The Ramsar Convention on Wetlands

Ramsar site management plans -- Bulgaria, Srebarna (file 3)


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BULGARIAN ACADEMY OF SCIENCES CENTRAL LABORATORY OF GENERAL ECOLOGY

MANAGEMENT PLAN OF THE SREBARNA BIOSPHERE RESERVE

Sofia, 2000


1.17. Noteworthy Flora

1.17.1. Algae and Fungi (incl. Lichens)

The information referred to below has been taken from the Synopsis on the Srebarna Biosphere Reserve (1998).

Algae

Stoyneva (1998a) found 1123 algal taxa (1010 species, 75 varieties and 38 forms). The best-studied ecological group is that of the phytoplankton (see Part 1.16.2.1) while the neuston, edaphyton and aerophyton are hardly ever studied.

Fungi

The checklist of this group, compiled by Denchev and Stoyneva (1998) includes 17 species of 16 genera, 10 families, 7 orders of 5 classes and 3 phyla. The species found represent different ecological groups from various habitats and hosts in the lake proper and in the Reserve buffer zone. However, it is obvious that further mycological investigations would reveal much greater species abundance. Special attention has also to be given to the fungi on the Danube island of Devnya, which belongs to the reserve total area and has never been studied for this group.

Lichens

The lichens of the Biosphere Reserve Srebarna have never been studied thoroughly. Data presented were taken from Ivanov (1998), who has reported 15 species belonging to 5 families.

1.17.2. Vascular Plants

Historical Data Review

The following botanists have carried out some research studies on the lake vascular plant species composition: Petkov (1911) described 31 species of vascular plants; Bonchev (1929) found 33 species; Yordanov (1946 and 1947) described 47 species; Ganchev (1957) found 40 species; Ivanov et al. (1964) described 34 species; Kochev & Yordanov (1984), 72 species; Kochev (1987a, b), 82 species; Baeva (1987, 1988a, b, 1992) described 139 species.

The 139 taxa of vascular plants found so far in Srebarna belong to 45 families and 97 genera. According to Stoianov, Stefanov, Kitanov (1966 – 1967) the lake’s floristic composition makes up 4.5% of Bulgarian flora, or 3.9% according to the Guide to the Vascular Plants (Andreev et al., 1992).

Srebarna gives home to 53% of the species, 75% of the genera and 78% of all plant families comprising the floral gene pool of the Bulgarian wetlands.

Actual State

For the purpose of this study the method of observation was applied. The investigations were performed by walking along routes of preliminary laid down transections. For working out a map of the vegetation draft maps of scale 1: 5000 were used. Transpiration by the reed-beds and by the cultivated poplar stands was measured by the weighing method of A. Ivanov (1980). The picture of the floristic and plant-community status of the Srebarna Biosphere Reserve and the full inventory of its species richness together with its floristic, ecological, ecophysiological and sozological analysis is the basis for the following findings:

The vegetation cover of the Srebarna Biosphere Reserve water catchment area consists of the following types of vegetation:

  1. Mesosclerothermal grassy vegetation dominated by Poa bulbosa, Rye-grass (Lolium perennae), Bermuda-grass (Cynodon dactilon), at places also by Beard-grass (Dichantium ischaemum) and more rarely Chrysopogon gryllus, mostly on the village pastures.
  2. Arable land where oak forests consisting of Turkey Oak (Quercus cerris) and Quercus virgiliana frequently mixed with Quercus pedunculiflora used to stand in the past.
  3. Mixed forests composed of Hungarian Oak (Quercus frainetto) and Oriental Hornbeam (Carpinus orientalis) at places mixed with sucker growth of Mediterranean elements.
  4. Forests of Silver Lime (Tilia tomentosa), at places being a secondary growth.
  5. Mixed oak forests composed of Turkey Oak (Quercus cerris), White Oak (Quercus pubescens) and Quercus virgiliana.
  6. Marsh and bog hygrophytic (at places also hydrophytic) vegetation dominated by the Reed (Phragmites australis), Lesser and Greater Reedmace (Typha angustifolia and Typha latifolia), Schoenoplectus lacustris, Sch. triqetra, Sch. tabernemontana, etc.

Proposed Measures

Main negative and threatening factors for the vegetation of the reserve are for the most part deviations from the optimum hydrological conditions.

No specific measures for the conservation of plant species have been taken so far with the exception of the nine species placed under legal protection.

In order to avoid undesired processes of degradation and to improve the qualitative composition of the Reserve plant communities as well as to optimize the Reserve hydrologic conditions it is necessary:

1.17.3. Forests & Arboreal Plants

Historical Data Review

According to the "Geobotanic division of Bulgaria" (Bondev, 1997) Srebarna Biosphere Reserve is located in the region of Silistra. It belongs to and is a part of the European-Asiatic Steppe and Forest-Steppe Area, the Lower Danube Province, District of Dobrudzha.

Srebarna Reserve and its buffer zone lies within the area run by the Silistra Forestry. The last forest management plan has been worked out in 1989; the next and new one is due in 2001.

According to the current forest management plan the reserve and the Danube protective strip encompass the forestry sections 13 and 14 with a total surface area of 74.0 ha (App. 1, Map 3). The buffer zone encompasses forestry sections 49, 50, 51, 52 with a total area of 202.5 ha. In the reserve’s immediate vicinity there are woods that belong to the Agricultural Land Fund and are designated for commercial use. However, it is our opinion that they have direct bearing to the Reserve and its hydrologic conditions. These are forest section 1, part of section 5 (subsections a, b, v, g) and section 6 with a total area of 115.7 ha.

Actual State

For the purposes of this study the method of observation was applied. Observations were made by walking along routes of preliminary laid down transections. We have also used information from forest management plans worked out in 1979 and in 1989 (App. 9) together with the maps attached to them.

The river Danube and the reserve protective strip: Forest stands that belong to the reserve and to the Danube protective strip are in forestry sections 13 and 14 and are of economic class Special Purpose Poplar Stand. The type of habitat is M-I-1, D-2,3 (flooded, fresh to humid, on alluvial soils – the typical poplar one). The afforestation with hybrid poplar saplings of type ‘u 214’ was done according to the schedule 5X4. The spacing index of the plantations (measured as the proportion of the total surface area of the cross-sections of all the trees and the unit area on which they grow, in square meters) varies from 0.7 to 1.0 with the exception of forest section 13 which is a low density plantation. The state of the plantations is good. According to the forest management plan these plantations were intended for intensive use and turning into pure poplar ones.

Reserve buffer zone: Species composition of trees in the buffer zone is diverse and includes both local and introduced, alien for this region, species like the Black Pine (Pinus nigra), Black Locust (Robinia pseudacaia), Common Gloxinia (Gleditschia triacanthos). Planting of Robinia pseudacacia trees over considerable land tracts years ago has completely changed the look of the forests surrounding the reserve. At present over 30% of the buffer zone is occupied by this species. It should be noted that this is quite an aggressive species spreading fast and easy. According to the instructions contained in the forest management plan all forestry sections with R. pseudacacia, which were rated 10 (i.e. pure plantation) have been planned for a clear felling down followed by a reconstruction as a mixed forest of Fraxinus oxycarpa, Silver Lime (Tilia tomentosa, Quercus cerris and Sessile Oak (Quercus sessiliflora). From the on-site survey we carried out we have found such sites of clear felling and consequent planting with Quercus sessiliflora in several forestry sections.

Section 49

This section includes plantations and sucker forests (the area is 85.8 ha) belonging to economic classes: Broad-leafed low-stemmed, Broad-leafed high-stemmed, Coniferous (in two subsections), and Special Function Forests – those in the reserve buffer zone. The Black Pine (Pinus nigra) is planted by man and occurs in two subsections, "b" and "d". Afforestation was done 30 years ago to strengthen the slopes. In those times it was a quick effect that was sought by creating a Black Pine (Pinus nigra) plantation. According to the forest management plan the only management activity accomplished in this pure P. nigra plantation has been the thinning-out, which is believed to have brought local species to settle as undergrowth. The pure R. pseudacacia stands cover a total area of 40.1 ha which makes up almost half the area of this forestry section. These subsections have also been intended for a clear felling with consecutive reconstruction with Tilia tomentosa, Fraxinus oxycarpa, Quercus cerris, and Quercus sessiliflora by mixing in groups. Dominating spacing index of the stand is 0.9. Types of habitats are M-I-2, D-2 (flat and on slopes, fresh on carbonate leached chernozems) rarely D-1 (dry on leached chernozems). The state of plantations is from good to average, from 1st to 4th class of productivity.

Section 50

The area of this section is 41.3 ha. It includes forest plantations and sucker forests of economic (commercial) classes Broad-leafed low-stemmed, Broad-leafed high-stemmed, as well as Coniferous (subsection 50-v). The state of plantations may be determined as good to average. Pinus nigra occurs only in one subsection mixed with Tilia tomentosa, Fraxinus oxycarpa, Acer pseudoplatanus, Quercus sessiliflora on an area of about 7.1 ha. Here the forestry measure undertaken was landscape felling to thin out and lighten the forest. Pure Robinia pseudacacia plantations predominate on a total area of 28.8 ha and are intended for reconstructing with local tree and shrub species following a clear felling. The spacing index is predominantly 0.9 with the exception of subsection 50-zh – a thinned-out plantation (0.3) in a poor state. Types of habitats are M-I-2, D-1 and 2 – flat and on slopes, dry and fresh on carbonate leached chernozems.

Section 51

Here again in this section with a total area of 47.4 ha the stands are plantations and sucker forests of economic classes Broad-leafed high-stemmed and Broad-leafed low-stemmed forests. Here again the pure R. pseudacacia plantations predominate covering a total of 33.4 ha, and are also intended for a full reconstruction, not yet accomplished. At present their state may be determined as of 3rd and 4th class of productivity. Planned measures for the remaining stands of mixed high-stemmed broad-leafed plantations are landscape and sanitary felling. Their state is good. Predominating spacing index is 0.9 (between 0.5 and 0.9). Types of habitat are M-I-2, D-1 – flat and on slopes, dry, on carbonate leached chernozems.

Section 52

The total area of this section is 28.0 ha. Pure and mixed plantations of Pinus nigra with some participation of Acer pseudoplatanus, Tilia tomentosa, Fraxinus oxycarpa dominate over 21.2 ha. Only sanitary felling was planned for this plantation. The rest of this section area, totaling 4.6 ha, is covered by R. pseudacacia sucker forest that has occupied the area after a non-reconstructed (or maybe not well reconstructed) clear felling.

It has been planned to completely reconstruct these plantations by the end of the period (i.e. the year 2000). Predominant spacing index is 0.9.

Types of habitats are M-I-2, D-1 – on the plain and on slopes, dry, on carbonate leached chernozems.

Forests within the agricultural lands: According to the forest management plan of 1989 those forests do not belong to the reserve buffer zone and are not forests of special function but for commercial use only. These are mostly man-made plantations – of hybrid poplar, pure R. pseudacacia stands, mixed R. pseudacacia and Tilia tomentosa plantations. They are located immediately by the reserve boundaries and it is our opinion that they influence in a direct way the reserve hydrological conditions. Immediately by the bridge over the rivulet Srebarnenska along the riverbed in the southwest direction our survey found a poplar plantation in a good state which was not shown on the management plan maps. This plantation, at an age of about 15 years covers an area of about 12 ha. Here we are going to comment on forest sections 1, 5 (subsections a, b, v, g) and 6 which have some relation to the reserve. The state of plantation is good except section 1, subsection ‘zh’ which was in poor condition. Predominant spacing index is 0.8 (between 0.5 to 1.0). Most of the R. pseudacacia stands are planned for clear felling. Types of habitats are M-I-1, D-2,3.

Proposed Measures

Invasion of forest-arboreal species not typical for the region’s vegetation as well as their associations may be considered as a negative and threatening factor. It should be noted that, on the one hand, the young, newly planted forest has not been properly cultivated and, on the other hand, as the R. pseudacacia stands have not been uprooted and its sucker potential is very big it is quite possible that the R. pseudacacia sucker growth may well choke the young oak undergrowth and invade the area anew.

