THE INFLUENCE OF DAMMING ON THE DISTRIBUTION OF BROWN [619523]

THE INFLUENCE OF DAMMING ON THE DISTRIBUTION OF BROWN
TROUT Salmo trutta LINNAEUS, 1758 AND EUROPEAN GRAYLING
Thymallus thymallus LINNAEUS, 1758 (PISCES: SALMONIDAE) FROM
SOME ȘUL CALD RIVER

Călin LAȚIU1, Daniel COCAN1*, Paul UIUIU1, Maria -Cătălina MATEI2, Andrada IHUȚ1,
Sabin -Alexandru NICULA3,4 , Ioan LAȚIU5, Radu CONSTANTINESCU1,
Vioara MIREȘAN1*

1University of Agricultural Sciences and Veterinary Medicine Cluj -Napoca, Cluj County, Romania,
Mănăștur Street 3 -5, 400372, Faculty of Animal Science and Biotechnologies, Department I
Fundamental Sciences (Romania)
2University of Agricultural Sciences and Veterinary Medicine Cluj -Napoca, Cluj County, Romania,
Mănăștur Street 3 -5, 400372, Faculty of Veterinary Medicine, Department I Preclinics (Romania)
3 Centre for Research on Settlements and Urbanism, Faculty of Geography, “Babeș -Bolyai”
University, Cluj -Napoca, 5 -7 Clinicilor St., RO -400006, (Romania)
4 National Institute for Economic Research “Costin C. Kirițescu”, Romanian Academy, Bucharest,
Casa Academiei Române, 13 Septembrie St., no. 13, RO -05071 (Romania)
“Timotei Cipariu” Tehnological Highschool, D r. Vasile Suciu St. no. 25, Blaj, (Romania)

*Corresponding author s: vioara.mireșan@usamvcluj.ro; [anonimizat]
Abstract
Monitoring fish fauna in altered aquatic habitats may provide relevant information regarding the distribution, presence
or absence, and d ynamics of fish species. Someșul Cald River is the main tributary of Beliș -Fântânele Reservoir and
Dam, build from 1970 to 1974. The presence o f the dam could have affected fish fauna, especially potamodromous brown
trout Salmo trutta and European grayling Thymallus thymallus because of habitat obstruction. Altitude, riverbed width,
water depth, and water velocity are easy to determine aquatic en vironmental parameters. River altitude and riverbed
width played an important role in European grayling preference regarding the auspicious environment. Correlation
coefficients showed that increasing altitude is a limiting factor for European grayling (r= -6024*, p<0.05). Wider riverbed
is preferred by the same species (r=0.627*, p<0.05). Beliș -Fântânele Dam blocked the migration of fishes and made the
grayling ecological zone framed by two trout ecological zone ( upstream and downstream ). The distribution r ange on the
altitude of the brown trout in Someșul Cald River was from 518.5m to 1153.5m and 577.5m to 1068.5m for the European
grayling.
Key words: altered aquatic environment, icht hyofauna, electrofishing, endangered species.

INTRODUCTION
Anthropic activities such as dam constructions,
reservoirs, cascade dams, hydropower plants,
and other hydro -technical constructions lead to
major fragmentation of river systems and
diversity loss (Kang et al. 2009; Jonsson et al.
2018; Kirin et al. 2019 ). Nilsson (2005) stated
that dams have dramatically altered over half
of the river systems in the world. The main
habitat alteration mechanisms consist of: lotic
habitats converted to lentic habitats (Martinez et al. 1994), construction of phys ical barrie rs
(Watters, 1996) and constant change of water
parameters regimes (pH, temperature,
turbidity) (Magilligan and Nislow 2005).
Migration of fish is essential and artificial
barriers limit or obstruct their movement. Also,
fish species like brown trout, European
grayling, Danube salmon, Black Sea trout, that
are associated with fast -flowing waters tend to
diminish in numbers and sometimes disappear
(Jansson, 2006). Similar phenomena is

