 1,18; F = 8.13; P = 0.011). Almost 

three times as many western mosquitofish, and twice the number of red swamp crayfish, were 

captured from Typha marshes than were captured from Juncus marshes; however, mosquitofish 

and crayfish captures outnumbered pupfish even in Juncus marshes. There was no significant 

difference in the number of crayfish (df = 1,18; F = 1.102; P = 0.308) or mosquitofish (df =1,18; 

F = 0.916 P = 0.351) between the two marsh types. The lowest captures for pupfish, 

mosquitofish, and crayfish were in winter (fig. A.1), but the greatest capture for pupfish was in 

spring, mosquitofish was in summer, and crayfish was in fall.

Mean cover at Typha marshes was 81 percent compared to 50 percent at Juncus marsh 

sites, and this difference was significant (df = 1,18; F = 7.242; p = 0.015). Mean water depth was 

193 mm at Typha sites compared to 89 mm at Juncus sites, and this difference was significant (df 

= 1,18; F = 8.419; P = 0.010). Mean water temperature was slightly higher (24.1o C) at Juncus 

sites than Typha (22.9o C), but this difference was not significant (df = 1,18; F = 1.451; p = 

0.244). 
33

The best model included both marsh type and crayfish density in estimating pupfish 

occupancy (ψ 1), but model weight (ω) was relatively low (0.22), indicating little separation 

from competing models. The marsh type was important in 12 of the top 17 models, with a 

combined model weight of 0.79 indicating that marsh type is important to pupfish distribution 

(table 3.1). Of the site covariates, only crayfish and mosquitofish density had weight, but these 

were low compared to marsh vegetative type.

Discussion

The Juncus marsh community supported a significantly greater density of Amargosa 

pupfish than the shallow Typha marsh community. Among Juncus marshes, there was 

significantly greater open-water habitat, allowing greater sunlight exposure, and presumably 

increased algae growth, which is important forage for Amargosa pupfish (Naiman, 1975). 

Shallow Typha marshes were densely vegetated, with the plants eight to ten times higher than 

Juncus, creating areas of 100 percent cover. Solar radiation in open waters presumably provides 

water temperatures warm enough for pupfish reproduction (Soltz and Niaman, 1978); however, 

our spot temperature measurements were insufficient to evaluate temperate suitability between 

the two marsh habitat types. Another possible advantage of the shallow open-water marsh is the 

occurrence of fewer invasive mosquitofish and crayfish, both of which have been proven to 

impact native fishes negatively (Courtenay and Meffe, 1989; Freeman and others, 2010; Larson 

and Olden, 2011). 

Red swamp crayfish that feed on a wide array of food stuffs (Whiteledge and Rabeni, 

1997; Kennedy and others, 2006) were captured with greater frequency in the Typha marsh 

community than the Juncus community. Western mosquitofish also were captured with greater 

frequency in the Typha community. Although these invasive species were captured in twice the 

numbers in Typha than Juncus, the difference was not significant and may have been due to our 

small sample size.

Again, we suspect that open water is an important habitat component affecting Amargosa 

pupfish abundance in shallow marsh habitat, and an important consideration in developing 

shallow marsh habitat on the AMNWR. Water availability typically is the primary driving force 

in plant distribution and abundance, and might be an important focus when developing shallow 

marsh habitat. For example, Juncus generally has a fairly extensive root system, and can thrive in 

areas of high groundwater (Mata-González and others, 2012). When surface water is the primary 

water source, we have observed water shifting when Juncus becomes dense enough to deflect 

streamflow (Point of Rocks Marsh, and South Scruggs Marsh); this dynamic is especially true on 

flat terrain. Thus, selecting flat over entrenched terrain for the development of shallow marsh 

habitat may enhance opportunity for greater open-water habitat by allowing the marsh to shift as 

emergent vegetation thickens. This dynamic also has a secondary effect of restricting the 

establishment of Typha, which thrives in permanently boggy habitat. 
34

Rehabilitating marsh habitat most conducive to Amargosa pupfish probably is most 

important in low-water-volume systems offering little to no spring-pool habitat, and only modest 

pupfish habitat availability in the spring-brook. More open-water marsh habitat may offer a 

substantial portion of pupfish habitat in such low-water-volume systems as occur in the Warm 

Springs complex, and Soda and Cold Springs. Marsh habitat probably is important habitat in Ash 

Meadows’ more cool-water springs (Bradford 1, Bradford 2, and Cold Spring). Because water 

discharged from these springs at temperatures well below the 26oC required for pupfish 

reproduction, open marsh habitat with water temperatures influenced by ambient air temperature 

and solar radiation may become important reproductive habitat in these cool-water systems.

