Sandu (Calin) P. G. et. al./Scientific Papers: 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, 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 with 17 species. The numerical abundance ranged between 1fish/species (, Danube and trout-rare species) and 2035 fish/specie (pontic shad - abundant specie). The pontic shad (43.98%), common bream (12.09%) and Prussian (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 1. Introduction decline and even to the extinction of some fish species [4]. Many human uses of Danube River (i.e. Therefore, in order to take some efficient transportation, wastes, pollution) are potentially in conservation measures, a good knowledge of the conflict with the aquatic living resources. In species ecobiology and of their interaction with addition, human activities not only have an impact their living environment is necessary [5]. In this on fish communities, but in the same way also work there are presented some aspects regarding rebound in human communities associated with the structure and the ecological assessment of the the exploitation of these resources [1, 2].The fish communities from predeltaic Danube. The structure and the diversity of fish communities is aim of the researches is to highlight the structural an important feature in the system dynamics changes from the level of the ichthyofauna, by because changes in diversity reflect changes in the using some analytical and synthetic ecological ecosystem processes, such as productivity, energy indices. pathways and material flow, disturbance regimes, abiotic stress and biological interactions [3]. A good management of the interactive 2. Materials and methods components of the fishery should always lead to a durable exploitation, in terms of biodiversity Fishing area conservation and protection. In the last years, The study area is represented by a region in the however, unfortunately, the over-exploitation of predeltaic Danube, located between the Siret River Mouth (km 155) and the Prut River Mouth (Mm  * Corresponding author: Georgiana (Călin) Sandu, 72.5). This region has approximately 22 km, Email: [email protected] representing the length of the Danube sector in Galati County. Monthly, systematic measurements

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have been made in 4 fishing areas: Galati area (km methods, on areas, with filtering gear: gill net and 150-151), Condrea area (Mm 77-78), Muresanu trammel net . The constructive characteristics area (Mm 76-77) and Plopi area (Mm 74-74.5) of these varied, depending on the targeted species (Figure 1). 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 Fishing effort, fishing gears and methods 2.5-4.0; a 40-80 mm). The used method for The structure of a fishing unit (FU) is the obtaining the capture data is the simple following: the fishing boat, the gear and 2 randomized samples. The caught specimens have fishermen. On the average, in an area more FU been identified and divided on species; biometric operate, making 2-3 operations/fishing day [6]. and gravimetric measurements have been made. The fishing has been made through active The identification of the fish species was made by analyzing the specialized literature [7-10].

Figure 1. Map of fishing area (satellite image)

Fishermen teams, from ”Dunărea de Jos” Xij  Xik B   University of Galati, Department of Aquaculture, Xij  Xij Environmental Science and Cadastre and from the Institute of Research and Development for where: Xij, Xik – the number of individuals from Aquatic Ecology, Fishery and Aquaculture Galaţi, a species in each sample; have been making scientific fishing, according to Shannon-Wiener (H’) index: the conditions of the authorization issued by National Agency for Fishing and Aquaculture. S , H   piln pi i1 The calculation of the ecological indices and statistical approaches pi – the abundance ratio of breed i; ln – common The structural changes at the level of logarithm. ichtiocenoses are characterized by using some Simpson (D) index is among the first diversity analytical ecological indices (abundance, indices (Simpson 1949) [14]. dominance, constancy) and synthetic ones (the index of ecological significance), but also S 2 diversity and equitability indices [3]. D  1   pi The statistical methods of the data have been i1 made with the computer (MSOffice Excell) and with the software BioDiversity Pro. The Simpson (1-D) diversity index is used for the Formulas correct estimation of a finite population: The Bray-Curtis (B) dissimilarity index, takes n (n 1) values between 0-1 [12, 13]. 1 D  1 i i  N(N 1)

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ni–the number of individuals from breed i; 3. Results and discussion Ni–the total number of individuals from the analyzed sample. Between April-December 2012, there were caught The equitability refers to the example of 7121 fish, with a total biomass of 4910.34 kg, of individuals’ distribution between species [15]. The 31 species, from 7 families, respectively 6 orders. Shannon equitability index has been calculated The autochthon and allochthonous ichthyofauna in (relative diversity HR) but also the Simpson E1-D the predeltaic Danube is divided in two groups, equitability index. depending on salinity tolerance: euryhaline and stenohaline species (Table 1). The best H H 1 D H  S  E  represented family is Cyprinidae, of the R H log S 1 D Smxa (1 D) max order, with 17 species (Figure 2).