encountered on Someșul Cald River, located in
Cluj County, Nor th-Western Romania. The
distribution of fish species belonging to the
Salmonidae family could be affected by habitat
alteration caused by damming, in this case,
brown trout Salmo trutta and European
grayling Thymallus thymallus (Ombredane et
al. 1987). Con stant survey of the fragmented
river systems fish fauna will provide data to
generate the appropriate evolution and
distribution of fishes, and also the long term
effects of dams. The present study aimed to
provide an up -to-date image of the ant hropic
barriers from the Someșul Cald River and how
habitat alteration progresses.
MATERIALS AND METHODS
Sampling site
The study was conducted from August 2018 to
September 2018 on Someșul Cald River
(Someș -Tisa catchment, North -Western
Romania). The springs of Someșul Cald River
are located in Bihariei -Vlădeasa Masiff near
Piatra Arsă Peak (Burned Stone Peak) at 1550
m altitude and has a total length of 66.5 km
(Duma, 2016). On Someșul Cald River, four
dams were constructed during 1970 -1974:
Beliș -Fântânele Dam, Tarnița Dam, Someșul
Cald Dam and Gilău Dam. At Gilău Dam,
Someșul Rece River flows into Someșul Cald
River and form Someșul Mic River (Figure 1) .
Sampling method
Fish sampling was performed by single -pass
electrofishing techniques using a SAMUS 725
MP apparatus, powered by 12V and 24 A
rechargeable battery (Cocan et al. 2020). The
efficiency of freshwater fish sampling by
electrofishing methods is highly effective
especially in streams and small rivers
(Kubečka et al. 2012). Water conductivity was
tested before electrofishing to adjust the output
current and non -lethal frequencies
(www.fao.org) using Hannah HI9828 multi –
parameter (Uiuiu et al. 2020).
Habitat chara cterization Fish sampling stations were marked using
Garmin eTrex 20X GPS device. Each station ’s
altitude, width, depth, water velocity was
measured. The altitude of the stations was
measured based on GPS data using Garmin
BaseCamp software (ex -situ). Station riverbed
width was measured with a 50m measuring
tape. A total number of 5 measurements were
performed inside each station (1 measur ement
at the lowest point of the station and 1
measurement at the highest point of the station,
and 3 intermediary measurements). Water
depth and water velocity were measured in the
same locations as riverbed width.
Data analysis
The data was processed us ing MS Excel,
GraphPad Prism Ver. 8. Pearson correlations
were performed to highlight the “links”
between the amount of fish, presence or
absence of fish and river configuration.
RESULTS AND DISCUSSION
GPS coordinates and altitude of the sampling
stations
The sampling stations were grouped into two
sections based on the Beliș -Fântânele Dam
position as follows: the lower section (from
station 1 to station 8) positioned between
Tarnița Reservoir (downstream) and Beliș –
Fântânele Dam (upstream) and the superior
section (station 9 to station 20) positioned
between Beliș -Fântânele Dam and the springs
of Someșul Cald River. The altitude for each
sampling station was determined in two points
(1 point on the downstream limit of the station
and 1 point on the upstream limit of the
station). In Figure 2, the mean altitude
recorded values of the sampling stations are
presented. The lowest altitude was recorded in
station 1 (518.5 m) and the highest altitude was
recorded in station 20 (1153.5 m) . Beliș –
Fântânele Dam is situated between stations 8
and 9. GPS coordinates of each river section
with the corresponding stations are presented
in Table 1.
Altitude is one of the most important factors
which influence fish species richness. At low

altitudes , the trophic composition is more
diverse (Pouilly et al. 2006) and ecological
zones for fish species can be determined.
Barradas et al. (2012) concluded that the
historical and spatial distribution of fish
species can help to identify the potential
impact of damming. Based on altitude, brown
trout is present in both sections of the river and
in all the sampled stations. European grayling
is also present in both sections of the river but
in small number s in the lower section. The
highest point where Europea n grayling was
signaled was station 16 at the altitude of 1068.5 m. In this case, we can stipulate its limit
of habitat based on altitude. The ecological
zone of trout is above/upstream the grayling
zone. The influence of damming clearly
changed the distri bution based on the altitude
of the two species. The ecological zone of the
grayling is "framed" by two ecological trout
zones: one downstream the Beli ș-Fântânele
Dam and the second one upstream station 16 .
In an unaltered habitat, the grayling ecological
zone is below (downstream) the trout zone
(Aarts and Nienhuis, 2003; Lasne et al. 2007).

Table 1. GPS coordinates of the sampling stations

River section Station Downstream point Upstream point Lower section 1 N46° 42.413' E23° 12.932' N46° 42.454' E23° 12.816'
2 N46° 41.914' E23° 10.990' N46° 42.005' E23° 10.902'
3 N46° 41.892' E23° 09.538' N46° 41.926' E23° 09.286'
4 N46° 42.023' E23° 08.125' N46° 42.013' E23° 07.991'
5 N46° 42.080' E23° 07.781' N46° 42.153' E23° 07.672'
6 N46° 42.495' E23° 07.029' N46° 42.578' E23° 06.906'
7 N46° 42.609' E23° 06.465' N46° 42.612' E23° 06.363'
8 N46° 41.925' E23° 04.602' N46° 41.959' E23° 04.825' Superior section 9 N46° 38.766' E22° 52.112' N46° 38.787' E22° 51.952'
10 N46° 38.818' E22° 51.837' N46° 38.832' E22° 51.622'
11 N46° 38.834' E22° 51.457' N46° 38.786' E22° 51.326'
12 N46° 38.589' E22° 50.581' N46° 38.498' E22° 50.221'
13 N46° 38.429' E22° 49.409' N46° 38.378' E22° 49.323'
14 N46° 38.301' E22° 49.060' N46° 38.216' E22° 48.755'
15 N46° 37.955' E22° 48.284' N46° 37.814' E22° 48.080'
16 N46° 37.770' E22° 46.407' N46° 37.813' E22° 46.327'
17 N46° 38.092' E22° 45.022' N46° 38.112' E22° 44.932'
18 N46° 38.485' E22° 44.067' N46° 38.532' E22° 43.995'
19 N46° 38.653' E22° 43.712' N46° 38.649' E22° 43.616'
20 N46° 38.356' E22° 43.138' N46° 38.310' E22° 43.131'