References Cited

Burnham, K.P., and Anderson, D.R., 2002, Model selection and multi-model inference—

Practical information-theoretic approach: New York, Springer Science Business Media, 514 p. 

Courtenay, W.R., Jr. and Meffe, G.K., 1989, Small fishes in strange places—A review of 

introduced poeciliids, in Meffe, G.K., and Snelson, Jr., F.F., eds., Ecology and evolution of 

livebearing fishes (Poeciliidae): Englewood Cliffs, New Jersey, Prentice Hall, p. 319–331 

Deacon, J.E., and Williams, C.D., 1991, Ash Meadows and the legacy of Devils Hole pupfish, in

Minckley, W.L., and Deacon, J.E., eds., Battle against extinction—Native fish management in 

the American West: Tucson, The University of Arizona Press, p. 69–87. 

Freeman, M.A., Turnbull, J.F., Yeomans, W.E., and Bean, C.W., 2010, Prospects for 

management strategies of invasive crayfish populations with an emphasis on biological 

control, Aquatic Conservation: Marine and Freshwater Ecosystems, v. 20, p. 211–223. 

Hewitt, D.A., Fabrizio, M.C., Hewitt, A.H., and Ellis, J.K., 2008, Habitat selection by juvenile 

striped bass in lower Chesapeake Bay tributaries—Inferences from occupancy models: 

Gloucester Point, Virginia, Virginia Institute of Marine Science, Department of Fisheries 

Science, Final Report for NOAA Award NA04NMF4570375. 

Kennedy, T.A., Finlay, J.C., and Hobbie, S.E., 2006, Eradication of invasive Tamarix 

ramosissima along a desert stream increases native fish density: Ecological Application v. 15, 

p. 2,072–2,083. 

Larson, E.R., and Olden, J.D., 2011, The state of crayfish in the Pacific Northwest: Fisheries, v. 

36, no. 2, v. 61–73. 

Mata-González, R., McLendon, T., Marin, D.W., Trilica, M.J., and Pearce, R.A., 2012, 

Vegetation as affected by groundwater depth and microtopography in a shallow aquifer area of 

the Great Basin: Ecohydrology, v. 5, p. 54–63. 

Miller, R.R., 1948, The cyprinodont fishes of the Death Valley system of eastern California and 

southeastern California and southeastern Nevada: University of Michigan, Miscellaneous 

publications of the Museum of Zoology, v. 68, p. 1–155. 

Naiman, R.J., 1975, Food habits of the Amargosa pupfish in a thermal stream: Transaction of the 

American Fisheries Society, v. 104, p. 536–538. 

Pister, E.P., 1974, Desert fishes and their habitats: Transactions of the American Fisheries 

Society, v. 103, p. 531–540. 

Sada, D.W., 1990, Recovery plan for the endangered and threatened species of Ash Meadows, 

Nevada: Reno, Nevada, U.S. Fish and Wildlife Service. 

Scoppettone, G.G., Rissler, P.H., Byers, S., Shea, S., Nielsen, B., and Sjöberg, J., 1995, 

Information on the status and ecology of Ash Meadows Fishes and Ambrysus: National 

Biological Service, Reno Field Station, 111 p. 
35

Scoppettone, G.G., Rissler, P.H., Gourley, C., and Martinez, C., 2005, Habitat restoration as a 

means of controlling non-native fish in a Mojave Desert Oasis, Restoration Ecology, v. 13, 

p. 247-256. 

Scoppettone, G.G., Rissler, P.H., Johnson, D., and Hereford, M., 2011, Relative abundance and 

distribution of fishes and crayfish at Ash Meadows National Wildlife Refuge, Nye 

County, Nevada, 2007-08: U.S. Geological Survey Open-File Report 2011-1017, 56 p. 

Soltz, K.L. and Naiman, R.J., 1978, The natural history of native fishes in the Death Valley 

system: Natural History Museum of Los Angeles County, California, Science Series, 76 p. 

U.S. Fish and Wildlife Service, 1983, Endangered and threatened wildlife and plants 

determination of endangered status and critical habitats for two fish species in Ash 

Meadows, Nevada, Federal Register, v. 48, p. 40178-40186. 

White, G.C. and Burnham, K.P., 1999, Program MARK: survival estimation from populations of 

marked animals, Bird Study 46 Supplement, p. 120-138. 

