An Improvement of Migration Rate with Evasion Color of Plecoglossus Altivelis
Altivelis in Pool-And-Weir Fishway
Kouki Onitsuka a, Juichiro Akiyama a, Akira Shishido a, Tomoko Arisuda aand Shuhei Takamatsu aa

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

Abstract
Most of the fishway installed in Japanese rivers belongs to the pool-and-weir fishway type. This
fishway is usually made by concrete, so that the color of the pool side-wall and bed are gray. On the otherhand, it is pointed out that the fish behavior is affected by the wall color. Unfortunately, the effect of wallcolor in the fishway on the fish behavior has not been investigated. It has been found that Ayu (Plecoglossus
Altivelis Altivelis) evade red (5R4/14). In this study, the position where painted red were changed to poolside-wall and bottom. It was found that the migration rate increases by painting downstream and left banksidewall. It’s because Ayu evaded painted sidewall and center of fish’s school is located nearby upstream
notch.
Keywords: pool-and-weir fishway, evasion color, migration rate, center of fish’s school, Ayu

1. Introduction
Most of the fishway installed in Japanese rivers belongs to the pool-and-weir fishway type.
However, Noonam et al. (2012) revealed that, approximately, 30% Salmonidae and 60% nonSalmonidae has failed to migrate at the pool-and-weir fishway. The best way to maintain highmigration rate is to provide adequate flow regime to migrate. However, it is hard to upgrade
geometric construction an existing fishway, for example in terms of the cost of construction.
Therefore, one of the way to control fish behavior without changing geometric construction is using
sense of fish such as vision. Most pool-and-weir fishway is usually made by concrete, so that thecolor of the pool’s sidewall and bottom are gray. On the other hand, it is pointed out that Ayu’s
behavior is affected by the red (Simomura et al., 2002). So, by changing fishway’s sidewall andbottom color, there is a possibility that the behavior of Ayu changes. In this study, the position
where painted red were changed to pool side-wall and bottom, and observed the behavior of Ayu.
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) was0.7m and width (B) was 0.6m. The pool was connected in a staircase pattern. Thickness of thepartition wall (Δx) was 0.15m, pool drop (Δy) was 0.15m and notch width (Δz) was 0.12m. x axis
is taken 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.
Fig. 2 shows location of painted surface. For example, the painted case on the Right bank
Sidewall (x/L=0~1.0, y/h=0~0.2, z/B=0) was denominated “RS” (Fig 2 (a)), on the Upstream
Bottom (x/L=0~0.5, y/h=0 z/B=0~1.0) was denominated “UB” (Fig 2 (b)).

y / h=0~0.2

flow

x / L=0~0.5z / B=0.5~1.0

flow

flow

flow

xzyzyhBLx(a) RS(b) UB(c) LBFig. 2 Location of painted surface
1Fig. 1 Pool-and-weir fishway

Plecoglossus Altivelis AltivelisnN

SidewallBottomTab. 1 Experimental case
Pool condition
Standard pool (Non color)
Sidewall
Upstream
BottomSidewallDownstream
BottomPainted wall
Sidewall
Left bank
BottomSidewall
Right bank
BottomCase nameNonUSUB
DSDB
LS
LB
RSRB

DS

0.6

LS

0.4
LB

0.20NonRS
USDBRBUpstream Downst ream Left bank Right bank Non color

Fig. 3 Migration rate of Ayu

2.2. Experimental methodology
30 tails Ayu (Plecoglossus Alitvelis Altivelis) that average length ( BL ) is 80mm were put
into the second pool. Discharge was maintained at 5 (l/s). Recording was began with the video
camera from the sidewall and the upper part of the fishway for 20 minutes at the same time as net
for migration prevention was removed after confirming steady flow by watching. Number ofmigration, swimming position and fish angle was analyzed after recording. Three components offlow velocity were measured. Average of flow velocity (U, V, W) of each direction axis (x, y, z)
and synthetic flow velocity was calculated after measuring. When flow velocity is measured, Ayu
is not put in the fishway.

