Examination of Control of Suitable Area of Oikawa, Zacco Platypus, in Pool-andWeir Fishway with Partition
Kouki Onitsuka a, Juichiro Akiyama a, Saori Kuramoto b, Akira Shishido aand Yuka Kadota aa

Department of Civil Engineering, Kyushu Institute of Technology, Kitakyushu, 804-8550, Japanb
Hitachi, Ltd.

Abstract
It is important to keep suitable area for fish in pool-and-weir fishway to make migration rate high(Hyashida et al, 2000). In this study, control of suitable area was tried by installing of partition with variouspositions in pool-and-weir fishway. Migration rate of Oikawa (Zacco Platypus) was obtained with the aidof two sets of digital video cameras. It was found that migration rate of Oikawa takes high value byinstallation of partition to an area between upstream side notch and downstream one. This is because
suitable area of Oikawa was moved to upstream side of partition from middle part of pool, and migrationfrom slow flow area was induced.
Keywords: Zacco Platypus, partition, pool-and-weir fishway, migration rate, suitable area

1. Introduction
Dam is constructed for the purpose of water control and water utilization. However, theconstruction blocks fish’s migration that seeks to upstream. This is problem for migratory fishes
in river. Therefore, fishway is constructed in their rivers in order to comfort migration of fishes.
The most of fishway in Japan is pool-and-weir fishway (Nakamura, 1995). It is necessary tounderstand the most suitable geometric condition and flow condition in pool-and-weir fishway. In
the past study, fish’s migration rate takes high value when flow velocity is low (Takahashi &Nakamura, 1984). However, it is very difficult to make condition that flow velocity is low inpool-and-weir fishway that was set up at actual river. It is necessary to investigate position ofsuitable area in the pool. And also making suitable area in easy way is important. In this study,
suitable area was made by installing wooden partition with various positions in pool-and-weirfishway, and fish’s behavior was observed.
2. Materials and Methods
2.1. Experimental device
Fig. 1 shows pool-and-weir fishway that was made of wood. However, left bank sidewall
was made of an acrylic board for taking a picture. It was designed following. Pool length (L) was
0.7m and width (B) was 0.6m. The pool was connected in a staircase pattern. Thickness ofpartition (Δx) was 0.15m, pool drop (Δy) was 0.15m and notch width (Δz) was 0.12m. x axis istaken in the direction of flowing. y axis is taken in the vertical direction from bottom. z axis istaken in the direction of the crossing. Pool number was in ascending order toward downstream toupstream.
Partition was installed in a variety of positions in second pool. The partition that height is0.8m and width is 0.25m was fixed in position of x/L=0.5 and changed only crossing position asshown in Fig. 2 (a). A green arrowed line in Fig. 2 (b) shows installed range of partition.
Experiments were performed 5 cases in total. They were 4 cases as shown in Fig. 2 (b) and notinstalled partition (standard pool). The region that was projected notch section to direction offlowing was defined as notch area, and other regions were defined as pool area. Case name wasdefined as shown in Tab. 1.

up stream side notch

0.25mflowzyz 3④xz 2yhBLx①②③0.8mzyzFig. 1 Pool-and-weir fishwayz

Pool area

x/L=0.5
Notch area(a) Longitudinal position(b) Crossing position
Fig. 2 Installed position of partition

Tab. 1 Experimental case
Pool status
Case nameStandard poolSpPl
① Pool left
InstallationPr② Pool rightpositionNt③ Notch thirdof partition
Nh④ Notch half

2.2. Experimental methodology
30 tails Oikawa (Zacco Platypus) that average length ( BL ) is 80mm were put into thesecond pool. Discharge was maintained at 3 (l/s). Recording was began with the video camera
from sidewall and upper part of the fishway for 30 minutes at the same time as net for migration
prevention was removed after confirming steady flow by watching. Number of migration,swimming position and fish angle was analyzed after recording. Three components of flow
velocity were measured. Average of flow velocity (U, V, W) of each direction axis (x, y, z) andsynthetic flow velocity was calculated after measuring. When flow velocity is measured, Oikawa
is not put into the fishway.
3. Results and Discussion
3.1. Relation between installed position of partition and migration rate
Migration rate was defined as following equation.
Migration rate 

