Distribution and Movement of Humpback Chub in the

Colorado River, Grand Canyon, Based on Recaptures

CRAIG P. PAUKERT,*1 LEWIS G. COGGINS, JR., AND CHRISTOPHER E. FLACCUS

U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research

Center, 2255 North Gemini Drive, Flagstaff, Arizona 86001, USA

Abstract.—Mark–recapture data from the federally endangered humpback chub Gila cypha in the Colorado River,

Grand Canyon, were analyzed from 1989 to 2002 to determine

large-scale movement patterns and distribution. A total of

14,674 recaptures from 7,127 unique fish were documented;

87% of the recaptures occurred in the same main-stem river

reach or tributary as the original captures, suggesting restricted

distribution by most fish. A total of 99% of all recaptures were

from in and around the Little Colorado River (LCR),

a tributary of the Colorado River and primary aggregation

and spawning location of humpback chub in Grand Canyon.

Time at liberty averaged 394 d, but some fish were recaptured

near their main-stem capture location over 10 years later.

Proportionally fewer large (.300-mm) humpback chub

exhibited restricted distribution than small (,200-mm) fish.

However, several fish did move more than 154 km throughout

Grand Canyon between capture and recapture, suggesting that

limited movement occurs throughout Grand Canyon. The

majority of the recaptured fish remained in or returned to the

LCR or the Colorado River near the LCR. Although many

large-river fishes exhibit extensive migrations to fulfill their

life history requirements, most of the humpback chub in

Grand Canyon appear to remain in or come back to the LCR

and LCR confluence across multiple sizes and time scales.

Detecting trends in the overall abundance of this endangered

fish in Grand Canyon can probably be accomplished by

monitoring the area in and around the LCR.

The humpback chub Gila cypha is a federally

endangered species with only six remaining populations, the largest population located in the Little

Colorado River (LCR) and Colorado River in Grand

Canyon (Kaeding and Zimmerman 1983; USFWS

2002). Like many other big-river fishes in the

southwestern United States, humpback chub populations are declining because predation, competition from

nonnative fish, large-scale river regulation, or a combination thereof altered temperature and flow regimes

(Minckley et al. 2003). Recent research on humpback

chub has focused on population estimation and trends

to meet recovery goals of the U.S. Fish and Wildlife

Service (USFWS 2002; Coggins et al. 2006).

The LCR is the largest tributary to the Colorado

River in Grand Canyon (Figure 1) and is the primary

spawning location for humpback chub (Kaeding and

Zimmerman 1983; Douglas and Marsh 1996), these

fish inhabiting the lower 14.75 km. Recruitment of

humpback chub likely does not occur (or is extremely

limited) in the main-stem Colorado River because of

cold water temperatures (Kaeding and Zimmerman

1983). Humpback chub from the main stem move into

the LCR to spawn, some adults remaining in the LCR

for extended periods of time other than spawning

(Douglas and Marsh 1996; but see Gorman and Stone

1999; Coggins et al. 2006).

Humpback chub movement and distribution have

been previously examined with more spatially or

temporally limited data sets that recorded recaptures

only in the LCR, its inflow, or both (Kaeding and

Zimmerman 1983; Douglas and Marsh 1996; Gorman

and Stone 1999) or using telemetry with smaller

sample sizes (Keading et al. 1990; Valdez and

Hoffnagle 1999). In addition, these studies focused

on short time frames (usually under 1 year or fewer

seasons across 2 or fewer years). To our knowledge, no

one has evaluated site fidelity over a long (.10-year)

time period with sample sizes (.10,000 recaptures) as

large as this study.

Large-river fishes typically migrate long distances,

presumably to meet the life history requirements of

adults such as spawning (e.g., Pellett et al. 1998;

Paukert and Fisher 2001), and this also occurs in adult

desert river fishes (Tyus 1991; Modde and Irving

1998). However, the scale at which distribution and

movement is evaluated also affects how conservation

and management measures are implemented (Fausch

and Young 1995; Hay et al. 2001). Previous studies of

endangered or threatened desert fishes in the southwestern United States have shown mixed results.

Humpback chub show high fidelity (using short-term

telemetry transmitters) in main-stem riverine populations (Keading et al. 1990; Valdez and Hoffnagle

1999), whereas bonytail Gila elegans have less fidelity

during spawning (Keading et al. 1990). Colorado

* Corresponding author: cpaukert@ksu.edu

1 Present address: U.S. Geological Survey, Kansas Cooperative Fish and Wildlife Research Unit, 205 Leasure Hall,

Division of Biology, Kansas State University, Manhattan,

Kansas 66506, USA.

