DISPERSAL POTENTIAL AND MOVEMENT PATTERNS OF PECOS

BLUNTNOSE SHINER Notropis simus pecosensis IN THE

PECOS RIVER, NEW MEXICO

By

Nathan M. Chase, B.S.

A thesis submitted to the Graduate School

in partial fulfillment of the requirements

for the degree

Master of Science

Major Subject: Wildlife Science

New Mexico State University

Las Cruces, New Mexico

July 2014

“Dispersal potential and movement patterns of Pecos bluntnose shiner Notropis simus

pecosensis in the Pecos River, New Mexico,” a thesis prepared by Nathan M. Chase

in partial fulfillment of the requirements for the degree, Masters of Science, has been

approved and accepted by the following:

Loui ReyesInterim Dean of the Graduate School

Colleen A. CaldwellChair of the Examining Committee

Date

Committee in charge:

Dr. Colleen A. Caldwell, Chair

Dr. Scott A. Carleton

Dr. David E. Cowley

Dr. William R. Gould

Dr. Chris W. Hoagstrom

ii

ACKNOWLEDGMENTS

First, I would like to thank Dr. Colleen Caldwell for the opportunity to further

my education and pursue work I am passionate about. Her patience, guidance, and

support has taught me that persistence pays off. I thank Dr. Scott Carleton for

teaching me just a small glimpse into the vast ways isotope and elemental work can

be applied. Thanks to Dr. William Gould for his help in data analysis, without which I

would still be lost. I thank Dr. Christopher Hoagstrom for many hours of insight,

helping me understand the Pecos River, and showing passion for a river that most

lack appreciation for. I also thank Dr. David Cowley for help and ideas while working

on this thesis. I would also like to thank James Hobbs, Justin Glessner, Gry Barfod,

and Joel Commisso of the University of California – Davis for assistance in isotopic

analysis, instrument time, and otolith processing.

I would like to thank Susan Oetker, Melissa Mata, and Stephen Davenport of

the U.S. Fish and Wildlife Service for the opportunity to conduct this work, without

the Research-SSP funding, I would not be here. I thank Stephen Davenport and Sara

Blocker for allowing me to go into the field with them, collecting fish, and helped me

understand the river with complex issues that surround water management in New

Mexico. I would like to thank Manuel Ulibarri, William Knight, and Catherine Sykes

of the Dexter National Fish Hatchery and Technology Center for their help during the

swimming stamina trials, allowing me to use their stamina tunnel and raising Pecos

bluntnose shiners for the trials.

I would like to thank many students that have become close friends here at

New Mexico State University, including Bradley Kalb, Seth Hall, Jasmine Johnson,

iii

Chance Roberts, Hunter Falco, Dominique Lujan, Lindsey McCord, Guillermo

Alvarez, Matthew Zeigler, Darren James, and many others that could always make a

frustrating situation seem less serious and manageable.

Finally I would like to thank and dedicate this work to my family and soon to

be wife Stephanie Laird. I thank them for all of their encouragement, support and

patience while pursuing this degree, without them I would not be where I am today.

My father and grandfather taught me how to fish, an obsession I doubt anyone

thought would grow into the passion I have for all things fishy.

iv

VITA

July 18, 1988 Born in Show Low, Arizona

May 2007 Graduated from Blue Ridge High School, Pinetop-Lakeside, Arizona

May 2009 A.S. Northland Pioneer College, Show Low, Arizona

May 2011 B.S. in Biological Sciences, minor in Chemistry, Northern Arizona University, Flagstaff, Arizona

2011-Present Graduate Research Assistant, New Mexico State University, Las Cruces, New Mexico

v

ABSTRACT

DISPERSAL POTENTIAL AND MOVEMENT PATTERNS OF PECOS

BLUNTNOSE SHINER Notropis simus pecosensis IN THE

PECOS RIVER, NEW MEXICO

By

Nathan M. Chase, B.S.

Master of Science

New Mexico State University

Las Cruces, New Mexico

Dr. Colleen A. Caldwell, Chair

Movement patterns and dispersal potential of the federally-threatened Pecos

bluntnose shiner Notropis simus pecosensis (member of a pelagic broadcast spawning

guild) were successfully characterized using otolith microchemistry. Strontium

isotope ratios (87Sr:86Sr) within fish otoliths were used as a biological tag to track fish

movements from larvae to adult between three isotopically distinct reaches that

encompass 297 km of the Pecos River. Plains killifish Fundulus zebrinus was used to

characterize spatial and temporal patterns of 87Sr:86Sr of the Pecos River. Passive

vi

downriver displacement of propagules was detected followed by upriver dispersal of

young fish within the first year of life with some fish achieving a minimum of 56 km

movement upriver. Retention of propagules was also documented with upriver

resident Pecos bluntnose shiners throughout their lives revealing two dominant life

history movement patterns. Swimming ability of Pecos bluntnose shiner was tested in

a range of age classes revealing upper critical swimming speeds (Ucrit) as high as 43.8

cm/s and 20.6 body lengths/s in 30 d post-hatch fish. Strong swimming ability early

in life supports early upriver dispersal as was observed using otolith microchemistry

in relation to age and confirms movement patterns that were previously unknown for

the species. Pecos bluntnose shiner movement was documented in the population

during years of perennial flow (fish hatched in 2010 and 2011). In contrast,

recruitment was limited during intermittent flow due to drought in 2012. Extremes in

flow regime and habitat degradation continue to threaten freshwater pelagic broadcast

spawning fishes. Understanding movement patterns and dispersal potential may help

conservation and management efforts by improving how flows are managed and

where habitat can be improved for the best allocation of resources available.

vii

TABLE OF CONTENTS

Page

Abstract............................................................................................................. vi

LIST OF TABLES............................................................................................ ix

LIST OF FIGURES.......................................................................................... x

DISPERSAL POTENTIAL AND MOVEMENT PATTERNS OF PECOS BLUNTNOSE SHINER Notropis simus pecosensis IN THE PECOS RIVER, NEW MEXICO................................................................................... 1

Introduction...................................................................................... 1

Methods............................................................................................ 5

Study Area................................................................................... 5

Bedrock and Pecos River Water Chemistry................................. 8

Movement Assessment using Otoliths from the Plains Killifish and Pecos Bluntnose Shiner................................ 9

Fish Collection and Otolith Preparation...................................... 10

Age at Movement......................................................................... 13

Swimming Performance............................................................... 13

Data Analysis............................................................................... 14

Results ............................................................................................. 16

