Prolonged Swimmhg Performance of Northern Squawfhh
U.S. Fish and WiIdl~eSmlce. ffafional Flsheri~sRrsmrch Cemreh!krtt/e
Columbia River Fleld S~ation.Cwk,Washingron 98605. USA
Absrracr. -We determined the prolonged swimrnin~performance oftwo s i z e - c h ~ aof nodern
squawfish Plychachtilw orrgonensls at 12 and 18T. The percentage of fish htigucd was positively
related to water velodty and best dmxibrol by an exponentid model. At 12C. the velocity at
which 50% of the fish Rtipucd (FVSO) was tstimatcd to be 2.91 fork Itngths ptr stcond (Wm:100
c d s ) for medium-sized Ash (3&39 cm) and 2.45 FUs (104 cmh) for lama fish ( 4 0 9 9 crn). At
IST. emtimated FVSO w a ~3.12 FUs (107 cmh) for medium Ash md 2.65 F y s (I I2 cmh) for
large fish. Rate of change in percent fatigue was affected by fish size and water temperature. Large
fish htigucd at a higher rate than medium-sized Ash; all Iish fatigued faster at 12 than at 1 8 T .
The mean times to fntigue at vclocitits of 102-1 15 cmh ran8cd Rorn 14 to 28 min and wart not
aflkted by fish size or water tempernturn. Our rcaults indicate that water velocities from 100 to
I30 cm/s may exclude or reduce predation by northern sqruwf~aharound juvenile snlmonid bypau
outRIIs at Columbia River dams, at learnt during certain urnern of the y m . We rccommcnd lhat
consuunion or modififation ofjuvenilc almonid byparr lircilitics p l m the outfall in an uea of
high watcr valocity and distant from eddies. submewd cover, mnd littoral a r m .
The northern squawfish Rychochdlus oregortensis is a major predator on juvenile salmonide
in a variety of waters (Jeppsan and Platts 1959;
Thompson and Tufts 1967; Poe et al. 1991). In
thc Columbia River. norihem squawfish prcdation on juvenile d m o n i d s is most intense in h c
tailrace areas downstream from dams (Poe et al.
199 1). a sccnario accurately predicted for rivcrine
systems by Brown and Moyle (1981). Predation
ntar dams is severe partly btCPuse prey arc concentrated ntar juvtnilc fish bypass outfalls and
may be less able to avoid predaloru because of
passage-related disorientation. stress, or injury
(Matthews et al. 1986; Maule et al. 1988).
Concern over the decline of many stocks of Pacihc salmon Oncorhynchw spp. hag led to efforts
aimed at increasing juvenile salmonid survival,
includin~a reduction in predation-related mortality. Although predator removal efforts arc currently underway in the Columbia River, other
methods designed to protect juvenile salmon as
they migrate downstream might be as efficient.
ecologically more prudent. and less costly. One
method of protecting juvenile ~ l m o n i d sis the
construction o r improvement of Iish bypass facilities, which help intercept fish in forebay areas,
divert them away fiom turbines, and allow them
relatively safe p a w e through the dam before they
exit into the tailrace. &cause nonhern squawfish
Present address: Pacific Power. 920 Southwent Sixth
Avenue, 1000 PSB,Portland w o n 97204, USA.
appear to prefer low water velocities around bypass outfalls (Falcr et al. 1988). a higher water
velocity there might exclude them or reduce their
numbers and thus decrease predation. Faler et al.
(1988) found that radio-tapped nonhern squawfish did no1 use water velocities greater than 70
cmls. However, their study did not filly address
the awimming ability of northern squawfish in high
water velocitics.
Although h e swimming performance of many
Rsh species has been documented (see reviews by
h m i s h 1978 and Vidclcr and Wardle 1991).