3. Results and Discussion
3.1. Relation between painted position 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 Ayu for each case. Compared Sidewall and Bottom,
former’s migration rate was high in any case. Especially, DS and LS gained high migration rate.
Therefore, by changing painted position, migration rate was changed.
3.2. The velocity in the pool and the point of swimming position of Ayu
Fig. 4 shows contour figure of three components of flow velocity VV in vertical section at
y/h=0.15, 0.35 for each case. Although the velocity near the right bank (z/B=0~0.2) is around 0.5m/s, the other region has less approximately 0.3 m/s.
Fig. 5 (a), (b) shows instantaneous position of swimming for each case. In horizontal
section “Bottom”, center of fish’s school is located on the relatively left bank side, the differenceFig. 4 Contour of flow velocity in vertical section
11

center of fish's school
top-viewzB

center of fish's schoolside-viewyh

0.155368421
US0.111061552
DS0.429973968
LS
0.168753247
RS
0.085238095
Non

0.6

0.6

0.4

0.4
0.789433962
US
0.638216561
DS0.289252729
LS
0.57433665
RS
0.643709399
Non

0.2
00

0.2

0.2
0

0.4

0.6

x/L

1

00.2

0.4

0.6x/L1(a) Sidewall
11

center of fish's school
top-view

zB

center of fish's schoolside-viewyh

0.6

0.154744901
UB
0.227163996
DB0.190911068
LB
0.149247492
RB0.085238095
Non

0.6
0.4

0.4
0.60711311
UB
0.725645873
DB0.590494252
LB
0.573573574
RB
0.643709399
Non

0.2
000.2

0.2
00.4

0.6x/L

1

00.2

0.4

0.6x/L

1(b) Bottom
Fig. 5 Instantaneous position of center of fish’s school

between the cases are not significant. However, in “Sidewall”, the position is varied by the case.
Particularly, “LS” is located on the right bank side significantly than other cases.
On the other hand, focusing on both the vertical cross section, there were no clear differenceby the case.
3.3. The distance between the center of fish’s school and painted wall of Ayu
Fig. 6 (a), (b) show the instantaneous distance ( ~c /L， ~c /B， ~c /h) between the center offish’s school and painted wall of Ayu for each case. Focusing Fig 6 (a), center of fish’s school was1~1c
Plecoglossus Altivelis Altivelis
B~cL
0.6

Plecoglossus Altivelis Altivelis~chUBDBLBRB

0.60.50.40.40.2

USDSLSRS

0.2000200400600800t (s) 1200

0200400600800t (s) 1200(a) Sidewall(b) Bottom
Fig. 6 The distance between the center of fish’s school and painted wall of Ayu
cL1

c0.8
B

Plecoglossus Altivelis Altivelis

SidewallBottomDSUSLS

ch

RS

0.6
0.50.4UBDBLB

0.2

RB0Upstream

Downstream

Left bank

Right bankFig. 7 The average of distance between the center of fish’s school and painted wall of Ayu

moving away more than half of the pool length and width from painted wall in all case. This isestimated that Ayu evaded painted wall. On the other hand, focusing Fig 6 (b), center of fish’sschool was always below a half depth, there were no clear difference for each case. Therefore, inFig 5 (a) for center of fish’s school are difference, in Fig 5 (b), there are similar in all cases.
Fig 7 shows the average of the distance between the center of fish’s school and painted
wall of Ayu (  c /L，  c /B，  c /h) for each case. In Sidewall, in all cases,  c /L and  c /B are larger
than 0.5. Thus, this is estimated that Ayu evaded painted wall clearly too. By the way, Onitsuka etal. (2009) was carried out Ayu induction experiments by installing a mirror on the sidewall andbottom of the open channel. As a result, though there was no change Ayu’s behavior to be installed
mirror on the bottom, Ayu be mistaken for a fellow the figure of himself in the mirror and to change
the swimming behavior by installing mirror on the sidewall. This shows Ayu is influenced by thevisual information got from the horizontal direction than vertical direction. In this study, similar
results were obtained.

3.4. The distance between the center of fish’s school and upstream side notch
Fig. 8 (a), (b) show the frequency distribution of distance ( d xz / BL ， d xy / BL ) between thecenter of fish’s school and upstream side notch for each case ( d xz = horizontal distance between

0.4
nd xz

0.4
nd xy Plecoglossus Altivelis Altivelis

Plecoglossus Altivelis Altivelis

N d xz0.3

N d xy0.3

USDSUSDSLS
0.2

LS
0.2

RS

0.1

RS0.1

0345679 d xz / BL801234567

9 d xy / BL 128(a) Sidewall
0.4
nd xz

0.4
nd xy

Plecoglossus Altivelis Altivelis

N d xz0.3

Plecoglossus Altivelis Altivelis

N d xy0.3

UBUBDBDBLB

LB

0.2

0.2

RB

RB
0.1

0.1

003

4

567

9 d xz / BL81234567

9 d xy / BL 128(b) Bottom
Fig. 8 The frequency distribution of distance between the center of fish’s school and upstream notch
18d̂16xz
B14L