Otolith Microchemistry of Plains Killifish.................................. 16

Otolith Microchemistry of Pecos Bluntnose Shiner.................... 18

Swimming Performance of Pecos Bluntnose Shiner................... 24

Discussion......................................................................................... 27

Literature Cited................................................................................. 33

viii

LIST OF TABLES

Table Page

1. Dispersal from below Highway 70 to above Highway 70 (movements upriver) and retention of Pecos bluntnose shiners as upriver residents (propagules retained above Highway 70) throughout life. Distance from Hwy 70 is the minimum detectable distance Pecos bluntnose shiners swam from downriver isotopically distinct areas to the capture location..................................................................................... 19

2. Upriver and downriver movement counts of Pecos bluntnose shiner by age class. Age at movement is the age of the fish when movement occurred. Age at capture indicates fish age at time of capture............. 23

3. Source areas of deposited Pecos bluntnose shiner progeny based on isotopic analyses for near core (early life) compared to where fish were captured. Capture location from top to bottom are sites from upriver to downriver, respectively........................................................ 23

4. Average total length (TL, mm), critical swimming speed (Ucrit, cm/s), swimming rate (Body Length/s), and average total distance swam by four age classes of Pecos bluntnose shiner during swimming stamina tests. Values in parentheses are two standard errors (SE). Sample size of 30 fish was used for 30, 60 d, and adult age classes, while 15 fish were tested for 90 d age class. ....................................................... 26

ix

LIST OF FIGURES

Figure Page

1. Study area depicting three reaches of the Pecos River and sample collection sites. The three reaches (from north to south) represent anthropogenic influences of Sumner Dam (Tailwater Reach), undisturbed open range (Rangelands Reach), and agricultural influences (Farmlands Reach)............................................................... 7

2. Collection sites from upriver to downriver are depicted on the x-axis from left to right. Bars represent mean (± 2 standard error, SE) of 87Sr:86Sr values from otoliths of plains killifish. Number of fish captured at each site is in parentheses. Solid circles represent 87Sr:86Sr values for water samples taken at four sites. Overall average of 87Sr:86Sr values for plains killifish from sites above Highway 70 are depicted by dash-dotted line (0.7083 ± 0.00002) and below Highway 70 is depicted by dotted line (0.7077 ± 0.000051)........................................ 17

3. Timing and direction of movement for all age classes of Pecos bluntnose shiner exhibiting dispersal up and downriver. Age at movement timing represented on the x-axis and movement counts on the y-axis. Black bars represent downriver movements, gray bars represent upriver movements. Age at movement: 0+ early, within 30 d post-hatch; 0+ mid, 30-60 d post-hatch; 0+ late, 60 d – pre-first winter; 0+ winter, first winter; 1+ early, early second summer; 1+ mid, mid-second summer; 1+ late, pre-second winter.......................................... 20

4. Age distribution from otoliths of Pecos bluntnose shiner used in isotopic analysis. X-axis from left to right are sites from upriver to downriver respectively, y-axis are counts. 0+ have not formed an annulus, 1+ have one annulus, and 2+ have two annuli........................................... 25

x

INTRODUCTION

Rivers throughout the southwestern Great Plains have experienced dramatic

changes in flow regimes the last 100 years. Altered flow is the result of river

modification that includes damming, channelization, water diversion and ground-

water pumping for municipal, industrial, and agricultural uses (Dodds et al. 2004;

Hoagstrom 2008b; Durham and Wilde 2009). Flow intermittency, decreased habitat

complexity, and increased salinity have negatively impacted native fish populations,

especially pelagic broadcast spawning species (pelagophils; Bestgen et al. 1989;

Durham and Wilde 2009; Hoagstrom et al. 2011). For these fishes, spawning occurs

throughout the summer and is cued to high flow, a bet-hedging strategy which

spreads reproduction over several spawning events giving larval fishes multiple

opportunities to recruit (replace the previous generation as adults) into the population

(Durham and Wilde 2005; USFWS 2006). These fishes utilize a reproductive strategy

in which the female releases eggs into the water column whereupon the male

fertilizes them. These eggs are non-adhesive and semi-buoyant which allows them to

remain suspended within the water column and drift downriver while development

occurs (Platania and Altenbach 1998; Propst 1999; USFWS 2006; Cowley et al.

2009). Downriver drift (displacement) facilitates dispersal; however, eggs and fry

(propagules) are at risk if swept into unfavorable habitat such as large impoundments

where they would perish (USFWS 2006; Dudley and Platania 2007). Propagule

retention in slack-water nursery habitat reduces downriver displacement and may be a

key driver for successful recruitment into the population (Dudley and Platania 2007;

1

Hoagstrom and turner 2013). Understanding movement patterns of pelagophils may

assist in recovery of these fishes.

Movement assessments have revealed life history characteristics that were

previously unknown supporting potential changes in management practices

(Gillanders and Kingsford 2000; Hobbs et al. 2010, Wolff et al. 2012). Applications

of these techniques have been used successfully in other systems in a variety of ways,

providing information on stock identification, population mixing, natal origin, and

return of adults to natal streams in a variety of freshwater and saltwater fish species

across the globe (Thorrold et al. 1998; Campana et al. 2000; Barnett-Johnson et al.

2008; Hobbs et al. 2010; Wolff et al. 2012). Isotopic analysis of otoliths have also

revealed information other tagging techniques cannot access, particularly for small

bodied fish species (Hobbs et al. 2010). Fish must reach a minimum size for survival

and successful tag retention (Walther et al. 2008; Muhlfeld et al. 2010). As an

alternative, otolith microchemistry has been used to elucidate movement and life-

history characteristics (Kennedy et al. 1997; Campana 1999; Barnett-Johnson et al.

2008; Elsdon et al. 2008; Amano et al. 2013). These calcium carbonate structures

record water chemistry (Elsdon et al. 2008) and are viewed as biological recording

devices both spatially (where the fish spent it life) and temporally (how long they

remained in an area) (Campana 1999). Within the otoliths, divalent cations

(magnesium, barium, strontium) are readily substituted for calcium within the

aragonite matrix (calcium-carbonate crystal structure; Fodrie and Herzka 2008;

Muhlfeld et al. 2012). While environmental variables of temperature, salinity, and

2

food influence elemental concentrations, isotopic ratios (87Sr:86Sr) are not affected

(Kennedy et al. 2000). Thus, if the bedrock geology (source of Sr in water) is known,

then the otolith can be used as a reliable biological tag which yield isotopic patterns

of natal origin and movement over a fish’s live span (Campana 1999).