The main ideal (long-term) goal to achieve with regard to the forest-arboreal vegetation in the Reserve buffer zone is the competent interference called to recover and secure maintenance of vegetation composed of native species around the reserve and to create pre-requisites for optimal hydrological conditions in the reserve itself.

Based on the data from the forest management plan for Silistra Forestry as well as on personal observations we could give the following recommendations to achieve the realistic objectives and to undertake practical measures for the management of the forest-arboreal vegetation in the reserve and its buffer zone:

1.18. Noteworthy Fauna:

1.18.1. Invertebrates (Helminths and Insects excluded)

Historical Data Review

Data on the non-insect invertebrate animal's diversity in the Biosphere Reserve Srebarna are available in 74 papers, mostly by Bulgarian authors. The first two articles were by Chichkoff (1909) on free-living Copepod crustaceans and by Consuloff (1912) on Rotifers.

Research on invertebrate fauna of the Reserve was urged mainly by two factors. The first was that the relatively extensive hydrobiological investigations into the lake ecosystems have revealed the importance of several groups of animals for the species composition of the zooplankton (crustaceans, rotifers), the phytoplankton (mastigophoran protozoans) and the zoobenthos (oligochaetes, nematodes, aquatic molluscs and crustaceans). The latter was the fact that in 1962 a natural focus of the 'rabbit fever' (Tularemia) and some other diseases of importance to humans and animals was discovered within the boundaries of the Reserve. This provoked extensive epizootiological and parasitological studies resulting in abundance of data on helminths, parasitic protozoans and arthropods. Parasitological studies have also supplied data on several invertebrate groups, which were intermediate hosts for parasites (e.g. terrestrial oligochaetes and molluscs).

The only attempt to summarize data on the species diversity (including non-insect invertebrate groups) of the Srebarna Biosphere Reserve is the checklist by Michev et al. (1998). The relevant parts of the chapter on invertebrates (edited by this author) were written by leading Bulgarian experts on each group.

Actual State

Most of the data given below are based on parts of the above-mentioned chapter on invertebrates from the work of Michev et al. (1998).

A report, especially prepared for the purposes of this management plan by T. Genov, V. Y. Biserkov and B. B. Georgiev entitled Helminth parasites as a biotic factor affecting the vertebrate animal populations in the Biosphere reserve Srebarna was also incorporated (see 1.18.2).

Research for this report was based on the re-evaluation of the already published data and the results from two helminthological field studies in the Reserve carried out in 1998 and 1999.

Assessment of the knowledge on any given group of invertebrates from the Srebarna Biosphere Reserve was based on the approximate estimate of the expected number of species. Generally, it was either taken in a ready-made form from the relevant publications, or was arrived at after consultations with an expert on the relevant groups. The 20 invertebrate phyla given below either have been already recorded or may occur in the Srebarna Biosphere Reserve. They are: Sarcomastigophora, Apicomplexa (=Sporozoa), Microspora, Ascetyospora, Myxozoa, Ciliophora, Spongia, Coelenterata, Platyhelminthes, Rotifera, Gastrotricha, Nematoda, Nematomorpha, Acanthocephala, Mollusca, Annelida, Arthropoda, Tardigrada, Pentastomida and Ectoprocta. The number of species recorded in the Reserve and the number of species expected to be found there are shown in App. 11. It is apparent from it, that data are available only on 10 of all the 20 phyla that may be found in the Reserve. The number of species likely to be found there is 3 to 6 times as big as the number of those already recorded.

Here below are the comments on the species diversity and the degree of our knowledge on some of the groups.

Phylum Sarcomastigophora. Autotrophic specis of the subphylum Mastigophora are a well-studied group for the Reserve as they are considered algae and make up a substantial part of the lake phytoplankton (Stoyneva, 1998). Species known as flagellate sarcomastigophorans all belong to the algal divisions Euglenophyta with 154 species recorded from the Reserve, and Cryptophyta with 19 species along with some taxa belonging to the algal divisions Chrysophyta (49 species), Pyrrhophyta (16 species) and Chlorophyta (55 species). The total number of the species pertaining to this group and found in the reserve is 293. Though species diversity of the plankton flagellates has been thoroughly studied, it is quite possible to find new species when dealing with some of the so far unstudied ecological groups like neuston, edaphophyton, aerophyton, etc. (Michev et al., 1998). There are no information on parasitic and commensal flagellates occurring in vertebrate and invertebrate hosts in the Reserve. There are no data on another two phyla, Opalinata (parasites of cold-blooded vertebrates, 1 to 10 expected species) and Sarcodina (free-living and parasitic, 100 to 500 expected species).

Phylum Apicomplexa (= Sporozoa) includes parasitic protozoans only. The species diversity of the coccidians parasitic in small mammals (rodents and insectivores) has been studied almost in full (14 species, see Golemansky, 1998). The following 3 species were originally described on specimens collected in Srebarna Biosphere Reserve: Eimeria arkutinae Golemansky, 1978, Eimeria micromydis Golemansky, 1978 and Isospora talpae Golemansky, 1978. Srebarna Biosphere Reserve is the only known locality for Eimeria micromydis in the world. There are no data on sporozoan parasites in other vertebrate and invertebrate groups occurring in the Reserve or its vicinity.

Phylum Myxozoa. A single species was recorded for the Reserve (Margaritov, 1959; Golemansky, 1998). The abundant fish fauna of Srebarna Lake is a pre-requisite for a relatively diverse species list of myxozoans parasites in fishes (up to 20 expected species).

Phylum Ciliophora. There are no records of cilian protozoans in Srebarna. Numerous free-living species (both aquatic and soil) and parasitic or commensal on/in fishes, mammals and invertebrates are expected (up to 200 species).

Phyla Spongia, Coelenterata, Gastrotricha, Tardigrada and Ectoprocta. No research was ever conducted on these groups in Srebarna Reserve. Members of these groups are frequent components of temperate freshwater ecosystems. Further hydrofaunistic studies may reveal their presence in the lake. Gastrotricha and Tardigrada are generally poorly known in Bulgaria as there are no experts on these groups in the research institutions of the country.

Phylum Platyhelminthes includes free-living, mostly benthic (Class Turbellaria) and parasitic organisms (Classes Monogenea, Trematoda and Cestoda). There are no records on turbellarians from Srebarna; between 5 and 10 species may occur in the lake ecosystem. The parasitic flatworms are represented by 117 species: 49 cestodes and 68 trematodes. The trematode Troglotrema srebarni Genov, 1964 and the cestodes Paranoplocephala aquatica Genov, Vasileva & Georgiev, 1996, Catenotaenia matovi Genov, 1971 and Hilmylepis prokopici Genov, 1970 were originally described from Srebarna Biosphere Reserve. The number of expected platyhelminth species may exceed 300 to 500.

Phylum Rotifera. Only 18 species of planktonic rotifers have been studied so far (see Naidenow, 1998). No data are available on the soil representatives of this group.

Phylum Nematoda. Represented by 106 species-group taxa in Srebarna Reserve. These include three major ecological groups: benhtic (9 species, see Stoychev, 1998), soil (16 species, see Peneva, 1998) and zooparasitic nematodes (81 species, see the survey by Genov & Georgiev, 1998). Each of these groups should be further investigated. The number of the expected species may be 5 to 10 times higher. The zooparasitic nematode Paracrenosoma kontrimavichusi Genov, 1978 was originally described from Srebarna Reserve. For further comments on parasitic nematodes see 1.18.2.

Phylum Molusca. Two ecological groups occur in the Reserve. The freshwater moluscs numbering 29 snails and 12 bivalve species are well studied and no new species are expected (Angelov, 1998). Information on the diversity of terrestrial snails is limited (see Dedov, 1998). Two freshwater species occurring in the Reserve, the snail Segmentina nitida and the bivalve Unio crassus, are included in the European red List of Globally Threatened with Extinction Animals and Plants (1991).

Phylum Annelida. As a whole, the group is poorly known from the Reserve. There are data on 26 oligochaete species (Uzunov, 1998) and 3 leeches (Vidinova, 1998). The leech Hirudo medicinalis is included in the European Red List of Globally Threatened with Extinction Animals and Plants (1991). The expected total number of annelids in the Reserve is probably not less than 50 species.¤

Phylum Arthropoda (with the exception of Insects). There are 171 species known from the reserve. The species diversity of the planktonic branchiopod and copepod, and the benthic ostracod crustaceans is relatively well studied (see Nadenow, 1998). Information on higher crustaceans has been gathered sporadically (Andreev, 1998). Terrestrial non-insect arthropod species are presented by 2 opiliones (Mitov, 1998), 57 spiders (Deltschev and Blagoev, 1998) and 65 mites and ticks (Dobrev, 1998). It is expected to find many new species belonging to all these groups. Data on myriapods and terrestrial isopods are not available. The expected total number of this group is between 500 and 1000 species.

Facts from the above survey of the invertebrate fauna (Class Insecta excluded) of Srebarna Biosphere Reserve allow for the following conclusions:

Our knowledge on the non-insect invertebrate fauna of Srebarna Biosphere Reserve should be considered as insufficient and a preliminary one. The known number of species (803) appears to be only 15% to 30% of their expected number in the reserve ecosystem. Some major invertebrate groups have never been studied or, at least, have not been sufficiently studied. These are: the free-living protozoans; the parasitic protozoans of fishes, birds and invertebrates; hydrozoans; free-living flatworms; helminth parasites of fishes and many birds; soil nematodes; terrestrial gastropods; terrestrial oligochaetes; myriapods; terrestrial isopods.

The major gaps in our knowledge are due to the scarcity of faunistic data on the groups mentioned above and to the lack of quantitative assessment of invertebrate populations. Extensive studies on the fauna and ecology of invertebrate animals in the Reserve should be carried out.

The value of Srebarna Biosphere Reserve for the biodiversity conservation both on a national and a global scale is mainly related to its importance for the protection of ecosystems, typical for the Lower Danube freshwater wetlands. It is further enhanced by the considerable species diversity of the non-insect invertebrates, the fact of three species of them (2 moluscs and 1 annelid) being included in the European Red List of Globally Threatened with Extinction Animals & Plants (1991) and by the fact that 8 species (3 sporozoans, 3 cestodes, 1 trematode and 1 nematode) were originally described on specimens from the Reserve and for one sporozoan species the Reserve is the only known locality in the world. The above species were found in Srebarna in the period of 1964 through 1966. This is an indication that more new members of the global species diversity may exist in the Reserve among the poorly studied groups.

Proposed measures

The following factors may negatively affect the invertebrate species diversity in the Biosphere Reserve Srebarna:

The long-term goals involve conservation of the entire species diversity of the non-insect invertebrates and its comprehensive description.

Taking into account the negative factors, the operational objectives should be:

  1. Conservation of the entire habitat diversity in the Reserve. This relates mainly to the appropriate management of the lake hydraulic facilities in order to ensure both a lower degree of eutrophication of the lake and preservation of the shallow-water and terrestrial habitats. All habitats within the Reserve are important for the maintenance of its considerable invertebrate diversity, including small pools in the reed-beds, surrounding scrub and forest belts, grassy plants communities, etc. The maximum water level (the one reached in 1999) has a destructive impact on many valuable habitats in the reserve.
  2. Control on the farming practices in the lake watershed. Since the watershed of the lake is almost entirely under cultivation, the agricultural techniques applied there have to be managed in order to reduce the influx of pesticides and nutrients into the lake. This management, among others, may include free consultations for local farmers and compensations for the reduced income they would receive from their property as a result of implementing ecologically-friendly techniques.
  3. Control on the farming practices in the lake watershed. Since the watershed of the lake is almost entirely under cultivation, the agricultural techniques applied there have to be managed in order to reduce the influx of pesticides and nutrients into the lake. This management, among others, may include free consultations for local farmers and compensations for the reduced income they would receive from their property as a result of implementing ecologically-friendly techniques.
  4. Working-out of an environmentally friendly strategy for mosquitoe control. This has to be done in cooperation with local health authorities.
  5. Monitoring the quality of the Danube water. This is essential for the prevention of the influx of toxic substances and nutrients into the lake.
  6. Development and implementation of an extensive research programme for the comprehensive description of the species diversity of Srebarna Biosphere Reserve. Working-out of such a programme, involving qualified taxonomists from research institutes of the Bulgarian Academy of Sciences or from the universities in the country would increase the amount of scientific information on the invertebrate species diversity of the Srebarna Reserve by about 70% to 80% in only a 3-year period. This is necessary for a better understanding of the Reserve conservation value and for a proper selection of management strategies and activities. The main difficulty in elaborating such a programme will be the lack of adequate sources of funding in the country.
  7. Programme for bio monitoring on Reserve ecosystems. Biomonitoring involves systematic observations on the structure and function of the reserve ecosystem. The work on this Programme will cover several major invertebrate groups of primary indicative value (phytoplankton, zooplankton, zoobenthos, aquatic mollusks, some helminth parasites as indicators of the stability of the food web and as a negative factor, as well as several groups of insects).