Number of fish that succeeded in migration n
Number of fish that used to experiment N ( 30)(1)

Fig. 3 shows migration rate (n/N) of Oikawa for each case. Migration rate indicated just samevalue in the case that partition was not installed (Sp) and the case that partition was installed inleft bank side of pool area (Pl). Therefore, existence or non-existence of partition in left bank sideof pool has a no impact on migration rate. However, migration rate of the case that partition wasinstalled in right bank side of pool area (Pr) was lower than Case (Sp). In addition, migration rateof the case that partition was installed in notch area (Nt), (Nh) were higher than Case (Sp). From
the above results, migration rate of Oikawa was changed by changing position of partition in Case(Pr), (Nt) and (Nh).
3.2. Suitable area of Oikawa in poolFig. 4 (a) shows center of fish’s school in vertical section (x-y) and Fig. 4 (b) shows
center of fish’s school in horizontal section (x-z) that were given for each 10 seconds. h is water
depth. Fish’s center moved with time in all cases in vertical and horizontal section. However,moving region is narrow. Therefore, this is estimated that Oikawa recesses at nearly this region.
Focusing on vertical section in Fig. 4 (a), suitable area of Oikawa is half water depth or less in allcases. There were no differences between the case that partition was not installed (Sp) and others.

11

migration rate
The number of migration fish n
The number of experiment al fish N0.3nNy0.8
h1Spcentar of fish' s school

Plside - viewcentar of fish' s school

top- view

z0.8
BPr
Nt

0.6

0.6

0.4

0.4

0.4

Pr

0.2

0.2

0.2

NtNh0.6

NhSp
PlSpPlPr

Nt0Nh

0.2

0.4

0.6x0.8L

1

0.4

nd xy

Sp

N d xy

PlPl

nd xz
0.3
N d xz

Pr
Nt

Nt
0.2

Nh

0.2

0.4x0.8L

0.6

10
distance between fish' s schoold̂ xy
and up stream side notch
B9Ld̂xyd xy BLxy BLd̂ xz
d yz BLxzd̂Byz
LB8LSpPr0.107068 d xy BL 10(a) Vertical sectiond xz
6BL4264d xy
8BLstandard deviation

0.1210Nh0.0501(a) Vertical section(b) Horizontal section
Fig. 4 Moving condition of center of fish’s school

Fig. 3 Migration rate of Oikawa
0.15Installation position of partition

0004567 d xz BL 805Sp

PlPr

NtNh(b) Horizontal section(c) Mode value and standard
deviation
Fig. 5 Instantaneous position of swimming and distance between fish’s school and upstream side notch

On the other hand, focusing on horizontal section in Fig. 4 (b), Oikawa recesses at nearly
left bank sidewall in Case (Sp). In Case (Pl), Oikawa recesses at nearly right bank side more thanCase (Sp). In Case (Pr), Oikawa recesses at downstream side of partition. Furthermore, suitablearea concentrates at 0.2<x/L<0.5 in Case (Nt) and (Nh) that migration rate is high. This meansthat Oikawa recesses at nearly upstream side of partition. This is considered that suitable area of
Oikawa was controlled by installing partition.
3.3. Instantaneous position of swimming and distance between fish’s school and upstream sidenotch
Fig. 5 (a), (b) shows instantaneous position of swimming and frequency distribution of
the value ( d xy BL ) and ( d xz BL ) in vertical section (x-y) and horizontal section (x-z) for each case.
Vertical and horizontal distance between fish’s school and upstream side notch ( d xy ), ( d xz ) weredivided by average length of Oikawa ( BL ). Distribution configuration and range are differed ineach case and section. This means that instantaneous position of swimming and distance between
fish’s school and upstream side notch were changed by installing partition.
Mode value of ( d xy ) and ( d xz ) are ( d̂ xy ) and ( d̂ xz ). They were divided by ( BL ). Bar
chart in Fig. 5 (c) shows mode value ( d̂ xy BL ) and ( d̂ xz BL ) for each case. Furthermore, ). They were divided by ( BL ).
 ) and ( d xz
standard deviation of ( d xy ) and ( d xz ) are ( d xy
Polygonal line in Fig. 5 (c) shows value of standard deviation ( d xy BL ) and ( d xz BL ) foreach case. The mode of Case (Nh) that indicated the highest value of migration rate
indicated the lowest value. In contrast, the mode of Case (Pr) that indicated the lowestvalue of migration rate indicated the highest value. This is estimated that migration isinduced when distance between instantaneous position of swimming and upstream side
notch is near. On the other hand, differences among the case are not as noticeable as1.0 Case:Sp