The Pecos River is characterized by wide and shallow braided flows and

unstable erosive sand banks that support fishes well adapted to shifting sand beds

(Bestgen and Platania 1990; Platania and Altenbach 1998; Hoagstrom 2000;

Hoagstrom et al. 2008a) and represents one of the last Great Plains rivers with a long

stretch of unobstructed flow (297 km between Fort Diversion Dam and Brantley

Reservoir). Water diversion and obstruction through damming threatens a guild of

pelagophils that include native speckled chub (Macrhybopsis aestivalis), Rio Grande

shiner (Notropis jemezanus), Pecos bluntnose shiner (N. simus pecosensis), non-

native plains minnow (Hybognathus placitus), and non-native Arkansas River shiner

(N. girardi) (Platania and Altenbach 1998; Dudley and Platania 2007; Hoagstrom et

al. 2011). Though the guild continues to persist, individual species are in decline; Rio

Grande silvery minnow (H. amarus) was extirpated from the Pecos River in the late

1960s (Bestgen and Platania 1991; Platania and Altenbach 1998).

The Pecos bluntnose shiner was state-listed by New Mexico as threatened in

1975 (NMDGF 2012) and federally-listed as threatened in 1987 (USFWS 1987). The

subspecies is relatively short-lived with a lifespan of two to three years in the wild

(Hatch et al. 1985; Bestgen and Platania 1990; Hoagstrom et al. 2008b). From May

through the end of September, spawning was historically cued by high-flow events

3

from snowmelt runoff and summer monsoon rains that increased flow from a few

hours to a few days. Spawning cues currently include summer precipitation, block

releases (large volume and long duration water release) from a large impoundment

(Sumner Dam), and flooding from non-regulated tributary inputs (Hatch et al. 1985;

USFWS 2006; Hoagstrom et al. 2008b). The subspecies was once found throughout

631 river kilometers between Santa Rosa, New Mexico and the Delaware River

Confluence of the New Mexico-Texas border. The range of the species has been

greatly reduced, currently persisting between Sumner Dam and Brantley Reservoir

(Hatch et al. 1985; Platania 1995; Hoagstrom 2000; Hoagstrom et al. 2008b).

Mitigating threats to the species may aid in their recovery, however, little is

known about movement patterns and dispersal potential of this species after larval

development occurs. Movement patterns of juvenile and adult Pecos bluntnose shiner

have not been studied in depth (Hoagstrom et al. 2008b). Hoagstrom et al. (2008b)

documented a notable size reduction from upriver to downriver. The absence of many

adult Pecos bluntnose shiner in the southern-most occupied portion of the river above

Brantley Reservoir (Farmlands Reach) suggests that fish in this lower reach are either

not recruiting into the population or they are moving out of this reach (Hoagstrom et

al. 2008b). In addition, source areas where propagules are deposited, larvae develop,

and eventually recruit into the core population are also unknown (Platania and

Altenbach 2007; Hoagstrom 2008a). Ultimately, recruitment of Pecos bluntnose

shiner is dependent upon where eggs disperse, hatch, and if larvae find refugia in

nursery habitat. If the source of recruitment comes from downriver, those individuals

4

likely must swim upriver to successfully reproduce or their eggs potentially disperse

further downriver into Brantley Reservoir (Platania and Altenbach 1998; Dudley and

Platania; 2007). The success of the fish is further complicated by the timing and

magnitude of block releases from Sumner Dam, which are intended to decrease

evaporative loss between reservoirs and efficiently deliver water for agricultural use.

Without knowing dispersal patterns or movement related to reproduction of the fish,

managers could only presume environmental variables that affect successful

reproduction and recruitment.

The goal of this research was to provide managers with an assessment of

movement patterns such that informed management decisions can be made about

areas in the Pecos River vital to movement and recruitment of Pecos bluntnose shiner

thereby aiding in the conservation of the species. The objectives were to assess

movement patterns, timing, and dispersal potential of Pecos bluntnose shiner utilizing

otolith microchemistry, aging techniques, and swimming performance.

METHODS

Study Area

Currently, the Pecos bluntnose shiner is restricted to the Pecos River main-

stem from Sumner Dam to Brantley Reservoir, a distance of 330 km with three

distinct reaches (Propst 1999; Hoagstrom 2003a, 2003b). As part of a long term

monitoring program, the U.S. Fish and Wildlife Service (USFWS) has monitored the

population of Pecos bluntnose shiner throughout a series of permanent sampling sites

5

(Davenport 2010). A subset of these sites was selected in this study. From north to

south, the Tailwater Reach is the most northern reach between Sumner Dam and the

confluence of the River at Taiban Creek for a total of 33 km (Figure 1). The release of

sediment-free water from Sumner Dam leads to channel scour creating unsuitable

habitat where the species has not been collected since 1999 (Kondolf 1997;

Hoagstrom 2003a; Hoagstrom et al. 2008b; Davenport 2010). Sampling was not

conducted in the Tailwater Reach for this study. The middle or Rangelands Reach

contained the following sample sites from north to south: Willow, 6 Mile Draw,

Crockett Draw, Cortez Gasline, Bosque Draw, Gasline, and Highway 70. This reach

is characterized by the most suitable habitat of shifting sand-bed and a braided river

channel extending from Taiban Creek to the Rio Hondo confluence (155 km; Figure

1). All size classes of Pecos bluntnose shiner have been routinely documented within

this reach (Hoagstrom 2003a,b). The Farmlands Reach contained the following

sample sites from north to south: Dexter, Lake Arthur Falls, Highway 82, and

Brantley Inflow. This reach is the most southern section that extends from the Rio

Hondo confluence to Brantley Reservoir (142 km; Figure 1) and is characterized as a

deeply incised narrow channel with a compacted river bed, modified more effective

water delivery (Tashjian 1993). Salinity is elevated in this reach due to the cumulative

effects of diminished stream flow, increased evapotranspiration, saline irrigation

return flows, and brine aquifer intrusion (Hoagstrom et al. 2008a; Hoagstrom 2009).

Dudley and Platania (2007) suggested that transport distances of propagules might

occur three times further during sustained reservoir release flows. Thus, large number

6

Figure 1. Study area depicting three reaches of the Pecos River and sample collection sites. The three reaches (from north to south) represent anthropogenic influences of Sumner Dam (Tailwater Reach), undisturbed open range (Rangelands Reach), and agricultural influences (Farmlands Reach).

7

of propagule and juvenile Pecos bluntnose shiner have been collected in the

Farmlands Reach, likely due to increased downriver displacement of eggs and larvae

caused by the combined effects of block releases and decreased backwater areas

important for retention (Brooks et al. 1994; Platania and Altenbach 1998; Hoagstrom

2000).

