Download Estimating Fish Communities Structure and Diversity from Predeltaic

Sandu (Calin) P. G. et. al./Scientific Papers: Animal Science and Biotechnologies, 2013, 46 (2)
Estimating Fish Communities Structure and Diversity
from Predeltaic Danube Area
Petronela Georgiana (Călin) Sandu*, Lucian Oprea
"Dunarea de Jos" University of Galati, Romania
Department of Aquaculture, Environmental Science and Cadastre
Abstract
The paper is presenting some aspects regarding the structure of fish communities from 22 Km of predeltaic sector of
Danube River, between the mouth of Siret River (km 155) and Prut River (Mm 72.5). The aim of the study is to
assess the ecological status of the area, using some analytical and synthetic ecological indices, but also diversity and
equitability indices. From April to December 2012, in four fishing areas (km 150-151, Mm 77-78, Mm 76-77, Mm
74-74.5), 7121 fish of 31 species, from 7 famillies and 6 orders, were collected. The best represented family is
Cyprinidae with 17 species. The numerical abundance ranged between 1fish/species (zingel, Danube streber and
Black Sea trout-rare species) and 2035 fish/specie (pontic shad - abundant specie). The pontic shad (43.98%),
common bream (12.09%) and Prussian carp (10.66%) are eudominant species, having the biggest potential in fish
productivity.
Keywords: abundance, Danube, diversity, ecological significance fish communities
the fish communities at the same time as the
continuous degradation of the habitats led to the
decline and even to the extinction of some fish
species [4].
Therefore, in order to take some efficient
conservation measures, a good knowledge of the
species ecobiology and of their interaction with
their living environment is necessary [5]. In this
work there are presented some aspects regarding
the structure and the ecological assessment of the
fish communities from predeltaic Danube. The
aim of the researches is to highlight the structural
changes from the level of the ichthyofauna, by
using some analytical and synthetic ecological
indices.
1. Introduction
Many human uses of Danube River (i.e.
transportation, wastes, pollution) are potentially in
conflict with the aquatic living resources. In
addition, human activities not only have an impact
on fish communities, but in the same way also
rebound in human communities associated with
the exploitation of these resources [1, 2].The
structure and the diversity of fish communities is
an important feature in the system dynamics
because changes in diversity reflect changes in the
ecosystem processes, such as productivity, energy
pathways and material flow, disturbance regimes,
abiotic stress and biological interactions [3].
A good management of the interactive
components of the fishery should always lead to a
durable exploitation, in terms of biodiversity
conservation and protection. In the last years,
however, unfortunately, the over-exploitation of
2. Materials and methods
Fishing area
The study area is represented by a region in the
predeltaic Danube, located between the Siret River
Mouth (km 155) and the Prut River Mouth (Mm
72.5). This region has approximately 22 km,
representing the length of the Danube sector in
Galati County. Monthly, systematic measurements

* Corresponding author: Georgiana (Călin) Sandu,
Email: [email protected]
227
Sandu (Calin) P. G. et. al./Scientific Papers: Animal Science and Biotechnologies, 2013, 46 (2)
have been made in 4 fishing areas: Galati area (km
150-151), Condrea area (Mm 77-78), Muresanu
area (Mm 76-77) and Plopi area (Mm 74-74.5)
(Figure 1).
methods, on areas, with filtering gear: gill net and
trammel net type. The constructive characteristics
of these varied, depending on the targeted species
to be caught: gill nets (Lp 100-150 m; Hp 2.5-3.5;
a 30-60 mm), trammel nets (Lp 150-200 m; Hp
2.5-4.0; a 40-80 mm). The used method for
obtaining the capture data is the simple
randomized samples. The caught specimens have
been identified and divided on species; biometric
and gravimetric measurements have been made.
The identification of the fish species was made by
analyzing the specialized literature [7-10].
Fishing effort, fishing gears and methods
The structure of a fishing unit (FU) is the
following: the fishing boat, the gear and 2
fishermen. On the average, in an area more FU
operate, making 2-3 operations/fishing day [6].
The fishing has been made through active
Figure 1. Map of fishing area (satellite image)
Fishermen teams, from ”Dunărea de Jos”
University of Galati, Department of Aquaculture,
Environmental Science and Cadastre and from the
Institute of Research and Development for
Aquatic Ecology, Fishery and Aquaculture Galaţi,
have been making scientific fishing, according to
the conditions of the authorization issued by
National Agency for Fishing and Aquaculture.
B
 Xij  Xik
  Xij  Xij 
where: Xij, Xik – the number of individuals from
a species in each sample;
Shannon-Wiener (H’) index:
S
H ,   pi ln pi
i 1
The calculation of the ecological indices and
statistical approaches
The structural changes at the level of
ichtiocenoses are characterized by using some
analytical
ecological
indices
(abundance,
dominance, constancy) and synthetic ones (the
index of ecological significance), but also
diversity and equitability indices [3].
