12th International Conference on Hydroscience & Engineering
Hydro-Science & Engineering for Environmental Resilience
November 6-10, 2016, Tainan, Taiwan.

Influence of Turbidity on Fish School Behavior of Plecoglossus Altivelis Altivelis in Static Water
Kouki Onitsuka, Juichiro Akiyama, Keisuke Kasugai, Kazuya Momotani
Noriaki Ohara, Kento Joji
Department of Civil Engineering, Kyushu Institute of Technology
Kitakyushu, JapanABSTRACT
Most fish use eyes and lateral line during swimming so that theturbidity may affect the swimming behavior of fish school. However,no study has been made on the relations between turbidity andswimming behavior of fish school. In this study, the swimming
behaviors of fish school of Plecoglossus altivelis altivelis, by changing
the turbidity and the number of fish in static water, were recorded. It
was found that the fish school is divided into some fish school with anincrease of turbidity. This is because Plecoglossus altivelis altivelis
cannot find the other individuals by view due to turbidity.

KEY WORDS:

turbidity, fish behavior, Plecoglossus altivelis
altivelis, fish school, static water

INTRODUCTIONThe water includes turbidity during and after the flood. It is required for
an aquatic organism to be able to live also in various quality of water.
Therefore, it is necessary to investigate the influence of turbidity on
swimming behavior of fish.
At first the elucidation of the feeding behavior of fish in the turbid
water was tried. Gregory and Northcote pointed out that an eating
action of small fish of the salmon was controlled with turbidity increase(Gregory and Northcote, 1993). Hazelton and Grossman showed asimilar conclusion with rosyside dance (Hazelton and Grossman, 2009).
Utne-Palm nominates a lowering the visibility in the water by turbidity
increase for the reason why a feeding behavior is controlled (Utne-Palm,2002). On the other hand, Andersen showed that Salvelinus fontinails
move more active in high turbidity (Andersen et al., 2008), andPrchalová showed that activity pattern of Rutilus rutilus and Perca
fluviatilis were equally in static water and muddy water thattransparency is 0.35m (Prchalová, 2010). Mayama changed quantity of
the clay to issue in an open channel flow which velocity is 0.2m/s, andhaving observed feeding behavior of Oncorhynchus masou. As a result,feeding behavior became more active in muddy water, but feeding
behavior is controlled when density exceed a fixed value (Mayama,1998).
Then elucidation of survival rate of fish of muddy water and evasion
action for the muddy water were studied. Muraoka inserted the muddy
water which was eight kinds of high density as the figure of the adultfish of Plecoglossus altivelis altivelis can not be confirmed by viewing

in a water tank of 610 410 315mm and lived and confirmed it (Muraokaet al., 2011). As a result, it was elucidated that gills died fromsuffocation because a particle in the range of 1.2-36μm attach to gills.
Newcombe & MacDonald showed that survival of fish depend on
not only density but also duration (Newcombe & MacDonald,1991). Honda poured clear water into one waterway and inserted
clay, diatom and kaolin which changed density with each casesand counted the number of migration of Plecoglossus altivelis
altivelis which are released downstream than a junction in the device
that two waterways join. As a result, Honda showed that evasion
behavior was not observed when all injection materials are less than
15ppm. (Homda, 1983).
From above studies, it is estimated that fish do not evade low
concentrated turbid water, and evasion behavior become
remarkable depending on increase in density. Moreover, theelucidation of swimming behavior in turbid water was studied.
Inoue et al. observed rheotropism of Tribolodon hakonensis inrotary tank. Transparency was changed to 28, 17, 13cm. As a result
positive rheotropism increase with turbidity increase is elucidated(Inoue et al., 1982). Berg & Northcote made clear that ordercharacteristics in the fish school of the salmonidae collapse inhighly concentrated floating sand (Berg and Northcote, 1985).
Onitsuka et al. changed turbidity and observed the behavior of
one Plecoglossus altivelis altivelis (Onitsuka et al., 2013). As a result,the swimming speed of the Plecoglossus altivelis altivelis decreased
with turbidity increase was elucidated. However, the behavior is known
to be different from the case fish school consist of three or more in thecase fish school consist of one or two (Partridge and Pitcher, 1980),(Onitsuka et al., 2014). Therefore, this result (Onitsuka et al., 2013)
is not necessarily applicable for the fish swimming in the fish school ina river. This study elucidated influence of turbidity on fish school
behavior of Plecoglossus altivelis altivelis in static water.