Bedrock and Pecos River Water Chemistry

A geologic map revealed differences in bedrock formation throughout the

Pecos River drainage (NMBGR 2003). The dominant bedrock throughout the upper

reaches of the Pecos River is reflected by the Guadalupian Formation from the

Permian period (270-260 million years ago). In contrast, the dominant bedrock

throughout lower reaches of the river was reflected by Piedmont Alluvial Slopes from

the Holocene to lower Pleistocene which spans the most recent glaciations from 2.5

million years ago to present (NMBGR 2003; Walker and Geissman 2009). The

Quaternary Alluvium deposit begins about 16 km north of Roswell (located near

Highway 70 monitoring site) and extends through the rest of the Roswell Basin

(lowest portion of the Pecos bluntnose shiner range) and lies above the Grayburg and

Queen Formations (http://pubs.usgs.gov/ha/ha730/ch_c/C-text7.html, accessioned

May 19, 2013). These formations consist of carbonate (limestone and dolomite) and

evaporite (gypsum and halite). Thus, older bedrock in the upper River reach would be

manifested as higher 87Sr:86Sr values (more time for 87Rb decay to occur) while

younger bedrock in the lower River reach would be manifested as lower 87Sr:86Sr

8

values. Brine aquifer intrusion throughout the lower reach increases sodium, chloride,

magnesium, and calcium (constituents of increased salinity in the Farmlands Reach)

compared to the upper reaches (Rangelands and Tailwater reaches; Miyamoto et al.

2008). Noteworthy changes in dominant bedrock were evident near the Highway 70

sampling site. Thus, 87Sr:86Sr was analyzed from water samples collected above

Highway 70 (Willow), at Highway 70, and below Highway 70 (Highway 82 and

Dexter). Water samples (n = 4) were collected 23-25 April 2012 during base flows to

assess 87Sr:86Sr values of the Pecos River within the Pecos bluntnose shiner range.

The samples were analyzed using Inductively-Coupled Plasma Mass Spectrometry

(ICPMS) at the University of California - Davis Interdisciplinary Center for Plasma

Mass Spectrometry. Values for 87Sr:86Sr in water varied from 0.7082 to 0.7083 in the

upriver reaches (Willow and Highway 70) and from 0.7078 to 0.7079 in the

downriver reaches (Dexter and Highway 82; Figure 3).

Movement Assessment using Otoliths from the Plains Killifish and Pecos Bluntnose

Shiner

While water chemistry revealed differences in 87Sr:86Sr that supports geologic

rock types and where the brine aquifer intrusion begins, these samples represent only

a snapshot for each location and were used only to assess feasibility (if isotopic

values in different areas of the Pecos River did not vary, a movement assessment

using isotopes would not be possible). Plains killifish (Fundulus zebrinus) were

investigated for their use as a reference for 87Sr:86Sr values in place of water samples

at each site. Analysis of 87Sr:86Sr values from fish otoliths is more cost effective than

9

analysis of water samples, in addition, only a single trip to the Pecos River was

necessary to collect fish since plains killifish otoliths record water chemistry while

living side-by-side Pecos bluntnose shiner. The plains killifish is present throughout

the home range of the Pecos bluntnose shiner (Davenport 2010), and typically form

schools containing a variety of size classes (Minckley and Klaassen 1969a). Plains

killifish prefer low velocity shallow water and can tolerate a wide range of

temperatures and salinities (Rahel and Thel 2004). Though considered highly mobile,

movement patterns in this species have not been previously assessed. Plains killifish

may be considered a non-migratory species occupying limited segments of a stream

(Minckley and Klaassen 1969a). Thus, a movement assessment of this species was

conducted prior to their use as a surrogate in place of water samples to characterize

isotopic values of strontium specific to sample collection sites throughout the Pecos

River. As a resident, the species is more likely to remain in one area their entire lives

and presumably capture ambient water chemistry at a particular location (from time

of hatch to the time of capture).

Fish Collection and Otolith Preparation

A variety of sizes of Pecos bluntnose shiner (n = 120, range 29.7-60.1 mm

standard length, SL) and plains killifish (n = 97, range 19.4-55.4 mm SL) were

collected 7-9 November 2012 using a 3.0 m x 1.2 m seine with 3.2 mm mesh. Plains

killifish were collected at nine sites (from north to south: Willow, 6 Mile Draw,

Crockett Draw, Bosque, Gasline, Highway 70, Dexter, Lake Arthur, and Highway 82)

10

while Pecos bluntnose shiners were collected at seven sites (the shiner was not

collected at Lake Arthur Falls or Highway 82 because they were not detected). Fish

were collected just before the onset of winter allowing young fish to grow large

enough to be captured in seines and to ensure that movement during the prior summer

could be detected within otoliths. Fish were euthanized, placed on dry ice, and

transported to the laboratory. Sagittal otoliths were removed, placed into vials with

ultrapure (milli-Q) water and cleaned using an ultrasonic water-bath for 5 minutes to

remove tissue. Otoliths were then rinsed again with milli-Q water, placed in acid

washed vials and allowed to dry under a class 100 laminar-flow hood. After 48 h dry-

time, otoliths were mounted sulcus side up and affixed to a microscope slide with

Crystalbond (Crystalbond™ 509, Ted Pella Inc. Redding, CA) and sanded using a

MTI Corporation UNIPOL-1210 grinding/polishing machine (1200 grit sand paper

wetted with milli-Q water) to reveal the core to the edge (Thorrold et al. 1998; Hobbs

et al. 2010). Due to the small size of otoliths (600-1200 µm) for both fish species,

cross-sectioning techniques were not used. Otoliths were then rinsed again with milli-

Q water and re-mounted onto petrographic slides (sanded side up), affixed with

Crystalbond for isotopic analysis.

