The Structure and Diversity of Fish Communities from Predeltaic Danube Area

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1 Bulletin UASVM Animal Science and Biotechnologies 70(1)/2013, Print ISSN ; Electronic ISSN X The Structure and Diversity of Fish Communities from Predeltaic Danube Area Petronela G. (CĂLIN) SANDU 1), Lucian OPREA 1), Victor CRISTEA 1), George TIGANOV 2) 1) Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, 47 Domnească Street, Galati, Romania; 2) National Institute for Marine Research and Development Grigore Antipa, 300 Mamaia Blvd., ConstanŃa, Romania 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 March to December 2010, in four fishing areas (km , Mm 77-78, Mm 76-77, Mm ), fish of 29 species, from 6 families and 6 orders, were collected. The best-represented family is Cyprinidae with 16 species. The numerical abundance ranged between 1fish/species (zingel, Danube streber and schraetzer -rare species) and 7019 fish/species (pontic shad -abundant specie). The Pontic shad (47.77%) and Azov shad (11.20%) are eudominant species, having the biggest potential in fish productivity; common bream (9.15%) and common carp (7.36%) are dominant species. Keywords: Danube, fish communities, abundance, diversity, ecological significance INTRODUCTION 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 (Grall et al., 2005). 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 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 (Bram et al., 2003). 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 have been made in 4 fishing areas: Galati area (km ), Condrea area (Mm 77-78), Muresanu area (Mm 76-77) and Plopi area (Mm ). Fishing effort, fishing gears and methods. The fishing has being made through active methods, on areas, with filtering gear: gill net and trammel net type. The constructive 168

2 characteristics of these varied, depending on the targeted species to be caught: gill nets (Lp m; Hp ; a mm), trammel nets (Lp m; Hp ; a mm). The calculation of the ecological indices and statistical approaches. The structural changes at the level of ichthyocoenoses 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 (Grall J. et al., 2005). The statistical methods of the data have being made with MSOffice Excell and with the software BioDiversity Pro. RESULTS AND DISCUSSIONS The autochthon and allochthonous ichthyofauna in the predeltaic Danube is divided in two groups, depending on salinity tolerance: euryhaline and stenohaline species (Tab. 1). The family Cyprinidae, belonging to Cypriniformes order, is the most diverse with 16 species (Fig. 1). Tab. 1 The qualitative structure of ichthyofauna and their salinity tolerance No. Latin name of species Common name Eurihaline Stenohaline crt. 1 Aspius aspius (Linnaeus, 1758) Asp x 2 Blicca bjöerkna (Linnaeus, 1758) White bream x 3 Carassius gibelio (Bloch, 1782) Prussian carp x 4 Abramis sapa (Pallas, 1814) White-eye bream x 5 Ctenopharyngodon idella (Valenciennes,1844) Grass carp 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) Bighead carp x 10 Abramis brama (Linnaeus,1758) Common bream x 11 Pelecus cultratus (Linnaeus,1758) Ziege x 12 Hypophthalmichthys molitrix (Valenciennes,1844) Silver carp 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 Acipenser ruthenus (Linnaeus,1758) Sterlet x 18 Huso huso (Linnaeus,1758) Beluga sturgeon x 19 Acipenser stellatus (Pallas,1771) Stellate sturgeon x 20 Acipenser gueldenstaedti (Brandt, 1833) Danube sturgeon x 21 Alosa immaculata (Bennett, 1835) Pontic shad x 22 Alosa tanaica (Grimm, 1901) Azov shad x 23 Zinger streber (Linnaeus, 1758) Danube streber x 24 Zingel zingel (Linnaeus, 1758) Zingel x 25 Sander lucioperca (Linnaeus, 1758) Pike-perch x 26 Gymnocephalus schraetzer (Linnaeus, 1758) Schraetzer x 27 Perca fluviatilis (Linnaeus, 1758) Perch x 28 Silurus glanis (Linnaeus, 1758) Wels catfish x 29 Esox lucius (Linnaeus,1758) Northern pike x Between March and December 2010, there were caught fish, with a total biomass of kg, of 29 species, from 6 families, respectively 6 orders. 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 2 and 3. It ranged between 1 fish/species (zingel, Danube streber and schraetzer rare species) and 169

3 7019 fish/specie (pontic shad -abundant species). The total values of the biomass ranged between 0.12 and kg/species. Fig. 1. The numerical structure of fish species Fig. 2. The abundance of fish Fig. 3. The abundance of fish biomass Concerning the dominance (D), the species are grouped on 5 classes, depending on the percentage. The pontic shad and Azov shad are eudominant species (over 10% from the fish production), which influence decisively the fishing productivity. The common bream and common carp are the dominant species (5.1-10%). The Prussian carp, common barbel, wels catfish and ziege are subdominant species (2.1-5%). The asp, sterlet, pike-perch, vimba and white-eye bream are recedent species (1.2-2%), and the other sixteen identified species are under-recedent, with percentage under 1.1%. Dependent on the value of the constancy (C), which represents the continuity in the biotope, the species are divided in the following categories: euconstant present in % of the months (Prussian carp, common carp, vimba, common barbel, common bream, sterlet, wels catfish). The constant species are asp, bighead carp, stellate sturgeon, pike-perch, white-eye bream, silver carp, Danube sturgeon, ide ( %). The accessory species ( %) are beluga, white bream, ziege, pontic shad, Azov shad and common nase. There are eight accidental species (1-25%), less common during the year: rudd, roach, grass carp, Northern pike, Danube streber, zingel, perch and schraetzer. The values of the ecological significance index (W) show us that pontic shad (W5) is a eudominant species, common bream (W4), and common carp (W4) are dominant species; these two classes are characteristic species (over 5.1%). There are seventeen accessory species (0.1-5%): Azov shad, Prussian carp, common barbel, wels catfish, asp, sterlet, vimba 170