Figure 1. Someșul Cald River catchment and constructed dams

Figure 2 . The altitude of sampling stations
Tarnița Reservoir

Water depth
Water depth in the lower section of Someșul
Cald River ranged from 20.4 cm (station 5) to
55.8 cm (station 1). The mean value of water
depth was 37.2 cm. In the superior section of
the river, water depth ranged from 11.9 (station
17) cm to 42 cm (station 16) (Figure 3) . The
mean value of water depth was 25.6 cm . The
coefficient of variation (CV%) was highly
similar for the two sections: 34.14% for the
lower section and 35.47% for the superior
section. In this case, water depth did not
influence the presence or absence of both
species. Large specimens of European grayling
prefer deeper water than small specimens (Mallet et al. 2000) but in this case, in the
deeper pools from the lower section of the
river, we did not encounter any specimen. The
two specimens caught in the lower section
were caught in stati ons 2 and 3 where the mean
water depth was 24.2 cm respectively 26 cm.
The highest number of brown trout Salmo
trutta was caught in station 4 (lower section)
and station 12 (superior section). The mean
water depth in both cases was similar (40.6 cm
and 38 cm). Water depth is not related to the
number of specimens but rather for their size,
a fact confirmed by Vismara et al. (2001 ) who
stated that adult brown trout prefer deeper
water than smaller specimens.
Water width
Water width in the lower section of the
Someșul Cald River ranged from 4.48 m
(station 4) to 9.53 m (station 1). The mean
value of the water width was 6.433 m. In the
superior section of the river, water width
ranged from 2.348 m (station 20) to 24.68 m
(station 9). The mean value of water depth was
11.30 m. The coefficient of variation (CV%)
was 23.45% for the lower section and 66.26%
for the superior section. The alteration of the habitat can be best visualized in Figure 4.
Water width is constantly increasing from
station 20 to station 9, where the Beliș –
Fântânele Dam is positioned. Downstream of
station 9, and implicitly the Beliș -Fântânele
Dam the width of the river is much narrower.
Fish migration is stopped by the dam and also
the habitat continuity is alter ed. In figure 4 can
be observed as a similarity in the lower section
and the superior section of the river. The mean
width of stations from 2 to 8 (lower section)
Figure 3. Mean water depth of the sampling stations

is almost identical to the mean width of
stations from 14 to 20 (superior section) (2 to
8= 5.99m vs. 14 to 20= 5.97m). The number of
brown trout specimens in stations from 2 to 8
is 483 and in stations f rom 14 to 20 is 312. In
the case of European grayling, in stations from
2 to 8 two specimens were caught and in stations from 14 to 20, 35 specimens were
caught. In the superior section (stations 9 to 13)
the total number of European grayling is
higher tha n the number of brown trout (181 vs.
119). In the same stations, the mean width of
the river is 18.76 m, 3 times wider than the
stations interval 2 to 8 and 14 to 20.
Water velocity
The mean recorded velocity in the lower
section of the river was highly similar to the
velocity recorded in the superior section (0.335
m/s vs. 0.363 m/s). The smallest value for the
lower section was 0.14 m/s (station 1) and the
highest value was 0.44 m/s (station 5). The
superior section of th e river showed more
homogenous water velocity . The smallest
value was recorded in station 16 (0.3 m/s) and
the highest values were recorded in sectors 10
and 19 (0.42 m/s) (Figure 5 ). Both brown trout
and European grayling have great swimming
capacity and their presence can be influenced
by water velocity. For spawning, they use slow
flow habitats (10 -30 cm/s). The data presented
in Figure 5 may indicate spawning sites since
velocity is one of the most important variable s
together with substrate composition (Fukuda et
al. 2013). Fish samples
A total number of 1235 fishes were caught
from the Someșul Cald River of which 938
brown trout Salmo trutta specimens (488 in the
lower section and 450 in the superior section)
and 297 European Grayling Thymallus
thymallus (2 in the lower section and 295 in the
superior section) (Figure 6) . Brown trout
represented 75.95% of the total number of fish
caught and European grayling represented
24.05%. In the lower section of the river ,
brown trout represented 99.59% and European
grayling represented 0.41%. A different
situation was noticed in the case of the superior
section of the river, where brown trout
represented 60.40% and European grayling
represented 39.60%. The largest number of
brown trout specimens were
Figure 4. Mean water width of the sampling stations