Laser ablation multi-collector inductively coupled mass spectrometry was

used to assess 87Sr:86Sr in otoliths throughout the life of each fish. Otolith analysis

was conducted at the University of California - Davis Interdisciplinary Center for

Plasma Mass Spectrometry using a New Wave Research UP213 laser ablation system

coupled with a Nu Plasma HR (Nu032) multiple-collection high-resolution double-

11

focusing plasma mass spectrometer system. Line scans across the face of the otolith

from the core to the edge generated 87Sr:86Sr profiles throughout the fish’s life. A

scanning speed of 10 μm/s, laser pulse frequency of 10 Hz, and 65% laser power were

used. A carrier gas (Helium) was used to carry ablated material into the mass

spectrometer where it was mixed with Argon gas before entering the plasma. 87Sr:86Sr

values were normalized in relation to 87Sr:88Sr (0.1135) to correct for instrumental

mass fractionation. 87Rb interference of 87Sr (a possible contaminant found in

industrial argon gas) was monitored by measuring 85Rb minimizing interference

(Hobbs et al. 2010). Instrumental accuracy was ensured using a modern marine

mollusk (an in-house calcium carbonate standard). By ablating this standard, a

comparison was made for each standard run to values known for modern day

seawater to account for any instrumental drift throughout runs (87Sr:86Sr = 0.70918;

Hobbs et al. 2010). Ablations of the standard yielded 87Sr:86Sr = 0.70920 (± 0.000098;

n = 49). Samples were adjusted throughout sessions to known values of the mollusk

standard.

After isotopic analysis, otoliths were photographed using a Leica DME

microscope with Leica ICC50 Camera Module with Leica Live Image Building

Software (LAS Software Version 4.4.0, October 2013, Heerbrugg, Switzerland) to

generate whole otolith photographs using a 20x microscope objective. Otolith

photographs were viewed by two independent analysts and the assigned ages were

compared (Miller and Storck 1982). Briefly stated, where age discrepancy occurred at

greater than 10%, a third analysis was performed and ages of the fish were accepted if

12

the third age analysis fell within 10% of one of the first two aging attempts. If no

consensus could be reached, the age for that fish was excluded. Data from the isotopic

analysis was overlaid following the ablation path for each otolith and the ages at

which isotopic shifts occurred were then recorded for each fish.

Age at Movement

For each Pecos bluntnose shiner, the age at which an isotopic shift occurred

was identified from digital images using ImageJ software (Version 1.48i, National

Institute of Health). Distance (microns) was calibrated using a calibration slide to

measure distance from the core to each shift in 87Sr:86Sr values. Fish growth varies

between the warmer summer months (majority of growth occurring during this

season) and cooler autumn/winter (growth is very slow). Daily rings were easily

counted the first year of life. Thus, age at which fish moved were binned into groups

with 0+early representing within 30 days post-hatch, 0+mid representing 30-60 days

post-hatch, 0+late representing 60 days post-hatch to pre-annulus formation, 0+

winter representing within the first annulus (winter), 1+ early representing early

growth after winter (second growth season), 1+ mid representing mid-summer growth

(second growth season), and 1+ late representing late summer-fall growth (second

growth season).

Swimming Performance

Captive propagated Pecos bluntnose shiner were tested at 30 d (n=30, average

20.63 mm total length, TL), 60 d (n=30, average 33.93 mm TL), 90 d (n=15, average

13

46.33 mm TL) post-hatch and wild-caught adults (n=30, 69.13 mm TL) from the

Pecos River using a swim tunnel (Loligo® Systems, Denmark). Water quality was

monitored and maintained such that it did not influence swimming performance

among age classes. Fish were acclimated at one cm/s flow one week prior to the

swimming trials. On test day, individual fish were placed in the stamina tunnel and

allowed to acclimate for one hour at five cm/s. Flow was increased by ten cm/s

increments at five-minute intervals until the fish fatigued and became pinned against

the back screen for more than five seconds (the conclusion of the test). At the

termination of each test, fish were measured for total and standard lengths (mm) and

placed in a recovery tank. Critical swimming speed (Ucrit) was calculated using the

equation from Beamish (1978):

Ucrit = Ui + [(ti/tii) × Uii],

and body lengths per second:

BL/s = Ucrit/TL,

where, Ui = the full interval swam at the highest velocity (cm/s), Uii = the velocity

increment (cm/s), ti = time (s) fish swam in the final increment until becoming pinned,

tii = duration of each increment, TL = total length of individual fish run (Beamish

1978; Adams et al. 1999).

Data Analysis

For both species, a ten-point moving average was used to smooth the 87Sr:86Sr

values. If no isotopic shifts were evident through visual inspection of the data (full

14

data profiles matching one location throughout the fish’s life), the fish was deemed a

resident. When otoliths revealed an isotopic shift (segments of data matching multiple

locations throughout the fish’s life), then it was presumed the fish moved between

areas of unique 87Sr:86Sr chemistry. If an isotopic shift was evident, the isotopic

values between all shifts was partitioned and fish were presumed to have spent that

period of time within one of three isotopically unique reaches. For example, a fish

that spent an early portion of its life in one isotopically unique reach and a later

portion of its life in another isotopically unique reach will be reflected by two

different isotopic values. Each segment of partitioned data was classified

independently of other data segments.

Discriminant function analysis was performed using the PROC DISCRIM

function in SAS (version 9.3, SAS Institute) to assess movement in both species.

Discriminant function analysis was used to assess where fish had spent portions of

their lives by classifying visually partitioned line scan data to isotopically unique

areas. Similar to Clarke et al. (1997), line scans from the core to the edge of otoliths

were used; however, they were not able to quantify fish movements. In other work,

natal origins were determined using discriminant function analysis for near core

isotopic values to classify fish to natal origin (Barnett-Johnson 2008; Humston et al.

2010). The research presented here may be the first attempt to quantify movements by

visually partitioning entire life data-sets from line scans, then classifying partitioned

segments of isotopic values to an area.

15

87Sr:86Sr data from plains killifish otoliths were used as training data set to

classify all fish into isotopically distinct areas. The test for equal within-group

covariance was not met (χ2 = 10.14, p = 0.006), and was not pooled. The Jackknife

procedure was used for plains killifish data in a cross-validation technique (one

observation is left out) to assess model validity by comparing the predicted to the

known capture location.

Isotopic profiles were inspected for each otolith from Pecos bluntnose shiner

and visually partitioned to assess movement (similar to the plains killifish).

Discriminant function analysis was then used to classify partitioned data to one of the

three areas. Movements were then assessed by differences in isotopic values where

fish spent time from early to late life. For example, an upriver movement was

identified if the isotopic values near the otolith core were classified to downriver

reaches and isotopic values near the otolith edge classified to upriver reaches. The

area fish spent time early in life is unknown and thus early life classification accuracy

cannot be assessed, however, near edge isotopic value classifications were compared

to known capture location to assess classification success rate.