The statistical methods of the data have been
made with the computer (MSOffice Excell) and
with the software BioDiversity Pro.
Formulas
The Bray-Curtis (B) dissimilarity index, takes
values between 0-1 [12, 13].
pi – the abundance ratio of breed i; ln – common
logarithm.
Simpson (D) index is among the first diversity
indices (Simpson 1949) [14].
S
D  1   pi
2
i 1
The Simpson (1-D) diversity index is used for the
correct estimation of a finite population:
1 D 1 
228
ni (ni  1)
N ( N  1)
Sandu (Calin) P. G. et. al./Scientific Papers: Animal Science and Biotechnologies, 2013, 46 (2)
ni–the number of individuals from breed i;
Ni–the total number of individuals from the
analyzed sample.
The equitability refers to the example of
individuals’ distribution between species [15]. The
Shannon equitability index has been calculated
(relative diversity HR) but also the Simpson E1-D
equitability index.
HR 
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
HS
H

H Smxa log S
E 1 D 
3. Results and discussion
Between April-December 2012, there were caught
7121 fish, with a total biomass of 4910.34 kg, of
31 species, from 7 families, respectively 6 orders.
The autochthon and allochthonous ichthyofauna in
the predeltaic Danube is divided in two groups,
depending on salinity tolerance: euryhaline and
stenohaline species (Table 1). The best
represented family is Cyprinidae, of the
Cypriniformes order, with 17 species (Figure 2).
1 D
(1  D ) max
Table 1. The qualitative structure of ichthyofauna and their salinity tolerance
Latin name of species
Eurihaline
Common name
x
Aspius aspius (Linnaeus, 1758)
Asp
Blicca bjöerkna (Linnaeus, 1758)
White bream
x
Carassius gibelio (Bloch, 1782)
Prussian carp
Abramis sapa (Pallas, 1814)
White-eye bream
Ctenopharyngodon idella (Valenciennes,1844)
Grass carp
x
Cyprinus carpio (Linnaeus,1758)
Carp
Vimba vimba (Linnaeus,1758)
Vimba
Barbus barbus (Linnaeus,1758)
Common barbel
Hypophthalmichthys nobilis (Richardson,1845)
Bighead carp
Abramis brama (Linnaeus,1758)
Common bream
x
Pelecus cultratus (Linnaeus,1758)
Ziege
Hypophthalmichthys molitrix (Valenciennes,1844) Silver carp
Chondrostoma nassus (Linnaeus,1758)
Common nase
Leuciscus idus (Linnaeus,1758)
Ide
Scardinius erythrophthalmus (Linnaeus,1758)
Rudd
Rutilus rutilus (Linnaeus,1758)
Roach
Alburnus alburnus (Linnaeus,1758)
Bleak
Acipenser ruthenus (Linnaeus,1758)
Sterlet
x
Huso huso (Linnaeus,1758)
Beluga sturgeon
x
Acipenser stellatus (Pallas,1771)
Stellate sturgeon
x
Acipenser gueldenstaedti (Brandt, 1833)
Danube sturgeon
x
Alosa immaculata (Bennett, 1835)
Pontic shad
x
Alosa tanaica (Grimm, 1901)
Azov shad
Zinger streber (Linnaeus, 1758)
Danube streber
Zingel zingel (Linnaeus, 1758)
Zingel
x
Sander lucioperca (Linnaeus, 1758)
Pike-perch
Gymnocephalus schraetzer (Linnaeus, 1758)
Schraetzer
x
Perca fluviatilis (Linnaeus, 1758)
Perch
x
Silurus glanis (Linnaeus, 1758)
Wels catfish
Esox lucius (Linnaeus,1758)
Northern pike
x
Salmo labrax (Pallas, 1814)
Black Sea trout
229
Stenohaline
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Sandu (Calin) P. G. et. al./Scientific Papers: Animal Science and Biotechnologies, 2013, 46 (2)
Figure 2. The numerical structure of fish species
Figure 3. The abundance of fish
Figure 4. The abundance of fish biomass
breeds are divided in the following categories:
constant, present in 50.1-75% of the months (asp,
prussian carp, common carp, vimba, common
barbel, bighead carp, common bream, silver carp,
pike-perch, wels catfish, white-eye bream, ide,
sterlet, white bream, stellate sturgeon). The
accessory species (25.1-50%) are ziege, beluga,
Northern pike, common nase, rudd and pontic
shad. There are ten accidental species (1-25%),
less common during the year: grass carp, Azov
shad, roach, Danube sturgeon, perch, schraetzer,
bleak, zingel, Danube streber and Black Sea trout.