1.18.1.1. Helminth parasites

Background Information

Results from helminthologic studies carried out in the Srebarna Biosphere Reserve are reported in 33 publications. The first reports were on helminth parasites of Pelicans and White Storks (Yanchev, 1958). Detailed helminthological investigations were carried out on small mammals only. Two monographs (Procopic & Genov, 1974 and Genov, 1984) were based on the results from these. The host groups listed below have been studied sporadically: fishes (Margaritov, 1959), frogs (Boschkow, 1965), reptiles (Biserkov, 1989), birds (Kornyushin et al., 1984), artiodactyls (Genov, 1971b) and carnivores (Genov, 1971c). Data from literature have been summarized by Michev et al. (1998).

Actual State

A total of 204 helminth species have so far been recorded from Srebarna: 49 cestodes, 68 trematodes, 81 nematodes and 6 acanthocephalans. As a whole, the group has not been adequately studied and further investigations may significantly lengthen the list of species. It might be expected that the longest list of new species will be the one of trematode and cestode parasites of birds and fishes. Probably the overall number of helminth species found in vertebrates from the reserve may exceed 600.

Helminths are parasitic worms to be found in many vertebrate and invertebrate hosts. In cases of massive infestations, they cause severe health problems in both wild and domestic animals and in humans. Their diversity is very great in wetlands and freshwater basins. The helminth parasites are substantial biotic factor in all ecosystems of the reserve. In a number of cases they are agents of parasitic diseases, and at times parasitic infestations may prove fatal. Besides, infested animals are very vulnerable to the negative combined effects of the parasitic worms and other pathogenic agents. Some parasitic larvae are very dangerous because their life strategies are directed to changing the host behavior in such a way as to render it an easy prey for carnivores. This is usually caused by larvae inflicting damages to the nervous system, eyes, muscles, swim bladder of fishes, etc.

Helminth parasites affect all vertebrate animals in wetlands like Srebarna. Means available for controlling the influence of parasites are limited but their implementation is justified. Regarding this control it should be noted that the relation between biodiversity and the helminth influence on populations of the final hosts is of utmost importance. Two of the aspects of this relation are of a great significance: (1) It is a known fact that the increase in the biodiversity leads to the stabilization of infestation parameters thus limiting the cases of extremely high infestation levels. (2) The high degree of system biodiversity is a pre-requisite for a high helminth diversity which results in competitive interactions at the level of the intermediate hosts, rarely at the level of the final hosts. These competitive interactions also limit the helminth infestation to a certain degree.

Another important relation is between the degree of the eutrophication of the water body and the parameters of helminth infestation in it. In the course of successions as the one now observed in the Reserve, the rule is that the high level of eutrophication results into suitable conditions for the helminth circulation, respectively into a stronger impact on the host populations.

The impact of the helminth parasites is often combined with the impact of other biotic and abiotic factors. The food resources available to the hosts are very important. Among starving animals the negative effects are more pronounced in those infested by helminth parasites.

Proposed measures

The ideal goal is to control the helminth populations by maintaining a high level of biodiversity simultaneously with a low level of eutrophication of the lake.

Since natural processes in this type of ecosystem lead to the increase of eutrophication level, the priority realistic objective should be to artificially maintain a low level of eutrophication. Control of helminth parasites in a natural ecosystem cannot be direct, i.e. it has to be carried out mainly by using other ecosystem components (parameters of host populations, water conditions, etc.) as a tool.

In order to limit the negative impact of the helminth parasites on the populations of vertebrates in the reserve, a high level of biodiversity has to be maintained based on native species assemblages typical for the region. It will also be necessary to optimize the Reserve ecosystem biological productivity in such a manner as to provide for optimum food resources for the most important protected animal groups in the reserve. If a choice can be made between different trophic conditions in the lake, then those ensuring lower eutrophication level of the lake should be the choice.

In order to limit the spreading of helminthoses endangering human health it will be necessary to strictly observe instructions for controlling of echinococcosis, spirometriasis and alariasis.

The effect of fish-eating birds on spreading parasites, including their own helminth populations, cannot be eliminated under conditions of a nature reserve. Therefore, in order to maintain the fish populations, an artificial stocking of the lake is desirable at certain time intervals. When the lake is to be stocked with fish from a fish farm, then a thorough parasitological control should be exerted in order to avoid the introduction of new helminth species. As a preliminary step a detailed ichthyohelminthologic study should be carried out within the frame of the overall research programme for the reserve.

General measures for the reserve and for the region

1.18.3. Insects

Historical Data Review

Studies carried out so far on the insect fauna of the reserve (with the exception of two groups of insects) are partial and insufficient. This was the main difficulty in making an overall assessment of the species abundance, biodiversity and the extent of human impact. The most complete faunal synopsis was made in the species checklist (Michev et al., 1998). According to this work the total number of insects found so far is about 560 species belonging to 9 orders and nearly 80 families:

Ephemeroptera – 1 species (Vidinova, 1998)
Odonata – 35 species (Beshovski &Marinov, 1998)
Mallophaga – 7 species (Georgiev, 1998)
Anoplura – 3 species (Georgiev, 1998)
Coleoptera- 298 species (Kodzhabashev & Penev, 1998)
Hymenoptera – 8 species (Stoyanov, 1998)
Siphonaptera – 18 species (Vasileva & Georgiev, 1998)
Diptera – 13 species (Michailova, 1998)
Lepidoptera – 105 species (Beshkov, 1998)

Actual state

The only group of terrestrial insect that is well studied and can be used as a model for typifying the strato- and epigeobiotic habitats of invertebrate land animals are the Carabid, or Ground Beetles (family Carabidae). Representatives of this group have been successfully used as bioindicators and for monitoring of the animal communities in a work of recording the extent of human impact and of finding and predicting ecological trends and changes in the succession.

The study of the contemporary state of the epigeo- and stratobiotic invertebrate fauna as well as its assessment from community point of view has been performed by the method of pitfall traps with monitoring group the family Carabidae (Carabid, or Ground Beetles). During the study 150 traps were set in 6 different land habitats for a period of 24 months. Each month (winter period excepted) we collected biological material from the traps. The software used for processing and analysing results from the terrastic monitoring were BIODIV, CANOCO and TWINSPAN.

The two-year Carabids-community monitoring carried out in the area of the reserve gave us the opportunity to find a number of ecological regularities and to predict trends in the succession of the land ecosystems in the reserve and its buffer zone. The habitat- and ecosystem typifying of the epigeo- and stratobiotic insect fauna has been made with the help of cluster- and structure- multidimensional analysis while the extent of human impact has been measured with the help of a system of ecological indicators and coefficients in reading various biotic parameters of alpha and beta diversity.

The main types of land habitats in the reserve area that were found with the help of the above analyses can be grouped in 6 habitat categories:

The lack of thorough field studies and the limited available information on most of the insect groups do not allow us to make a full assessment of the reserve role with regard to conservation of rare and endangered species of insects as well as of the importance of the taxonomic group (Class) for maintaining the biological equilibrium.

Proposed measures

The main negative and biodiversity threatening factors with regard to the terrestrial insects are listed below:

The preservation of the aboriginal insect communities as well as the restoration of the negatively affected ones may only be possible if the full reconstruction of the native vegetation becomes a fact. The time needed for such a restoration is comparatively long and is equal to the period of the ecosystem reaching a climax stage. So it should be recommended to start gradually, stage by stage, with afforestation with typical for the forest-steppe zones tree- and shrub- species. It should also be recommended to restrict to a minimum the grazing of domestic animals in the reserve or in its buffer zone. This will limit the ruderalization of the open areas thus slowing down the loss of species and the provocation of undesired changes in the structure of the biological communities.

The main goal in increasing the conservation importance of the reserve is to restore the native insect fauna and to preserve its natural (original, not one disturbed by man) qualitative and quantitative structure. To achieve this goal it is necessary to undertake the following actions stage by stage:

1.18.4. Fishes

Historical Data Review

Indirect information on the fish populations inhabiting Srebarna Lake till the beginning of the 1950-s can be found in research publications concerning the lake ichthyofauna and fisheries in the river and adjacent basins (Antipa, 1909; Ivanov, 1910; Kovachev, 1922; Morov, 1931; Bacescu, 1942, Drensky, 1951). Bulgurkov (1958) carried out the first more extensive ichthyological study of Srebarna Lake in 1952 through 1953. According to his data and the information from official fishing statistics (Statistical information of the town of Rouse Inspectorate of Fishing – quoted after Bulgurkov, 1958), the lake was extremely rich in fish and fishing was an important means of livelihood for the local people. For the years that follow Bulgurkov’s work there are data only on the species composition of fishes from occasional observations related mainly to the fish-eating birds’ feeding habits (Michev, 1968; Michev, 1981; Michev et al., 1993; Karapetkova, 1998).

Actual State

We have analyzed ichthyological material collected in the spring, summer, autumn and winter of 1998/1999 by the means of nets and fishing rods. Information was supplied by officers and workers with the Reserve Administration, by local people and by associates with Central Laboratory of General Ecology Field Research Station.

In the lake proper we found 18 species of fish belonging to 6 families (App. 12). All of them are representatives of the Danube fish fauna. On the first place by the number of species is the family Cyprinidae. The most numerous species are the Goldfish (Carassius auratus gibelio), the Roach (Rutilus rutilus), the Rudd (Scardinius erythrophthalmus) of the family Cyprinidae and the Perch (Perca fluviatilis) of the family Percidae. As was in the past so at present the numbers of Pike (Esox lucius) of the family Esocidae remained comparatively high. Potential inhabitants of Srebarna Lake are two species of Gobies – Neogobius fluviatilis and Neogobius melanostomus (family Gobiidae) – caught in the canal outside the lake proper. Occasionally single Silver Carps (Hypophthalmichthys molitrix) and Asp (Aspius aspius) have been observed.

Six of the found fish species are protected in compliance with the Bern Convention. These are: Asp (Aspius aspius), Shemaya (Chalcalburnus chalcoides), Belica (Leucaspius delineatus), Bitterling (Rhodeus sericeus amarus), Weather Loach (Misgurnis fossilis) and Ukrainian Stickleback (Pungitius platygaster), listed in App. III of the Convention. In the National Strategy for Biodiversity Conservation the Shemaya (Chalcalburnus chalcoides) has been classified as a rare for Bulgaria species, the Belica as a "medium rare" while the Ukrainian Stickleback has been classified as a "very rare" species.

Those same species were listed in the Red Book of Bulgaria as "endangered". No special measures for preserving these species have been taken so far.

Thirteen out of the 18 species found in the lake are potentially subject to commercial or sporting fishing. They are: the Pike (Esox lucius), the Pikeperch (Stizostedion lucioperca), the Carp (Cyprinus carpio), the Bream (Abramis brama), the Tench (Tinca tinca), the Goldfish (Carassius auratus gibelio), the Silver Carp (Hypophthalmichthys molitrix), the Asp (Aspius aspius), the Perch (Perca fluviatilis), the Bleak (Alburnus alburnus), the Roach (Rutilus rutilus), the Rudd (Scardinius erythrophthalmus) and a local species of Goby - Neogobius melanostomus.