Whiteledge, G.W. and Rabeni, C.F., 1997, Energy sources and ecological role of crayfish in an 

Ozark stream: insights from stable isotopes and gut analysis, Canadian Journal of Aquatic 

Sciences, v. 54, p. 2555-2563. 
36

Figure 3.1. Study sites at the Northern and Southern spring systems at Ash Meadows National Wildlife 

Refuge.
37

Figure 3.1. Study sites at the Northern and Southern spring systems at Ash Meadows National Wildlife 

Refuge.—Continued 
38

 

 

 

 

 

 Count

 

 

 

 

 

 

 

 

 

 

 

Species

 

 

37

848

520

281

372

290

0 

100

200

300

400

500

600

700

800

900

Pupfish Mosquitofish Crayfish

Typha

Juncus

Figure 3.2. Total number of Amargosa pupfish, western mosquitofish, and red swamp crayfish captured 

from Typha and Juncus marshes in four seasons, 2009 and 2010.
39

Table 3.1. Values of the Akaike's information criterion corrected for small sample size used to select the 

best model from 53 candidate models of marsh occupancy during 2009-10 (the top 17 models are shown). 

A period (.) indicates that the parameter is constant over that attribute; x denotes full model, + denotes an 

additive model. The best model (lowest AICc value) is presented first; ΔAICc is the difference between 

AICc values of the individual models and that of the best model. Akaike weights (ω) provide a measure of 

each model's relative weight or likelihood of being the best model in the data set given. Number of 

parameters (K) is the total number that is theoretically estimable by the model.

Modela AICc ΔAICc ω K

ѱ1(marsh x CFden) ѱ2(.) p1(.) p2(.) δ(season) 135.82 0.00 0.22 7

ѱ1(marsh) ѱ2(.) p1(.) p2(.) δ(season) 136.19 0.37 0.18 7

ѱ1(.) ѱ2(.) p1(.) p2(.) δ(season) 137.25 1.44 0.11 6

ѱ1(marsh x CFden) ѱ2(.) p1(.) p2(.) δ(winter) 137.50 1.68 0.09 7

ѱ1(marsh) ѱ2(.) p1(.) p2(.) δ(winter) 137.88 2.06 0.08 7

ѱ1(marsh x Gamden) ѱ2(.) p1(.) p2(.) δ(season) 138.19 2.38 0.07 7

ѱ1(marsh x CFden) ѱ2(.) p1(.) p2(.) δ(.) 138.74 2.92 0.05 6

ѱ1(marsh) ѱ2(.) p1(.) p2(.) δ(.) 139.11 3.29 0.04 6

ѱ1(marsh x Gamden) ѱ2(.) p1(.) p2(.) δ(winter) 139.87 4.06 0.03 7

ѱ1(.) ѱ2(.) p1(.) p2(.) δ(.) 140.87 5.05 0.02 5

ѱ1(Gamden) ѱ2(.) p1(.) p2(.) δ(season) 141.36 5.54 0.01 7

ѱ1(.) ѱ2(.) p1(marsh) p2(.) δ(marsh) 141.79 5.97 0.01 7

ѱ1(marsh) ѱ2(.) p1(.) p2(.) δ(marsh + season) 141.89 6.07 0.01 8

ѱ1(CFden) ѱ2(.) p1(.) p2(.) δ(season) 141.93 6.11 0.01 7

ѱ1(marsh) ѱ2(marsh) p1(.) p2(.) δ(marsh) 142.39 6.57 0.01 7

ѱ1(marsh x CFden) ѱ2(.) p1(winter) p2(.) δ(winter) 142.48 6.66 0.01 8

ѱ1(marsh) ѱ2(.) p1(.) p2(.) δ(marsh) 142.56 6.74 0.01 7

a model variables represent ѱ1 = probability that a site is occupied regardless of density; ѱ2 = probability that a site 

has high density given that the site is occupied; p1 = probability that occupancy is detected for a site for a given 

time period given that it is actually occupied; p2 = probability that occupancy is detected for a site for a given time 

period given that it is actually occupied with high density; δ = probability that evidence of high density is found, 

given detection of occupancy at the site at a given time period; site covariates represent marsh = juncus or typha 

CFden = crayfish density; Gamden = mosquitofish density; season = summer, fall, winter, spring; winter = winter 

is separated from the other seasons.
40

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41

Population Dynamics of Amargosa Ash Meadows Pupfish in Five Springs, 

Ash Meadows, Nye County Nevada

By G. Gary Scoppettone, Peter H. Rissler, Mark E. Hereford, and Danielle M. Johnson, U.S. Geological 

Survey

Management of any resource requires inventory and monitoring (LaRoe and others, 

1995), and effective monitoring requires an understanding of species’ seasonal population trends. 

Population size can be influenced by seasonal changes in biotic and abiotic conditions (Williams 

and others, 2002; Riggs and Deacon, 2003). In thermal-spring systems, such as Ash Meadows, 

many abiotic conditions (temperature, dissolved oxygen, flow, pH, and conductivity) remain 

fairly constant year round. Day length is an abiotic factor that does change, which in turn affects 

primary productivity (Naiman, 1976). The seasonal shift in pupfish population number as a result 

of primary productivity changes should be a consideration when evaluating relative population 

health. 

