Effects of Particle Diameter Over River Bed on Swimming Behavior of
Nipponocypris Temminckii
Kouki Onitsuka a, Juichiro Akiyama a, Youichi Hirano Shishido a, and Kazuya Momotani aa

Department of Civil Engineering, Kyushu Institute of Technology, Kitakyushu, 804-8550, Japan.

Abstract
Fish has the ordinary and dark muscle. When fish uses ordinary muscle, fish gets tired. In such asituation, fish needs a rest (Nakamura, 1995). In this study, particle diameter over river bed and flow velocity
are changed. The trajectories of Kawamutsu (Nipponocypris temminckii) were observed. It was found that
Kawamutsu attaches underpart at river bed to decrease fatigue in the rest time. The total rest time ofKawamutsu increases with increase of particle diameter and also velocity. The migration speed decreases
with an increase of velocity. Kawamutsu turns to the upstream in the rest time.
Keywords: rest time; ordinary muscle; dark muscle; particle diameter; Nipponocypris temminckii

1. Introduction
River development in consideration of river environment is desired. Therefore,preservation and control of river environment are necessary. It is important to investigate andunderstand river ecosystem to maintain and manage river environment. Further, it is necessary tounderstand habitat and the swimming behavior of fish to maintain the livable river environment of
the fish. Therefore, the relations of river environment and the habitat of fish were investigated.
Nogami et al (2002) performed field experiment about the habitat environment of demersal fish in
the Makomanai River. They pointed out that it is necessary to increase velocity and make particle
size large for improvement in habitat environment where the population density of Hanakajika(Cottus nozawae) is small. However, the study was not analyzed in detail on relations of the particle
size and swimming behavior of fish yet. This study elucidated swimming properties of Kawamutsu
when particle diameter over river bed and flow velocity are changed.
2. Materials and Methods
2.1. Experimental device
Fig. 1 shows the open-channel that was used for experiment. It was designed following.
The length L, width B and height H are 4.0m, 0.8m and 0.2m, respectively. x y and z are thecoordinates of the streamwise, vertical and crosswise directions, respectively.
2.2. Experimental methodology
Averaged body length of Kawamutsu BL is 60mm. Tab. 1 shows experimental case. Water
depth was set to 0.04m. Particle diameter over river bed was set to 1.2mm, 2.5mm, 5mm, 10mm.
The flow velocity divided by averaged body length of Kawamutsu U m / BL was set to 2, 4, 6, 10.
Experiment was conducted 16 cases in total. A circular wire net of 0.25m in diameter is set up 2mdownstream from upstream edge and isolated Kawamutsu is inserted. After it is confirmed that theKawamutsu settled down, the circular wire net is taken up. Further, trajectory of Kawamutsu wasrecorded with a digital video camera set up the upside of the open-channel. Recording speed ofvideo camera is 30 frames per second and the number of pixels is 1440×1080. Experiments wereperformed 50 times in each case, and 800 times in total. Number of swimming position wasanalyzed after recording. Furthermore, ground distance, ground speed, swimming speed andswimming distance were calculated from swimming position. Meanwhile, Fig. 2 shows turning
angle in swimming.
3. Results and Discussion
3.1. Swimming trajectory in each particle diameter
Fig. 3 shows arbitrary swimming trajectory of Kawamustu in each particle diameter whenvelocity divided by averaged body length is 4. The points in Fig. 3 show swimming position foreach 0.4 seconds. From Fig. 3, it is shown swimming range decreases and distance of between
points approach with grow of particle diameter. As particle size increases, Kawamutsu tends to stay.

top-viewx
universal area

measurements section

0.25m

flow

1.0m

initial position of fish

0.80m

z0.8
P012-04z (m)0.6x

side-view
0.04m
4.0m

0.20m

y00

0.5

1(a)

Tab. 1 Experimental caseh (m)U m B L 1 / s 

0.04

24610246102461024610

1.5 x(m)2P012-04

0.8
z (m) P025-04
0.6

Fig. 1. Experimental setup.

case name Particle size(mm) BL (mm)P012-02P012-04
1.2
P012-06
P012-10P025-02P025-04
2.5P025-06
P025-1060P050-02
P050-04
5P050-06
P050-10
P100-02
P100-0410
P100-06
P100-10

0.4
0.2

2.0m
flow

N.temminckii
per 0.4s

N.temminckii
per 0.4s

0.4
0.2
000.5

1(b)