Table 1. The qualitative structure of ichthyofauna and their salinity tolerance No. Latin name of species Common name Eurihaline Stenohaline 1 Aspius aspius (Linnaeus, 1758) Asp x 2 Blicca bjöerkna (Linnaeus, 1758) White bream x 3 Carassius gibelio (Bloch, 1782) x 4 Abramis sapa (Pallas, 1814) White-eye bream x 5 Ctenopharyngodon idella (Valenciennes,1844) x 6 Cyprinus carpio (Linnaeus,1758) Carp x 7 Vimba vimba (Linnaeus,1758) Vimba x 8 Barbus barbus (Linnaeus,1758) Common barbel x 9 Hypophthalmichthys nobilis (Richardson,1845) x 10 Abramis brama (Linnaeus,1758) Common bream x 11 (Linnaeus,1758) Ziege x 12 Hypophthalmichthys molitrix (Valenciennes,1844) x 13 Chondrostoma nassus (Linnaeus,1758) Common nase x 14 Leuciscus idus (Linnaeus,1758) Ide x 15 Scardinius erythrophthalmus (Linnaeus,1758) Rudd x 16 Rutilus rutilus (Linnaeus,1758) Roach x 17 Alburnus alburnus (Linnaeus,1758) Bleak x 18 Acipenser ruthenus (Linnaeus,1758) Sterlet x 19 Huso huso (Linnaeus,1758) Beluga sturgeon x 20 Acipenser stellatus (Pallas,1771) Stellate sturgeon x 21 Acipenser gueldenstaedti (Brandt, 1833) Danube sturgeon x 22 Alosa immaculata (Bennett, 1835) Pontic shad x 23 Alosa tanaica (Grimm, 1901) Azov shad x 24 Zinger streber (Linnaeus, 1758) Danube streber x 25 Zingel zingel (Linnaeus, 1758) Zingel x 26 Sander lucioperca (Linnaeus, 1758) Pike-perch x 27 Gymnocephalus schraetzer (Linnaeus, 1758) Schraetzer x 28 Perca fluviatilis (Linnaeus, 1758) Perch x 29 Silurus glanis (Linnaeus, 1758) Wels catfish x 30 Esox lucius (Linnaeus,1758) Northern pike x 31 Salmo labrax (Pallas, 1814) Black Sea trout x

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Figure 2. The numerical structure of fish species

Figure 3. The abundance of fish Figure 4. The abundance of fish biomass

In table 2 there are presented the main analytic breeds are divided in the following categories: and synthetic ecological indices. constant, present in 50.1-75% of the months (asp, The numerical abundance of the species and the prussian carp, , vimba, common biomass is given in Figures 3 and 4. It ranged barbel, bighead carp, common bream, silver carp, between 1 fish/species (zingel, Danube streber and pike-perch, wels catfish, white-eye bream, ide, Black Sea trout–species) and 2035 fish/specie sterlet, white bream, stellate sturgeon). The (pontic shad–abundant specie). The total values of accessory species (25.1-50%) are ziege, beluga, the biomass ranged between 0.01-1018.51 Northern pike, common nase, rudd and pontic kg/specie. shad. There are ten accidental species (1-25%), Concerning the dominance (D), the species are less common during the year: grass carp, Azov grouped on 5 classes, depending on the shad, roach, Danube sturgeon, perch, schraetzer, percentage. The pontic shad, common bream and bleak, zingel, Danube streber and Black Sea trout. Prussian carp are eudominant species (over 10% The values of the ecological significance index from the fish production), which influence (W) shows us that pontic shad (W5) is a decisively the fishing productivity. The common eudominant species, common bream (W4), and carp, common barbel, ziege, white-eye bream, asp, Prussian carp (W4) are dominant species; these vimba, wels catfish and pike-perch are two classes are characteristic species (over 5.1%). subdominant species (2.1-5%). The Azov shad There are seventeen accessory species (0.1-5%): and sterlet are recedent species (1.2-2%), and the common carp, common barbel, white-eye bream, other eighteen identified species are under- asp, vimba, wels catfish, pike-perch, ziege, sterlet recedent, with percentage under 1.1%. (W3-subdominant species) and bighead carp, Dependent on the value of the constant (C), which silver carp, Azov shad, white bream, ide, stellate represents the continuity in the biotope, the sturgeon, rudd, beluga (W2-recedent species).