Received August 5, 2005; accepted November 29, 2005

Published online March 28, 2006

539

Transactions of the American Fisheries Society 135:539–544, 2006

American Fisheries Society 2006

DOI: 10.1577/T05-204.1

[Note]
pikeminnow Ptychocheilus lucius make substantial

migrations during spawning (Tyus 1991; Irving and

Modde 2000), whereas razorback sucker Xyrauchen

texanus also migrate substantial distances but may use

different spawning locations in different years (Modde

and Irving 1998), emphasizing the need to evaluate

distribution and movement over multiple years. Understanding the distribution and movement of humpback chub in Grand Canyon is needed before

conservation and management strategies to recover

this species can be fully evaluated.

The objective of this study was to summarize

recaptures of passive integrated transponder (PIT)-

tagged fish to determine the distribution and movement

of humpback chub throughout Grand Canyon in all

seasons. We wanted to determine if movement patterns

and distribution differed by fish size or temporal scale,

and if their distribution and movement was similar to

that of other large-river fishes. Our study focused on

the large-scale movement throughout Grand Canyon

over a 12-year period as other studies have focused on

the movement of fish within the LCR and within-year

movements, including the spawning season (e.g.,

Kaeding and Zimmerman 1983; Douglas and Marsh

1996; Gorman and Stone 1999; Valdez and Hoffnagle

1999).

Methods

We used a long-term monitoring data set to

determine the distribution and large-scale movement

of humpback chub throughout 389 km of the Colorado

River in Grand Canyon from the Paria River to

Diamond Creek (Figure 1). Patterns in distribution

and movement were evaluated to determine the extent

of movement of humpback chub between the mainstem Colorado River and the tributaries (e.g., LCR). To

minimize bias and pseudoreplication associated with

fish recaptured immediately after capture, we used only

recaptures that were at large at least 14 d between

capture and recapture, which would minimize the

effects of fish recaptured during the same multiday

sampling events (typically 8–14 d) and would provide

time for fish to allow movement among river reaches.

The fish were separated into three categories by total

length (average of length recorded at capture and

recapture): less than 200 mm, 200–299 mm, and 300

mm or larger. The minimum size of adult humpback

chub is about 200 mm (Meretsky et al. 2000; USFWS

2002).

Humpback chub were collected from 1989 to 2002

by a variety of gears in the main-stem Colorado River

(e.g., trammel nets, hoop nets, and boat electrofishing),

but primarily by hoop nets in the tributaries (Figure 2;

Valdez and Ryel 1995; Gorman and Stone 1999;

Coggins et al. 2006). Sampling effort was variable

across seasons in the main-stem Colorado River and

more focused during early spring in the Little Colorado

River (Figure 2). Although variable, effort was

FIGURE 1.—Location of the Little Colorado River in relation

to the Colorado River and Grand Canyon, Arizona. Sampling

for humpback chub primarily occurs between the Paria River

(rkm 27) and Diamond Creek (rkm 389).

FIGURE 2.—Proportion of sampling effort by month (1 1⁄4

January, etc.) for trammel nets (net sets), hoop nets (net sets),

and electrofishing (stations) used to collect humpback chub in

the main-stem Colorado River and Little Colorado River, May

1989 to October 2002.

540 PAUKERT ET AL.
substantial: over 7,000 electrofishing samples (typically 5-min stations) were collected in the main-stem

Colorado River, and there were over 34,000 overnight

hoop net sets in the main-stem Colorado River and

LCR (Figure 2). For each fish, total length (mm) and

capture location (usually to the nearest 0.1 river km)

were recorded and a PIT tag was implanted in the

abdominal cavity to serve as a unique fish identifier for

fish larger than 150 mm total length. Each fish was

then released near its capture location.

Captures and recaptures were recorded in seven

main-stem Colorado River reaches that were determined based on geomorphology, logistics, and

easily identifiable areas (Figure 1; Table 1). In addition,

two tributaries (LCR and Havasu Creek) were also

identified as reaches along with the inflow areas of

these tributaries (e.g., main-stem Colorado River near

the confluence of these tributaries). Restricted distribution was defined as recapture and previous capture

location within the same river reach or tributary. Since

other studies have suggested that the humpback chub

population in the main-stem Colorado River within 12

km of the LCR (i.e., LCR inflow) is the same

population (Douglas and Marsh 1996; Gorman and

Stone 1999), we also analyzed distribution by combining the LCR inflow and the LCR as one river reach,

thus creating six river reaches instead of seven.

Logistic regression was used to determine if a sizegroup of fish was more likely to exhibit restricted

distribution based on odds ratios (Stokes et al. 1995).