Bcrry and Pirnentel (I 985) cautioned againat uring
these data to predict the capabilities of unstudied
s&es. Our objective, therefore, was to determine
the endurance of northern squawfish s~prolongcd
swimming speeds. Prolonged swimming speeds are
those that a Bsh can maintain for up to 200 min
before fatiguing (Beamish 1978). We also aascwed
the effects of fish size and watcr tcrnpcrature on
swimming pcrfonnancc. Wc anticipate that lhis
information could aid in developing biological criteria for the location and operation of bypasa systems for protecting juvenile salmonids from prcdation by nonhcrn aquawfish.
Northern aquawfish were captured as nteded
ftom the Columbia River by eltctroflshing, with
a Mtrwin trap, and by angling and were transported to o w laboratory. They were held outdoom
under natural photoperiod in circular tanks (1.2
rn in diameter. 0.8 m deep) that received well
SWIMMING PERFORMANCE OF NORTHERN SQUAWFISH
water heated to f I T of the selected experimental
temperature. Water flow in the tanks produced a
circular current for orientation. All Ash wcre acclimated at least I week prior to testing and were
fed to excess with live juvenile coho salmon 0.
kisurch. Fish showing signs of diaeaw, injury, or
other abnormalities were excluded from testing.
Swimming teats wcre conducted from April
through Octobtr in 199 1 and 1992.
Swimming performance was measured in a
stamina tunnel similar to that used by Thomas ct
al. (1964) and Berry and Pimentel (1985). The
tunnel consisted of two 500-L reservoirs connected by two plexiglas pipcs. one a return-flow pipe
and the other a 0.2-m-diameter x 2.0-m-long
swimming chamber. An electric pump rccirculated water in the tunnel; motor awed was electronically controlled to product a wide range of water
velocities. We used linear regression to assess the
relation between water velocity (measured in cm/s
with P Pygmy flow meter) and motor speed. We
then calculated the motor speed (Hz) necessary to
produce a desired test velocity using the equation
(N 10, r Z = 0.99):
-
Hz
-
0.38 1
+ 0.533(velocity).
Fish were tested individually and encouraged to
swim by manually operating electrified s c m n s (510-V AC) located at each end of the swimming
chamber. The upstream screen kept fish from remaining at the chamber entrance, whereas the
downatream screen encouraged tiring fish to keep
swimming. About 1.5 m of the middle of the
swimming chamber was wrapped with black plastic except for the top, which allowed entrance of
light from above. This isolated the fish from outside disturbance and provided an aid for its orientation.
The presence ofa fish in the swimming chamber
can cause a solid blocking effect, whereby the object blocking the flow through part of the tunnel
cross section causes an inmast in flow velocity
around the object (Bell and Terhune 1970). To
correct for this, we determined the cross-sectional
area of a sample of our 6ah by cutting a fish at its
thickast point, tracing an impression of the cut
surface on blank paper. and measuring the area
with a digitizer, We then eatablished the relation
between cross-sectional (XC)srca and weight, using linear regression. as
-
XC (cm2)
-
-
17.8
+ 0.033(weight, g)
(N 37. r2 0.94). Bccauac 98% of our fish exceeded 10% of the cross-sectional area of the
1 105
chamber. we calculated corrected swimming velocities using the formula
- -
where V F = corrected velocity, VTP tcsl velocity,
t
0.8, A 0.7 length/thichess, A, = maximum
cross-8ectional area of fish, and A, = cross-scctional area of tunnel (Bcll and Terhune 1970).
Swimming performance of northern squawfiah
was asscssd at 1 2 T and 18°C for two size-groups.
medium (3CL39 cm fork length, FL)and large (4049 cm FL).These temperatures represent the average water temperature in the Columbia River
during the spring and summer juvenile salmonid
migrations. The size-groups are representative of
piscivorous northern squawfish in the Columbia
River (Poe et al. 199 1).