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Table 2. The ecological indices of fish communities from predeltaic Danube River Ecological indices Abundance (A) Ecological Dominance (D) Constancy (C) Specie significance (W)

No crt. crt. No Number Biomass (kg) % Class % Class % Class 1. Asp 214 245.12 3.005 D3 75.00 C3 2.254 W3 2. White bream 46 11.15 0.646 D1 58.33 C3 0.377 W2 3. Prussian carp 759 220.87 10.65 D5 75.00 C3 7.994 W4 4. White-eye bream 249 37.55 3.497 D3 66.67 C3 2.331 W3 5. Grass carp 3 14.06 0.042 D1 25.00 C1 0.011 W1 6. Carp 323 1018.51 4.536 D3 75.00 C3 3.402 W3 7. Vimba 188 80.04 2.640 D3 75.00 C3 1.980 W3 8. Barbel 258 434.72 3.623 D3 75.00 C3 2.717 W3 9. Bighead carp 48 221.10 0.674 D1 75.00 C3 0.506 W2 10. Common bream 861 348.56 12.09 D5 75.00 C3 9.068 W4 11. Ziege 252 53.42 3.539 D3 41.67 C2 1.475 W3 12. Silver carp 42 109.19 0.590 D1 75.00 C3 0.442 W2 13. Common nase 9 2.45 0.126 D1 33.33 C2 0.042 W1 14. Ide 30 18.20 0.421 D1 66.67 C3 0.281 W2 15. Rudd 46 4.88 0.646 D1 33.33 C2 0.215 W2 16. Roach 7 2.04 0.098 D1 16.67 C1 0.016 W1 17. Bleak 2 0.01 0.028 D1 8.33 C1 0.002 W1 18. Sterlet 110 83.73 1.545 D2 66.67 C3 1.030 W2 19. Beluga sturgeon 33 1.69 0.463 D1 41.67 C2 0.193 W2 20. Stellate sturgeon 30 76.68 0.421 D1 58.33 C3 0.246 W2 21. Danube strugeon 5 3.10 0.070 D1 16.67 C1 0.012 W1 22. Pontic shad 3132 787.85 43.98 D5 33.33 C2 14.661 W5 23. Azov shad 117 12.64 1.643 D2 25.00 C1 0.411 W2 24. Danube streber 1 0.12 0.014 D1 8.33 C1 0.001 W1 25. Zingel 1 0.26 0.014 D1 8.33 C1 0.001 W1 26. Pike-perch 22 0.66 0.309 D1 16.67 C1 0.051 W1 27. Schraetzer 2 0.14 0.028 D1 16.67 C1 0.005 W1 28. Perch 152 141.76 2.135 D3 75.00 C3 1.601 W3 29. Wels catfish 163 838.12 2.289 D3 75.00 C3 1.717 W3 30. Northern pike 15 18.90 0.211 D1 41.67 C2 0.088 W1 31. Black Sea trout 1 0.08 0.014 D1 8.33 C1 0.001 W1 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%);

In category W1 there are eleven accidental sturgeon) and three species (zingel, Danube species, with an index lower than 0.1% (nortern- streber and Black Sea trout) have a high maximum pike, perch, common nase, roach, Danube similarity. From this point of view, there is a great sturgeon, grass carp, schraetzer, bleak, zingel, resemblance between the ziege and the white-eye Danube streber and Black Sea trout). Concerning bream (99.40%), which occurred in catches 252 the frequency in the catch (the numerical times and respectively 249 times. Other groups of abundance), from the analysis of the Bray-Curtis high similarity: between sterlet and Azov shad similarity dendrogram of the fish species, it can be (96.92%), also between the perch and the wels seen that two species (white bream and rudd) have catfish (96.51%). The pontic shad (43.13%) is a maximum coefficient of 100%, because they isolated from the other breeds, because it registers occurred in the catches only twice (Figure 5). the highest percent in the catches, during the Other clusters of two species (ide and stellate spring season, when it migrates for reproduction. In figure 6 are presented the Shannon-Wiener Simpson diversity index (1-D) and equitability indices values (H’), the equitability (HR), the (E1-D). The Shannon-Wiener index has the value

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(H’) of 2.12, and the teoretical maximum (H’max) The Simpson diversity index (1-D), has value of 3.433. The specialised literature mentions that between 0-1 [5]. By calculating, a good value has for (H’) values between 0 (when there is only one been obtained (0.77), the maximum theoretical breed in the sample) and 5 (when there are more value is 0.967. The equitability (E1-D) is 0,80; this species) [4, 15]. The equitability (HR ) is 0.62 represents 80% from the real maximum diversity. 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 62% 2,5 2 1,5 2,12 0,968 1 80% 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 The main ecological indices of the fish aspius, Pelecus cultratus, Chondrostoma nasus, communities from predeltaic Danube Rivers area, Ctenopharingodon idella, Hypophthalmichthys between Siret and Prut River Mouth, were molitrix, Hypophthalmichthys nobilis, Scardinius analyzed. erythrophthalmus, Rutilus rutilus, Alburnus In terms of taxonomic point of view, the overall alburnus). number of fish species caught in 2012 year, was Other orders and families had the following 31, belonging 7 families and 6 orders. structure: Clupeiformes order, Clupeidae family, From Cypriniformes order, Cyprinidae, the with two species (Alosa immaculata and Alosa dominant family, was represented by 17 species tanaica), Acipenseriformes order, Acipenseridae (Cyprinus carpio, Carassius gibelio, Barbus family with 4 species (Huso huso, Acipenser