1.5 x(m)2P025-04

0.8
z (m) P050-04

N.temminckii
per 0.4s

0.6
0.4
0.2
00

θt < 00.51(c)1.5x(m) 2

P050-04

0.8
P100-04z (m)0.6

N.temminckii
per 0.4s

0.4

θt > 00.2
0Fig. 3. Diagram of turning angle

00.5

1

1.5x(m)2(d) P100-04
Fig. 3. Arbitrary swimming trajectory ofKawamustu when velocity divided by averaged
body length is 4trts

P12P25P50

P100

24N.temminckii

10.5

Fig. 4. Kawamutsu in rest time0U m B6L (1 / s) 10Fig. 5. Rest time divided by stay time in each case.

1tr
T
0.75

P12P50N.temminckii

P25
P100

0.15

Nr(1/ s)T

N.temminckii

P12P25
P50

0.1

P100

0.5

0.05
0.25

024U m B6L (1 / s) 10Fig. 6. Total rest time in each case.

024 U m BL6(1 / s)

10Fig. 7. Averaged the number of restin each case.

3.2. Swimming behavior of Kawanutsu in rest
3.2.1. Definition of the rest
Fig. 4 shows Kawamutsu in rest time. From Fig. 4, it is shown that Kawamustu attaches
underpart at river bed. It is probable that Kawamutsu attaches underpart at river bed for decrease
fatigue in rest time. Therefore in this study, “rest time” is defined when Kawamutsu attaches
underpart in river bed and swimming speed is less than the speed divided by the body of fish is 0.5.
3.2.2. Relation between rest time and swimming behavior of Kawamutsu
Fig. 5 shows rest time divided by stay time in each case. From Fig. 5, it is shown
Kawamutsu takes rest when Kawamutsu stays in flow.
Fig. 6 shows rest time per unit time of in each case. From Fig. 6, it is shown rest timeincreases with grow of particle diameter. This results are assumed that rest is facilitated by increaseof irregularity of river bed. Furthermore, From Fig. 6, it is shown rest time increases with increaseof velocity. This results are assumed that fatigue is accumulated with increase of velocity.
Fig. 7 shows averaged the number of rest by divided total experiment time. From Fig. 7, itis shown the number of rest does not change when particle diameter grows. This results are assumed
that rest time increases in of the once.

11U m BL (1 / s)  2 N.temminckiinθdn

P12P250.50060(a)1120

N.temminckii
P12P25

P50

P50

P100

P1000.50θd1800U m / BL  2U m BL (1 / s)  6nθdnU m BL (1 / s)  4nθdn60

P121nθdn

U m BL (1 / s)  100060(c)120P12P25

P50P50P100P100

θd180

N.temminckii

P250.5θdU m / BL  4(b)N.temminckii

120

0.501800(d)U m / BL  6Fig. 8. Fish direction in rest time.

60

120

θd180

U m / BL  103.3. Fish direction in rest time
In this study, “fish direction” is defined angle formed by line connecting head and tailwith x-axis  d . Furthermore, fish direction  d  0 when fish turns to downstream and fishdirection  d  180 when fish turns to upstream. Fig. 8 shows the frequency distribution ofabsolute value of fish direction in each case. From Fig. 8, it is shown distribution of d  0～20
shows high-frequency in all case. Therefore, Kawamutsu turns to upstream to decrease fatigue inrest time.

3.4. Ground distance and speed in rest time
Fig. 9 shows averaged ground distance in x-direction LGx divided by averaged bodylength in each case. In case of P12 and P25, ground distance in x-direction decreases remarkably
when flow velocity divided by averaged body length of Kawamutsu increases from 6 to 10. Thisis because rest time increases by increase of velocity. Meanwhile, in case of P100, ground distancein x-direction does not change when flow velocity divided by averaged body length of Kawamutsu
increases from 6 to 10. This is because rest time is long in all velocity.
Fig. 10 shows averaged ground distance in z-direction LGz divided by averaged bodylength of Kawamutsu in each case. When velocity increases, ground distance in z-directionchanges. However, change amount of ground distance in z-direction is small compared withchange amount of ground distance in x-direction. This is because swimming range in z-direction
decreases with increase of velocity.

80
N.temminckii
LGx
BL
60

P12P25P50

80
N.temminckii
LGz
BL60

P12P25
P50

P100

80
N.temminckii
LGBL
60

40

2020204

U m B6L (1 / s)

0102Fig. 9. Ground distancein x-direction
4N.temminckii

VG
BL34U m B6L (1 / s)

0102Fig. 10. Ground distancein z-direction.