4

Plecoglossus Altivelis Altivelis
SidewallBottomstandard deviation

12108642LBUS UBDBDSd xz
3BL10RS

6124

Plecoglossus Altivelis Altivelis
SidewallBottomstandard deviation

128RB

LS

18d̂16xy
B
14Ld xy
3
BLUSDB
UB
DSLB

RS

RB

2

LS

1

4
200
Upstream Downstream Left bank Right bank00
Upstream Downstream Left bank Right bank(a) Horizontal section(b) Vertical section
Fig. 9 The standard deviation of distance between the center of fish’s school and upstream notch

center of fish’s school d xy = vertical direction between center of fish’s school ). In Sidewall,distribution range of the distance is different for each case. This shows that the distance werechanged by changing painted wall. On the other hand, in Bottom there were no difference by thecase.
 /Fig 9 (a), (b) show the mode ( d̂ xz / BL ， d̂ xy / BL ) and standard deviation ( d xz / BL ， d xyBL ) of distance for each case. Focusing Fig 9 (a), d̂ xz / BL was comparatively lower in DS andLS (These got high migration rate.). This shows Ayu evaded painted wall and moves awayfrom there, as a result, it’s estimated that center of fish’s school was close to the upstreamside notch in DS and LS. On the other hand, it’s no difference in the mode of Bottom. In
the standard deviation, Sidewall was below the Bottom in many cases. So, it’s estimatedthat the Sidewall’s movement of the center of fish’s school is less than Bottom’ s.

3.5. The distance of migration and the direction of Ayu
Fig. 10 shows the average of migration distance ( S m / BL ) for each cases. Migration
distance of DS and LS are shorter than the other cases. As observed Fig 5 (a), center of fish’s schoolof DS and LS has been crowded left bank. Most of individual start to migrate from center of fish’sschool. Thus, migration distance is shorter both DS and LS cases due to move to nearby upstream
notch by painted wall. As a result, fatigue accumulation of Ayu is suppressed, migration rateincreases.
Fig 11 shows the definition of the direction of Ayu. Fig 12 (a), (b) show the frequencydistribution of the direction of Ayu ( n / N ). Fig 12 (a) shows that they were swimming in parallelto the bottom surface in US and RS. On the other hand, DS and LS show a peak value at 60°~80°.
This corresponds to direction of upstream notch. Since it becomes easier to recognize the flow, it
estimates that migration rate increased.

14SmBL
10Plecoglossus Altivelis Altivelis
SidewallUSRB

Bottom RSDBLB

8DSLS

6420Upstream Downstream Left bank Right bankFig. 10 Migration distance of Ayu0.3nN0.20.15

Fig 11 Definition of the direction of Ayu
0.3

Plecoglossus Altivelis Altivelis
USnNDS0.2

LS0.15

Plecoglossus Altivelis Altivelis
UBDBLBRBRS
0.1

0.1

0.05

0.05

0 180  120  60

060  (deg .) 1800 180  120  60

060  (deg .) 180(a) Sidewall(b) Bottom
Fig 12 Frequency distribution of the direction of Ayu

4. Conclusion
In this study, the position where painted red were changed to pool side-wall and bed, andexperiments of migration with Ayu. As a result, it was found that following.
(1) It was found that it’s a little effect for Ayu to paint pool bottom, however, by painting sidewall,
we are able to control Ayu’s swimming position.
(2) It was found that the migration rate increases by painting downstream and left bank sidewall.

Acknowledgements
This study was received assistance from Grants-in-aid for Scientific Research when the study
conduct.
References
Onitsuka K, Akiyama J, Yamamoto A and Ikeno M. Guidance control of school of Ayu using a mirror.
Annual Journal of Hydraulic Engineering. JSCE. 2009. Vol. 53. 1231-36.
Noonan M, Grant J W A, Jackson C D. A quantitative assessment of fish passage efficiency. Fish andFisheries 2002, Vol.13: 450-64.
Simomura M, Shirakawa H, Fukui Y, Sekiya A. Methods for preventing Ayu from straying analysis of thebehavior of fishes by random walk method. Kasengijyutsuronbunnsyuu 2002, Vol.8: 337-42.