Previous population estimates were based on spring-pool samples and conducted at 

various times of the year (Threloff, 1990; St. George, 1999). The spring-pools were sampled 

open systems with pupfish free to enter or leave the spring-pool via its outflow. Most Ash 

Meadows spring systems flow into marsh-like habitat, making it difficult to conduct seasonal 

population counts. The only pupfish population in Ash Meadows with numerical estimates of the 

entire population is Devils Hole pupfish (Cyprinodon diabolis) (Andersen and Deacon, 2001); 

because its habitat is sufficiently minute to facilitate annual and seasonal counts of the entire 

population. However, because it is a cavernous limnocrene and light-limited for much of the 

year, there have been wide swings in primary productivity and fish population numbers (Wilson 

and Blinn, 2007). 

The Five Springs system is a complex that harbors Amargosa Ash Meadows pupfish 

(Cyprinodon nevadensis mionectes) and is sufficiently diminutive and easy to sample as a closed

system. Its exposure to sunlight is more representative of Ash Meadow limnocrenes, and thus 

may serve as a model for population fluctuations in Ash Meadows spring systems. 

Description of Area 

Five Springs is located in Ash Meadows’ northern springs, and is comprised of a series of 

small springs and seeps (Dudley and Larson, 1976). Situated just east of Longstreet Spring, Five 

Springs had a cumulative discharge of 617 L/min when measured by Dudley and Larson (1976). 

Situated at an elevation of 2,350 m, Five Springs complex is the highest of Ash Meadows 

springs. During this study, the discharges of the spring complex flowed into a single channel, and 

dissipated less than 140 m downstream of the highest spring. The spring complex is inhabited by 

two native spring snails (Gastropoda: Hydrobiidae) (Hershler and Sada, 1987) and the invasive 

red-rim melania (Melonoides tuberculata), red swamp crayfish (Procambarus clarki), and 

western mosquitofish (Gambusia affinis) (Scoppettone and others, 2011). 
42

Materials and Methods

We estimated population numbers for adult pupfish (equal to or greater than 25 mm total 

length - TL) bimonthly in the Five Springs system from October 2009 to October 2010. We used 

modified minnow traps described by Scoppettone and others (2011) and set 38 traps in 37 

locations; two standard Gee minnow traps with 3.3 mm mesh were set at Spring 6 because it was 

a large pool and harbored the majority of Five Springs pupfish. Baited with dry dog food, the 

minnow traps were spaced every 10 m throughout the Five Springs system. All pupfish were 

within 5 m of a baited minnow trap, and all were considered to have an equal capture probability. 

To reduce stress on captured fish, minnow traps were only set for 2 to 4 hours. Pupfish equal to 

or greater than 25 mm TL were marked by clipping the caudal fin. All fish were then released 

halfway between capture sites. From 1 to 3 days later, minnow traps were set in the same 

location and the number of unmarked and the marked adult fish was counted. We estimated the 

adult pupfish population using the Lincoln-Petersen estimator adjusted for sample size bias 

(Williams and others, 2002). We calculated 95 percent asymptotic confidence intervals as per 

Seber (1982). For length frequency analysis, we measured all pupfish captured on the first day of 

sampling. All fish were measured to the nearest 1 mm, and then grouped into 3 mm increments. 

At least one spring was detected to be quite warm so we set four HOBO® thermographs at four 

selected sites to determine if pupfish distribution might be affected by water temperature. 

Results

Population Dynamics

Population estimates of adult pupfish ranged from 143 (April 2010) to 307 (October 

2010) (fig. 4.1). Generally, population numbers were lower in winter and spring and higher in 

summer and fall. The number of adult pupfish captured shows relatively small changes between 

sampling times and may indicate that the Five Springs pupfish population is actually more stable 

than what is shown with the population estimates (fig. 4.1). We did not estimate population size 

of mosquitofish and crayfish, but compared capture trends with that of pupfish. Similar to 

pupfish, more mosquitofish were captured in the fall, but substantially less were captured in the 

spring. Crayfish captures were lowest in the fall and greatest in spring and summer. 

Pupfish were captured at 24 of 37 stations during sampling (fig. 4.2). Fish were absent 

from the upper seven sampling stations of Spring 5 (fig. 4.2), which probably was due to warmer 

temperatures; water temperature ranged from 32.5 to 33.9o C (x̅ = 32.9o C) 20 m downstream of 

the spring source. A HOBO® that was placed 120 m downstream of the spring sources had much 

greater daily and seasonal fluctuation (fig. 4.3). Captures at lower stations upstream of Spring 6 

(fig. 4.2) occurred in the cooler months (November–April) when maximum water temperatures 

remained lower than 30o C. The greatest capture rate occurred at the large pool at Spring 6, 

accounting for 57 percent of the pupfish captured from the Five Springs system; seasonal and 

daily shift in temperature was greater in Spring 6 outflow than it was in the Spring 5 outflow. 