We used a test protocol similar to that of &rry
and Pimentel (1985). The day before testing. three
northern squawhh were seltctcd randomly and
transfemd to an isolation tank; food was withheld
kom these 5sh to minimize the effect of feeding
on standard metabolism (Btamish 1964; &rnatchez and Dodson 1985). The next morning. the
tunnel was filled with water at the acclimation
temperature of the fish. A single fish was netted
from the isolation tank, rapidly rneasurcd to the
nearest centimeter. and placed into the swimming
chamber, where it was allowed to acclimate for 30
min at a water velocity of 0.75 fork lengths per
second (FUs). Following this acclimation, water
velocity was gradually incrcaaed over about 5 min
to a selected test velocity that ranged from 1.4 to
3.0 F U a .
Test velocities were aclectcd baaed on data we
obtained from preliminary experiments. In this
preliminary work. we subjected 13 fish to a range
of velocities (based on velocities used by Berry
and Pimentel 1985) and determined when swimming became very difficult or ceami completely.
This procedure provided an approximate flow
range that pr&luced rapid fatigue. We chose 1.4
FVs as the low end of the range because all fish
could swim easily at this speed and we could divide the total range into enough incraments to
fully characterize Ash performance. During the first
year, we used data from test fish to increase the
precision of the high end of the range.
Fish were tested for 120 min or until fatigued;
sample aize varied at each test velocity because of
variability In wrformanct. We defined a fish as
fatigucd when it became impinged on and would
not leave the downstream screen despite several
shocks. Following a teat, swimming tirnc was re-
MESA AND OLSON
FIOUREI.-Rtlrtionships between pcrantpLc of fatigued finh and mtcr velocity at 12 and 18'C for medium
(3&39 cm FL) and large (40-49 cm FL)northern squawfish. All vclocitia ut c o r n e d for solid blockir~effect#
and are h s c d on the average vcloci~yof all fish tented in each group. Clrcln IX,bhnglts I B t . Curves arc
61s orthe exponential model: % fatigued b . P V . I ~ Y .
-
-
corded, and fish were removed. aacrificad. and
weighed to the nearest 25 g.
Wc used a "doueresponse" approach to describe the relation between percentage of fish fatigued and water velocity for both size-groups and
tempcraturts (Brett 1967). Scatter plots augge~ttd
h a t the relation bctwecn percent fatigue and water
velocity was curvilinear. To provide a ~eneraldescription ofthis relation, we used an iterative, leastsquares procedure to 6t the exponential model
-
water velocity
whart y = parcent fatigued. x
(Fys), and b and m are coeflicients. Wa estimated
the velocity at which 50% of the Ash htiguad
(EV50) by refitting the data to a linear model. To
do this, we added I to all percent fatigue valucs
and transformed them to their natural logaritbrns.
We then used simple linear regression to inversely
predict water velocity at 50% fatigue. Standard
deviations and the I-atatistic were used to d c u late 95% confidence limitn for predicted water velodies (Neter et al. 1983).
To araeas the effects of Bsh aize and water temperaturt on percent fatigue, we did pairwise comparisons of homogeneity of slope for the linear
repmion equations (Zar 1984). We compared
slopes for each tcrnperntm between Bsh sizegroups and for each s i z e - p u p between temper-
-
atures. Homogenous slopes would indicate that
the rate of change in wrctnt fatigue elicited by an
increase in water velocity was similar between
group$.
We calculated the mean time to fatigue for tach
group using the fatigue times from d l individuals
that htigued at the two or t h m highest velocities
tested. We exprtssad the water velocity for the
mean htipue time as tho average of the velocities
in which thew Bsh had fatigued. A 2 x 2 factorial
analyuis of variance was ustd to a s m s the effects
of fish size and water temperature on m a n fatigue
time.
Rerdtr
We tertcd 345 fish; difimnces in rizc bttwcen
large (N 172; average length SE 43.5 f 0.2
cm;average weight + SE = 976.6 3~ 15.7 0) and
medium (N 173; 35.5 + 0.2 cm; 530.8 f 1 1.4
g) northern squawfish wem significant (two-sumple I-tests, P < 0.05). The percentage of fish fatigued was positively related to water velocity and
well described by the exponential model (Figure
1). Coefficients of determination for the four exponential curves ranged from 0.92 to 0.95. Estimates of FV5O values in W s for larpe fish were
lower than those for medium Bsh. but when expremed in absolute sptads, swimming speed was
positively rclatcd to L h size (Table 1).