Srebarna ichthyofauna is composed mainly of I and II order consumers which are the main intermediary link in the trophic structure of the ecosystem. Their staple diet are the macrophytes consumed directly or in the form of detritus and the zoobenthos. Final consumers in the ichthyofauna are represented by the Pike, mature Perch and the Pikeperch, though the latter is a rather scarce species. For the ecosystem as a whole final consumers are various species of fish-eating birds, otter and man. Main resource for all groups of final consumers are most of all the abundant species of Cyprinids and Percids and for man also the Pike.

Fish are important link in the energy-transfer along the detritus food-chain. Their participation in the grazing one is comparatively weak. They obviously can limit the abundance of certain groups of bottom-dwelling and phytophilic invertebrate animals (insect larvae, oligochaet worms, cladocerans of the family Chydoridae) but they are not crucial for the development of pelagic plankton in the parts of the lake with open water.

The relatively numerous small-sized fish provide a good feeding grounds for the Pike and the other fish-eating fishes being at the same time easily available food resource for the fish-eating birds.

Populations of all valuable as a natural resource species (i.e. from commercial point of view) in Srebarna, with the exception of the Pike, are relatively sparse and unstable. With most of them the low numbers are due to the intensive illegal fishing with nets and with cyprinid fishes in particular, a destabilizing factor of importance is the insufficiency of adequate nourishing food. Populations of less valuable species like the Roach, Rudd, Goldfish and Perch are numerous but the size of individual fishes is small. With the exception of Asp the populations of rare and endangered species, though not numerous are stable and probably they have not undergone any significant fluctuations in recent years. Most of the found species also reproduce in the lake. The Silver Carp and the Asp definitely do not spawn here while for the Carp, Bream and the Pikeperch the question of reproduction has not been answered yet.

Species occurring in Srebarna in very big numbers like the Pumpkinseed (Lepomis gibbosus) and the Bleak (Alburnus alburnus) inhabit both the main body of the lake and the peripheral pools. The greater part of the fishes school together mainly in the shallower and close to the shore parts of the lake, overgrown with submerged aquatic vegetation (Ceratophyllum). Open water areas of the main water body are scarcely populated by fish.

Proposed measures

No factors have been recorded at present that might pose a threat to the existence of fishes in Srebarna lake. However, there are factors that limit the development of the fish fauna as a whole or of individual group of fishes. These factors are: 1) lack of permanent connection between the lake and the Danube; 2) massive "blooms" of planktonic algae; 3) the insufficiency of adequate nourishing food due to the lack of suitable substrate for the development of bottom invertebrate fauna limits the numbers and/or individual growth of many "peaceful" species of fish; 4) the limited spawning grounds for phytophilic species of fish as all of the fish inhabitants of Srebarna are; 5) illegal catching of commercially valuable species with fishing nets and other illegal fishing gear practiced all year round including the spawning season.

Realistic goals to achieve:

Following operational objectives can be formulated on these grounds:

1) Forming a stable lake fish community based on the Danube fish species which should be able to most completely utilize the available trophic resources and whose characteristics should meet two basic requirements:

  1. Populations of the wide-spread and numerous fish species to make up the basic trophic source for the fish-eating birds;
  2. Commercially valuable species to become a sustainable basis for the development of limited fishing activities the role of which will be, on the one hand, social and, on the other hand, to serve as an element of the system for water quality control through the methods of the so called biomanipulation.

2) Creating such conditions in the lake as to permit conservation and recovery of the populations of endemic, rare and endangered Danube fish species.

3) Displaying the fish fauna in a spectacular way in order to increase attractiveness and educational role of the Visitor’s Centre.

To achieve the above objectives it will be necessary first of all to provide for an efficient control against illegal fishing, most of all against the use of nets and during the spawning season (April-June). Commercial fishing to be suspended for a period of at least two years. It is absolutely imperative to create pre-requisites for involving local people and local authorities in the execution of this task.

It is also necessary to start activities for stabilizing the existing populations of commercially valuable species like Carp, Bream, Tench and Pikeperch through:

  1. Supporting their natural spawning on the spot; guarding the spawning grounds and fixing artificial ones at suitable places in the lake;
  2. Stocking the lake with young fishes from the Danube; the wild form to be preferred when stocking the lake with Carp.

Recovery of the fish species abundance may also be accelerated by introduction of species that inhabited the lake in a more distant past. It is recommendable to start with the reintroduction of the European Wels (Silurus glanis), a species protected in compliance with the Bern Convention (App. 12) and is also of commercial and sporting value. The lake has sufficient food resources to support the Wels population there and, being a consumer of a higher order, the species can be used in the management of the aquatic ecosystem through the methods of biomanipulation. Another similar species that are of commercial and/or conservation value are: the Asp (Aspius aspius), the Blue Bream (Abramis balerus), the White-eye Bream (Abramis sapa), the Striped Ruff (Gymnocephalus schraetzer). The lake should not be stocked with Grass Carp (Ctenopharyngodon idella) as this may cause the destruction of the Ceratophyllum growth while stocking with Silver Carp (Hypophthalmichthys molitrix) should be done with great caution! Some other Danube species may be additionally introduced in Srebarna like Volga Pikeperch (Stizostedion volgensis) and Czech Ruff (Gymnocephalus baloni) as there are potential ecological niches and all three of them are protected by the Bern Convention.

The stock of the 5 most widely spread fish species should allow for the legalization of limited fishing activities by stages and under efficient control according to the following schedule: (1) during the first 2 or 3 years to permit only sport fishing in 1 or 2 carefully selected zones of the lake under strict regulations regarding the species and quantities of the catches; (2) in 2 or 3 years, if conditions are favorable, to permit limited commercial fishing under the same conditions. Species and quantities of catches should be determined each year depending on the actual state of fish stocks. To this end it will be necessary to carry out additional research for more precisely determining the numbers and population size of the commercial species.

The fish fauna as an important component of the reserve ecosystem should find its place in the future visitor’s center (or museum) at the reserve. Suitable education programmes may also be developed. Such an exhibition of local Bulgarian fresh-water fish fauna will attract visitors and will certainly have great cognitive value.

Measures for the recovery, conservation and rational use of the fish resources of the Srebarna Lake should be supported by a relevant research programme in several major directions:

1.18.5. Amphibians

Historical Data Review

Amphibians in Srebarna Reserve have not been a subject of special research. Data published so far have been summarized in the checklist by Michev et al. (1998). They were in 7 publications on various topics containing also some information on the amphibians in Srebarna (Beshkov, 1965, 1972; Beshkov & Beron, 1964; Bozhkov, 1965; Ivanov et al. 1964; Michev et al., 1993; Paspaleva-Antonova, 1961).

Actual State

Twelve species of amphibians have so far been recorded for the reserve (Michev et al., 1998), of them the Eastern Spadefoot (Pelobates syriacus) was reported by Michev et al. (1998) for the first time.

The importance of this group for Srebarna Biosphere Reserve is determined by the fact that there is one species, Eastern Spadefoot (Pelobates syriacus), included in the Red Book of Bulgaria and eight more species protected by the Bulgarian Law. These latter are: the Danube Crested Newt (Triturus dobrogicus), the Smooth Newt (Triturus vulgaris vulgaris), the Fire-bellied Toad (Bombina bombina), the Yellow-bellied Toad (Bombina variegata), the Common Spadefoot (Pelobates fuscus) the Common Toad (Bufo bufo bufo), the Green Toad (Bufo viridis) and the Common Tree Frog (Hyla arborea arborea).

The most abundant and most significant are the frogs Rana ridibunda and Rana esculenta. They are a food source for many predatory fishes, Grass Snakes, birds, insectivore and carnivore mammals. The proportion of these species of frogs in the diet of the above mentioned predators increases by the end of their period of metamorphosis when they shift from aquatic to a terrestrial way of life. Amphibian larvae on their part are a food source for a considerable range of aquatic birds. At the same time frogs and toads themselves consume large amounts of arthropods, mainly insects. The tadpoles are exclusively herbivorous, eating algae and vascular aquatic plants.

Proposed measures

The following measures have been undertaken for the protection of the group:

The entire Reserve amphibian fauna is composed of the species described above. The knowledge on group could be defined as incomplete. Though no new amphibian species can be expected in the reserve (i.e. their species diversity has been thoroughly studied), it is obvious that further investigations are needed to assess the population parameters of each species.

The main deficiencies in our knowledge on the group are the lack of quantitative data on the populations of various amphibian species and of data on the breeding habitats of the two species of Pelobates toads.

Factors listed below may have a negative impact on amphibians in the Biosphere Reserve Srebarna:

The long-term objective is to preserve amphibian species richness in Srebarna by maintaining stable and viable populations of all species occurring there.

Proposals for specific projects/programmes (for counteraction):

On the lake's mirror. The main possibilities to achieve and maintain the high biodiversity and bioproductivity are:

On the ecotone in the lake's periphery.

The shrub belt and the isolated patches of old trees contribute to the biodiversity in the Reserve with regard to numerous animal species: Common Tree Frog (Hyla arborea), Common Toad (Bufo bufo), Green Toad (Bufo viridis), Aesculapian Snake (Elaphe longissima), Large Whip Snake (Coluber jugularis), Green Lizard (Lacerta viridis), song birds, small mammals, etc. Therefore, it is necessary to maintain the shrub belt and the small woods growing in the Reserve periphery.

1.18.6. Reptiles

Historical Data Review

There are no special publications on reptiles of Srebarna Reserve. Data published so far have been summarized in the checklist by Michev et al. (1998). These are contained in ten previously published works on other aspects of Srebarna (Beshkov, 1984, 1986; Beshkov & Beron, 1964; Biserkov, 1987, 1989; Genov, 1969; Ivanov et al., 1964; Michev et al., 1993; Paspaleva-Antonova, 1961).

Actual State

Two expeditions for field observations and data collection were carried out. Fifteen species of reptiles have been recorded for the reserve. Five of them are mentioned by Michev et al. (1998) for the first time. In addition in 1999 a new species for the Reserve area, Slow Worm (Anguis fragilis), was found in the forest along the Danube riverside.

The importance of the group for the Reserve is determined by the fact that it includes a species listed in the UICN Red Data Book and in the Red Book of Bulgaria - the Aesculapian Snake (Elaphe longissima). Another six species are protected by the Law: Spur-thighed Tortoise (Testudo graeca), European Pond Terrapin (Emys orbicularis), Green Lizard (Lacerta viridis), Large Whip Snake (Coluber jugularis), Smooth Snake (Coronella austriaca), Four-lined Snake (Elaphe quatuorlineata sauromates).

Measures so far undertaken for the protection of the group are: (1) One species -Aesculapian Snake (Elaphe longissima) - is included in the Red Book of Bulgaria. (2) Six more species are in the List of legally protected animals (under the Law for the Protection of Nature): Spur-tighed Tortoise (Testudo graecca) European Pond Terrapin (Emys orbicularis), Green Lizard (Lacerta viridis), Slow Worm (Anguis fragilis), Large Whip Snake (Coluber jugularis), Smooth Snake (Coronella austriaca), Four-lined Snake (Elaphe quatuorlineata sauromates).

There are only 3 reptile species, which are widespread in the reserve: the Grass Snake (Natrix natrix), the Dice Snake (Natrix tesselata) and the European Pond Terrapin (Emys orbicularis). The remaining species occur mainly in the reserve periphery and surroundings. As a whole, the reptiles do not play a role of any significance in the reserve ecosystem functioning.

The chances of discovering a new species of the reptile fauna of the reserve are very slim. The only species which might be found there is the Sand Lizard (Lacerta agilis).

