Effects of Time and Velocity Increments on the
Critical Swimming Speed of Largemouth Bass
(Micropterm salmoides)
S. FAFIUNCER
AND F. W. H. BEAMISH
De artment of Zoolo
19 7 7
N I Ef?~ W I
&iversity ofCutl
Guclph, Ontario
ABSTRACT
Critical swimming rpmd wae rnoasured for largemouth baar and found to be related to the
increments of both tlmc and water velocity. Critical speed decreased with increaat: in time Interval,
and reached a p e d and declined thereafter wlth Increasing velocity increment.
Fish locomotion can be classified within the critical speed or to intervals of 20 to 40
three categories: sustained, prolonged, and min between increments.
burst swimming (Beamiah 1977). Each cateThe preeent study was undertaken to
gory reflects the conetrainte imposed by examine the relationship between rate of vetime and by the biochemical processes locity increase and critical swimming speed
which supply the fuel for its application. for largemouth bass.
Sustained swimming is applied to those
METHODS
speeds which can be mairitained for long
periods without resulting in muscular
Largemouth base of mean fork length 10.4
fatigue. Prolonged speeds are higher than crn (range %12 cm) and mean total wet
sustained, last for a shorter ~ e r i o dof time. weight 13.9 g (range 8.6-24.1 g) were capand depend on both aerobic and anaerobic tured from a private pond near Stratford,
metabolism. Burst apeeds represent the Ontario and transported to holding tanks
highest velocities which fish can attain, are supplied with aerated, non-chlorinated well
maintained for periods of only a few sec- water. Temperature of holding tanks wae
onds, and are fueled to a great extent from eimilar to that of the pond when fish were
energy released through anaerobic pro- captured, 15 C, but thereafter was increased 2 C daily to 25 C. Base were mainA special category of prolonged speed, tained at this temperature for 8 weeka becritical swimming speed. was defined and fore experimentation. Photoperiod was 16 h
employed by Brett (1964) as a measure pf of light and 8 h of darknese with !h h of
the maximum velocity 'fish could maintain brightening or dimming at each end of the
for a preciae time period. Brett used a time light period. Fish were fed to satiation daily
period of 60 min following a stepwise pro- on a diet developed by Cho et al. 1974
gression of 10 cm s-' incremente. Recently (GRT-7-2).
the concept of critical swimming speed has
Base were conditioned in an annular
been applied frequently in performance trough (Grayton 1975) to swim againat a curstudies but without a standard rate of veloc- rent of 15 to 20 cm a-' for 10 days prior to
ity increase (Jones 1971; Webb 1971; Glova experimentation. During conditioning, bass
1972; Griffithe and Alderdice 1972; Greer- were fed daily until the find 24 h before an
Walker and Pull 1973; Otto and Rice 1974). experiment when food wae withheld to asIndeed, the influence of velocity rate sure a post-absorptive state (Niimi and
change on critical speed has received al- Beamish 1974).
most no attention, the notable exception
Swimming performance was measured in
being the investigation by Jones (1971). He a 200-liter recirculating water tunnel
found critical performance of rainbow trout, (Farmer and Beamish 1969) modified by the
Salmo guirdneri,did not change in response addition of a vertical chimney at the
to narrow velocity increases of 1/6 to 119 of downstream end of the swimming compart-
FARLINGER AND BEAMISH--CRITICAL SPEED OF BASS
ment (80 x 18 cm) to facilitate the addition
and removal of fieh. The velocity profile
throughout the swimming section of the
water tunnel was essentially rectilinear. Inflow of water from an aerated and thermally
regulated reeervoir assured an oxygen content in excess of air saturation and a temperature of 25 C.
Fish were placed in the water tunnel 12 h
before experimentation and forced to swim
againet a current of 20 cm B-l. At the end of
this period, velocity was increased in a conetant ertepwise progression. Time increments used were 5, 10, 30, and 60 min; velocity increments were 2.5, 5, 10, and 20 cm
s-'. For each combination, two groups of five
fish were tested; 32 groups were used in
randomized order. Fish were considered
fatigued when they failed to leave the
downstream retaining screen despite the
application of mild electrical stimuli (6-12
VDC).
Critical swimming speed was determined
for each individual using the formula described by Brett (I=),
437
FIGURE l.-Median
critical swimming peed of
largemouth b u s in relation to time and velocity increment. The mean length and weight were 10.4 crn
and 13.9 g, rupcctively.