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stellatus, Acipenser ruthenus, Acipenser References gueldenstaedtii), order, family with 5 species (Sander lucioperca, Zingel 1. Gutierrez-Estrada J. C. R., Vasconcelos, R. and zingel, Zingel streber, Gymnocephalus schraetzer, Costa, M. J., Estimating fish community diversity from Perca fluviatilis), Siluriformes order, Siluridae environmental features in the Tagus estuary (Portugal), family, with one species (Silurus glanis) and J. Appl. Ichth. 24, 2008, 150–162 Salmoniformes order, Esocidae family with one 2. Terrance, J. Q. and Deriso, R.B., Quantitative Fish Dynamics, Oxford Univ. Press, SUA, 1999 species (Esox lucius) and Salmonidae family with 3. Grall, J. and Coic, N., Summary of methods for one species (Salmo labrax). The most abundant assessing the quality of benthos in coastal, REF. species was the pontic shad, followed by common Ifremer DYNECO/VIGIES/06-13/REBENT, 2005 bream and Prussian carp. 4. Bram, G. W. Aarts, Piet H. Nienhuis, Fish zonations Analytical ecological indices (absolute abundance, and guilds as the basis for assessment of ecological constancy, dominance) and synthetic (ecological integrity of large rivers, Aquatic Biodiversity, significance) were calculated, in order to establish Developments in Hydrobiology, 2003, 171, 157-178 the structure and composition of fish communities 5. Pătroescu, M., Rozylowicz, L. and Iojă, C., in the sampling sites. The values of diversity Conservation of biological diversity, Ed. Tehnica, indices showed that the degree of the structural Bucharest, 2002, pp.57-59 6. Năvodaru, I., The estimation of the fish and fisheries stability of the ichthyocoenoses is relatively good; stocks, Ed. Dobrogea, Constanta, 2008, pp.163-168; an important number of species live and growth 7. Bănărescu, P., Class Osteichthyes, Diversity in normally. It’s being observed that the best adapted Living World, Vol II, Inland Waters, Ed. Bucura species to living in this sector of the Danube and Mond, 2002, pp. 692 which bring an important contribution to the 8. Greenhalgh, M., Freshwhater Fish, Hardcover, productivity area are cyprinids, like common Octopus Publishing Group, ISBN 1-84000-144-5, 2000 bream, Prussian carp, common carp and common 9. Otel, V., Atlas of fish from the Danube Delta barbel. Biosphere Reserve, Publishing Delta Center for The structure of the fish communities is various, Information Technology, 2007, pp.14-18 well balanced. It can be seen that the impact of the 10. http://research.calacademy.org/catalog of fishes; 11. http://www.fishbase.org/search.php. anthropic activities is quite significant. Thus, fish 12. Gomoiu, M. T. and Skolka, M., ECOLOGY community diversity is a basic ecological aspect, Methodologies for environmental studies, Ovidius knowledge of which is necessary for the correct University Press, Constanta, 2001, pp. 63-130 exploitation, regulation and management of 13. Ţicalo, I., Comparative Research on the structure fishing resources since it can provide a first and dynamics of Bistrita river ichthyofauna and Jjijia approach to the health level of the Danube system (Upper Basin), PhD Thesis, “Alexandru Ioan Cuza” and allows for the identification of response University of Iasi, 2010, pp. 125 patterns to possible environmental impacts. 14. Simpson, E. H., Measurement of diversity, Nature, 163, 1949, 688 Acknowledgements 15. Gheorghe, D. C., Research on the foundation of sustainable exploitation of fishery resources in the Danube and Danube Meadow, PhD Thesis, „Dunărea Researches was conducted in the framework of the de Jos” University of Galati, 2010, pp.52-55 project POSDRU “Quality and continuity of training in 16. Gheorghe, D. C., Cristea V. and Ciolac A., the doctoral studies – no. 76822 - TOP ACADEMIC”, Ecological aspects of the ichthyofauna from Fundu funded by the European Union and Romanian Mare Island and Cravia Arms, Scientific Papers- Government. The authors thank to the management Animal Series, 2010, 54, 348 staff of the project for their support. 17. Washington, H. G., Diversity, biotic and similarity indices: a review with special relevance to aquatic ecosystems, Water Res., 1984, 18, 653-694.

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