Our knowledge on reptiles of the Srebarna Reserve can be defined as incomplete. Though species composition is almost thoroughly known, it is necessary to carry out further investigations on the population dynamics of each species.

The main deficiency in our knowledge on the group is the lack of quantitative data on reptile populations.

Proposed measures

The ideal goal is to preserve the species abundance by maintaining stable and viable populations of all reptile species occurring in the reserve.

In order to improve the ecological conditions it is suggested to construct snake wintering dens at suitable places in the Reserve (App. 16). In order to extend habitats preferred by reptiles and to improve their food resources is shall be necessary to:

1.18.5. Birds

Historical Data Review

Srebarna Lake drew the attention of a number of European and Bulgarian ornithologists as early as in the middle of the last century. The most exhaustive scientific work on the reserve avifauna was published by Paspaleva-Antonova (1961). The list of research and scientific literature on Srebarna avifauna comprises 77 titles (Michev et al., 1998).

Birds are by far the most significant biological group in Srebarna reserve. Thanks mostly to them, and to Dalmatian Pelicans, in particular the reserve earned its present worldwide fame. The rare and threatened by extinction species on a local, national, regional and global scale increase considerably the value of Srebarna as an important place for preserving Earth’s biodiversity. Other species of birds on their part are valuable nature resource or are valuable as subject of the cognitive tourism.

The reserve bird species composition is determined to a large extend by its bio-geographic location. The number of bird species found in the reserve and its vicinities is 223, or 55% of the total of 400 species found so far for Bulgaria. Fifty-four of them are breeding and 2 of these – the Dalmatian Pelican and the Great White Egret breed only in Srebarna. Another two species, the Pygmy Cormorant and the Ferruginous Duck have one of their most important breeding grounds there, while the Red-breasted Goose has in Srebarna one of its most important wintering grounds.

Srebarna avifauna conservation status is as follows: the number of protected species is 195; species listed in The Red Book of Bulgaria are 57; globally threatened species are 12.

Actual State

The changes in the reserve avifauna for the past 20 years have been reviewed for three major periods:

In all three above periods the species composition of the breeding birds in the reserve has been studied in May-June using one and the same technique – by visual observations from the west and south banks of the lake. An overview of the results is given in Fig. 1, App. 13. As may be seen on that figure, during the second one of the above periods, when ecological conditions in the reserve were extremely unfavourable, the number of the observed bird species was very low. During the third period, when the connection of the lake with the Danube was restored and negative factors removed, the usual number of bird species has recovered to a great extend too. The numbers of the Dalmatian Pelican (Pelecanus crispus) varies greatly during all three periods but recently it showed a tendency for increasing (App. 13, Fig. 2).

Another important change in the reserve avifauna for the past 20 years has been related to the species composition of Cormorants, Herons & Egrets, Glossy Ibis and Spoonbill. According to Michev & Stoyneva (1994) these species and most of all the Glossy Ibis can be used as biological indicators for the overall state of wetlands in general and Srebarna in particular. During the first of the above periods both species bred in the two large reed-beds (north and south ones) in the reserve. During the second period Cormorants and Herons/Egrets (with the exception of Glossy Ibis and Spoonbill) moved to the nearby Danube island of ‘Komlouka’ (recently added to the reserve area proper). Two species have not yet returned to their traditional breeding sites (the north and south reed-beds). The first species, the Cormorant, breeds still in the colony on Komlouka Island, while the second one, the Glossy Ibis, visits the reserve only during migrations. In the year 2000, however, it also returned and bred in the big colony to the north of the Pelican Pool.

There are still some blank spots in our information on the birds of Srebarna for quite a long period of time – from 1894 till 1947. Data on places where Dalmatian Pelicans, Herons/Egrets, Glossy Ibises and Spoonbills used to feed in Romanian marshes, fish ponds and reservoirs are insufficient. It is not very clear where are the places of greatest importance in this respect and what are the negative factors affecting birds when they happen to be there.

Proposed measures

Srebarna has undergone a number of negative impacts, which basically may be grouped in two:

Direct impact factors:

Indirect impact factors:

The main goal with respect to the avifauna is to prevent the breeding, passing and wintering species to become extinct from the reserve as well as to preserve and stabilize their numbers. It is impossible to achieve this goal given the existing surface area and boundaries of the reserve because the greater part of the feeding grounds for the greater part of the birds is outside the reserve and even outside Bulgaria. The above goal concerns the 24 bird species that determine Srebarna’s great conservation and/or economic value.

Measures undertaken to preserve the group or its individual representatives:

During the reserve’ 50 years of existence a number of measures have been undertaken aimed directly or indirectly at preserving the avifauna or individual species:

Very successful measures:

Successful measures:

Unsuccessful measures:

Measures to be taken in the future for preserving individual species of birds:

For Dalmatian Pelican:

These measures should also include the following activities:

For Pygmy Cormorant:

For Lesser White-fronted Goose:

For Red-breasted Goose:

For Ferruginous Duck:

For Corncrake:

For Great Bustard:

For Great White Egret:

For Purple Heron:

For Spoonbill

For Glossy Ibis:

For Graylag Goose:

For Ruddy Shelduck:

For White-tailed Sea Eagle:

The avifauna of Srebarna Lake will be substantially influenced by some activities related to the conservation status, changes in the hydrologic conditions and the possible exploitation of the reserve natural resources:

Increasing the total surface area of the buffer zone and planting there suitable native tree species like the white willow (Salix alba), White Poplar (Populus albus), Quercus robur, etc. In the future these trees will give a good substrate for building nests by various aquatic birds and raptors;

Dredging the lake bowl, including dredging of the Pelican Pool and removing of the 3 to 5 m thick layer of silt & debris. Increasing water volume shall bring about substantial increase of the fish stock followed by an increase in the numbers of many waterfowl and other aquatic species of birds. This in turn shall affect considerably the hunting tactics of the fish-eating birds, which at present feed mostly in the wetlands on the Danube left (Romanian) riverside. When the food resources of the reserve proper become richer, most of the birds will remain to feed in it instead to undertake every day risky flights. Pelicans with their typical use of additional feeding grounds in the neighbourhood of the breeding colonies will, most likely, continue to visit the wetlands across the river in Romania. The increase of the water volume (resp. the depth) will affect also the processes of ice forming in the lake. It will freeze less frequently and for shorter periods of time. This will tempt the wintering geese flocks to remain longer there. The increase of the lake water volume will favourably affect the microclimate around the reserve – something of importance both for man and for the numerous flocks of songbirds passing by during migration;

Setting aside a small part of the reserve for anglers (for fishing for sport). This certainly will not have an impact on the reserve avifauna, the more so if this is some of the peripheral parts near the village of Srebarna where the human presence is most pronounced.

The strategy for the future management of Srebarna reserve may be based on the requirements for preserving reserve’s avifauna. This strategy should include the following principles:

1.18.7. Mammals

Historical Data Review

Mammals of the Srebarna Biosphere Reserve were studied by Christov (1961), Racheva (1963), Peshev and Angelova (1985). Mammals in that region had been subjected to much more intensive studies in connection with their parasitological status and as vectors of naturally transmitted infectious diseases. There are over 20 scientific publications in this respect (Michev et al., 1998).

In studying rodents and other small mammals researchers have applied standard methods of catching and preserving material. For 14 species there is habitat clustering based on data on the relative quantitative records for prolonged periods of time Information on big mammals has been supplied by the Union of hunters and fishermen in Bulgaria.

Actual State

As a result of these studies as well as on the basis of not published field studies carried out by the biologists T. Genov, B. Georgiev, N. Kodzhabashev and S. Gerasimov 41 species of mammals have been found in the region of Srebarna reserve at present. However, in a more detailed examination of collected specimens and their identification it was found that there might be three duplicate species – Apodemus sp., Mus sp. and Microtus sp. Then the overall number of species may grow to a total of 45. In this way practically half of the Bulgaria’s mammal fauna was found in the reserve and in its buffer zone.

Mammal species found for Srebarna, systematically are grouped in the following way: seven insectivorous mammals; 2 bats; 4 carnivores; 7 mustelids, 3 ungulates, 18 (21) rodents and 1 hare. Three of those did not occur in this region in the past. They are:

The Jackal (Canis aureus) following the expansion of its range in 1960-ies settled permanently in the area of the lake and has been in very high numbers since;

The Muskrat (Ondatra zibethica) was introduced in the lake in 1950-ies and suffers considerable fluctuations in its numbers through the years;

The Raccoon-like dog (Nyctereutes procyonoides) is a newcomer to the reserve and has come here from the Danube Delta in recent years.

The population density of all mammals found for Srebarna Reserve has been evaluated by experts on a 5-grade assessment system for the different zones in the reserve: zone 1 is the open water area in the central part of the lake; 2 is the wet reed; 3 is the pastureland and agricultural associations; 4 is the forest community. Data are shown on Table 1, App. 13.

From ecological viewpoint we have found the following grouping of mammals: in the lake proper and immediately around it the aquatic and hydrophilic mammals (12 species) predominate while in the lake periphery and in the buffer zone occur steppe and forest-steppe species. These are most of the rodent species, the carnivores and ungulates. Typically steppe mammals like Hedgehog (Erinaceus concolor), Stone Marten (Martes foina), Eversmann's Polecat (Mustella eversmanni), Souslik (Spermophilus citellus), Hungarian Molerat (Spalax leucodon), Mus spicilegus, Dobrudzha (Romanian) Hamster (Mesocricetus newtoni) and Steppe sicista (or Southern birch mouse) (Sicista subtilis) occur in dry places and in agricultural communities in the buffer zone. As species of isolated distribution for Dobrudzha (resp. for Srebarna) are the populations of the two species of Red-toothed Shrews – the Eurasian Common Shrew (Sorex araneus) and the Eurasian Pygmy Shrew (Sorex minutus) which at present are typical for mountain forest ecosystems in Bulgaria.

Game mammals. From spring field assessment of the game animals stock and from the killings in 1997-1998 and 1998-1999 hunting seasons done by the organised hunters from the villages of Srebarna, Vetren and Aidemir with a total area of their hunting grounds amounting to 10 600 ha, the following values have been found out: Hare (Lepus europaeus) main stock is 45 animals per 1000 ha, killings amount to 48% of the main stock; European Roe-deer (Capreolus capreolus) main stock is 4 animals per 1000 ha, killings have been only selective, amounting to 5% of the stock; the Red Deer (Cervus elaphus) main stock is 0.5 animals per 1000 ha, there were no legal killings; the Wild Boar (Sus scrofa) main stock is 1.2 animals per 1000 ha, killings amount to 48% of the stock. It has been found from the data on killings of carnivorous mammals that the Jackal and the Fox have almost the same relative numbers – 1.7 and 1.5 annual average killings per 1000 ha and 0.2 animals per 1000 ha for the European Wild Cat (App. 14, Table 2).

Rare and endangered mammalian species:

The Otter (Lutra lutra), an inhabitant of the reserve, is a globally threatened species. In the European Red Book the following species are listed as rare or endangered:

It may be seen from the above that no specialized mammalogical researches in ecological and conservation aspect have been carried out in Srebarna. There are no data on the numbers and its dynamics for the Otter, the Marbled and Steppe Polecats, which are mammals of very high conservation significance.

Proposed Measures

  1. To take all possible measures not to allow for direct destruction of mammals by poaching, use of pesticides, by conflagrations;
  2. To avoid destruction of habitats y draining wetlands, construction works, etc.;
  3. To avoid fragmenting of habitats by constructing hydraulic facilities in the Reserve or its vicinity;
  4. To prevent worsening of the living conditions through water pollution, structural changes in the communities surrounding the Reserve, disturbance of animals;
  5. To control the numbers of the Jackal and Wild Boar in the Reserve. To undertake the necessary steps when the lake freezes in January and then organize shooting parties with hunters licensed for selective killing of game animals in the presence of the MoEW representative;
  6. To provide for suitable habitats where natural refuges for Otters can be constructed by digging canals through groups of old trees on the lake east shores.