Logistic regression was also used to determine if the

proportion of fish that exhibited restricted distribution

differed by time at liberty. In this analysis, time at

liberty was separated into eight categories: 14–30 d,

31–90 d, 91–120 d, 121–365 d, 1–3 years, 3–5 five

years, 5–10 years, and more than 10 years. An analysis

of variance was used to determine if the mean distance

between capture and recapture location (for fish that

exhibited restricted distribution) differed by fish size

and by river (i.e., main-stem Colorado River and the

LCR) for three times between capture and recapture

(14–90 d, 91–365 d, .365 d).

Results

A total of 14,674 recaptures of 7,127 unique fish

were recorded in Grand Canyon from May 1989 to

October 2002. Of the 7,127 unique fish, 3,322 (46%)

were recaptured only once, whereas 219 (3%) were

recaptured more than five times and one was recaptured

15 times. The mean number of days between captures

was 394 (range 1⁄4 14–4,713). However, 75% of the

recaptures occurred in less than 404 d.

Of the 14,674 total recaptures, 12,868 (87.7%) were

recaptured in the same tributary or area of the main-stem

Colorado River (Table 1) and thus exhibited restricted

distribution. For fish exhibiting a restricted distribution,

the mean number of days between capture and recapture

was 532 (range1⁄422–3,700) for the main-stem Colorado

River, and 354 (range1⁄414–4,713) for the LCR. For fish

not exhibiting a restricted distribution, the mean number

of days between capture and recapture was 773 (range:

14–3,742) for the main-stem Colorado River and 515

(range 1⁄4 14–3,808) for the LCR.

Of the total recaptures, 12,508 (85.2%) were

captured and recaptured in the LCR, whereas an

additional 241 (1.6%) were captured and recaptured in

the main-stem Colorado River within 12 km of the

LCR confluence (Table 1). When we considered the

LCR and LCR inflow as one population, 14,526

(99.0%) of recaptures occurred in the LCR or the main

stem near the LCR confluence and thus exhibited

a restricted distribution to this reach. Although a high

percentage of fish showed restricted distribution to the

LCR and surrounding areas, there was evidence a few

TABLE 1.—Recaptures of humpback chub collected throughout the Colorado River in Grand Canyon, Arizona, 1989–2002.

Values along the diagonal (bold italics) indicate that the capture and recapture locations were the same (i.e., site fidelity). Major

tributaries are the Little Colorado River (LCR) and Havasu Creek; rkm 1⁄4 river kilometers. Values above the diagonal represent

downstream movement, values below the diagonal upstream movement.

Tag location (rkm)

Recapture location (rkm)

Total

0–117 124 (LCR) 117–136 136–199 199–201 201–227 227–244

278

(Havasu Creek) 244–389 recaptures

0–117 26 1

124 1 12,508 868 5 4

117–136 909 241 3 11

136–199 2 1 1 1

199–201 1 8

201–227 1 1

227–244 2 77

278 1 1 5 1

244–389 2

14,674

NOTE 541
fish moved throughout Grand Canyon. Two fish

moved to and from the main stem near rkm 72 and

the LCR (rkm 124) within 1 year, and five fish moved

to and from Havasu Creek (rkm 278) and the LCR with

the period between capture and recapture (Table 1)

ranging from 2 to 5 years.

Proportionally fewer large fish exhibited restricted

distribution than small fish. Only 76.5% of fish 300

mm or larger exhibited restricted distribution compared

with 93.5% of fish 200–299 mm, and 98.7% of fish

smaller than 200 mm (v2 1⁄4 881; df 1⁄4 2; P , 0.001).

Odds ratios revealed that small fish were 23 times more

likely to exhibit a restricted distribution compared with

large fish, and five times more likely compared with

medium-sized fish. Of the fish that exhibited a restricted

distribution, mean distance between capture and

recapture was typically lower for smaller fish.

Humpback chub 300 mm or larger had a longer

displacement between capture and recapture in the

main-stem Colorado River (F 1⁄4 4.39; df 1⁄4 2, 352; P 1⁄4

0.013) and the LCR (F 1⁄4 396, df 1⁄4 2, 9,584, P ,

0.001; Figure 3).

The percentage of fish exhibiting restricted distribution did differ by time at liberty (v2 1⁄4 592; df 1⁄4 7; P ,

0.0001), but it was never less than 71% (for fish at

liberty 5–10 years; N 1⁄4 666). The percentage of fish

exhibiting restricted distribution was greater than 90%

for fish at liberty 14–30 d (N 1⁄4 1,554), 31–90 d (N 1⁄4

3,283, and more than 10 years (N 1⁄4 29). When we

considered the LCR and LCR inflow as one river reach,

the proportion of fish that exhibited restricted distribution increased to 100% for fish at liberty 14–30 d, 31–

90 d, and more than 5 years, and never was below

99.3%.