RESULTS

Otolith Microchemistry of Plains Killifish

Isotopic values of the Pecos River throughout sampling locations were

successfully characterized using plains killifish otoliths (Figure 2). Discriminant

function analysis of 87Sr:86Sr values from otoliths of plains killifish captured at all

16

Willow 6 Mile Draw

Crockett Draw

Bosque Gasline Hwy. 70 Dexter Lake Arthur

Hwy. 820.7074

0.7076

0.7078

0.7080

0.7082

0.7084(n=7)

(n=12) (n=14)

(n=7) (n=8)

(n=9)

(n=13) (n=9)

(n=12)

Killifish Otolith Mean Values Upstream Killifish Mean Value Downstream Killifish Mean Value

87Sr

:86S

r

Figure 2. Collection sites from upriver to downriver are depicted on the x-axis from left to right. Bars represent mean (± 2 standard error, SE) of 87Sr:86Sr values from otoliths of plains killifish. Number of fish captured at each site is in parentheses. Overall average of 87Sr:86Sr values for plains killifish from sites above Highway 70 are depicted by dash-dotted line (0.7083 ± 0.00002) and below Highway 70 is depicted by dotted line (0.7077 ± 0.000051).

17

sites indicated no isotopic shifts occurred revealing no movement detected among

three isotopically unique areas (above Highway 70, at Highway 70, and below

Highway 70). In addition, no seasonal shifts in isotopic values of the Pecos River

were detected (stability of isotopic values throughout the lives of plains killifish).

Thus, the plains killifish was a suitable surrogate for characterizing Pecos River water

87Sr:86Sr throughout the study area both spatially (all sites where fishes were captured)

and temporally (throughout the lives of the fishes). Of plains killifish captured above

Highway 70, 91% (50/55) were classified correctly, 56% (5/9) were classified

correctly to Highway 70, and all 34 plains killifish captured below Highway 70 were

classified correctly (100%) using cross validation. Thus, the plains killifish revealed

Highway 70 as an area of mixing or a transition zone of isotopic values, as expected,

due to the shift in bedrock between the two isotopically distinct areas.

Otolith Microchemistry of Pecos Bluntnose Shiner

Isotopic analysis of otoliths from Pecos bluntnose shiner revealed fish either

moved upriver from below Highway 70, or were life-long residents above Highway

70 (propagule retention in upriver reaches; Table 1). The majority of upriver

movements (74/89) occurred during the growing season (summer and fall) in the first

year of life (0+ age class) before the first annulus was formed (Figure 3). Fish that

moved to the reach above Highway 70 remained within this reach for the remainder

18

Table 1. Dispersal from below Highway 70 to above Highway 70 (movements upriver) and retention of Pecos bluntnose shiners as upriver residents (propagules retained above Highway 70) throughout life. Distance from Hwy 70 is the minimum detectable distance Pecos bluntnose shiners swam from downriver isotopically distinct areas to the capture location.Site Movement upriver Residents Distance from

Hwy 70Willow 25/32 (78%) 7/32 (22%) 56 km6 Mile 16/19 (84%) 3/19 (16%) 45 kmCrockett 20/23 (87%) 3/23 (13%) 37 kmBosque 18/23 (78%) 5/23 (22%) 27 kmGasline 4/4 (100%) 0/4 (0%) 11 kmTotal 83/101 (82%) 18/101 (18%)

19

0+ early 0+ mid 0+ late 0+ winter 1+ early 1+ mid 1+ late0

5

10

15

20

25

30

35

40

DownriverUpriver

Age at Movement

Num

ber o

f Mov

emen

ts

Figure 3. Timing and direction of movement for all age classes of Pecos bluntnose shiner exhibiting dispersal up and downriver. Age at movement timing represented on the x-axis and movement counts on the y-axis. Black bars represent downriver movements, gray bars represent upriver movements. Age at movement: 0+ early, within 30 d post-hatch; 0+ mid, 30-60 d post-hatch; 0+ late, 60 d – pre-first winter; 0+ winter, first winter; 1+ early, early second summer; 1+ mid, mid-second summer; 1+ late, pre-second winter.

20

of their lives and propagules that were retained within this reach remained residents

until the time of capture. Nineteen of twenty movements by fish downriver were

associated with movement upriver later in life. Only four Pecos bluntnose shiners

were captured below Highway 70 (all from the Dexter site) with three of four

classifying as residents in this downriver reach their entire lives (one fish captured in

the lower river reach at the Dexter site classified to Highway 70 throughout it’s life,

the only downriver movement not associated with a later upriver movement).

Dispersal potential of Pecos bluntnose shiner using otolith microchemistry

indicated a minimum upriver movement of 56 km (from Highway 70 to Willow) with

78% (25/32) Pecos bluntnose shiners captured at Willow achieving this distance

(Table 1). One shiner captured at Dexter moved downriver from Highway 70 (58 km)

at age 1+ late (Figure 3) just before the time of capture. The full isotopic profile

(entire life) of this fish classified to Highway 70, thus it was assumed that this fish did

not spend enough time below Highway 70 to allow the otolith to incorporate

downriver water chemistry to record this movement. Pecos bluntnose shiners that

exhibited upriver dispersal had either hatched above or below Highway 70. Of all fish

that dispersed upriver, 46% (38/82) had 87Sr:86Sr values classifying to above Highway

70 near the core of their otoliths indicating that spawning occurred above Highway 70

and these fish were displaced downriver post-hatch (i.e., hatched above Highway 70,

displaced to below Highway 70, then returned to above Highway 70). The remaining

54% (44/82) hatched below Highway 70. In other words, there was no detectable

upriver 87Sr:86Sr value within or near the core suggesting that these fish developed

21

from eggs that drifted below Highway 70 before hatching or that spawning occurred

below Highway 70.

Downriver movements were evident for the earlier portion of life for Pecos

bluntnose shiner before upriver movements occurred (Figure 3). All shiners captured

above Highway 70 exhibiting early life downriver displacement dispersed back

upriver. Movement patterns for both age classes 1+ and 2+ that hatched in 2011 and

2010, respectively, were consistent within one another (Table 2). Progeny were

deposited in river reaches downriver from where shiners were captured, or eggs were

retained within that river segment (Table 3). Isotopic analysis of otoliths revealed all

Pecos bluntnose shiners captured at Gasline, Highway 70, and Dexter sites contained

no near core (early life) 87Sr:86Sr values classifying to above Highway 70 indicating

that these fish hatched at or below Highway 70.