Spring 3 (fig. 4.2) was actually a well and not accessible to pupfish, while other downstream 

locations not directly on the Spring 5 discharge were very shallow high-gradient reaches that 

were difficult to trap effectively. Distribution of mosquitofish and crayfish was more restricted 

than pupfish; mosquitofish were captured at nine stations and crayfish at seven (figs. 4.4, 4.5). 
43

The greatest mosquitofish capture rate was from traps set at a pool on Spring 6 accounting for 77 

percent of the captures. One individual was captured at the source, where water temperature was 

nearly 33o C. The greatest capture success for crayfish was at the origin of Spring 2 (4.5) 

accounting for 43 percent of captures.

Mean total length of pupfish captured at Five Springs ranged from 26 to 29 mm TL, with 

August 2010 and October 2010 having the smallest mean size (fig. 4.6). Length frequencies 

suggest that reproduction may occur from late summer (August) through the winter (February), 

with little to no reproduction occurring in spring and early summer (April, June). The smallest 

pupfish (9–12 mm TL) were captured in December, February, August, and October.

Discussion

Five Springs pupfish demonstrated a similar population trend as the Devils Hole pupfish, 

with peak numbers occurring in fall and lowest numbers occurring in spring (Andersen and 

Deacon, 2001; Riggs and Deacon, 2003). Mosquitofish also displayed a similar spring trend, but 

with a wider swing from spring to fall than Ash Meadows pupfish and more similar to Devils 

Hole pupfish. Fluctuations in Amargosa pupfish numbers from fall to spring have been linked to 

day length and associated primary productivity (Naiman, 1976). Dramatic shifts in Devils Hole 

pupfish numbers have been linked to severe limitation in primary productivity due to light 

limitation within its cavernous environment. Mosquitofish in Five Springs probably are not as 

food limited as pupfish in Devils Hole, but like Devils Hole pupfish their life span is only about 

1 year (Swanson and others, 1996; Moyle, 2002); Ash Meadows pupfish, however, can live for 

several years (Scoppettone and others, 1995) so a winter decline may not have a profound effect 

on the population. Crayfish numbers did not follow the trend of greatest numbers of individuals 

captured in fall and least in spring. This is not totally unexpected because their catholic diet may 

allow them to exploit a greater variety of carbon sources than pupfish or mosquitofish (Kennedy 

and others, 2006). Crayfish also are harder to capture when they burrow (Penn, 1943), but when 

burrowing may occur in Ash Meadows has not been studied. 

Consistent with the low discharge (less than 3.0 L/sec) springs situated higher (greater 

than 2,320 m) in Ash Meadows (Warm Springs complex and Point of Rocks complex), 

contributors to the Five Springs complex are quite warm, and these warm temperatures appear to 

influence pupfish distribution. The greatest concentration of pupfish occurred in the Spring 6 

pool. Water temperature in the pool generally was favorable for pupfish, and the pool was 

sufficiently large that it probably offered a variety of temperate micro-climates even during the 

very warm summer (Nielsen and others, 1994). Although our HOBO® reported very warm 

summer temperatures, we suspect there were localized areas of hospitable temperature, sufficient 

to permit summertime reproduction.

Mosquitofish and crayfish negatively impact native fish populations (Swanson and 

others, 1996; Whitledge and Rabeni, 1997), but to what degree the pupfish population is 

suppressed by these species in Five Springs is unknown. However, the Five Springs complex is 

sufficiently restricted that it may be feasible to eradicate these two invaders from the system. 

Once these species are eliminated, data from this study can be used to gauge the effect that their 

removal has on the pupfish population. Five Springs is scientifically interesting because it offers 

low-water-volume thermal-springs habitat qualities quite similar to the Warm Springs complex. 

Cursory morphological inspection of Five Spring pupfish suggests some degree of 

convergent evolution with Warm Springs pupfish (Cyprinodon nevadensis pectoralis). Similar to 

Warm Springs pupfish (Miller, 1948), the pelvic fins of Five Springs pupfish appear to be 
44

vestigial. The isolated Five Spring’s population of Amargosa Ash Meadows pupfish requires 

protection and management to ensure its persistence. 

Acknowledgments

We thank Ash Meadows National Wildlife Refuge for funding this project. We also thank 

Tom Strekal (Bureau of Indian Affairs, retired) and Mark Fabes (U.S. Geological Survey) for 

their critical review. 