-
+
-
-
1107
SWIMMINO PERFORMANCE OF NORTHERN SQUAWFISH
TABLE
1.-Redictcd water velocitiw at which 50% of
Rsh fatigued ( W 5 0 )and h e i r rssodattd 95% confidence
limits for northern squawfish during swimming pcrformancc ttlts. Values of FV5Oartexpmsed in fork length#
(FL)pcr stcond and the equivalent absolute swimming
apccd. All velocitita am comcttd for lolid blocking cfftcts.
Both fish size and water temperature significantly influenced the rate of change in percent fatigue, because all pairwise comparisons indicated
rcgrcs~ionslopes w e e nignifiantly different (Table 2). h r g e fish fatigued faater than medium fish
at both temperatures and all fifih fatiwed faster at
12°C than at 18T.
The mean times to fatigue for a11 fish ranged
from 14 to 28 min and were not significantly (P
> 0.05) affected by fish size or water temperature
(Table
3).
The prolonged swimming performance of
northern squawfish, as expressed by o w FVSO values, compares favorably with that of large Colorado squawfish P. lucius at 14 and 20°C (Berry
and Pimcnttl 1985), indicating that the performances of comparable sizes of these congeners
may be similar. The preference of Colorado
squawfish for large riverine systems (Moyle 1976;
Tyus et al. 1984) and their migratory behavior
(Tyus 1990) might imply a swimming performance advantage when compared with the pref-
TABLE
3.-Mean (and SE) fatigue times and auociattd
water velocitita for northern s q u a d a h duringawimming
performance tests. Mean fbtl~uetimes wcra derived from
all hdividluls thal fhtigucd at the two or t h m highest
velocities tested: warn vclocity is the avcrnge of theme
vclocitin m d is corrected for lolid blocking effccts.
erence of northern squnwllsh for low-velocity microhnbitats (Btnmesdcrfar 1983; Falcr et d. 1988).
Indeed. the life hintory forms of scveral aptcics
that undertake frequent swimming (e.g., extended
anadromous mijp-ations) posres~greater swimming capabilities tban those of more Btdentary
populations (Tsuyuki m d Williscroft 1977; Taylor and McPhail 1985; Taylor and Footc 1991).
Because Colorado squawfish wara (and still are)
threatened with extinction. Berry and Pimentel
(1985) had to use unexercid. hatchery-reared fish
and they did not correct for solid blocking effects.
Thus, the similarity in swimming performance bctween these two species r n i b t not adequately rcflcct their life hirtory differences.
Although lagt fish fatigued at a higher rate than
medium Rsh, this may in pan reflect the limitations of the swimming chamber. As fish size increased. a greater proportion of the cross-sectional
area of the chamber was occupied, which perhaps
made large fish feel more restrained and less Likely
to perform adequately. However, we saw no evidence that the tunnel restricted fish movements
and the diameter of our tunnel was the m e as
that uscd by Berry and Pimunte1(1985), who swam
larger fish than we did. Fish size is among the most
TABLE
2 . - ~ t - s q u m mgrmion equations for the relationship between p c r c t n a e of northern q u a w b h
fati~ued(I-)
and water velocity at two temperatures and two Ash size-classes. Water velocity is in fork lengths
per second. Asterisks denote slopes (i.e.. mlos of fatigue) that direr significantly between groupr. Vdum of the
r-statistic am significanl at P 5 0.05*, P 3 0.018*. or P 5 O.OOlm.
Gmup
Fish size
Ternpsrrturc (T)
I
Mcdium
12
2
I8
S l o p mrnprrlmn
Linrar cqluiion
l a % hugue)
lo&(% htlgue)
-
-6,76
+ 3.66~velocity
- -5.36 + 2.97.veloclry
N
rz
Tmr
6
0.84
1 vmuw 3
I vcraur 2
2 venus 4
7
0.87
I
5.27**
3.36.
