7mtutlcrion.r qf the Amcriro~lFisltrric~Socity 131:492- 497. 2002
bn Copyriyhr by the Amrrictln Fisheries Sul-iety 2 0 2
Effects of Temperature, Fish Length, and Exercise on
Swimming Performance of Age-0 Flannelmouth Sucker
Arizona Coup~rativeFish u d Wildlge Research Unit.
Universily ufdrizonu, 104 Bioscience,r East,
Tucson, Arlzona 85721, IJSA
School of K ~ n e w u b lNatural
~
Resources,
Universio of Ariznnu, 323 Bioscirnces East,
Tucson, Arizona 85721, USA
Ab.rtract.-The flunnelmouth sucker Cutostomus lotipinnis is one of the few native tish that persists
in the lower Colorado River basin. Little is known about the effects of hypolininetic relenses of
cold, swift wnter from Colorildo River dams on Rnnnelmouth ~uckerpopulntions. We conducted
fatigue velocity tests on nge-0 flunnelmouth suckers in the lnhoratory to cvaluute the effects of
water ternpernture and fish size on swimming ability. Fish of 25-1 14 mm totnl length ('TL) were
suhjectcd to incremental increases in water velocity until tfie upper limit of their swimming nbility
was reached. Swimming tmts were conducted nt 10, 14, hnd 20°C. Swimming ability increnaed
with tish length and was dircclly related to water temperalure at nll tish sizes. A decrease in wnter
temperature from 20°C to IO°C resultcd in an averngc decrease in swimming nbility oT40B. Meon
swimming ability of wild-caught flannelmouth sucker^ was 7 cmls higher than that of captivercnred flannelmouth suckcrg of similnr size at 20°C nnd 14'C. Flnnnelmouth suckers subjected to
an abrupt 10°C tempernture drop did not have signiticantly different swimming ability than Rnnnelrnouth suckers acclimated lo'10T over 4 d.
i
The construction nnd operiition of hydroelectric
dams have transformed ihc Colorado River from
a warm, turbid, and highly dynamic stream into a
system dominated by large reservoirs and cold tailwaters. These changes have dramatically affected
the abundance o f many native fishes, including the
flannelmouth sucker Cutostomus latipinnis. Rcduccd summer wnter temperature has been implicated in the decline of native fish in Glen and
Grand canyons (Kacding and Zimmermun 1983;
Childs nnd Clarkson 1996; Robinson et al. 1998;
Clarkson and Childs 2000). After conlpletion of
Glcn Canyon Dam in 1963, maximum summer river tcnlperaiures were reduced from 25-30°C to a
neurly constunt temperature of 10°C. and nonnative rainbow trout Oncorynckus mykiss and hrown
trout Salmo truttn were introduced. As a result,
naiive fish now experiencc colder water [emperatures and predation from the introduced trout,
conditions that may rcsult i n a low survivul rate
for young, native fish.
* Corresponding nuthor: dmward@)thcriver.com
'
Prcsenl addrcss: Arizonn Gume find Fish Dcparlmenl, Research Brunch, 2221 West Grccnway Road,
Phueniz, Arimna 85023, tJSA.
Rcccivrd 1)eccmbar 2 1. 2000; ucceptcd Novernbcr 9, 2001
Flannelmouth suckers spawn in the Paria River,
a tributary o r thc Colorado River located 25 km
below Glen Canyon Dam (Weiss 1993). Young
flannclmouth suckers use the mouths of tributaries
us nursery arcas until they move into thc Colorado
River m i i n stem in late summer (Thieme el al.
2001). Large numbers of a g e d flannclmouth suckers are commonly captured at the mouth of the
Paria River (Hoffnagle 1999), but cntch dattl from
a variety of sumpling methods indicutc that low
numbers of juvenile flannelmouth suckers are present in thc Colorado River in Glen and Grand canyons (Valdcz and Rye1 1995; McKinncy et al.
1999a). This lack of recruitment may lend to population declines and extirpation of flunnelmouth
suckers bclow Glen Canyon Dam. Three other species of fifih endemic to lhc Colorado River-the
Colorado pikcminnow Ptychochrilus lucius, the
bonylail chub Gila eIegun.v, and the ramrback
sucker Xymuchen texanu.s-havc already been extirpated or are exceedingly rare downstream of
Glen Canyon Dam (Minckley 1991).
Probable explanations for thc rarity o f agc-0 und
juvenile flannelnlouth suckers in thc Colorado River in Glen and Grand cunyons include ( 1 ) a cold
shock that causes the direct mortulity of age-0 flannelrnouth suckers as they exit warm tributaries and
494
WARD ET AL.
TABLE1.-Fatigue velocity (FV50; 95% confidence intervals in parentheses) of nge-0 flannelmouth suckers after
4 d of acclimation to test temperatures; FV50 is the velocity at which 50% of Hsh fail to swim for 30 min and become
impinged on a downstream screen.