1.19. Social, economic and cultural values

The Nature Reserve Srebarna borders with the land of 3 villages, all of which are part of the Silistra Municipality, District of Silistra. Since ancient times and till the present day the main economic activities throughout the region have been farming and fishing.

The three villages, though very alike, have some substantial differences as well, both in their social status and their economies. They will be described below one after the other.

The village of Aidemir has over 10,000 inhabitants and is the biggest village in Bulgaria. When Southern Dobrudzha was liberated from Romanian occupation in 1940 the village numbered only 3000 people. The fact that it was a borough of Silistra in the past and is located very close to the town was an important pre-condition for its growth and for its having a better developed economy and infrastructure. The village of Aidemir is divided into three neighbourhoods, named Delenkite, Aidemir and Tataritza. Ethnically the bulk of the population is Bulgarians. The inhabitants of Tataritza are Russians of the old Christian belief who left Russia about 300 years ago and settled here to escape persecution and to preserve their traditional belief. There are some Gypsies in Delenkite.

Aidemir’s economic structure is as follows: a rubber products plant of the name of "Kapitan Mamarchev", a timber-processing factories "Fazerles" and "Lesilhart". The last two are privatized parts of the former works for processing of timber and manufacturing of joinery and other wood products. It was this timber-processing works that provided most of the jobs in Aidemir in the past. At present most of the village people are employed in the industry in various plants and factories in the town of Silistra. However, the main share of the employment on a local level belongs to farming. Apart from the numerous private farms there are 1 cooperative (collective) farm and 3 agricultural companies. The countryside area called "Baltata", which in the past was a natural continuation of the Srebarna Lake as a marsh, known also as the ‘Aidemir Marsh’, has a surface area of about 1700 ha. It was drained in 1949 after the riverside protective dike 'Vetren–Silistra' was erected and its area reclaimed for cultivation. Today it is rented by the agricultural shareholding association "Green Market". The main crops are grains: barley, wheat, maize, sunflower seeds; vegetables like tomatoes, cucumbers, beans. The biggest percentage of the area under perennial plantations is planted with apricots and vineyards; peaches, cherries and sour cherries cover smaller areas.

Animal breeding is developed on a very small scale and is for the most part in the hands of private petty farmers. The governmental veterinary office has registered 200 cattle, 2000 sheep and goats, 130 horses, 1980 pigs, 3000 fowl, 350 dogs. The only pig-fattening big-scale farm which in the past used to discharge its liquid wastes in the rivulet Kalnezha (one of the feeders of Srebarna lake) has been privatized today and has about 200 pigs.

About 100 people are involved in the Danube fisheries operating from the fisherman’s village of Ivanovo (on the bank of the river). It is water- and electricity supplied. There are a few more fishermen villages on the bank further to the east. The village council has allocated 4.6 ha communal land to construct in the future a new and modern fisherman’s village. Historically the residents of Tataritza have been involved in fishing in Srebarna Lake. Nowadays only a few have committed themselves to the traditional commercial fishing in the Danube.

In Aidemir as well as in the other two villages another traditional occupation was the manufacturing of various articles from reed and bulrush – an almost extinct craft today. As a whole the village has a relatively well developed network of shops and places of public resort. There are two schools, a kindergarten and a high technical school of agriculture. The latter has its own 100 ha yard.

The main problem - as is the case almost everywhere in the country in these days - is the unemployment. At present over 180 families rely on social aid programmes for their existence. Authorities are afraid that the total unemployment may exceed 20% of all the inhabitants of the area under question.

The village of Srebarna is 18 km to the west from the town of Silistra and is located almost on the very western bank of the reserve. The residents are about 1100, only Bulgarians. Part of them has been moved here from North Dobrudzha in 1942 on the strength of the Kraiova Agreement of 1940. They have settled in the village’s northwest end in the neighbourhood ‘Preseltzi’ (Settlers). Until 1962 the village population numbered 2500 people. After Silistra was declared a district centre quite a number of peasants were almost forced to leave the nearby villages and to move to the town to provide labour for the newly erected and set into operation industrial enterprises.

There is no industry in the village and there was none before. Quite a number of the village inhabitants commute to Silistra where they have found a job.

Farming is also the main occupation of the village of Srebarna inhabitants. About 3800 ha of the village land are put under crops. The biggest share in the local farming hold two cooperatives tilling about 2/3 of the arable land. Of the individual farmers three till each one about 200 ha, mostly rented. There are no vast tracts of cultivated land. The main crops are again the grains - wheat, maize and sunflower. Vegetables are produced in negligible quantities, mainly for household consumption.

The animal husbandry has much shrunk in recent years and today it barely meets the needs of the individual village household. Registered domestic animals are 44 cows, 855 sheep and goats, 242 horses, 640 pigs, 6657 fowl and 215 dogs.

There are 1 carpenter, 1 blacksmith and 1 tailor. Groceries, or rather miscellaneous shops are 6, there are 1 bakery and 7 public places of resort. Children from Srebarna, 36 in all, visit the school in Aidemir. So far 22 children go to the kindergarten each day but it is expected to be closed down soon because shortly there will be no children of kindergarten age. About half of the villagers (540 people) are pensioners and 40 are unemployed relying on social aid programmes. The hidden unemployment is greater, though. It becomes somewhat reduced during the summer months when quite a number of people get hired on a day-pay basis by the larger-scale farmers.

The village of Vetren is the least one of the three that are in the reserve’s vicinities. It is some 3 km away from the northwest corner of the reserve, situated on an elevated Danube riverside terrace and reaches the very bank of the river to the north. Permanent residents are about 500 people but in summer the number of inhabitants reaches 1500. Quite a part of the village houses are used as summer villas or orchards mostly by permanent residents of the town of Silistra. In its economy Vetren is very much like Srebarna. Tilling of land is the most important economic activity followed by the commercial fishing in the Danube.

Vetren agriculture is structured in much the same way as that of Srebarna: 1 big farming cooperative tilling about 90% of all the land of the village (1750 ha), a lesser farming cooperative and three individual larger-scale farmers. In contrast to Srebarna, however, larger land areas are under plantations here – 140 ha are under vineyards, 30 ha are under apricots and some, much smaller, patches are planted with walnut and hazelnut trees. The main annual crops here are again the wheat, maize and sunflower. After 1992 when the reserve area has been expanded to the north and has incorporated lands belonging to the community of Vetren, villagers were compensated with lots from the countryside area "Baltata" which begins immediately from the reserve’s northeastern corner. When the canal that connects the lake with the river is full of water farmers have to go a roundabout way via the village of Tataritza in order to get to their land plots. Animal breeding is small-scale, primitive (as in Srebarna), the production is enough only to meet the needs of the household. There are about 500 sheep, 150 goats, several cows, etc.

Being on the very bank of the Danube Vetren has always been renown for its fisheries. There are about 50 fishing boats kept at two jetties. The larger one is situated very close to the village while the other is at the so-called "village of Tanasovo" situated at the very northwest corner of the Biosphere Reserve. The fish is sold right on the spot being kept alive in big wicker-baskets or keep-nets in the river, or in freezers. There are 1 bakery, 3 shops and 3 taverns in the village. There are also some rather good recreational facilities in Vetren both public and private. The governmental trading companies like the "Water Supply and Sewerage Co." or the "National Electricity Company" have their own country recreation houses. The former recreation facility for high- and middle level governmental servants is now managed by the Silistra Municipality as a hotel. The Bulgarian Tourist & Hikers Union also owns a recreation building in Vetren. There is a hotel with a restaurant called "Kalimanitza" built in the Dobrudzha traditional architectural style but is situated at some distance from the riverbank. By far the largest and most comfortable is the riverside chalet, erected before 1989 by the then official trade unions, now rented by a private tour-operating company from Silistra.

The village of Vetren and its vicinities abound in archeological sites. Only Thracian burial mounds are 27. There are also historic sites from the time of the Roman Empire.

The climate is unique and in its main parameters is very close to the climate of the low-mountain resort Varshetz, in the Northwest Stara Planina Mountain, known and visited as a place for recreation since pre-Roman times.

The summerhouses settlement called "Tanasovo" has been erected in the land of the village Vetren on the very edge of the Danube bank, very close to the northwest corner of the reserve. It consists of about 10 huts and has 1 permanent resident. In the beginning it was an illegal settlement for fishermen from the village of Srebarna, built on the place where in 1963 there was a single fisherman’s hut (called "bordey" by the locals) which was used as a resting place for two companies of fishermen from the local collective farm. Of some interest from that time are the remnants of the so-called "glaciers" – deep underground chambers where fishermen had kept ice blocks cut out from the river or from the lake in winter. At present the remnants of three such "glaciers" are preserved there. In the beginning of the existence of Tanasovo the owners of the huts had to pay annual fines for making use of illegal constructions. The settlement is still illegal nowadays. It was built on a tract of land belonging to the Forest Land Fund.

In summer part of the boats from one of the Vetren’s jetties is moved to Tanasovo and then, particularly on weekends, its population increases to some 20 people. There is no electricity; pot water is drawn from wells.

The animal husbandry in the region and its impact on the reserve

In the western part of the reserve buffer zone some 25 cows from the village of Srebarna graze regularly and in its northeastern part about 50 sheep and goats from the village of Vetren graze occasionally. Both herds are composed of animals, which are owned by individual households. Shepherds are hire hands. To the south of the reserve a small herd of about 10 sheep also graze. In 1999 because of the high water level in the lake this particular place was unsuitable for grazing. Most of the village of Srebarna domestic animals graze along the valley of the rivulet Srebarnenska to the south-west from the village. Animals are taken to water to the place called ‘Papratta’ where there is a spring called ‘Dyakovata cheshma’. To the east from the reserve there is no grazing range.

At the somewhat drier northwestern part of the reserve (at the feet of the hill Kodzha Bair) farmers mow the acid grasses (e.g. Sedges – Carex sp., and Great Bulrush - Scirpus lacustris) for hay. Rarely however the mowed patches exceed 200 square meters each. Grass for hay is also mowed in the shallow sprawling valleys (called in the local dialect "koulak") on the reserve west bank.

Just below the village proper, along the buffer zone boundary there is a place where quite a big number of fowl (chickens, turkeys, domestic ducks and geese) stay all day long feeding on the grass or in the lake shallow places close to the bank. At times there are also 1 or 2 horses grazing there.

The pig-fattening farm in the village of Aidemir is a private enterprise. It is located immediately by the rivulet Kalnezha, which is within the reserve watershed. The other pig-fattening farm in the village of Sitovo is also a private enterprise but now there are no pigs in it.

The purchase prices plummeting in 1999 had an adverse effect on animal breeding in the region causing a steep reduction in the numbers of the domestic animals, especially that of pigs. Many farmers give the milk they produce back to their own animals.

Another, as it seems a more lasting, trend in recent times is the increase in the number of goats. This is direct result of the mass impoverishment of the people. The goat, as the saying has it "the cow of the poor", is on the one hand the easiest for breeding, but, on the other hand, it is the most calamitous for the environment. So far the impact of the goats on the reserve is not significant since very few of them enter and browse within its buffer zone.

In conclusion we should note that animal breeding around the reserve Srebarna is extensive and generally a small-scale one (App. 2, Table 1). There are no indications for its undergoing some sharp quantitative or structural changes. The only obvious trend is the one mentioned above - the increase in the number of goats. As a whole the animal breeding does not affect the reserve and its buffer zone.

Around the reserve there are 5 comparatively larger apiaries (bee-gardens) with a total of about 350 beehives. Two of these are within the buffer zone in the place called "Kamaka" and one is just above the fishermen’s village of Tanasovo.

There is a pheasant-breeding farm at the "Kamaka" place, which is a property of the Union of Hunters and Fishermen of Bulgaria. In recent years the farm produces and releases in the wild 150 to 200 young pheasants.