EXPERIMENTAL SET UP AND HYDRAULICCONDITIONS
A blue circular tank that the radius r was 0.9m was used. The depth ofthe water h was 0.04m. Turbidity was changed five patterns with turbidwater. Table-1 shows experimental conditions. Measurement ofturbidity was performed as follows. Muddy water was put into thetransparent container and irradiated by the light of 120W light source.
The illumination was measured with the illuminometer. The case nameshows the initial of “Turbidity” and the illumination ratio. 3-7tails of12th International Conference on Hydroscience & Engineering
Hydro-Science & Engineering for Environmental Resilience
November 6-10, 2016, Tainan, Taiwan.

Plecoglossus altivelis altivelis put into the cylinder wire net in thecenter of circular tank. Averaged body length of Plecoglossus altivelis
altivelis BL is 70mm. Fig.1 shows five examples of the swimming
trajectory of Plecoglossus altivelis altivelis in each illumination. The
number of pixel of the digital video camera is 1440×1080, andrecording speed is 30fps. Exposure time is 1min with each cases. Afterthe experiment, the picture of swimming behavior of Plecoglossus
altivelis altivelis when Plecoglossus altivelis altivelis start theswimming until reach the side wall was captured at 1s interval.
Swimming distance, swimming speed, and the degree of angle ofrefraction were calculated with the statistic picture and coordinated plotsoftware.

EXPERIMENTAL RESULTS AND ANALYSISThe swimming trajectory
Fig. 1 shows the swimming trajectory of Plecoglossus altivelis altivelis
in each turbidity every one second in any 30 seconds with eachturbidity. The plots were shown with a different color every 5seconds
in this figure. The swimming positions were shown with different color
every five seconds. When turbidity is low, Plecoglossus altivelis
altivelis is often distributed over the region where the same colors
concentrate. The matter shows that ratio of individual acting in the fish
school is high. On the other hand, standard deviation of the plots of thesame color spread with turbidity increase. Therefore, proportion thatthe fish school separates and a fish swim alone is large.

Distance between the individual in all individuals
Fig. 2 (a), (b) shows the average of the distance between an individualin all individuals D and standard deviation D′ divided by the average
length BL in each turbidity, and approximation line. Considering fig. 2(a), it is understood that the distance between the individual increases inall cases. Considering fig. 2 (b), it is understood that standard deviationof the distance between the individual increase with turbidity increase

C00 − 5in all cases. It is judged that the distance between the individual of thePlecoglossus altivelis altivelis increases with turbidity increase, and thedegree spread. Therefore, it is suggested there is a tendency that it
becomes difficult to confirm the individual which is adjacent whenturbidity increase, and school of fish swim independent or separation.

Probability of the number of fish school in each school of fish
In this study, the situation that fish swim alone apart from a fish school
and fish school was divided into plural number was observed. However
the distance between the individuals depend on the fish class when fishschool is formed, the distance between an average individual is 1 timeof the length. A group of separated fish which the distance between theindividual leaves to some extent than 1 time of the length is notregarded as fish school. In this study, it is defined that the group of thefish which it was far more than 3 times of the mean length of thePlecoglossus altivelis altivelis, and was formed as a different school offish. Because it was confirmed that it was rare that the Plecoglossus
altivelis altivelis came close again when the distance between theindividuals more than 3 times of the length in each turbidity.
Table. 1 experimental conditions