Tempern-
Totnl length
(mm)
IUR
("c)
Men11
Kmge
or reduced swimming ability at each size. These
tests simulatcd the 10°C temperature change flannelrnouth suckers may experience as they exit
warm tributaries and enter the Colorado River. We
removed fish from the rearing tank at 20°C and
placed thcm directly into the test chamber at the
test temperaturc without an acclimation period.
Cold shocked fish wcrc returned to thc rcaring tank
following tesling and monitored for delayed mortality for 3 d. Thc procedures used for the cold
shock tests were identical to those used for the
acclimated fish in all othcr aspects. We used lugistic regression to estimate an FV50 for each of
the nine size groups at each tempcraturc. A twosample t-test was used to compare the differences
in mean fatigue velocity of acclimated versus nonacclimated fish.
ESfect of cuptivc rearing,-Seventy-five wild
flannelmouth suckers (averaging 50 m m TL) were
seined from the mouth of the Paria River and subjcctcd to fixed velocity swimming tests in the laboratory within 48 h of capture. We calculated FV50
values for these fish at each of the three tempcatures and compared those for wild and captivc-
Number of Number
volocitie~ of flsh
PV50 (cmds)
reared flannelmouth suckers of similar size by
comparing the 95% CIS.
Results
Fatigue velocities increased with fish size and
water temperaturc (Table 1). The relationship between fish size, water tcmperature, and the FV50
of age-0 flannelmouth suckers of 25-1 14 mm mean
TL was as follows:
FV50
=
3.78
+ 0.62 (temperature)
+ 0.07 (fish length)
-t 0.01 (tcmpernture X length interaction).
Temperature, fish length, and the interaction between temperature and fish length all had a significant effect on FV50 (P < 0.001). With all other
factors held constant, swimming ability was directly related to tcmperature. A decrease in temperature from 20°C to 14°C resulted in a 23.5%
average decrease in mean swimming ability
(range, 19.0-29.0%). A decrease in water temperature from 20°C to 10°C resulted in tl 40.2%
495
SUCKER S W I M M I N G PERFORMANCE
uth suckers t~ftcr
rnin and become
20 30 40 50 60 70 80 80 100110120
Mean Total Length (mm)
Temperature
FIOUREI .-Fatigue velocity (FV50)and 95% confidencc intcrvnls oi nge-0 flnnnelmouth suckers (total
length = 25-1 14 m m ) nt 20, 14, and 10°C following 4
d of ncclimation LO test temperatures; FV50 is the velocity nt which 50% of fish fnil to swim Tor' 30 min.
F I ~ L I R2.-Pnligue
E
velocity (FV50) nnd 95% confidence inlervals of wild versus cnptivc-rcnrcd flnnnelmoulh suckers (totnl length = 50 mm) nt 20, 14. and
10°C. Asterisks denotc stntisticnlly significnnt differences.
dearcase in mean swimming ability (range, 32.343.7%; Figure I).
EfSect ufretesting.-The
fatigue velocities of 40rnm flannclmouth suckcrs that had been previously
tested were not significantly differeni from thosc
of untested fish (P = 0.94). Repeated testing may
ultcr swimming ubility, but we saw no evidence
of such in our two test events.
Eff~vct~ g c n l dshock.-Flunnclmouth suckers acclimated to cold temperatures for 4 d hefore tcsting
did not have different fatigue velocities than coldshocked fish ( P = 0.1 H for 20-14°C thermal shock,
P = 0.12 for 20-10°C thermal shock). A lhcrmul
shock of IO"C or less rcsultcd in no mortality of
the 264 fish tested. Whether a 4-d acclimation period is adequate to ensure complete physiologic
acclimation to test temperatures is unknown for
this species.
Eflect oJ clrprivr rearing.-At
20°C und 14°C.
wild-caught flannclmouth suckers tested within 48
h of capture showed higher faiigue velocitics than
captive-reared, nonexercised individuals of about
the sumc size. At 20"C, the fatigue velocity of
wild-caught flannelmouth suckers (mean = 45.7
c d s ) was 7.1 cmls higher (95% CI = 4.6-9.6 cmd
s) than the fatigue velocity of cuptivc-rcared individuals. At 14°C. the fatigue veloci~yof wildcaught flannelmouth suckers (meun = 36.7 c d s )
wus 7.2 cmls higher (95% CI = 4.7-9.8 cmls) than
the fatigue velocity of captive-reared fish. At 1U0C,
the fatigue velocities of wild-caught flannelmouth
suckers and caplive-reared fish were not different
( P > 0 . 0 5 ; Figurc 2).
The swimming ability of flannelmouth suckers
was 40% lower at 10°C than at 20°C. This reduction in swimming pcrfvrmance may limit the ability of age-0 flnnnelmouth suckers to survive in the
Colorado River. The number of adult rainbow troul
in the area from Glen Cnnyon Dnm to Lees Ferry
is estimated to be ut least 7.800fkm (McKinney ct
al. 1909b). The high number of trout in Glen Canyon, comhincd with the reduced swimming ability
o r young fish, mny lead to n high predation mortiality of young flnnnelmouth suckers.