5.27"
1108
MESA A N D OLSON
imponant constraints on swimming performance
and can directly affect endurance (Ikamish 1978).
The size (and temperature) e k t s we observed in
our fish illustrate the importance ofanalyzing the
data separately among groupa. Compared to an
analysis of pooled data, our approach resulted in
mom accurate curve fitting and mctimates ofFV50.
Northern squawfish demonstrated a better prolonged swimming performance at l 8 T than at
I 2 T . The swimming performance of fish typically
increases with water temperature (Brett 1967;
Glova and McInerney 1977; Bernatchez and Dodson 1985) and peaks at an optimum temperature
at which physiological functions are most emcient.
As temperature increases, fish may have a greater
oxygen uptake capacity (Bcrnatchcz and Dodson
1985) o r may show increases in metabolic rates
or enzymatic proctssa (Brett 1967). B r o w and
Moyle (198 1) stated that nonhcm squswflsh prefer water temperatures ranging from 16 to 22°C.
Recent studies (Bcycr et al. 1988; Vigp and Burley
199 1) have shown that consumption and evacuation rates of northcrn squawfish peak near 2 I T .
This indimtes an optimum temperature for northem quawfiah greater than 1 8 T , so our data may
underestimate their maximum swimming capability.
Thc mean fatigue times of our Bsh, in contrast
to ptrcent fatigue, were not influenced by fish size
or water temperature. Other studies have shown
fatigue times of other Ashes to be significantly influenced by life history form (Tsuyuki and Williscroft 1977; Taylor and McPhail 1985), water tcmperature, water velocity, and fish size (Brett 1967;
Bernatchez and Dodson 1985). Although further
research is needed to filly understand the factors
influencing northcrn squawfish fatigue time, the
propensity of these fish to fatigue in a shon period
may have important implications for predatorprey interactions in faat-moving water.
Implications for PredutorcPrey Interactions
Information on the swimming performances of
fishes has been uacd for various management decisions. including assearments of tht design of fish
laddere (Collins et al. 1962; Slatick 197 I), water
intakes ( h m ct al. 1979), and culverts (Jones el
al. 1974) and of the sublethal effects of pollutants
(for a rcvicw scc kitingar and McCauley 1990).
In the Columbia River, the use of high water velocitiea to exclude o r limit predation by northern
squawfish on salmonids in the arca of dam bypass
outMls seems promising. Bypass outfalls could bt
located in areas with high water velocities, per-
haps reducing the eficiency of prtdatom. During
juvenile salmonid migrations in spring and early
summer. this scenario may already be working to
some extent. During this period, water ternpcratures are low, flows are high, consumption rates
by nonhcm squnwfich are relatively low (Vigg el
al. 199 1), and the swimming ability of these p r d
ators presumably is reduced. In addition to crcating an arca that excludes predators, high flows
should also move juvenile salmonids downstream
faster and keep them out of predator-inhabited
eddies o r littoral areas. As fish move d o r m s t r m ,
predation rates by northern squawfish decrease
(Vigg ct al. 199 I), perhaps because juvenile salmonids are dispersed and migrate in water offshore,
near the surface, and at night (Brown and Moyle
198 1).
During periods when river flows arc low and
thus d o not fatigue the fish, the energetic benefits
and costa of swimming may determine whether
nonhern squawfish would inhabit areas around
bypass outfslls. The metabolic costs associated
with prolonged swimming speeds and maintaining position increase with water velocity and may
involve aerobic and anaerobic processes (Bearnish
1978: F a a y and Grossman 1990). The high energetic demands o f a three-stage (approach, chase,
and strike) predatory strategy (Harper and Blake
1988), which we believe typifies northern squawfish behavior, would also presumably incrcasc directly with water velocity, perhaps precluding efficient feeding in areas of high water velocity. We
recommend that the outfalls of new or modified
bypass facilities for juvenile aalmonids be sited in
areas of high water velocity (e.g.. 100-1 30 cmh)
and dislant from eddies, submerged cover, and
littoral areas.
