ISPIV2017

The 12th International Symposium on Particle Image Velocimetery
June 19 (Mon) – 21 (Wed), 2017 / Grand Hotel, Busan, Korea

Evasion characteristics of PLECOGLOSSUS ALTIVELIS ALTIVELIS
in fish school against air bubbles in open-channel flows
Kouki ONITSUKA1, Juichiro AKIYAMA1 and Kento JOJI1
1 Department of Civil Engineering, Kyushu Institute of Technology, Kitakyushu, Japan

onitsuka@civil.kyutech.ac.jp
ABSTRACT
1. INTRODUCTION
Fish sometimes enter into an intake gate of weirs and dams, so that a lot of released larval Plecoglossus Altivelis
Altivelis and salmon are lost. Some techniques with air bubbles, electricity and transmitted light have been developed todeter fish from coming near an intake gate and an outlet gate. [1, 2, 3, 4, 5] At first, a study was done on the influence of the
air bubbles on the behavior of the fish that live in sea. In his experiment, Smith [6] cut off the course of the school ofClupea pallasii using air bubbles film. Arimoto et al. [7] succeeded in collecting the fish in the fixed shore net using airbubbles film. On the other hand, there are few studies on the influence of the air bubbles on the movement behavior of fishthat live in river. Onitsuka et al. [8] observed the influence that air bubbles gives to the behavior characteristics of Zacco
platypus and Nipponocypris temminckii. As a result, they pointed out that air bubbles hardly exert any behavioral change of
Zacco platypus and Nipponocypris temminckii.From the above, it is believed that the fish behavior characteristics in thepresence of air bubbles depend on fish species. There are few studies that examined the behavior characteristics with airbubbles about fish that live in the river. In this study, the air bubbles are injected from the bottom of channel with changing
the flow velocity, and trajectories of fish are recorded.
2. MATERIALS AND METHODS
Fig. 1 shows the open-channel used for experiment. The pool length Lx , width L z and height are 2.0m, 0.8m and0.3m, respectively. x , y and z are the coordinates of the streamwise, vertical and spanwise directions, respectively.
Interception wall was settled in upper reach ( z Lz =0.5). Thickness of interception wall was 0.02m. For the wall, range of0< z <0.39m and 0.41< z <0.8m are defined bubble area and non-bubble area. The other area is defined normal area. Table
1 shows hydraulic conditions. Water depth was set to 0.04m. Flow velocity divided by averaged body length of
Plecoglossus altivelis altivelis was set to three patterns within the range from 2 to 8. The quantity of air bubbles mixture is25.0(l/(m2・s)). Plecoglossus altivelis altivelis was used for the experiments. The number of used Plecoglossus altivelis
altivelis was 6 in one recording. The recording has been carried out 60 cases in each speed. Averaged body length BL wasabout 70mm. Further, trajectory of Plecoglossus altivelis altivelis was recorded with a digital video camera set up theupside of the open-channel. Recording speed of video camera is 30 frames per second and the number of pixels is1440×1080. This study is performed 60 times in each case, and 180 times in total. Three components of flow velocities in
the open-channel were measured with a 3-D electromagnetic current meter after removing the fish.
Tab. 1 Experimental casez

top - view

flow direction

non - bubble area

U m / B P (1/s)

Lz

0.02m

bubble area

case namenormal area

0.39m

initial position of fish

0.39m

air - bubble injector
x

0.6m
Lx

Fig. 1 Open-channel

2
V2

4V4

8V8

1
Plecoglossus altivelis altivelisn
U m BP  2(1/s)

N

0.6

20VEn
BPVEb
BP
10

Plecoglossus altivelis altivelis
U m BP  2(1/s)

nN

Plecoglossus altivelis altivelis

Plecoglossus altivelis altivelis
U m BP  2(1/s)

U m BP  28(1/s)

non bubble

bubblebubble area

0.1

bubble100

nonnon-bubble areanon  bubble area

%
60

0.4
4050.2

bubble area

200123456 Nt

Fig. 2 Rate of approach tobubble area

012345Fig. 3 ground speed

6 Nt

0030

6090  nb  b(deg.) 180

Fig. 4 Turning angle

012

34

56Nt

Fig. 5 staying time

3. RESULT AND DISCUSSION
Fig. 2 shows the relationship between the rate of approach to bubble area and number of fish. In the case of migration,
Plecoglossus altivelis altivelis evade the area with air bubble. This tendency is prominently when one fish swim alone.
However this tendency become lax with the number of fish school in each school of fish increase. Fig. 3 shows therelationship between the average of the approach speed from normal area to bubble area or non-bubble area V En or V Eb
divided by average length of Plecoglossus altivelis altivelis B p and the number of fish school in each school of fish. Theapproach speed at approaching to air bubble area decreased. The swimming speed also decrease in air bubble area. Thistendency is hardly influenced the number of fish school in each school of fish. Fig. 4 shows frequently distribution ofturning angle of Plecoglossus altivelis altivelis θ nb and θ b . In both of bubble area and non-bubble area, the turning
angle of Plecoglossus altivelis altivelis hardly change. Distribution profiles in bubble-area and non-bubble area are similar
and there are no remarkable difference. It is thought that, the turning angle of Plecoglossus altivelis altivelis is not affectedby air bubble. Finally, average staying time of Plecoglossus altivelis altivelis in bubble area and non-bubble area wascalculated each. Fig. 5 shows the relationship the time ratio and the number of fish school in each school of fish. It is foundthat average staying time ratio in bubble area is higher than average staying time ratio in non-bubble area. It is thought thatstaying tendency in bubble area was shown because air bubble let migration promotion of Plecoglossus altivelis altivelis
decline.
REFERENCES[1] Stewart PAM “An investigation into the reactions of fish to electrified barriers and bubble curtains” Fisheries Research 1 (1982) pp.3-22[2] Sekiya A and Urushiyama K and Fukui Y and Suzuki T “The way to prevent fish from stray (in Japanese)” Advances in River Engineering, 6(2001) pp.137-142[3] Sekiya A and Shimomura M and Sakamoto Y and Kouta A and Fukui Y “Research on methods for the prevention of the straying of ayu (inJapanese)”, Annual Journal of Hydraulic Engineering, JSCE 7 (2001) pp.233-238[4] Sekiya A and Fukui Y and Shimomura and Uchida T “Methods for preventing ayu from straying (in Japanese)” Annual Journal of HydraulicEngineering 46 (2002) pp.1133-1138[5] Shimomura, M. and Shirakawa H and Fukui Y and Sekiya A “Methods for preventing ayu from straying Analysis of the behaviour of fishes
by random walk method (in Japanese)” Advances in River Engineering 8 (2002) pp.337-342[6] Smith K A “Air-curtain fishing for Maine Sardines” Comm Fish Rev., 23(3) (1961) pp.1-14[7] Arimoto T and Akiyama S and Kikuya K and Kobayashi H “Fish-herding effect of an air bubble curtain and its application to set-net fisheries(in Japanese)” Fish Behaviour in Relation to Fishing Operations 196 (1993) pp.155-160[8] Onitsuka K and Akiyama J and Watanabe T and Iiguni Y and Kobayashi T 2008. “Effects of transmitted light and air bubbles on fish
behavior (in Japanese) ”, Annual Journal of Hydraulic Engineering, 52, pp.1207-1212.