0.4
Case:Pl
1.0z/B =0.1

0.4
Case:Pr
1.0z/B =0.1

z/B=0.1

0.4

0 0.2 0.4 0.6 x/L 1.00.4z/B =0.1

0y/hy/hy/h

0.6

0.6

0.6

0.4

0.4

0.4

0.2

0.2

0.2

00000.2 0.4 0.6 x/L 1.0
1.0 Case:Nt

0 0.2 0.4 0.6 x/L 1.00.4
Case:Nhz/B =0.1
1.0

0y/hy/h

0.6

0.6

0.4

0.4

0.2

0.2

00000.2 0.4 0.6 x/L 1.0

000.2 0.4 0.6 x/L 1.00Fig. 6 Contour of flow velocity at z/B=0.1 in vertical section
0.25

flow

1.0yz

0.5xy

1.0
0.4
0.6
0.6z/By/h

y/h

0.6
0.4
0.2
00.3

0.6
0.4
0.2
00.3

zy
1.0
0.4
0.5

0.4

x/L

0.2
0.8

Case:Sp

00.6
0.6

x0

flow

1.0

flow

1.0

y/h
0.6
0.4
0.2
00.3

0.25

0.25

z

z/B

0.5

0.4

x/L

0.2
0.8

0.6
0.6

x

0

Case:Pl

0

1.0
0.4

y0.8

flow

1.0

y/h

0.6
0.4
0.2
0
0.3

0.6
0.4
0.2
00.3

y
1.0
0.4
0.5

x

0.6
0.6
0.8

0

Case:Nt

1.0
0.5

0.4
0.2

x/L

00

flow

z 0.4

z/B

Case:Pr00.25

y/hz

0.4
0.2

x/L

0.25

1.0z/Bx

0.6
0.6z/B

0.4
0.2x/L
0.8

Case:Nh00Fig. 7 Vector of flow velocity at nearly partitionmode value in regard to standard deviation. This is considered that changing position ofpartition has no impact on dispersion of distance between instantaneous position ofswimming and upstream side notch.
3.4. Comparing flow condition in each poolFig. 6 shows contour figure of three components of flow velocity VV in vertical section
for each case. Fast velocity flow is present in just below upstream side notch. This is water fallthat flows into the pool. There are no differences between flow velocity of Case (Sp), (Pl) and(Pr). However, flow velocity of water fall in Case (Nt) and (Nh) are little slow compared with1Pool area

Case : Sp

1

Case : Pl

1 up stream region routez
Bz
Bz
B

0.6

0.6

0.6

0.4

0.4

0.2

0.2

0.4

Notch area

0.2

per 0.2sec.

000.2

0.4

0.6

x L

1

per 0.2sec.

01

00.2

0.4 0.5 00.6
1z
Bz
B

0.6

0.6x L

0.2

Case : Pr

down stream region route: per 0.2sec.

01 0.5 00.6

0.4

0.2

0.41 0.5 0.6

x L1

Case : Nhup stream region
route

0.4

0.4

up stream region route
0.2
0.13

Case : Nt
down stream region route : per 0.2sec.

000.2

0.4 0.5 0.6

x L

1

down stream region route

0.2
0.1

: per 0.2sec. 