For a given velocity increment, critical
speed decreased curvilinearly with increaae
CCS = Val
(tlAt)Av,
in time interval (Fig. 1). Thua, when the vewhere CSS is critical ewimming speed, locity increment was 5 cm s-', critical speed
decreased precipitously between 10 and 30
cm s-',
min time increment8 and changed little beAt is time increment, min,
tween 30 and 60 min. Similarly, Jones (1971)
Av is velocity increment, cm a-',
found that critical performance of rainbow
t is time elapsed at final velocity, rnin,
trout
did not change significantly between
and
time
intervals
of 20 and 40 min.
V - , is the higheet yelocity maintained for
Critical
ewimming
speed reached a peak,
the prescribed time period, cm s-'.
then deoreased with increasing velocity inThe median critical ewimming speed de- crement when the interval of time was held
termined by probit analysis for each group constant (Fig. 1). From 5 to 10 cm 8-l critical
of fish was taken to represent perform'ance performance roee to a maximum, and deand the results were analyzed by regression creased thereafter with continued velocity
increase to 20 cm s-'. Maximum values of
analysie (Draper and Smith 1966).
critical speed were obtained with a time and
velocity increment of 5 min and 10 cm s-'
RESULTS
Critical swimming speed responded both respectively. Overall critical performance
to time and velocity increments in a pattern varied almost twofold with increments of vedescribed by the equation below (R2 = 0.88) locity and time from a minimum of 30 to a
but was independent of length over the maximum of 50 cm s-l.
range, 9-12 cm:
DISCUSSION
+
log CSS
=
Ideally, critical performance ahould be
16,279.1 X lop4 - 43.3
x ~ O - ~ A-C 1.0 x 10-'A~AV measured under conditions in which fatigue
is the result of swimming, not of the method
4.0 x 1 O P A t 2 + 156.2
x ~O-'AV + 6.1 x ~ O - ~ A V ~ . applied. One major factor in fatigue is the
+
438
TRANS. AM. FISH. SOC., VOL. 106, NO. 5, 1977
accumulation of lactate reerulting from the
anaerobic catabolism of carbohydrates
(Black 1958). Lactate can result from stress
bther than severe exercise such as handling
(Black 1956; Wendt 1965). Webb (1971) and
Hudson (1973) have noticed that fish ewam
restlessly at low apeeds and sometimes
struggle violently with change in velocity at
high speed. In experiments where swimming epeed is increased by discrete intervals, Brett (1964) reported an oxygen debt at
each new level of activity which Webb
(1971) attributed to the change in velocity.
This debt is cumulative and has the result of
reducing the critical swimming speed. In
the present etudy, bass appeared to swim
with increased effort following velocity advancement by a large increment. Presumably this increase in effort, particularly at
high swimming speeds, would result in reduction in critical oerformance. The time
required to achieve critical performance increased when the increment of time or velocity was large or small, respectively.
However. the threehold of anaerobic
metabolism at which fatigue occurs would
be achieved at a lower swimming speed.
Just when anaerobic metabolism begine
will, of courae, vary with the procedure as
well as with the actual speed of swimming.
Driedzic and Kiceniuk (1976) reported that
rainbow trout expoaad to a stepwise propeesion of velocity increment8 of 10 cm s-'
each for 60 min showed no accumulation of
blood lactate at speeds as high as 93% of the
critical speed, indicating lactate is not produced in sufficient amounts to be leaked to
the blood. This also suggests that the fish
were dependent on mostly aerobic processes to this point and were swimming at
sustained speeds. However, critical swimming speeds reported by Driedzic and
Kiceniuk were verv low.
The present study supports the criteria
suggested by Brett (1964) for sockeye salmon, Oncorhynchus nerka-velocity increment of 10 cm s-' and time increment of 60
min-ae
being the most suitable of those
applied in meeting the objectives defined by
critical swimming speed. Increments of 5
crn 8-' and 30 rnin seem equally suitable for
these reasons: the test ie completed within
the same time period; the velocity incre-
ment is reduced: and. no differences in critical swimmina s ~ e e dcould be demonstrated
between the& criteria and those of Brett
(1964). Theee two combinatione appear to be
suitable for describing the critical swimming speed of largemouth baee.
.d
ACKNOWLEDGMENTS
The financial eurJaort of the National Research Council of &ada and the technical
assistance of Mrs. E. Thomas, were gratefully appreciated.
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4.39
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