caught in the lower section of the river in
station 4 (174 specimens) while the smallest
number was caught in the superior section in
station 20 (1 specimen). In terms of numbers,
in station 12 from th e superior section of the river, 104 European grayling specimens were
caught and the species was missing in stations:
1, 4, 5, 6, 7, 8 (lower section) and 17, 18, 19
and 20 (superior section).

Figure 5. Mean water velocity of the sampling stations

Figure 6 . Brown trout and European Grayling specimens from the two sections of the river

0.140.240.4 0.380.44
0.340.360.38
0.320.42
0.340.36
0.320.320.4
0.30.380.380.420.4
00.050.10.150.20.250.30.350.40.450.5
0510152025
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Station Mean water speed (m/s)
Superior section

Correlations of fish and habitat parameters
Pearson correlations were perform ed to
characterize the relationship between the
aquatic environment (in its current state) and
the distribution of the two salmonid fish
species under the present conditions (Figure 7
and 8). The brown trout was present in all the
analyzed stations and it appears that altitude,
water width, water depth and water velocity do
not affect its distribution and all the
correlations were not statistically significant
(for p<0.05). The correlation coefficient was
weak and moderate in the ca se of brown trout.
In biological terms, this may be explained by
the plasticity of the species which adapts very
well to different new environments with
different morphology (Valiente et al. 2010;
L’Abée -Lund and Vøllestad, 2017 ). The
presence of European grayling is affected by
two major parameters: altitude and water width
(Table 2). A strong negative correlation can be
observed (r= -0.6024) in the case of European grayling and altitude, meaning that the number
of fish decreases w hen altitude increases. An
almost identical situation is encountered in the
case of European grayling and water width
(r=0.672). The strong and positive correlation
between European grayling and river width
was observed only for the superior section of
the river. The presence of the Beliș -Fântânele
Dam had two negative side effects: first, the
dam is blocking the European grayling
upstream and downstream migration and
second, it is genetically isolating the upstream
existing population (Curtean -Bănăduc and
Bănăduc, 2016).
Petru Bănărescu (1964) mentioned that
European grayling was found in Someșul Cald
River, at the confluence of Someșul Cald River
and Someșul Rece River and downstream , in
Someșul Mic River (formed by Someșul Cald
River and Someșul Rece River) close to
Florești Village and Cluj -Napoca, Cluj
County. The species was not signalled in the
last 20 years in Someșul Mic River .
.

Table 2. Correlation of species ( Salmo trutta and Thymallus thymallus ) with habitat parameters
(*significant for p<0.05)

Altitude (m) Width (m) Depth (cm) Velocity (m/s)
River Section Species r p-value r p-value r p-value r p-value
L
Salmo trutta 0.4031 0.3221ns -0.5089 0.1978ns -0.01672 0.9687ns 0.5756 0.1354ns
S -0.2268 0.4784ns -0.0980 0.7617ns 0.34 0.2796ns -0.1756 0.5851ns
L+S -0.1959 0.4078ns -0.2165 0.3592ns 0.2239 0.3426ns 0.3178 0.1721ns
L
Thymallusthymallus -0.448 0.2656ns -0.2917 0.4832ns -0.588 0.1253ns -0.09463 0.8236ns
S -0.6024 0.0382* 0.672 0.0167* 0.4806 0.1137ns -0.3193 0.3116ns
L+S 0.2799 0.2320ns 0.7181 0.0004*** 0.0432 0.8565ns -0.04945 0.8360ns
Legend: L -lower section; S -superior section; L+S -both sections, r -correlation coefficient; p -statistical significance.

Figure 7 . Correlations and 95% confidence intervals between fish number and aquatic habitat parameter s – The
lower section of S omeșul Cald River

Figure 8 . Correlations and 95% confidence intervals between fish number and aquatic habitat parameter s –
Superior section of S omeșul Cald River

CONCLUSION
Brown trout Salmo trutta and European
Grayling Thymallus thymallus distribution is
affected by the damming from the Someșul
Cald River. Someșul Cald Ri ver configuration
is altered by the cascade dammings and as a consequence, fish ecological zones are
abnormal . There is also the risk of genetic drift
for the European grayling population located
in the superior section of the ri ver. Riverbed
width and altitude also influ ence the
distribution of the studied species.

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