The values of the ecological significance index
(W) shows us that pontic shad (W5) is a
eudominant species, common bream (W4), and
Prussian carp (W4) are dominant species; these
two classes are characteristic species (over 5.1%).
There are seventeen accessory species (0.1-5%):
common carp, common barbel, white-eye bream,
asp, vimba, wels catfish, pike-perch, ziege, sterlet
(W3-subdominant species) and bighead carp,
silver carp, Azov shad, white bream, ide, stellate
sturgeon, rudd, beluga (W2-recedent species).
In table 2 there are presented the main analytic
and synthetic ecological indices.
The numerical abundance of the species and the
biomass is given in Figures 3 and 4. It ranged
between 1 fish/species (zingel, Danube streber and
Black Sea trout–species) and 2035 fish/specie
(pontic shad–abundant specie). The total values of
the biomass ranged between 0.01-1018.51
kg/specie.
Concerning the dominance (D), the species are
grouped on 5 classes, depending on the
percentage. The pontic shad, common bream and
Prussian carp are eudominant species (over 10%
from the fish production), which influence
decisively the fishing productivity. The common
carp, common barbel, ziege, white-eye bream, asp,
vimba, wels catfish and pike-perch are
subdominant species (2.1-5%). The Azov shad
and sterlet are recedent species (1.2-2%), and the
other eighteen identified species are underrecedent, with percentage under 1.1%.
Dependent on the value of the constant (C), which
represents the continuity in the biotope, the
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Sandu (Calin) P. G. et. al./Scientific Papers: Animal Science and Biotechnologies, 2013, 46 (2)
Table 2. The ecological indices of fish communities from predeltaic Danube River
Ecological indices
Abundance (A)
No crt.
Ecological
significance (W)
Number
Biomass (kg)
%
Class
%
Class
%
Class
214
245.12
3.005
D3
75.00
C3
2.254
W3
Asp
1.
46
11.15
0.646
D1
58.33
C3
0.377
W2
White bream
2.
Prussian carp
759
220.87
10.65
D5
75.00
C3
7.994
W4
3.
249
37.55
3.497
D3
66.67
C3
2.331
W3
White-eye bream
4.
Grass carp
3
14.06
0.042
D1
25.00
C1
0.011
W1
5.
Carp
323
1018.51
4.536
D3
75.00
C3
3.402
W3
6.
Vimba
188
80.04
2.640
D3
75.00
C3
1.980
W3
7.
Barbel
258
434.72
3.623
D3
75.00
C3
2.717
W3
8.
Bighead carp
48
221.10
0.674
D1
75.00
C3
0.506
W2
9.
Common bream
861
348.56
12.09
D5
75.00
C3
9.068
W4
10.
252
53.42
3.539
D3
41.67
C2
1.475
W3
Ziege
11.
Silver carp
42
109.19
0.590
D1
75.00
C3
0.442
W2
12.
Common nase
9
2.45
0.126
D1
33.33
C2
0.042
W1
13.
Ide
30
18.20
0.421
D1
66.67
C3
0.281
W2
14.
46
4.88
0.646
D1
33.33
C2
0.215
W2
Rudd
15.
Roach
7
2.04
0.098
D1
16.67
C1
0.016
W1
16.
2
0.01
0.028
D1
8.33
C1
0.002
W1
Bleak
17.
110
83.73
1.545
D2
66.67
C3
1.030
W2
Sterlet
18.
33
1.69
0.463
D1
41.67
C2
0.193
W2
Beluga sturgeon
19.
30
76.68
0.421
D1
58.33
C3
0.246
W2
Stellate sturgeon
20.
Danube strugeon
5
3.10
0.070
D1
16.67
C1
0.012
W1
21.
3132
787.85
43.98
D5
33.33
C2
14.661
W5
Pontic shad
22.
117
12.64
1.643
D2
25.00
C1
0.411
W2
Azov shad
23.
1
0.12
0.014
D1
8.33
C1
0.001
W1
Danube streber
24.
1
0.26
0.014
D1
8.33
C1
0.001
W1
Zingel
25.
22
0.66
0.309
D1
16.67
C1
0.051
W1
Pike-perch
26.
2
0.14
0.028
D1
16.67
C1
0.005
W1
Schraetzer
27.
Perch
152
141.76
2.135
D3
75.00
C3
1.601
W3
28.
Wels catfish
163
838.12
2.289
D3
75.00
C3
1.717
W3
29.
Northern pike
15
18.90
0.211
D1
41.67
C2
0.088
W1
30.
Black Sea trout
1
0.08
0.014
D1
8.33
C1
0.001
W1
31.