References Cited

Andersen, M.E., and Deacon, J.E., 2001, Population size of Devils Hole pupfish (Cyprinodon 

diabolis) correlates with water level: Copeia, p. 224–228. 

Dudley, W.W., and Larson, J.D., 1976, Effect of irrigation pumping on desert pupfish habitat in 

Ash Meadows, Nye County, Nevada: U.S. Geological Survey Professional Paper 927, 52 p. 

Hershler, R., and Sada, D.W., 1987, Springsnails (Gastropoda: Hydrobiidae) of Ash Meadows, 

Amargosa Basin, California-Nevada, Proceedings: Proceedings of the Biological Society of 

Washington, v. 100, p. 776–843. 

Kennedy, T.A., Finlay, J.C., and Hobbie, S.E., 2006, Eradication on invasive Tamarix 

ramosissima along a desert stream increases native fish density: Ecological Application, v. 15, 

p. 2,072–2,083. 

LaRoe, E.T., Farris, G.S., Puckett, C.E., Doran, P.D., and Mac, M.J., 1995, Our living 

resources—A report to the Nation on the distribution, abundance, and health of U.S. plants, 

animals, and ecosystems: U.S. Department of the Interior, National Biological Service, 

Washington, D.C., 530 p. 

Miller, R.R., 1948, The cyprinodont fishes of the Death Valley System of eastern California and 

Southwestern Nevada: University of Michigan, Miscellaneous Publications Museum of 

Zoology, v. 68, 155 p. 

Moyle, P.B., 2002, Inland fishes of California: Barkeley, University of California Press, 502 p. 

Naiman, R. J., 1976, Productivity of a herbivorous pupfish population (Cyrinodon nevadensis) in 

a warm water desert stream: Journal of Fish Biology, v. 9, p. 125–137. 

Nielsen, J.L., Lisle, T.E., and Ozarki, V., 1994, Thermal stratified pools and their use by 

steelhead in Northern California Streams: Transactions of the American Fisheries Society, v. 

123, p. 613–626. 

Penn, G.H., Jr., 1943, A Study of the life history of the Louisiana red-crawfish, Cambarus clarkii

Girard: Ecology, v. 24, p. 1–18. 

Riggs, A.C., and Deacon, J.E., 2003, Connectivity in desert aquatic ecosystems—The Devils 

Hole story, in Sada, D.W., and Sharpe, S.E., eds., Spring-fed wetlands—Important scientific 

and cultural resources of the Intermountain Region, Las Vegas, Nevada, May 7–9, 2002, 

Proceedings: DHS Publication No. 41210, p. 1–38, accessed December 31, 2012, at 

http://www.wetlands.dri.edu. 

Scoppettone, G.G., Rissler, P.H., Byers, S., Shea, S., Nielsen, B., and Sjöberg, J., 1995, 

Information on the status and ecology of Ash Meadows Fishes and Ambrysus: National 

Biological Service, Reno Field Station, 111 p. 

Scoppettone, G.G., Rissler, P., Johnson, D., and Hereford, M., 2011, Relative abundance and 

distribution of fishes and crayfish at Ash Meadows National Wildlife Refuge, Nye County, 

Nevada, 2007-08: U.S. Geological Survey Open-File Report 2011-1017, 56 p. 
45

Seber, G.A.F., 1982, The estimation of animal abundance and related parameters: New York, 

New York, MacMillan, 506 p. 

St. George, D., 1999, Ash Meadows National Wildlife Refuge 1998 native fish survey—Ash 

Meadows National Wildlife Refuge: U.S. Fish and Wildlife Service, 7 p. 

Swanson, C., Cech, J.J., Jr., and Piedrahita, R.H., 1996, Mosquitofish biology, culture and use in 

mosquito control: Mosquito and Vector Control Association of California and The University 

of California Mosquito Research Program, 88 p. 

Threloff, D., 1990, Ash Meadows biannual fish count summary—Ash Meadows National 

Wildlife Refuge: U.S. Fish and Wildlife Service, 11 p. 

 Whitledge, G.W., and Rabeni, C.F., 1997, Energy sources and ecological role of crayfishes in an 

Ozaek stream—Insights from stable isotopes and gut analysis: Canadian Journal of Aquatic 

Sciences, v. 54, p. 2,555–2,563. 

 Williams, B.K., J.D., Nichols, and Conroy, M.J., 2002, Analysis and management of animal 

populations—Modeling, estimation and decision making: San Diego, California, Academic 

Press, 817 p. 