P12P25P50P100

 1s 400
LfBL300

P12N.temminckii

P25P50

10P25BL
7.5P50200

51100

2.54U m B6L (1 / s)

10Fig. 12. Ground speed024

U m 6BL (1 / s) 10Fig. 13. Swimming distance

P12Vf

224U m B6L (1 / s)

10Fig. 11. Ground distance 1s P100

0P50
P100

402P25P100

400P12N.temminckii

P100024U m B6L (1 / s)

10Fig. 14. Swimming speed

Fig. 11 shows averaged ground distance LG divided by averaged body length ofKawamutsu in each case. From Fig. 11, it is shown ground distance decreases with grow of particle
diameter. This is because rest time increases with grow of particle diameter.
Fig. 12 shows averaged ground speed VG divided by averaged body length of Kawamutsu
in each case. From Fig. 12, it is shown ground speed does not change when velocity increases inall particle diameter. This is because rest time increases with grow of particle diameter. However,ground speed decreases with grow of particle diameter in all velocity. This is because rest isfacilitated by increase of irregularity of river bed.
3.4. Swimming distance and speed
Fig. 13 shows averaged swimming distance L f divided by averaged body length of
Kawamutsu in each case. From Fig. 13, it is shown swimming distance increases with increase ofvelocity. Meanwhile, swimming distance decreases with grow of particle diameter. Furthermore,increase rate of swimming distance decreases with grow of particle diameter. This is because rest
time increases with grow of particle diameter.
Fig. 14 shows averaged swimming speed V f divided by averaged body length ofKawamutsu in each case. From Fig. 14, it is shown swimming speed increases with increase ofvelocity. Meanwhile, swimming speed decreases with grow of particle diameter. This is because
rest time increases with grow of particle diameter and increase of velocity.

0.4nθ t

U m BL (1 / s)  2 N.temminckii
P12n0.4nθ t

U m BL (1 / s)  4

nN.temminckii
P12P25

P25

P50

P50
P100

P100
0.2

0.2

0060(a)0.4nθ t120

θt0P120(c)1200.4nθ t120

θt

U m / BL  4nP25

P50P50

θtP1000.2

10180180U m BL (1 / s)  10 N.temminckii
P12P25P100

0.260(b)N.temminckii

n600180

U m / BL  2

U m BL (1 / s)  60

1060120

θt180(d) U m / BL  10
U m / BL  6Fig. 15. Tuning angle in each velocity.

3.4 Turning angle in each velocity divided by averaged body lengthFig. 8 shows the frequency distribution of absolute value of turning angle t in velocity
divided by averaged body length. In distribution of d  0～20 , case of P12 and P25 shows highfrequency than case of P5 and P10 when velocity divided by averaged body length is 2. Furthermore,in distribution of d  0～20 , case of P12 shows high-frequency than other case when velocity
divided by averaged body length is 4. However, distribution of each particle diameter does notshow difference when velocity divided by averaged body length are 6 and 10. This results are
assumed that turning angle is small when velocity and particle diameter are small. However, turning
angle does not change basically when particle diameter increases.
4. Conclusion
In this study, particle diameter over river bed and flow velocity are changed, and the fish's
behavior was analyzed . As a result, the following have been understood.
(1) Kawamutsu attaches underpart at river bed for decrease fatigue in rest time.
(2) Because rest is facilitated by increase of irregularity of river bed, rest time of Kawamutsu
increases with grow of particle diameter.
(3) Because fatigue is accumulated with increase of velocity, rest time of Kawamutsu increases
with increase of velocity.
(4) Swimming distance of Kawamutsu increases with increase of velocity, but decreases withgrow of particle diameter.
(5) Kawamutsu turns to upstream to decrease fatigue in rest time.
(6) Turning angle of Kawamutsu does not change basically when particle diameter increases.

It was found that Furthermore, it was found that rest time of Kawamutsu increases with grow ofparticle diameter and increase of flow velocity.
Acknowledgements
This study was received assistance from Grants-in-aid for Scientific Research when the study
conduct.
References
Nakamura S. gyodounohanashi. sankaidou 1995.
Nogami T, Watanabe Y, Kobayashi M, Hasegawa K. Research on Classification of Fish Habitat in Mountain
Rivers. Proceedings of JSCE 2002.