Case name
N （尾）(tails)
E n (lx) (E 1-E n)/E 1×100 3
57
E 1=1490
0C00-3 C00-5 C00-7
E 2=1192
20
C20-3 C20-5 C20-7
E 3= 89440C40-3 C40-5 C40-7
E 4= 596
60
C60-3 C60-5 C60-7
E 5= 29880
C80-3 C80-5 C80-7

t =0-5st =0-5st =6-10s

t =6-10s

t =11-15s

t =11-15s

t =16-20s

C40 − 5t =16-20s

t =21-25s

t =21-25s

t =25-30s

t =25-30s

t =0-5st =0-5st =6-10s

t =6-10s

t =11-15s

t =11-15s

C60 − 5t =16-20s

C80 − 5t =16-20s

t =21-25s

t =21-25s

t =25-30s

t =25-30s

Fig. 1 The swimming trajectory

12th International Conference on Hydroscience & EngineeringHydro-Science & Engineering for Environmental Resilience
November 6-10, 2016, Tainan, Taiwan.

1010DBLDBL6643N43N

25N

25N

7N

00204060

7N

0080

20406080

Turbidity
Turbidity(a) The average of distance between(b) Standard deviation of distance between
the individuals and all individuals
the individuals and all individuals
Fig. 2 Distance between the individual in all individuals

1
NtN51
Nt
N3
1N

0.6

1N
2N

0.6

3N

0.40.2

0.2

0001N

0.6

3N

2N

3N

2N

0.4

1
NtN74N
5N

5N
6N

0.2

7N0020 40 60 80

4N

0.4

20 40 60 800(a) 3tails(b) 5tails
Fig. 3 Probability of number of school fish in each school of fish

11

1t3
T

t5
Tt7
T

3N

5N

0.6

0.6

0.6

0.4

0.4

0.4

0.2

0.2

0.2

000

20 40 60 80
Turbidity(a) 3tails

20 40 60 80
Turbidity

Turbidity

Turbidity(c) 7tails

7N0020 40 60 80
Turbidity(b) 5tails
Fig. 4 Duration of fish school formation

Fig. 3 (a), (b), (c) shows the value which the number of the tails in thefish school in each school of fish N t divided by the number of the tails
inserted N n in each turbidity. The number of the tails in the fish school
decreases than the number of the tails inserted in each case. In addition,
it is thought that Plecoglossus altivelis altivelis do not form fish schoolwith individuals at a distance even if turbidity is low, because thistendency is remarkable when turbidity varied from 0 to 20.

Duration of fish school formation
In this study, a situation that Plecoglossus altivelis altivelis did notnecessarily form one fish school was observed. However, a situationthat Plecoglossus altivelis altivelis form plural fish schools wasobserved. Plural fish schools were not necessarily kept all in the020 40 60 80
Turbidity(c) 7tails

experiment. Furthermore, some fish schools are divided. Therefore, Fig.
4 (a), (b), (c) shows the value which formation duration t n of fish
school including the maximum number of fish during each experiment
divided by total experiment time T in each turbidity. The duration offish school decrease with the turbidity increase in all three cases. It isthought that because of deterioration of visibility by turbidity, it
became difficult to go back to an original fish school. In addition, thistendency is remarkable when turbidity varied from 0 to 20. Therefore,
when water is approximately clear, a tendency to keep the fish school isstrong. In contrast, even if it is low concentration, a tendency that fish
school divide in muddy water is strong.

12th International Conference on Hydroscience & Engineering
Hydro-Science & Engineering for Environmental Resilience
November 6-10, 2016, Tainan, Taiwan.

3337NDnBLDnBLDn
BL

6N

5N

3N

4N

2N

3N

5N
4N
3N

2N

2N

1110204060

80020Turbidity(a) 3tails

4060
Turbidity

80

0Fig. 5 (a), (b), (c) shows average Dn of the distance between theindividual divided by the average length BL of Plecoglossus altivelis
altivelis in each turbidity, and approximation line. Although there aresome exceptions, the distance between the individual almost decreases
with turbidity increase. It is thought that it occurred because
recognizable distance that can recognize individual decreases withturbidity increase.

CONCLUSIONSIn this study, the influence of turbidity and number of fish on
swimming behavior of fish school of Plecoglossus altivelis altivelis
in statistic water was analyzed. As a result, the following havebeen understood.
(1) In comparison with clear water, the tendency that fish school
divide into in muddy water towards higher. This tendency becomesremarkable with the turbidity increase.
(2) In comparison with clear water, the distance between the individualin the school of fish decrease in muddy water. This tendency
becomes remarkable with the turbidity increase. It is thought thatsuch a result was shown because visibility is worse with turbidity
increase. Therefore, distance that can recognize individuals nearby
in muddy water shorten.