Hunting and fishing in the Reserve vicinities

Fishing as the main means of living for the human population inhabiting the Lower Danube valley was known from very ancient times - as far back as 5000 to 3800 BC – from the times of the New Stone Age. Fish was also a means of exchange with settlements inland. The fishing developed in parallel with the development of the organised human society. The first specific information on some well-developed fishing practices is dated back to the Thracians. Until recently people in the village of Srebarna still applied an ancient fishing technique for catching the fish under the ice. An archeological expedition excavating at a site not far from the village of Vetren (called by the Romans ‘Tegulitium’) found clay tiles with the image of the Goddess Hekata considered a patroness of the travelers and hunters. Such tiles were found mostly in and around settlements where the fishing was a well-developed industry. During the First and the Second Bulgarian Czardom fishing was very important for the economy of local Boyars. There are well preserved documents (charter of endowments - chrysovuls) showing that the Czar used to grant the Boyars or monasteries fisheries. During the Otoman rule the main fisheries (called in Turkish ‘shinal’) in the Danube, in the riverside marshes incl. Srebarna and in canals connecting the marshes (called 'boaz'), were let by contract, publicly (auction, or 'mezar' in Turkish), for a term of 4 years at some initial price (called 'resim' in Turkish). According to a document dated 1814 the fish exported from the Turkish Empire to Austria and Romania had been caught and transported by the fishermen from the districts of Tutrakan and Silistra. The document also mentions that the entire population of the villages Srebarna, Vetren, Tataritza, Garvan and some others has been making its living from fishing. After liberation from the Otoman rule the situation did not changed tangibly. In 1922 many fishermen, oppressed by the occupational Romanian authorities moved to this region. Another wave of settlers arrived in 1940, after the liberation of Southern Dobrudzha from Romanian presence, when from the village of Dikilitash (Stalpishte in Bulgarian, district of Rouse) a multitudinous colony of Russians of the old belief moved to Srebarna Lake and formed today’s Tataritza. The importance of the region from Tutrakan to Silistra for the commercial fishing is also underlined by the fact that until 1878 the annual catch amounted to 1650 tones and the next year it grew to 2400 tones. In 1941 the first fishermen cooperatives were formed in Silistra and in Srebarna. In 1945 they merged forming the cooperation "Sharan" (Carp) with 65 members. In the 50 years that followed the number of member-cooperators decreased steadily. This cooperation fished in the reserve till 1965 but only during autumn-winter months. The maximum daily catch recorded was 3 tones of fish. The communist regime strove to develop Silistra region as a big industrial and agrarian region and all people of working age at that time were forcibly re-directed towards industrial enterprises and collective farms to look for jobs. Besides, the very big Aidemir marsh was drained as were almost all of the remaining riverside marshes but Srebarna, which was declared a game-birds breeding reserve and cut-off from the Danube.

Disruption of the hydraulic connection between the Danube and the riverside marshes and later their draining and turning into cultivated areas caused the cyprinid fishes to almost disappear as commercial fishery and to become replaced by the pelagic species of fish. Nowadays the number of people involved in commercial fishing is growing again and has already reached the levels from the beginning of the 20th century. The main cause for this trend is the unemployment, which is particularly high in the region; besides the farming, as practiced there, allows for working at another job. The fishermen’s bases are in Vetren, in the fishermen’s ‘villages’ proper like Tanasovo, Ivanovo and 2 or 3 lesser ones located further downstream towards Silistra, just after a group of the Danube islands called "Chayka". There are 50 to 60 fishing boats there as these villages are visited by fishermen from other parts of the region (for instance from Silistra). Here again the unemployment is the main cause for the increased number of fishermen. The second most important cause is the lack of suitable for fishing water bodies where members of the Union of Hunters and Fishermen of Bulgaria could enjoy their sporting hobby (for more information on poaching see chapter 1.22).

Hunting as a means of living is as old as the fishing. The greater control that had been exerted on hunting by the authorities during all the history of mankind made it not so broadly practiced and finally it had turned into a sport. On the other hand hunting, being out of reach for the greater part of the society, has caused the poaching to become a very popular though illegal practice. Nowadays hunting is regulated by the Law for Hunting Husbandry and may be practised only by members of the Union of Hunters and Fishermen in Bulgaria (UOHFIB) after passing examinations on the theory and practice of game biology, hunting and hunting legal regulations. Within the land of each village of the country a certain area is allocated for hunting needs. Any such area is managed by a local Hunt (company of hunters), which is the local subdivision of the Union. The number of hunters for a given hunting area is determined on the rule 1 hunter for 110 ha of the hunting area. The boundaries of the hunting areas of three local hunts (companies) meet at Srebarna Reserve. The average number of hunters in each of these hunts (companies) is 26 (26 for Srebarna, 27 for Vetren). Higher hunting charges introduced by the government in 1999 forced quite a number of hunters to give up the hunting altogether and the number of hunters in each company became reduced roughly by 25%. The major big-game animal in the region is the Wild boar (Sus scrofa), as the ecological conditions in and around the reserve are perfectly suited for these animals. Annually between 20 and 25 boars are killed there. Wild boars are the main game for poachers using snares, too. Hunting Roe deer (Capreolus capreolus) and Red-deer (Cervus elaphus) having their numbers drastically reduced have been completely banned in recent years. Their populations for the region are approximately estimated at being 30 for the Red-deer and 20 for the Roe-deer. Hunting the so called harmful game animals being before 1989 well paid by the government as well as a part of the annual economic plan (the number of individuals from a species that should be killed each year) now is a rather accidental event. In 1999 in Srebarna there were only 20 Jackals (Canis aureus) and 10 Foxes (Vulpes vulpes) killed. The population boom of the Jackal during the last 30 or so years deserves mentioning here, because in the more distant past it was completely unknown animal for the region. The Hare (Lepus europaeus), having almost disappeared some years ago, has again started to increase its numbers, particularly during the last 1 or 2 years. Hunting Hares is also suspended for the time being. Of the game fowl the most popular is the Colchian Pheasant. Depending on the annual population growth each village Hunt kills 30 to 50 pheasants for a hunting season. The river Danube, the Reserve proper as well as the spacious fields under winter wheat attract scores of thousand of wintering geese in the region. Hunting geese however is a difficult task even for skilled hunters and rarely a village hunts closes the hunting season with more than 50 geese bagged. Frequently geese and ducks hunting parties shoot from a boat in the Danube, which is an illegal hunting practice. This is an adopted manner of hunting ducks by the village hunts of Vetren and Aidemir. The hunting season opens with hunting of Quails (Coturnix coturnix), Turtle Doves (Streptopelia turtur) and Woodpidgeon (Columba palumbus) but later in the season hunters rarely go out for this particular game species.

CRAFTS

The main means of living were and still are, as described above, fishing and farming. An already almost forgotten craft - that of manufacturing goods from marsh vegetation - deserves mentioning here. This craft came from very ancient times but in 1954 it became developed on an industrial basis with the opening and setting into operation of a factory named "Kamashit" in Silistra. The factory used as a raw material the reed, mowed and collected from all riverside marshes. The first items produced by the factory were crude mats woven from reed (Phragmites australis - called by the local people "kamash") or Great Bulrush (Scirpus lacustris - called by the locals "kandara") used in house construction for making the so-called "blind ceilings". Later a new product was developed - the so-called "pressed mats" used for heat and sound insulation of the under-roof premises in buildings. Floor mats were produced from the two species of Reedmace (Typha latifolia and T. angustifolia - called by the local people "karakol") and from Great Bulrush (Scirpus lacustris). Sheaths of mowed reed or bulrush were tied with ropes made of sedge (Carex sp.).

Later on the "Kamashit" factory opened a workshop in the village of Srebarna for manufacturing mats in order to have the market product cheaper by cutting down the transportation cost. However, in 1975 mowing of reed in the reserve was banned. The factory continued to work for a few more years mowing reed, reedmace and bulrush mostly from the marsh of Kalimok. In the meantime the demand for mats stopped altogether and the factory managed to stay on the market by manufacturing some items from Purple Osier (Salix purpurea). There still are some people who are skilled in manufacturing reed and bulrush mats but the demand is mainly for decorative ones, as for instance to make a decorative fence around a summer restaurant.

1.20. Land tenure/ownership

The reserve is an exclusive governmental property and is managed by the Ministry of Environment and Waters (MoEW). It is surrounded by land plots, the property of which is of several types:

LAND OWNERSHIP OF THE AREAS AROUND SREBARNA (in ha)

Ownership

Aidemir

Srebarna

Vetren

Total

Of the Church

25.0

10.0

0

26.0

Private

354.0

406.1

331.9

1092.0

Municipal

153.6

352.1

150.6

656.4

State

232.0

694.8

652.8

1579.6

Total

764.7

1454.0

1135.3

3354.0

1.21. Current land use

Within the boundaries of the reserve there is no exploitation of natural resources. 10000 ha of crop-fields under wheat, maize, sunflower and vineyards surround the reserve. Before 1989 large quantities of fertilizer were applied in that land farming. Nowadays fertilizers are almost not used at all.

The reserve is surrounded also with 392 ha of woods most of which are Black Pine (Pinus nigra), Black Locust (Robinia pseudacacia), Hybrid Poplar (Populus sp. X Populus sp.) plantations (see 1.17.3).

1.22. Adverse factors affecting the ecological characteristics of the site

The factors are classified as 'existing' (ex), 'potential' (pt), 'internal' (int), 'external' (ext):

The most important factor that has substantially affected the change of the ecological characteristics of the Srebarna Lake and the areas that surround it was the building of dikes parallel to the riverbank in order to protect arable land from flooding as well as to reclaim new land for agriculture. The dike Vetren – Silistra was erected in 1948 and has served since to really protect several thousand ha of arable land and riverside marshes from flooding. Erection of dikes has caused the following adverse factors to affect the reserve natural character (ex; ext):

The increased eutrophication leads to hypoxia, anoxia, and changes in the living communities of the lake and destruction of the food web. Changes to the latter are responsible for a large part of the aquatic birds to abandon the reserve (ex; int).

The lake siltation is an outcome of the west bank soil erosion as well as of the increased productivity of the reed beds and the phytoplankton (ex; int).

The change of the Danube water conditions with the dam Zhelezni Vrata (Iron Gates) getting under construction and the natural process of lowering the river erosion basis have diminished the opportunities of the river water to enter the reserve at high water levels in the Danube (ex; ext).

The changes of the global climate leading to Europe's climate becoming drier (the last drought was in the period 1982 through 1994) which in turn has led to worsening of the water conditions and to lower water levels (ex; ext).

Polluting the reserve with nutrients and pesticides from diffuse sources within its water catchment area (ex, pt; ext), with nutrients and raw organic matter from a pig-fattening farm near the rivulet Kalnezha (ex; ext), with nutrients - NOx, SO2, NH3, etc. - through precipitation from the atmosphere (ex, pt; ext), with nutrients, heavy metals, pesticides, PCB, hydrocarbons with water flowing in from the Danube.

Changes in the ecology of the Srebarna Lake in the past were also due to the extensive use of fertilizer and pesticides in the crop fields around the reserve. At present almost no agricultural chemicals are in use (ex; pt; ext).

There also exists the danger of accidental discharge in the Danube of persistent compounds like heavy metals, chlorinated compounds, PCB, oil derivatives, etc. The same follows accidental releases in the atmosphere of H2S, SO2, chlorine derivatives, dioxine, etc. all of which may enter the water catchment area through precipitation (pt, ex; ext).

Another cause for changes in the ecological characteristics of the reserve surroundings was the afforestation of extensive areas using tree species that were either not native for the region like the Austrian (European Black) Pine (Pinus nigra), or were altogether alien species like the Hybrid Poplar (Populus sp. x Populus sp.), Black Locust (Robinia pseudacacia), Common Gloxinia (Gleditschia triacanthos), Oleaster (Eleagnus angustifolia).

Exotic or allochthonous species for the reserve Srebarna and its vicinities are:

A. Plant species:

B. Animal species:

Illegal fishing and taking away of considerable quantities of fish from the lake has the effect of a top predator as regards the trophic network (TN) in the lake with all the consequences for the trophic structure and aquatic birds trophic resources (ex, ext).