Wilson, K.P., and Blinn, D.W., 2007, Food Web structure energetic, and importance of 

allochthonous carbon in a desert cavernous limnocrene: Devils Hole, Nevada, v. 67, p. 185–

198. 
46

Month

Oct Dec Feb Apr Jun Aug Oct 

Population Size

0

50

100

150

200

250

300

350

400

203

(157-250)

159

(140-178)

171

(161-180)

143

(134-152)

215

(178-253)

192

(157-226)

307

(148-467)

124 129

159

132

146

131 136

Figure 4.1. Bimonthly population estimate (bar graph) and confidence interval of Ash Meadows pupfish in 

Five Springs from October 2009 to October 2010. The line graph is bimonthly capture of unmarked pupfish. 

Only pupfish equal to or greater than 26 mm total length were used for bimonthly population estimate and 

total unmarked pupfish captured. 
47

Figure 4.2. Ash Meadows pupfish distribution and relative abundance within the Five Springs system; 

captures are a composite of bimonthly sampling from October 2009 to October 2010. The four stations with 

a recording thermograph (HOBO®) are represented by a square symbol around the circular station.
48

Figure 4.3. Daily HOBO® temperature record at four locations within the Five Springs system.
49

Figure 4.4. Western mosquitofish distribution and relative abundance within the Five Springs system; 

captures are a composite of bimonthly sampling from October 2009 to October 2010. The four stations with 

a recording thermograph (HOBO®) are represented by a square symbol round the circular station.
50

Figure 4.5. Red swamp crayfish distribution and relative abundance within the Five Springs system; 

captures are a composite of bimonthly sampling from October 2009 to October 2010. The four stations with 

a recording thermograph (HOBO®) are represented by a square symbol round the circular station.
51

Figure 4.6. Bimonthly length-frequency distribution of Ash Meadows pupfish captured from Five Springs 

from October 2009 to October 2010.
52

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53

Appendix 

Table A.1. Seasonal food items consumed by Ash Meadows fishes and crayfish at four stations along Jackrabbit Spring 

system in 2009. In parenthesis is number of fish or crayfish with empty guts.

Spring 2009

Spring-pool

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish 93.6 2.5 0.0 0.0 0.0 3.3 0.6 0.0 8 (0)

speckled dace 0.0 0.0 0.0 5.0 0.0 45.0 50.0 0.0 2 (2)

mosquitofish 0.0 2.5 0.0 0.0 5.0 28.8 53.5 10.3 8 (0)

sailfin molly 60.0 38.3 1.7 0.0 0.0 0.0 0.0 0.0 6 (1)

crayfish 0.0 79.0 20.0 1.0 0.0 0.0 0.0 0.0 1(1)

700-m

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish 96.3 1.3 0.0 0.0 0.0 2.5 0.0 0.0 8 (0)

speckled dace 0.0 0.0 0.0 0.0 0.0 7.7 57.0 35.3 3 (1)

mosquitofish 6.3 8.4 0.0 0.0 0.0 34.1 22.8 28.5 8 (0)

sailfin molly 25.0 50.0 0.0 25.0 0.0 0.0 0.0 0.0 2 (0)

crayfish 20.0 40.0 0.0 6.0 0.0 0.0 20.0 14.0 5 (4)

1800-m

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish - - - - - - - - 0 (0)

speckled dace 5.0 79.8 0.0 0.0 0.8 0.0 14.5 0.0 4 (0)

mosquitofish 0.0 45.3 0.0 0.0 0.0 7.3 47.5 0.0 4 (0)

sailfin molly 0.0 50.0 0.0 50.0 0.0 0.0 0.0 0.0 1 (0)

crayfish 0.0 50.0 16.7 0.0 0.0 0.0 0.0 33.3 3 (3)

3600-m

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish 10.0 71.0 12.6 0.0 0.0 0.1 6.3 0.0 8 (0)

speckled dace 0.0 2.5 0.0 0.0 0.0 97.5 0.0 0.0 4 (0)

mosquitofish 0.0 9.4 0.0 0.0 0.0 18.1 61.9 10.6 8 (0)

sailfin molly - - - - - - - 0 (0)

crayfish 0.0 0.0 0.0 0.0 100.0 0.0 0.0 0.0 1 (7)

 
54

Table A.1. Seasonal food items consumed by Ash Meadows fishes and crayfish at four stations along Jackrabbit Spring 

system in 2009. In parenthesis is number of fish or crayfish with empty guts.—Continued

Summer 2009

Spring-pool

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish 94.4 3.8 0.6 1.3 0.0 0.0 0.0 0.0 8 (0)

speckled dace 37.5 0.0 6.5 0.0 6.0 12.5 37.5 0.0 2 (1)

mosquitofish 33.3 37.0 0.0 0.0 2.0 9.0 18.7 0.0 3 (1)

sailfin molly 100.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8 (0)

crayfish 4.5 73.1 18.8 0.0 3.4 0.3 0.0 0.0 8 (0)