000.2

0.4 0.5 0.6

x L

1

Fig. 8 Swimming trajectory of Oikawa

other cases. In Case (Nt) and (Nh) that were installed partition between upstream side notch anddown one. Therefore, water fall conflicts with partition and it is reduced.
Fig. 7 shows three components of flow velocity VV that is picked out of around thepartition discretionally and shows contour color and vector for each case. Observing flow
direction for each case, fast flow is present toward downstream side notch from upstream side
notch in Case (Sp). In other region, flow velocity is slow comparatively. In Case (Pl), a stream
around the partition is irregular. However, there is not so different from Case (Sp). In Case (Pr),(Nt) and (Nh), after water fall conflicts with partition, a stream is divided into upstream side anddownstream side of partition. Furthermore, the case changes as (Pr) to (Nt) to (Nh), flow velocityof upstream side of partition is fast with an increase in the rate of installed into the notch area. InFig. 4 (b), Oikawa recesses at upstream side of partition in Case (Nt) and (Nh). Therefore, this isconsidered that Oikawa finds a stream that flow in water fall to upstream side of partition simply.
However, flow velocity in upstream side of partition is faster than flow velocity of water fall.
3.5. Relation between installed position and migration behavior of Oikawa
3.5.1. Swimming trajectory of Oikawa
Fig. 8 shows swimming trajectory that Oikawa migrates before 20 seconds in horizontal
section for each case. This is an example figure of swimming trajectory is plotted per 0.2 seconds.
Furthermore, migration route of Case (Pr), (Nt) and (Nh) were present 2 patterns. One, the routethat migrate from upstream side of partition. The other one, the route that migrate fromdownstream side of partition. The former was defined up stream region route and the latter wasdefined down stream region route, and showed blue and red. Observing swimming trajectory foreach case. In Case (Sp), Oikawa migrates and passes notch area. Considering Fig. 6 and Fig. 7,
this is estimated that Oikawa migrates the region that flow velocity is fast comparatively. In Case(Pl), Oikawa deviates from notch area slightly. However, they migrate the region that flow
velocity is fast comparatively. In Case (Pr), (Nt) and (Nh), Oikawa migrates and passes notcharea along with Case (Sp) and (Pl) in down stream region route. In contrast, Oikawa migrates theregion that flow velocity is slow comparatively without passes notch area.

1nu
Nm
0.8ndNmup
stream region route
0.28
down
0.72 stream region route

0.6
0.4
0.2
0Pr

NtNhFig. 9 The selection rate of each migration route in Case (Pr), (Nt) and (Nh)

3.5.2. Relation between the selection rate of migration route and migration rate of Oikawa
Fig. 9 shows the selection rate of up stream region route and down stream region route( nu N m ) in Case (Pr), (Nt) and (Nh) for each case. The selection rate of up stream region route isincreased with an increase in the rate of installed into the notch area. In Fig. 7, the rate of water
fall flows into upstream side of partition is increased with an increase in the rate of installed into
the notch area. As a result, this is considered that migration of Oikawa was induced fromupstream side of partition. Furthermore, compared with Fig. 3, migration rate takes a high value
with an increase in the case that the selection rate of up stream region route is high. This meansthat Oikawa does not pass notch area that flow velocity is fast comparatively in up stream region
route. As a result, fatigue of Oikawa is difficult to accumulate compared with down stream region
route and increased individual that succeed in migration.
4. Conclusion
In this study, suitable area was made by installing wooden partition with various
positions in pool-and-weir fishway, and the fish’s behavior was observed. As a result, it wasfound that following.
(1) It was proved that suitable area is enabled to control by installing partition in pool-and-weirfishway.
(2) It was proved that migration rate is increased when distance between instantaneous
position of swimming and upstream side notch is more nearer.
(3) Water fall is divided in half by installing partition wall between region of upstreamside notch and downstream side notch. Therefore, migration of Oikawa is induced fromupstream side of partition that flow velocity is slow comparatively and fatigue of Oikawa
is not accumulated. As a result, it was proved that individual that succeed in migration isincrease.
Acknowledgements
This study was received assistance from Grants-in-aid for Scientific Research when the studyconduct.
References
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Nkamura S. gyodounohanashi. sankaidou 1995.
Takahashi N, Nakamura S. Experimental Study on the Behavior of Ayu in Fishladder. J HydraulicEngineering, JSCE 1984, 28: 358-353