D1-subrecedent species (<1.1%); D2-recedent species (1.2-2%); D3-subdominant species (2.1-5%);
D4-dominant species (5.1-10%); D5-eudominant species (>10%); C1-accidental species (1-25%);
C2-accessory species (25.1-50%); C3-constant species (50.1-75%); C4-euconstant species (75.1-100%);
W1-subrecedent species (accidental) (<0.1%); W2-recedent species (0.1-1%); W3-subdominant species (accessory)
(1.1-5%); W4 - dominant species (5.1-10%); W5-eudominant species (characteristic) (>10%);
Specie
Dominance (D)
Constancy (C)
sturgeon) and three species (zingel, Danube
streber and Black Sea trout) have a high maximum
similarity. From this point of view, there is a great
resemblance between the ziege and the white-eye
bream (99.40%), which occurred in catches 252
times and respectively 249 times. Other groups of
high similarity: between sterlet and Azov shad
(96.92%), also between the perch and the wels
catfish (96.51%). The pontic shad (43.13%) is
isolated from the other breeds, because it registers
the highest percent in the catches, during the
spring season, when it migrates for reproduction.
Simpson diversity index (1-D) and equitability
(E1-D). The Shannon-Wiener index has the value
In category W1 there are eleven accidental
species, with an index lower than 0.1% (norternpike, perch, common nase, roach, Danube
sturgeon, grass carp, schraetzer, bleak, zingel,
Danube streber and Black Sea trout). Concerning
the frequency in the catch (the numerical
abundance), from the analysis of the Bray-Curtis
similarity dendrogram of the fish species, it can be
seen that two species (white bream and rudd) have
a maximum coefficient of 100%, because they
occurred in the catches only twice (Figure 5).
Other clusters of two species (ide and stellate
In figure 6 are presented the Shannon-Wiener
indices values (H’), the equitability (HR), the
231
Sandu (Calin) P. G. et. al./Scientific Papers: Animal Science and Biotechnologies, 2013, 46 (2)
The Simpson diversity index (1-D), has value
between 0-1 [5]. By calculating, a good value has
been obtained (0.77), the maximum theoretical
value is 0.967. The equitability (E1-D) is 0,80; this
represents 80% from the real maximum diversity.
(H’) of 2.12, and the teoretical maximum (H’max)
of 3.433. The specialised literature mentions that
for (H’) values between 0 (when there is only one
breed in the sample) and 5 (when there are more
species) [4, 15]. The equitability (HR ) is 0.62
representing 62% from the real maximum
diversity.
Figure 5. The Bray-Curtis dendrogram of similarity, according with catch frequency
4
3,434
3,5
3
2,5
62%
2
1,5
1
0,968
80%
2,12
0,5
0,77
0
H'
1‐D
Figure 6. The variation of diversity and equitability indices
4. Conclusions
barbus, Abramis brama, Abramis sapa, Blicca
bjoerkna, Leuciscus idus, Vimba vimba, Aspius
aspius, Pelecus cultratus, Chondrostoma nasus,
Ctenopharingodon idella, Hypophthalmichthys
molitrix, Hypophthalmichthys nobilis, Scardinius
erythrophthalmus, Rutilus rutilus, Alburnus
alburnus).
Other orders and families had the following
structure: Clupeiformes order, Clupeidae family,
with two species (Alosa immaculata and Alosa
tanaica), Acipenseriformes order, Acipenseridae
family with 4 species (Huso huso, Acipenser
The main ecological indices of the fish
communities from predeltaic Danube Rivers area,
between Siret and Prut River Mouth, were
analyzed.
In terms of taxonomic point of view, the overall
number of fish species caught in 2012 year, was
31, belonging 7 families and 6 orders.
From Cypriniformes order, Cyprinidae, the
dominant family, was represented by 17 species
(Cyprinus carpio, Carassius gibelio, Barbus
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Sandu (Calin) P. G. et. al./Scientific Papers: Animal Science and Biotechnologies, 2013, 46 (2)
References
stellatus,
Acipenser
ruthenus,
Acipenser
gueldenstaedtii), Perciformes order, Percidae
family with 5 species (Sander lucioperca, Zingel
zingel, Zingel streber, Gymnocephalus schraetzer,
Perca fluviatilis), Siluriformes order, Siluridae
family, with one species (Silurus glanis) and
Salmoniformes order, Esocidae family with one
species (Esox lucius) and Salmonidae family with
one species (Salmo labrax). The most abundant
species was the pontic shad, followed by common
bream and Prussian carp.
Analytical ecological indices (absolute abundance,
constancy, dominance) and synthetic (ecological
significance) were calculated, in order to establish
the structure and composition of fish communities
in the sampling sites. The values of diversity
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Acknowledgements
Researches was conducted in the framework of the
project POSDRU “Quality and continuity of training in
the doctoral studies – no. 76822 - TOP ACADEMIC”,
funded by the European Union and Romanian
Government. The authors thank to the management
staff of the project for their support.
233