700-m

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish 96.4 0.0 0.0 0.3 2.5 0.9 0.0 0.0 8 (0)

speckled dace 19.0 31.0 0.0 0.0 0.0 0.0 50.0 0.0 2 (1)

mosquitofish 10.1 43.1 1.3 0.0 3.5 11.1 16.3 14.6 8 (0)

sailfin molly 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0 3 (0)

crayfish 0.0 64.1 11.9 5.0 19.0 0.0 0.0 0.0 8 (0)

1800-m

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish - - - - - - - 0 (0)

speckled dace 33.3 19.7 0.0 0.0 0.0 33.3 0.0 13.7 3 (0)

mosquitofish 0.0 32.4 0.0 0.0 0.0 2.0 36.9 28.7 7 (0)

sailfin molly 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0 3 (0)

crayfish 33.0 67.0 0.0 0.0 0.0 0.0 0.0 0.0 1 (1)

tadpole 0.0 87.5 0.0 12.5 0.0 0.0 0.0 0.0 2 (0)

3600-m

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish 65.2 33.7 0.0 0.3 0.8 0.0 0.0 6 (0)

speckled dace 0.0 66.7 0.0 33.3 0.0 0.0 0.0 3 (0)

mosquitofish 0.0 55.1 3.8 0.0 5.6 16.8 18.8 8 (0)

sailfin molly - - - - - - - 0 (0)

crayfish 0.0 100.0 0.0 0.0 0.0 0.0 0.0 2 (2)

 
55

Table A.1. Seasonal food items consumed by Ash Meadows fishes and crayfish at four stations along Jackrabbit Spring 

system in 2009. In parenthesis is number of fish or crayfish with empty guts.—Continued

Fall 2009

Spring-pool

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish 82.7 0.0 0.0 13.5 2.5 0.0 0.0 1.3 8 (0)

speckled dace 0.0 50.0 0.0 0.0 0.0 50.0 0.0 0.0 2 (1)

mosquitofish 40.0 26.0 0.0 0.0 0.0 30.0 4.0 0.0 5 (3)

sailfin molly 95.8 0.0 0.0 4.2 0.0 0.0 0.0 0.0 6 (0)

crayfish 13.0 29.2 24.0 0.0 30.4 3.0 0.4 0.0 5 (0)

700-m

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish 57.0 0.0 1.3 35.3 2.5 4.0 0.0 0.0 4 (0)

speckled dace 26.7 33.3 3.3 0.0 3.3 33.3 0.0 0.0 3 (0)

mosquitofish 26.7 16.7 0.0 0.8 0.0 19.2 36.7 0.0 6 (0)

sailfin molly 28.8 0.0 0.0 71.3 0.0 0.0 0.0 0.0 4 (0)

crayfish 77.5 0.0 0.0 15.0 5.0 3.5 0.0 0.0 2 (0)

1800-m

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish - - - - - - - 0 (0)

speckled dace 0.0 59.7 0.0 0.0 0.0 21.7 18.7 0.0 3 (0)

mosquitofish 0.0 40.0 0.0 0.0 0.0 29.5 13.0 17.5 2 (0)

sailfin molly - - - - - - - 0 (0)

crayfish 0.0 100.0 0.0 0.0 0.0 0.0 0.0 0.0 1 (0)

3600-m

Species Algae Detritus Plant Substrate Fish Aquatic 

Invert

Terrestrial 

Invert

Unidentified 

Invert Number

pupfish 0.0 0.0 3.8 96.3 0.0 0.0 0.0 0.0 8 (0)

speckled dace 11.0 54.3 0.0 0.0 0.0 24.0 10.7 0.0 3 (0)

mosquitofish 0.0 0.0 37.5 43.5 3.5 14.0 1.5 0.0 2 (0)

sailfin molly 0.0 0.0 0.0 100.0 0.0 0.0 0.0 0.0 3 (0)

crayfish 0.0 12.5 52.5 24.8 10.0 0.3 0.0 0.0 4 (0)

 
56

Figure A.1. Total number of western mosquitofish and red swamp crayfish from Typha and Juncus

marshes in four seasons, 2009 and 2010.

115

122

116

69

97

35

25

52

0 

20

40

60

80

100

120

140

July 2009 October 2009 December 2009 April 2010

Count

Season

Red swamp crayfish

Typha

Juncus

328

141

92

197

124

93

24 18

0 

50

100

150

200

250

300

350

July 2009 October 2009 December 2009 April 2010

Count

Season

Mosquitofish

Typha

Juncus
For additional information contact:

Director, Western Fisheries Research Center

U.S. Geological Survey

6505 NE 65th Street

Seattle, Washington 98115

http://wfrc.usgs.gov/

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