Mostly the inhabitants of Srebarna do illegal fishing. It is thought that there are about 20 'professional' poachers in the village who fish every night with fishing nets. Some of the nets are 150 to 200 m long and this is a direct proof that the catch does not go to meeting the family needs. Only in October 1999, in a single round-up, over 250 kg of nets, their length exceeding 4 km, were confiscated. Some of the illegal fishermen also use fykes but not so frequently. There is no direct way of measuring the illegal catches but the expert estimates have it about 1 ton per day (20 poachers each one catching 50 kg on the average). The most numerous fish in the catches is the Crucian Carp (Carassius carassius) followed by the Pike (Esox lucius) and other species of fish. During weekends and holidays illegal fishing increases first because the reserve guards have days off and second because there arrive people from Silistra and from other settlements of the region for angling. In winter catching Pikes through holes in the ice cover of the lake is a very popular way of illegal fishing. During high water levels when the lake is connected to the Danube poachers stretch their nets across about 500 m of the water stream entering the lake and catch almost all the fish that otherwise would enter the reserve.

In recent years the human pressure on areas surrounding reserve has diminished considerably. This refers particularly to the areas between the lake and the river proper. One of the possible explanations is the almost triple decrease of the population of the village of Srebarna and probably that of the village of Vetren, too. Illegal fishing however has increased which most likely is due to the continuous impoverishment of the local population and significant increase in the rate of unemployment in Silistra and in the villages around the reserve.

1.23. Conservation measures taken

Thanks to the studies performed by Bulgarian and foreign researchers as far back as at the turn of last century the broad public as well as the government have become aware of the necessity to preserve and protect Srebarna's extraordinary biodiversity as early as in 1940-s. Since that time a series of biodiversity conservation measures have been undertaken. They can be divided roughly in two: measures related to conservation legislation and measures related to restoring the hydraulic connection between the lake and the Danube.

A. Conservation legislation:

B. Attempts at restoring the hydraulic connection of the lake with the Danube:

1.24. Conservation measures proposed but not yet implemented

In 1994 there was a proposal to construct a second canal connecting the Danube and the lake in order to have circulation of the lake water at high water levels in the Danube. However, there are substantial doubts that such a circulation can take place at all.

1.25. Current scientific research and facilities

There is comparatively rich and topical database on the reserve biodiversity although the information, for the most part, is scattered and kept in different institutions: in the Central Laboratory of General Ecology and in other research institutes of the Bulgarian Academy of Sciences, in the Natural History Museum at Srebarna, in the Ministry of Environment and Waters (MoEW), in some conservation NGOs. This Management Plan has amassed and summarized almost all of the available information.

The first written information on Srebarna Lake was published by the Austrian naturalist Eduard Hodek in 1882 (Hodek, E., 1882. Der Wanderer Heim (Beschreibung des Besuches 1880 am Srebarna see). Mitteillingen des Ornithologishe Vereines in Wien, 6, 3: 25-26, 4: 31-34, 5: 58-59). After him Srebarna Lake had also been described in the works of Kalbermatten (1891), Lorenz- Liburnau (1893), Reiser (1894). The first Bulgarian biologist who turned an eye towards the lake was Prof. St. Petkov who published information on some plants from Srebarna in 1911. From 1919 till August of 1940 Srebarna was under Romanian rule and there are no data on the lake with the exception of some oral information given by elderly inhabitants of the villages Srebarna and Tataritza.

In 1950-s research and scientific studies were resumed. It was then that Mrs. Paspaleva-Antonova (1961 a, b) made the detailed study of the reserve birds and Christov (1961) studied the mammalian fauna.

Since 1955 numbers of the Dalmatian Pelican in the breeding colony (App. 13, Fig. 2) has been annually monitored and since 1958 the same monitoring procedures were applied with regard the Cormorants, Spoonbills and Herons, also breeding in colonies.

In 1961, on the initiative of Prof. Georgi Paspalev, a Biological Research Station was set up in Srebarna under the administration of the Institute of Zoology of the Bulgarian Academy of Sciences. The purpose of this Station was to carry out research and monitoring activities on the reserve ecosystems and their components. The Station ceased to exist in 1968. Since 1983 its functions have been assumed by the Research & Co-ordination Centre for Environmental Protection (today the Central Laboratory of General Ecology). Two health institutions of applied research – the Higher Military Medical Institute and the Republican Centre for Research and Control of Epidemic Diseases - started studying Srebarna as a region where rabbit fever occurred.

In 1984 an international symposium on conservation of wetlands was held in Srebarna. All presented papers were published in a separate collection of works under the editorship of the then director of the Centre and some of his assistants (Nedyalkov et al., 1987).

Since 1994 water level of the lake has been regularly monitored. Readings have been taken once a week and an average value for the month entered in the records.

Since 1998 hydrological and hydrobiological monitoring has been regularly performed. Monitoring procedures include taking monthly measurements of the hydrochemical conditions, phytoplankton, zooplankton, zoobenthos, production and reduction of organic matter.

Dr. Gergana Baeva defended her doctor’s degree on the ecology of the reserve vegetation (Baeva, 1988a)

Until 1998 273 research papers, reports, reviews, ecological assessments, etc. have been published on Srebarna Biosphere Reserve.

An Ecological Field Researche Station has been situated on the lake's west shore, very close to the village of Srebarna. The Station is a subdivision of the Central Laboratory of General Ecology of the Bulgarian Academy of Sciences. There is a chemical laboratory, an all-purpose laboratory, a sleeping room and a storage, all premises comprising 60 m2. Research equipment consists of an UV-VIS spectrophotometer, a field multiline pH, oxygen, conductivity and temperature-meter, microscopes and other basic laboratory equipment. Researchers and research students on the lake hydrochemistry, hydrobiology, biodiversity or other fields of ecology may work in the Station.

At present the following research and scientific projects have been executed or are under way in the reserve:

1.26. Current conservation education

Education goals as well as activities for attracting public to Srebarna reserve have several aspects:

A number of Bulgarian and foreign organisations (the Ramsar Convention Bureau, the EUROSITE, BSPB, Le Balkan, the Green Balkans, etc.) helped to carry out projects aimed at broadening public relations by providing funds for several workshops; by updating data base; by organising work camps for cleaning reserve area; by holding photographs and drawings exhibitions and competitions, guessing-what competitions, young scientists meetings, etc. The National Environmental Conservation Fund provided part of the funds necessary to produce folders, posters, a reference book on the reserve, etc.

Since 1973 a Natural History Museum has been opened in the village of Srebarna. In the beginning the Museum was accommodated in an ordinary peasant house in the center of the village but in 1983 a building was erected especially to house the museum. During the period when the reserve was managed by the Municipality of Silistra the Natural History Museum was in charge of organising and carrying out the reserve protection and management. After the reserve was transferred under the Ministry of Environment and Waters (MoEW) subordination, the Museum was relieved from the execution of these duties and at present it has no formal relations to the reserve.

The Museum has a show room, large panoramic windows and a spot for observing the Reserve. The Srebarna Natural History museum has a standard exhibition with stuffed birds displayed in glass cases. It is rather obsolete and fallen behind the modern trends in the museum art. It cannot give a full idea of the reserve's present state. Annually about 15 000 tourists visit the museum, 35% of which are secondary and high school students arriving here on organized tours from their home schools at the beginning and the end of the school year. They spend here about an hour, mainly going over the exhibition. The show room in the Museum building is not used adequately for conservation education and for building conservation awareness in local people and visitors. In 1980-s a remote-observation system was fixed in the Pelicans colony in order to translate direct real-time video-picture of the colony in the museum lobby. This system has been out of order for years.

In the autumn of 1994 a workshop was held on the "Sustainable Land Use and Water Management in the Biosphere Reserve Srebarna Watershed" with local public taking an active part in the event. The education programme main goals were to make local people better understand the necessity to protect underground and surface waters from pollution, to introduce organic farming, to develop environmentally friendly (green) tourism, etc. Events like the latter stimulated local public to get more actively involved in the permanently going campaigns for improving the state of the countryside surrounding reserve, for better servicing the increased flow of tourists, etc. The national and local mass media have been especially active in this field by constantly illuminating the successes achieved and difficulties encountered by the Biosphere Reserve Srebarna.

In the autumn of 1999 a training workshop for the local public was organised and carried in the Reserve Administration facilities. The workshop topic was "Srebarna Biosphere Reserve is a key site in the European Ecological Network". Representatives of MoEW, the Central Laboratory of General Ecology (CLGE), the local NGOs, BirdLife International, journalists, etc. discussed questions relating to NATURA 2000, to the necessity of setting up bilateral and multilateral protected areas along the Lower Danube and the important place Srebarna Reserve occupies in the new European initiatives.

1.27. Current recreation and tourism

Srebarna Biosphere Reserve is perhaps one of the most suitable places for cognitive tourism in the district of Silistra. It offers opportunities for ordinary, hobby-related and rural tourism. Being one of the best known Bulgarian nature reserves, both in-country and abroad it attracts a lot of common people, without any special interests. An additional attraction is the Natural History Museum.

Unfortunately the hotel keeping is not well developed industry for the region. Only the rest-house on the Danube bank in the village of Vetren offers rooms with 70 beds and 3 flats. Half the rooms have en-suite WC and bathroom. The hotel "Kalimanitza" has 7 double-bed rooms and the Hiker's Union facility has 40 beds but conditions there are hardly acceptable. This is the reason why most of the tourist go to Silistra, where there are 4 hotels, for the night, although they can sleep in Vetren, too.

At present there are two recreational sites in the Srebarna Biosphere Reserve vicinity:

  1. The village of Vetren. During the last several years the village (being for quite a time a dying away settlement because of the decreasing population and an economy coming to a standstill) has changed into a summer house area for the well-to-do inhabitants of the town of Silistra - the district center. Not far from the village there is a recreational house of the former Trade Unions. Currently it is rented by a private company and is used as a hotel;
  2. A summer holiday village on the very bank of the Danube just across the western end of the Danube island 'Vetren' known as "the village of Tanasovo". That 'village' consists of about 20 little, ramshackle summer huts, probably all of them illegally erected. In summer, when the water level of the Danube drops significantly, large sand bars form by the Danube islands of Devnya and Vetren just across the fishermen summer village of "Tanasovo". Local people, including visitors from Silistra use these sand bars for beach bathing because they offer best bathing conditions in the whole region.

During the summer season the reserve attracts several categories of tourists:

1.28. Jurisdiction

a) Authority with territorial jurisdiction over the wetland: District of Silistra, Municipality of Silistra

The District is governed by a District Governor appointed by the Central Government. A Mayor and a Municipal Council govern the Municipality, both elected by the local population. The Reserve, being an exclusive state property, is under the jurisdiction of the government (governmental structures).

b) Authority with functional jurisdiction for conservation purposes:

The Ministry of Environment and Waters, Sofia National Nature Protection Service.

1.29. Management Authority

Since it was declared in 1948 till present times the Reserve Srebarna has been run and managed by several differened by their character and competency institutions:

Since 1993 the Reserve has been managed by the Ministry of Environment and Waters. It has appointed a reserve manager and 2 guards. In 1997 a new modern building has been erected for the Reserve Administration subordinated to the Regional Inspectorate of Environment and Waters in the town of Rouse. Here below follows the exact heading and address of the Biosphere Reserve Administration:

Administration of the Biosphere Reserve 'Srebarna", village of Srebarna, District of Silistra.
Manager of the Reserve: Yordan Kutzarov, Srebarna, Silistra Region, Bulgaria
Director of RIEW-Rouse: Dipl. Eng. Todor Moskov, 20 Priduvski Str., 7000 Rouse, Bulgaria.

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For further information about the Ramsar Convention on Wetlands, please contact the Ramsar Convention Bureau, Rue Mauverney 28, CH-1196 Gland, Switzerland (tel +41 22 999 0170, fax +41 22 999 0169, e-mail ramsar@ramsar.org). Posted on this Web site, 11 May 2001, Dwight Peck, Ramsar.

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