REFERENCES
Andersen, M., Jacobsen, L., Grønkjær, P. and Skov, C. (2008).
Turbidity increases behavioural diversity in northern pike. Fisheries
Management and Ecology, Vol.15, pp.377-383.
Berg, L. and Northcote, T.G. (1985). Changes in territorial, gill-flaring,and feeding behavior in juvenile coho salmon (Oncorhynchuskisutch) following short-term pulses of suspended sediment.
Canadian Journal of Fisheries and Aquatic Sciences, Vol.42,pp.1410-1417.
Gregory, R.S. and Northcote, T.G. (1993). Surface, planktonic, andbenthic foraging by juvenile chinook salmon (Oncorhynchustshawytscha) in turbid laboratory conditions. Canadian Journal ofFisheries and Aquatic Sciences, Vol.50, pp.233-240, 1993.

406080Turbidity(b) 5tails
Fig. 5 Distance between the individual in all each fish school

Distance between the individual in all each school of fish20(c) 7tails

Hazelton, P.D. and Grossman, G.D. (2009). The effects of turbidity andan invasive species on foraging success of rosyside dace
(Clinostomus funduloides). Freshwater Biology, Vol.54, pp.19771989.
Honda, H. (1983). Effect of turbidity density and lowering watertemperature on Migration Characteristics of Plecoglossus altivelis
altivelis. Marine sciences monthly. Vol.15, No.4, pp.233-255.
Inoue, M., Wei G.N. and Arimoto, T. (1983). Upstream Movement ofFresh water Fishes under Bright and Dark Conditions. Bulletin of theJapanese Society of Scientific Fisheries, Vol.48, No.12, pp.233-255.
Ishikawa, M. (2000). An Experimental Study on Evaluation of Fish
Schooling Behavior Properties. Advances in river engineering, Vol.6,
pp.101-106.
Mayama, H. (1998). Effects of Turbidity on the Feeding Behavior ofJuvenile Masu Salmon (Oncorhynchus masou). Bulletin of theNational Salmon Resources Center, No.1, pp1-11.
Muraoka, K., Amano, K., Kubota, H. and Miwa, J. (2011). Effects ofsuspended solid concentrations and particle size on survival of Ayu(Plecoglossus altivelis altivelis). Japanese Journal of Ichthyology,Vol.58, No.2, pp.141-151.
Newcombe, C.P. and MacDonald, D.D. (1991). Effects of suspended
sediments on aquatic ecosystems. North American Journal ofFisheries Management, Vol.11, No.1, pp.72-82.
Onitsuka, K., Akiyama, J., Kuramoto, S., Noguchi, S. and Ueda, S.
(2013). Swimming Behavior of Isolated Ayu in Statistic Water. The
Journal of Japan Society of Civil Engineering, Ser. G, JSCE, Vol.69,No.6, pp.337-342.
Onitsuka, K., Akiyama, J., Mihara, K., Shiraoka, B. and Hirano, Y.
(2014). Comparison of Effects of Velocity on Swimming Behaviorof Ayu by Number Change. The Journal of Japan Society of Civil
Engineering, Ser. B1, JSCE, Vol.70, No.2, pp.37-48.
Partridge, B.L. and Pitcher, T.J. (1980). The sensory basis of fishschools. Journal of Comparative Physiology, Vol.135, pp.315-325,
1980.
Prchalová, M., Mrkvička, T., Kubečka, J., Peterka, J., Čech, M., Muška,M., Kratochvíl, M. and Vašek, M. (2010). Fish activity as
determined by gillnet catch, Fisheries Research. Vol.102, pp.291-296.
Utne-Palm, A.C. (2002). Visual feeding of fish in a turbid environment:
Physical and behavioural aspects. Marine and Freshwater Behaviour
and Physiology, Vol.35, pp.111-128.