We thnnk A. Murphy and T. McGuirt for conducting some of the performance tests, J. Bloodgood for his exceptional ttchniad assistance, and
W . R. Nelson, B. Muir, T. Poc, and J. Zuboy for
reviewing the manuscript. This work was funded
v ~ ~ Administration (conmct DEby B o M ~ Power
A179-88BP9 1964).
Ekrmesdcrfer. R.C. 1983. Reproductive biology.early
life history. and mlcrobabitnt of northorn lquawRsh
(Plychmhriltcr oregonemis) in the St. Joe River,
Idaho. Master's thesis. University of Idaho, MoaCOW.
SWIMMfNO PERFORMANCE OF NORTHERN SQUAWFISH
Bcamirh, F. W. H. 1964. Respiration of fishes with
aptcia1 emphanis on standard oxygen consumption.
11. Influence of weight and temperature on m p i ration of rcveral specits. Canadian Journal of 20ology 42: 177-1 88.
Beamirh. F. W. H. 1978. Swimming capacity. Pages
101-175 in W. S. Hoar and D. J. Randall, editors.
Fish physiology. Academic Pms. New York.
Ekitinger. T. I..and R. W. McCaulcy. 1990. Wholeanimal physiological proccsscs for the asscssmtnl
of stress in Rshn, Journal of Great Lakes Research
16542-575.
Bell. W. H., and I.D. 8. Terhune. 1970. Water tunncl
desilpl for fisheries mearch. Fiaherita Research
Board of Canada Technical Report 195.
krnatchez. L., and J. J. Dodmn. 1985. Influence of
ttmpcraturc and cumnt aped on the nwimming
capacity or lake whitefish (Coregonus c/upeqlbrmis)
and cisco (C. artcdi~).Canadian Journal of Fishcrics
and Aquntic Scicnccr 42: 1522-1 529.
Bcrry. C. R.. Jr.. and R. Pimentel. 1985. Swimrninp
pcrformanccs or t h m rare Colorado River fishes.
Transactioru of the American Fisheries Society 1 14:
397402.
Beyer, J , M., 0.Lucchctti. and G . Gny. 1988. Digcstive tnct evacualion in nonhtrn squawfish (Prychochdlur oregonensis). Canadian Journal of Fiaheries
and Aquatic Sdences 45:548-553.
Brett. J. R. 1967. Swimminl pcrfonnmcc of sockeye
salmon (Oncorhynchm nerka) in relation to fatiaue
time and temperature. Journal of the Fisheries Research Board of Canada 24: 1731-1 74 I.
Brown, L. R., and P. B. Moyle. 1981. The impact of
squawflsh on ralmonid populations: a review. Nonh
American Journal of Fiaheries Management 1 : 104111.
Collins, G. B., J. R. Gauley, and C. H. Elling. 1962.
Ability ofsalmonidr to aaetnd high fishways. Transactions of the American Flaherlca Society 9 1 :1-7.
Dorn. P.. L. Johnson, m d C. Darby. 1979. The swimming ptrformance or nine specla of common Californim inshore fishes. Transactions of the American
Fisheries Swicty 108366372,
Fscey. D. E.. and a. D. Qmssmnn. 1990. The mehbolic cost of maintaining position for four North
Amcrican s t m m fishes: e&ts or season and velocity. Physiological Zoology 63357-176.
Fslcr. M. P., L. M. Millar, and K. I. Welke. 1988. Effern of variation in flow on distributions of northern squawfish in the Columbia Rivcr below McNary
Dam. Nonh American Journal of Fisheries Management 8:3&35.
Glove. G.J.. and J. E. Mclnerney. 1977. Critical swimming speeds of coho salmon (Oncorhynchm kisurch) Try 10 smolt stages in relation to salinity and
tcrnptfllture. Journal of the Fishcriea Rcacarch Board
of Cmn& 34: 151-1 54.