Discriminant function analysis misclassified 25 Pecos bluntnose shiners to

Highway 70 when the fish were actually captured above Highway 70 (75%

classification success rate). Of these shiners misclassified, 9 had high a posteriori

probabilities (> 80% classification probability to the wrong area). All 25

misclassifications were from fish that spent the early part of their lives below

Highway 70. The misclassifications were included in the 89 upriver movements due

to known capture location above Highway 70. Discriminant function analysis

misclassified 10 Pecos bluntnose shiners to above or below Highway 70 when fish

were actually captured at Highway 70 (six classifying to above Highway 70 and four

classifying to below Highway 70; 29% classification success rate). Discriminant

22

Table 2. Upriver and downriver movement counts of Pecos bluntnose shiner by age class. Age at movement is the age of the fish when movement occurred. Age at capture indicates fish age at time of capture.

Age at Movement

Age atCapture

0+Early

0+Mid

0+Late

0+Winter

1+Early

1+Mid

1+Late

Upriver 1+ 3 25 29 1 5 2 02+ 6 4 7 1 2 1 3

Downriver 1+ 9 3 0 0 0 0 02+ 5 1 1 0 0 0 0

Table 3. Source areas of deposited Pecos bluntnose shiner progeny based on isotopic analyses for near core (early life) compared to where fish were captured. Capture location from top to bottom are sites from upriver to downriver, respectively.Site Above Highway 70 Highway 70 Below Highway 70Willow 7/32 (22%) 8/32 (25%) 17/32 (53%)6 Mile 16/32 (50%) 9/32 (28%) 7/32 (22%)Crockett 3/23 (13%) 3/23 (13%) 17/23 (74%)Bosque 5/23 (22%) 5/23 (22%) 13/23 (56%)Gasline 0/4 (0%) 1/4 (25%) 3/4 (75%)Hwy. 70 0/14 (0%) 3/14 (21%) 11/14 (79%)Dexter 0/4 (0%) 1/4 (25%) 3/4 (75%)

23

function analysis misclassified one Pecos bluntnose shiner to Highway 70 when the

fish was actually captured below Highway 70 (3/4 shiners were residents below

Highway 70 throughout life indicating a 75% classification success rate). Age class

distribution was quantified from otoliths revealing that the majority of Pecos

bluntnose shiners captured were 1+ age class followed by the 2+ age class.

Unexpectedly, the least abundant age class captured was 0+ (young-of-year) with

only two captured in the study (both at 6 Mile Draw; Figure 4). All shiners captured

below Highway 70 (Dexter) were 1+ age class while the majority of 2+ age classes

were captured above Highway 70 in the Rangelands Reach (Figure 4). Five Pecos

bluntnose shiners could not be aged, but were residents at sites throughout their lives,

thus eliminating the need for the age at movement assessment.

Swimming Performance of Pecos Bluntnose Shiner

Pecos bluntnose shiner exhibited strong swimming ability, even at an early

age of 30 days post-hatch (Table 4). Upper critical swimming speed (Ucrit) increased

with total length indicating that larger fish perform better at higher flow rates. When

considering size of fish, higher swimming performance (BL/s) was observed in the

youngest fish (30 d post-hatch). Fish younger than 30 days post-hatch could not be

tested with the stamina tunnel (several 30 d shiners escaped from the stamina tunnel

resulting in test termination and were not included in calculations). Total distance

swam was also calculated during swimming trials revealing 30 d post-hatch fish

swam a distance of 0.55 km in 83 min and adult fish swam a distance of 1.04 km in

24

Willow 6 Mile Crockett Bosque Gasline Highway 70

Dexter0

5

10

15

20

25

0+ 1+ 2+

Age

Cou

nts

Age Class

Figure 4. Age distribution from otoliths of Pecos bluntnose shiner used in isotopic analysis. X-axis from left to right are sites from upriver to downriver respectively, y-axis are counts. 0+ have not formed an annulus, 1+ have one annulus, and 2+ have two annuli.

25

Table 4. Average total length (TL, mm), critical swimming speed (Ucrit, cm/s), swimming rate (Body Length/s), and average total distance swam of four age classes of Pecos bluntnose shiner during swimming stamina tests. Values in parentheses are 95% CI. Sample size of 30 fish was used for 30, 60 d, and adult age classes, while 15 fish were tested for 90 d age class.

Age Class TL (mm) Ucrit (cm/s) BL/s Total Distance (km)

30 d 21.3 (0.62) 43.8 (4.46) 20.6 (2.02) 0.55 (0.094)

60 d 33.9 (0.92) 49.2 (1.94) 14.5 (0.52) 0.62 (0.031)

90 d 46.3 (0.82) 52.5 (2.48) 11.3 (0.62) 0.68 (0.042)

Adult 69.1 (2.28) 70.3 (3.26) 10.2 (0.54) 1.04 (0.074)

26

96 min (Table 4). Water quality was acceptable and consistent throughout all

swimming challenges. Water temperature ranged from 19.7 to 20.6 ˚C, dissolved

oxygen ranged from 7.32 to 7.83 mg/L, pH ranged from 7.51 to 7.74, conductivity

ranged from 2.26 to 2.31 mS/cm.

DISCUSSION

Pecos bluntnose shiner exhibited two patterns of movement lending to

successful recruitment into the population. The first was displacement of propagules

downriver, followed by dispersal upriver after development (43% of fish captured at

or above Highway 70). The second pattern was retention of propagules in upriver

segments where residents remained at or above Highway 70 throughout their lives

(57% of fish captured at or above Highway 70). The combination of propagule

retention and upriver dispersal of juveniles and adults from propagules displaced

downriver suggest that successful fish move to the upriver reach or fish were retained

upriver.

Downriver movements were detected in 14 fish within the first 30 days post-

hatch indicating that displacement occurred in early life (i.e., post-hatch through

larval stage). Dispersal upriver occurred before formation of the first annulus most

likely after development of the myomeres. Presumably, dispersal upriver allows for

re-colonization and ensures adequate distance for egg development while drifting

downriver (Cross et al. 1985; Durham and Wilde 2008). Cowley et al. (2009)

suggested that bidirectional dispersal (downriver displacement and upriver dispersal)

27

was important prior to construction of impoundments in the historical distribution of

Rio Grande silvery minnow, though impoundments now limit these movements.

Propagules not deposited into slack-water nursery habitat are at risk of further

displacement downriver, especially during high-flow events until they are sufficiently

developed to seek optimal habitat. For example, Hoagstrom et al. (2008a) recorded

high densities of young Pecos bluntnose shiner at Brantley Reservoir Inflow in the

Farmlands Reach during a long block release from Sumner Dam. Many pelagophils

likely spawn during declining flows shortly after peak flows have passed; Low water

velocity (<1cm/s) is sufficient to maintain eggs in suspension (Platania and Altenbach

1998; Dudley and Platania 1999; Dudley and Platania 2007). Timing of spawning

may increase retention rates if high flows alter the river channel and increased water

volume raise the stage of the river out of the main channel and onto the floodplain,

thereby increasing availability of slack-water habitat where retention occurs

(Hoagstrom and Turner 2013).