Cold shock often is cited us u potential cause of
mortality for uge-0 ni~tivefish that exit seasonally
warm tributaries and enter cold water in the Colorudo River (Lupher and Clarkson 1993; Valdez
and Rycl 1995; Thierne et al. 2001). In our expcriments, a 10°C cold shock (which represents
the temperature change age-0 flannelmouth suckers experience when exiting the Puria River) did
not result in mortality. Plannelmouth sucker lurvue
7-43 d posthatch also showed no direct mo~tulity
due to cold shock (Clarkson m d Childs 2000).
Flannelmouth suckers therefore appear tci have the
ability to withstand relatively large lernpcruture
fluctuations.
The size at which flannclinouth suckers enter
the Colorado Rivcr varies among years (Hoffnagle
1999), This may have important implications for
recruitment bccnuse larger fish have greater swimming uhility iind may have a higher rate of survival. Areas with waier velocity above the maximum swimming ability of small, a g e 4 fish are not
iivailable for use (Scheidegger and Bain 1995;
Discussion
.'
milar size by
fish size and
:lationship beand thc FV50
-1 1 4 m m m e a n
I
th interaction).
interaction beall hud a sigWith all other
bility was di:Tease in tem:d in u 23.5%
lming ability
in watcr tcm-
496
WARD ET AL.
Ruetz and Jcnnings 2000). Midchanncl watcr vel ~ c i t i c sin the Colorado River (Garrett et al. 1993)
are several times higher than the fatigue velocities
we measured in the laboratory and may block the
nlovetnent of age-0 fish between low-velocity environments. In muny areas, water velocity within
2.5 m of the bank exceeds the fatigue velocities
we measured for age-0 flannelinouth suckers at
10°C (Cunverse 1996). Subyearling flannelmouth
suckers that arc unable to access low-vclocity arcas or find refuge behind instreain objccts may
become cntraincd in high-velocity currents and
consequently be injured or killed by turbulence or
abrusion against substrates (Clarkson and Childs
2000).
Fish rearcd in nonmoving water have significantly reduced swimming ability compared with
wild fish or exercised individuals (reviewed in Davidson 1997). Our results agree with these findings
at 20°C and 14'C. Water temperature limited swimming ability at 10°C for both wild and captiverearcd fish. Our estimates of swimming ability at
10°C using captive-reared fish are likely to accurately reflect the swimming ability of wild fish
when they exit the Paria Kiver and enter the Colpfudo Rivcr. Our estimates of swimming ability at
' 14°C und 20°C are likely to b e low due to the
greater swimming nbility of cxcrcised wild fish at
these temperatures. The increased swimming ability of wild fish is consistent with swimming tests
performed on wild-caught und captive-reared salmonids (Grecn 1964). The addition of 7 cmls to
the FV50 at 14'C and 20°C corrects for the increased swimming ability of wild fish and is morc
likely to accurately represent the swimming ability
of wild flanneln~outhsuckers in the Paria River.
Inforninticm on the swimming ability of flannelmouth suckers may give insight into why the
p o p ~ ~ l a t i o nofs other nativc Colorado River fish nre
declining, The Colorado pikeminnow, humpback
chub, and bonytuil chub all have thermal prcfercnces similar to that of the flnnnelmouth sucker
(Bulkley et al. 1981) und exhibit comparable
swimming nbililies for similar-sized fish (Berry
and Pimentel 19KS). Humpback chub spiiwn in
tributaries lo the Colorado River similar to those
uscd by thc flannelrnouth sucker. A g e 4 hunipbuck
chub may also expcrience dccreases in swimming
ability that rcsult in increased predation or displacement when exiting seasonully warmed tributaries.
Low water temperature below hydroelectric
dams can impair the swimming ability of uge-0
flannelmouth suckers. Thus. modifications to Glen
Canyon Dam that increase summer water tcmperatures downstream are likely to increase the swimming ability of age-0 flannelmouth suckers.
Whcther an increase in temperature will allow a
higher rute of survival of flannelmouth suckers in
the Colorado River is unknown, but increased
swimming ability may reduce predation risk and
increase the range of areas uge-0 flannelmouth
suckers may occupy.
Acknowledgments
Funding for this project was provided by the
U.S. Fish and Wildlife Service, Intra-Agency
Agreement Number 1448-201 8 l-9X-H72O. We
thank Munuel Uliberri and Chester Figiel of the
Willow Beach National Fish Hatchery for their
suggestions on fish culture. We me also grateful
to Mike Childs, Scott Rogers. Tim Hoffnagle, and
Pam Sponholtz of the Arizona Game and Fish Dcpurtment for their advice on swimming tcsts and
for their hclp with collecting fish. We express our
appreciation to Kevin Fitzsimmons and Gary
Dickenson of the Environmcnlal Research Laboratory in Tucson, Arizona, for their helpful reviews
of this manuscript and valuable technical nssistance.
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