Harper, D. G., and R. W. Blake. 1988. Energetics of
pircivorour prtdatovrey intcmctions. Journal of
Theoretical Blology 134:59-76.
Jcppson, P. W., md W. S. Platts, 1959. Ecolofy and
control orthe Columbia squawfish in n o n h e i Ida-
1109
ho lakes. Tranmctiona of the A m e r i m Fisherita
Society 88: 197-202.
Jontr, D. R., J. W. Kiccniuk, and 0. S.Barnford. 1974.
Evaluation of the swimming parformma of mvenl
hsh species from the Macktnzie River. Journal of
the Fisheries Research Board or Canada 3 1: 164 11647.
Manhem. 0.M., D. L. Pork. S. Achord, and T. E.
Ruehle. 1986. Static leawater challenge test to
mearum relative strtsa kvels in spring chinook
d m o n smoits. T r n n l ~ d o n of
s lhe American Fisherfts Society 112236-244.
Maulc, A. G.,C. B. Schnck. C. S. Bradford, and B. A.
W o n . 1988. Physiological cffms of collecting
and trnnsponinp emigrating juvenile chinook d m on past damn on the Columbia River. Trnnwctiona
of the American Fisheries Society 1 17:24>26 1.
Moyle. P. B. 1976. Inland fishes of California. University of Cdifomia Reu. Bcrkclcy.
Netar, J., W. Wnssennan. and M. H. Kurner. 1983.
Applied Hnar regrcuion mdels. Imin, Homew d , Illinois.
Poc, T.P.. H. C. Hansel, S. Vigg, D. E. Palmer. and L.
A. Prmdergast. 1991. Feeding of predaceous fishes on out-migr~tingjuveniltmlmonids in John Day
Rcatrvoir, Columbia Rivcr. Transactions of the
American Fisheries Society 120:405-420.
Shtick. E. 1971. Paasage of adult salmon and trout
through an inclined pipe. Transuctions of Lhc Amcrican Fisheries W e t y 100:448455.
Taylor. E. 9.. andC. J. Foole. 1991. Critical swimming
velocitica of juvenile cockcyc d m o n and kokanec,
the nnadromousand non-anadromous forms of Oncorhynchlls nerka (Walbaum). Journal of Fish Biology 38:407419.
Taylor, E. B., and J. D. McPhail. 1985. Variation in
bunt and prolonged swimming pcrfonnance among
British Columbia populntions of coho d m o n . Oncorhynchru kisurch. Canadian Journal of Fisherits
and Aquatic Sciences 422029-2033.
Thomas. A. E.. R. E. Burrowa, and H. H. Chenoweh
1964. A device for stamina rntaaumncnr of fingerling salmonids. U.S. Fish and Wildlife Strvicc
Rerearch Repon 67.
Thompson, R. B.. and D. F. Tuns. 1967. Predation
by Dolly Varden and northern squawfish on hatche r y - r t a d mkeye salmon in W e Wenatchcc,
Washington. T n n ~ c t i o n rof the American Fiaharias Society 96:424427.
Tsuyuki. H., and N. Willimft. 1977. Swimming
rtamina differences between genotypically diatinct
rorms of ninbow (Salmo gairdnrri) and stmlhmd
trout. Journal of Ihe Fiaherica Rcar~rchb a r d of
Canadn 34:996-1003.
Tyus. H. M. 1990. Potamdromy and reproducrion of
Colorado squawfish in tho Oman River Basin, Colorado and Utah. Transactions of the A m c r i m
Fishcrics Socicty 1 19: 1035-1 047.
Tyus. H. M..B. D. Burdick, and C. McAda. 1984. UBC
of rmdiotelemetry for obtaining habitat preference
datn on Colorado squnwfish. Nonh American Journ d of Flshcrln ~ a n a g c m c n4:
t 177-180.