Retention of propagules and active swimming of juvenile and adult Pecos

bluntnose shiner upriver presumably counter displacement of young fish; however,

those displaced downriver into Brantley Reservoir likely do not recruit into the

population (Dudley and Platania 2007). Downriver displacement of propagules was

advantageous in fishes of Great Plains Rivers with variable flow regimes and long

unobstructed stretches such as the Pecos River, however, persistence of pelagophils is

currently threatened by dams and reservoirs in a region where water is in limited

supply. Minimum distances of unobstructed rivers required by pelagophils to

28

successfully complete their life cycle are difficult to calculate with egg and larval

stages the most vulnerable to downriver displacement (Bestgen et al. 1989; Dudley

and Platania 2007; Hoagstrom et al. 2008b; Worthington et al. 2014). Habitat

complexity and flow regime contributing to propagule retention may be equally if not

more important for the successful recruitment of Pecos bluntnose shiner by

decreasing the number of propagules reaching Brantley Reservoir.

Pecos bluntnose shiner prefers shallower depths coupled with relatively swift

velocity water typical of wide shifting sand bed rivers (Hoagstrom et al 2008a).

Hoagstrom et al. (2008b) associated length classes of Pecos bluntnose shiner with

water velocity and found a positive relationship between increasing water velocity

and fish size. Upper critical swimming speeds (Ucrit, 43 cm/s) for fish as young as 30

d post-hatch and 21 mm total length (TL) revealed that the upper threshold of aerobic

swimming capacity is high for this species at an early age. Caldwell et al. (2010)

reported upper critical swimming speeds (Ucrit, 34.3-44.1 cm/s and 6.3-8.7 BL/s) for

Rio Grande silvery minnow at 116 d post-hatch during a feed optimization study. In

comparison, 90 d post-hatch Pecos bluntnose shiner exhibited higher swimming

capacity (Ucrit, 52.5 cm/s and 11.4 BL/s). Bestgen et al. (2010) reported upper critical

swimming speeds of 51.5 cm/s (53-75 mm TL) for Rio Grande silvery minnow noting

that swimming ability increased with fish size. Though Pecos bluntnose shiner

exhibited strong swimming ability and upriver dispersal, downriver transport of

propagules has potentially tripled from pre-dam/pre-channelization of the river to

distances up to 142 km (Dudley and Platania 2007). Successful fish passage upriver

29

and maintaining position in flow relies on individual fish size, morphology, behavior,

river channel morphology, and flow velocity (Ward et al. 2003; Leavy and Bonner

2009; Bestgen et al. 2010).

Habitat degradation and loss of habitat complexity (backwater nursery habitat

and river connectivity to the floodplain) within the Farmlands Reach may be a

contributing factor to the decline of the species due to channelization of the river,

reducing retention of propagules above Brantley Reservoir before fish have the ability

to swim well (Dudley and Platania 2007). Worthington et al. (2014) suggested that

both increased water velocity and decreased habitat complexity increase transport

distance and rate of propagules thus reducing retention of propagules in rivers of the

Great Plains. In support of Hoagstrom et al. (2008a), isotopic analysis of otoliths

revealed that many Pecos bluntnose shiner propagules swept into the Farmlands

Reach eventually returned upriver after development and recruited into the

population, though unsuccessful fish cannot be accounted for (such as those swept

further downriver into Brantley Reservoir).

Persistence of Pecos bluntnose shiner relies on a multitude of environmental

factors that include timing of pulse flows that cue spawning events, habitat quality,

and perennial flow that maintain river connectivity for bidirectional dispersal to

complete their life cycle. The Southwest experienced one of the most severe droughts

on record during the summers of 2011 and 2012 (http://www.droughtmonitor.unl.ed-

u/archive.h-tml, accessioned November 10, 2012). From 17 July to 20 August 2012,

55 km of the Pecos River dried affecting quality habitat within the Rangeland Reach

30

(Stephen Davenport, personal communication). Davenport (2012) reported very few

0+ age class in 2012 indicating limited spawning success. In addition, river

intermittency presumably halted fish movement. Notably, 6 Mile Draw had the

highest number of fish retained above Highway 70 and was the only site where

young-of-year Pecos bluntnose shiners were captured. This site did not go dry during

the study and consisted of good quality habitat. The majority of fish captured in this

study were age class 1+ with fewer 2+, while no older age class was captured.

Overall, movement of Pecos bluntnose shiner coincided with years of perennial flow

throughout summer and fall before the onset of their first winter.

The use of a surrogate species (plains killifish) provided insight into Pecos

River water chemistry both spatially and temporally. Gillanders (2002) suggested that

variability of water chemistry through time in the water fish inhabit must be

accounted for. The stability of 87Sr:86Sr values in otoliths of plains killifish revealed

that they not only remained within respective river segments, there were also no

detectable seasonal shifts in isotopic values within the study area. Isotopically unique

reaches were larger than movements made by plains killifish, thus allowing the use of

killifish as a surrogate for water samples in this study. The use of a resident fish

species may have future utility in assessing movements of a highly mobile species

such as the Pecos bluntnose shiner.

Use of these techniques revealed new information on life history movement

patterns of both Pecos bluntnose shiner and plains killifish that were previously

undocumented. In summary, this may be the first study that used stable isotopes

31

(87Sr:86Sr) to characterize life history movement patterns and dispersal potential of a

small-bodied Plains River fish. As a relatively short-lived species, Pecos bluntnose

shiner must move upriver (out of poor quality habitat) early in life such that when the

opportunity to spawn occurs, propagules have sufficient distance to drift while

developing. Swimming performance testing confirmed that young Pecos bluntnose

shiner were capable of dispersing upriver early in life. Fish retained in upriver reaches

will have the reproductive advantage during spawning season. Habitat restoration in

the Farmlands Reach would likely benefit the species by returning a perennial reach

of the Pecos River to shifting sand and erosive banks. This would increase backwater

areas important for nursery habitat and retention of young fish above Brantley

Reservoir and potentially increase the success of spawning in lower river sections,

thus, bolstering recruitment into the population. Applications of these techniques are

not limited to the Pecos River, and have been applied elsewhere in a variety of ways,

their use will likely continue to provide information bettering management practices

in the future.

32

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