4 (W3 -subdominant species) and pike-perch, ziege, white-eye bream, stellate sturgeon, bighead carp, ide, silver carp, white bream, beluga, Danube sturgeon (W2 -recedent species). In category W1 there are eleven accidental species, with an index lower than 0.1% (rudd, roach, common nase, perch, Northern-pike, grass carp, Danube streber, zingel and schraetzer). Tab. 2 The ecological indices of fish communities from predeltaic Danube River Ecological indices Abundance Dominance Constancy Ecological Species (A) (D) (C) significance (W) Number Biomass (kg) % Class % Class % Class Asp D C W3 White bream D C W2 Prussian carp D C W3 White-eye bream D C W2 Grass carp D C W1 Carp D C W4 Vimba D C W3 Barbel D C W3 Bighead carp D C W2 Common bream D C W4 Ziege D C W2 Silver carp D C W2 Common nase D C W1 Ide D C W2 Rudd D C W1 Roach D C W1 Sterlet D C W3 Beluga sturgeon D C W2 Stellate sturgeon D C W2 Danube strugeon D C W2 Pontic shad D C W5 Azov shad D C W3 Danube streber D C W1 Zingel D C W1 Pike-perch D C W1 Schraetzer D C W1 Perch D C W3 Wels catfish D C W3 Northern pike D C W1 Note: 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 ( %); C3-constant species ( %); C4-euconstant species ( %); 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%); 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 ide) have a maximum coefficient of 100%, because they occurred in the catches only twice (Fig. 4). Other cluster of three species (zingel, Danube streber and schraetzer) has a high maximum similarity. From this point of view, there is a great resemblance between the vimba and the pike-perch (99.23%), which occurred in catches 194 times and respectively 197 times. Other groups of high similarity: between roach and Danube sturgeon (95.83%), also between the ziege and the wels catfish (94.07%). The pontic shad (37.99%) is isolated from the other 171

5 breeds, because it registers the highest percent in the catches, during the spring season, when it migrates for reproduction. Fig. 4. The Bray-Curtis dendrogram of similarity, according with catch frequency In Figure 5 are presented the Shannon-Wiener indices values (H ), the equitability (HR), the Simpson diversity index (1-D) and equitability (E1-D). Fig. 5. Variation of diversity and equitability indices, in 2010 The Shannon-Wiener index has the value (H ) of 1.97, and the theoretical maximum (H max) of The specialized literature mentions that for (H ) values between 0 (when there is only one breed in the sample) and 5 (when there are more species) (Gheorghe et al., 2010; łicalo, 2010). The equitability (HR) is 0.59 representing 59% from the real maximum diversity. The Simpson diversity index (1-D) has value between 0 and 1 (Gomoiu et al., 2001). By calculating, a good value has being obtained (0.74), the maximum theoretical value is The equitability (E1-D) is 0.77; this represents 77% from the real maximum diversity. CONCLUSION 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. In terms of 172

6 taxonomic point of view, the overall number of fish species caught in 2010 year, was 29, belonging 6 families and 6 orders. From Cypriniformes order, Cyprinidae, the dominant family, was represented by 16 species (Cyprinus carpio, Carassius gibelio, Barbus 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). Other orders and families have 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 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). The most abundant species was the pontic shad, followed by Azov shad, common bream and common carp. The values of diversity indices showed that the degree of the structural stability of the ichthyocoenoses is relatively good; an important number of species lives and growths normally. It s being observed that the best adapted species to living in this sector of the Danube and which bring an important contribution to the productivity area are cyprinids, like common bream, common carp, Prussian carp and common barbel. The structure of the fish communities is various, well balanced. It can be seen that the impact of the anthropic activities is quite significant. Thus, fish community diversity is a basic ecological aspect, knowledge of which is necessary for the correct exploitation, regulation and management of fishing resources since it can provide a first approach to the health level of the Danube system and allows for the identification of response patterns to possible environmental impacts. Acknowledgments. Researches were conducted in the framework of the project POSDRU Quality and continuity of training in the doctoral studies no TOP ACADEMIC, funded by the European Union and Romanian Government. REFERENCES 1. Bănărescu, P. (2002). Class Osteichthyes, Diversity in Living World, Inland Waters, Ed. Bucura Mond, Vol II: Bram, G.W. Aarts, Piet H. Nienhuis (2003). Fish zonations and guilds as the basis for assessment of ecological integrity of large rivers, Aquatic Biodiversity, Developments in Hydrobiology, 171: Gheorghe, D.C. (2010). Research on the foundation of sustainable exploitation of fishery resources in the Danube and Danube Meadow, PhD Thesis, Dunărea de Jos University of Galati, Gheorghe, D.C., Cristea V., Ciolac A. (2010). Ecological aspects of the ichthyofauna from Fundu Mare Island and Cravia Arms, Scientific Papers-Animal Series, 54: Gomoiu, M.T., Skolka, M. (2001). Ecology, Methodologies for environmental studies, Ovidius University Press, Constanta, Grall J., Coic N. (2005). Summary of methods for assessing the quality of benthos in coastal, REF. Ifremer DYNECO/VIGIES/06-13/REBENT. 7. Năvodaru, I. (2008). The estimation of the fish and fisheries stocks, Ed. Dobrogea, Constanta, Greenhalgh, M. (2000). Freshwhater Fish, Hardcover, Octopus Publishing Group, ISBN Otel, V. (2007). Atlas of fish from the Danube Delta Biosphere Reserve, Publishing Delta Center for Information Technology,

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