Discussion

Humpback chub showed restricted distribution

within the Colorado River in Grand Canyon regardless

of the spatial and temporal scale analyzed. Previous

studies at shorter temporal scales demonstrated that

humpback chub may remain in the same areas during

spawning (Douglas and Marsh 1996; Gorman and

Stone 1999), and other studies have suggested that this

may occur annually as well (Keading et al. 1990;

Valdez and Ryel 1995; Gorman and Stone 1999).

Other large-river fishes have also shown substantial

migrations to the same areas (Pellett et al. 1998;

Stancill et al. 2002) and it has been suggested that this

may not differ even to 5 years (Hay et al. 2001). Our

study even found that fish at liberty over 10 (main-stem

Colorado River) to 12 (LCR) years were recaptured

near their same capture location. Other southwestern

desert fishes (e.g., Colorado pikeminnow) have shown

substantial migrations and a fidelity to spawning

locations across long (up to 10-year) temporal scales

(Tyus 1991), but others (e.g., razorback suckers) may

move among several spawning locations over 3 years

(Modde and Irving 1998), suggesting that some fish

may not imprint to specific spawning locations.

We could not confirm that all fish exhibiting restricted

distribution remained in the same area between capture

and recapture. Localized movements of adult humpback

chub within the LCR have been documented (Douglas

and Marsh 1996; Gorman and Stone 1999), and some of

these fish may remain in the LCR all year (Douglas and

Marsh 1996). However, these resident LCR fish were

typically smaller than 300 mm (Gorman and Stone

1999), likely explaining why this study found increased

fidelity of small (,200-mm) fish.

Our study suggests that the most movement between

rivers occurred at the confluence area (LCR inflow) of

the LCR and main-stem Colorado River. This is not

unusual, and it has been suggested that these fish are

part of the same population (Kaeding and Zimmerman

1983; Douglas and Marsh 1996; Valdez and Hoffnagle

1999; Meretsky et al. 2000). However, there were a few

humpback chub that moved at least 52 km upstream

and 154 km downstream of the LCR confluence,

suggesting that the LCR population does extend to

a large part of the Colorado River and that limited

movement may occur throughout Grand Canyon.

Scale can have important influences on the management and conservation of fishes (Fausch and Young

1995; Hay et al. 2001). Since short-term tagging

studies may miss important information relating to

distribution and movement (Hay et al. 2001), a longer

term evaluation of tag recaptures is necessary for

a more complete understanding of distribution and

movement in fishes. Our study involved 12 years of

recaptures of over 7,000 individual fish. The determination of whether fish remained in the same area

throughout the year or returned to the same area could

not be evaluated in this study. However, the larger

temporal scale suggests that restricted movement exists

over longer periods of time. Distribution and movement of humpback chub in Grand Canyon appear to be

primarily restricted to the LCR and LCR inflow area

and is in contrast to other southwestern river fishes that

may move long distances to meet their life history

requirements.

There appears to be little to no humpback chub

reproduction or recruitment occurring in the main-stem

Colorado River, probably because of the regulated,

stenothermic environment, the invasion by nonnatives

in the main stem (Clarkson and Childs 2000), and the

fact that the humpback chub population in Grand

Canyon is focused in and around the LCR. Management and monitoring of the humpback chub population

542 PAUKERT ET AL.
in Grand Canyon may be most logistically feasible on

a smaller scale that focuses on the LCR and its

confluence with the Colorado River. Researchers need

to choose the optimum sampling methodology to

accomplish their goals given reduced numbers of

endangered species, limited funds, and logistical

constraints (Tate et al. 2003). Although main-stem

Colorado River monitoring of humpback chub may be

needed to meet specific objectives (e.g., influence of

increased main-stem water temperature in the Colorado

River; Petersen and Paukert 2005), the trends in the

overall abundance of humpback chub in Grand Canyon

may be accomplished by focusing efforts in the LCR.

Acknowledgments

A special thanks to all the people who collected

humpback chub in Grand Canyon, including Arizona

Game and Fish Department, SWCA Environmental

FIGURE 3.—Displacement between capture and recapture for three sizes of fish that exhibited restricted distribution in the

Colorado River and its tributaries, Arizona, at three different temporal scales: 14–90 d, 91–365 d, and more than 365 d. Sizes of

fish were based on the mean lengths of the fish between the capture and recapture periods and were classified as small (,200

mm), medium (200–299 mm), and large (300 mm).

NOTE 543
Consultants, Inc., BIO/WEST, Humphrey Summit

Support, Arizona State University, and the U.S. Fish

and Wildlife Service. Ted Kennedy, Bill Persons,

David Ward, Dennis Stone, Dave Willis, and three

anonymous reviewers provided helpful comments on

this paper. This work could not have been completed

without the help of Cory Lochridge.

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