Status and Assessment of Bulgarian Fish Resources

Nickolai Kissiov, Petar Kolarov, Tzvetan Dikov, Sonia Zlatanova, Atanas Boyadjiev, and Petar Petrov

Summary

Bulgaria, although relatively deficient in water resources, has sufficient water to support an important fish industry. Fishing as a means of livelihood is developing intensively along the Black Sea coast and the Danube River, and along the valleys of the larger rivers - the Maritsa, Iskar, Vatcha, Mesta, Strouma, Vit, Kamchia, Chaia, Tundzha, and others. Many hydrotechnical projects (large, medium, and small dams) designed to produce energy and/or to provide flood control have been built during the last several decades. These provide good conditions for natural and artificial fish breeding and for relatively intensive fish exploitation. There is a well developed network of specialized fish-farms in which the main species of commercially important fresh water fish in Bulgaria - carp (Hypophthalmichthys molitrix (Val.) and Ctenopharyngodony idella) and trout - are bred and cultivated.

The aim of this report is to describe on the basis of existing information the state of the country's ichthyofauna and to estimate its importance as an economic resource for commercial fishing, fish-farming, and recreational fishing. Estimates of the fish resources of Bulgaria are provided for the Black Sea, the specialized fish farms, the reservoirs, and the Danube and other rivers. The dynamics and present state of fish resources are considered, stressing the trend toward permanent deterioration of water quality and the diminishing of water stocks in the main water basins and watersheds.

Status and Assessment of Fish Resources Along the Bulgarian Black Sea Coast

The specific hydrological and hydrochemical regime of the Black Sea is characterized by a clear stratification with two main layers: (1) a superficial productive layer with oxygen present down to a depth of 140-160 m; and (2) beneath this, to the sea bottom (maximum depth - 2245 m), a zone high in hydrogen sulphide, rendering the waters lifeless. It is a typical example of a land-locked basin that has been intensively influenced by anthropogenic activities over the last 20-25 years. Pollution of the Black Sea with phosphates, nitrates, pesticides, heavy metals, oil, and oil products from the inflowing rivers (83 mil. ton suspensions annually) and from coastal sources, is well documented. As a result of pollution, the processes of eutrophication have advanced quickly; phytoplankton blooms and the accumulation of organic matter in the bottom sediment and in the pelagic zone occur widely. These negative phenomena, and the spread of the abundant ctenophore Mnemia maccradyi (or Mnemiopsis), which was introduced from the northwest Atlantic by ship ballast water in the 1980s, directly and indirectly influence the status and dynamics of the fish resources.

The recorded volumes of commercial catches provide, to a great extent, an accurate sense of the dynamics of the fish populations. In the Bulgarian Black Sea waters, their volumes varied in the period 1959-1992 between 2,900 (1990) and 19,800 (1981) t (Table 1). These figures do not correlate directly to fluctuations in the abundance of resources, since catch volumes are also directly dependant on the market, the development of fishing gear, and other trends in the development of the fishing sector. For example, the development and employment of trawling equipment has had a significant effect on the Bulgarian Black Sea fishery. Pelagic trawls, which increased quickly in the early 1970s, resulted in significant increases in the volume of the catches. Decommissioning the trawlers and selling fewer to foreign companies have had an opposite effect. The trawling fleet was reduced from 20 units in 1988 to 11 units in 1992.

Sprat (Sprattus sprattus)

Sprat is the most abundant commercial fish. It is of boreal origin, with local vertical migrations to the coast. It has a comparatively short lifespan of 4-5 years. Most important are the first two age groups, which usually include 90-92% of the total population. Because sprat spawn in the open sea from October to March, the eggs and larvae are less negatively influenced by Mnemia maccradyi, the biomass of which is very low in the same period. Sprat is caught mainly by trawlers on virtually a year-round basis, as well as by trap nets from April to June. Then, after the spawning period ends, the species enters the coastal waters to feed. The mean size of sprat is 9-10 cm (in length) and 5 g (in weight) (Table 2). In the last 15 years, the mean length appears to have declined.

Table 1. Annual fish catch in the Bulgarian part of the Black Sea during the period 1959-1992

Year Thousands of tons Year Thousands of tons Year Thousands of tons Year Thousands of tons
1959 5.1 1968 3.6 1977 10.1 1985 16.7
1960 8.4 1969 3.6 1978 12.0 1986 12.8
1961 4.3 1970 3.1 1979 15.1 1987 12.0
1962 3.8 1971 3.6 1980 17.9 1988 8.1
1963 3.8 1972 3.9 1981 19.8 1989 8.6
1964 4.5 1973 5.0 1982 17.3 1990 2.9 (est.)
1965 5.5 1974 7.5 1983 13.4 1991 2.7 (est.)
1966 3.4 1975 8.6 1984 15.5 1992 3.9 (est.)
1967 4.4 1976 9.9        

Table 2. Mean measurements of the sprat (Sprattus sprattus)

Absolute length Individual Weight
Year Quarter Average Length (cm) Year Quarter Average Weight (g)
1978-88 I
II
III
IV 		10.20
9.56
9.53
10.12 		1990 I
II
III
IV 		4.90
3.75
4.47
4.25
1989-91 I
II
III
IV

8.85
9.42
8.80
9.07

1991 I
II
III
IV 		3.50
4.52
4.53
4.09
1992 I
II
III
IV 		8.69
8.80
8.73
9.22 		1992 I
II
III
IV 		3.67
4.73
4.05
4.54

The catch of sprat provides some 95% of the total Bulgarian Black Sea catch. The total biomass of the sprat undergoes annual fluctuations depending on the survival of the new generations and the size of the recruitment class. The biomass is assessed by trawler hydroacoustic survey and by analytical methods (mainly VPA, or virtual population analysis). A 1982 instrument assessment determined that the sprat biomass in the western part of the Black Sea was in the range of 170-200,000 tons The assessment along the Bulgarian Black Sea coast was as follows:

Year Thousand Tons
1984 24
1985 69
1986 77
1987 21
1988 74
1990 27

These figures, especially for 1984 and 1987, are considered to be underestimates.

Horse mackerel (Trachurus mediterraneus ponticus)

The horse mackerel is a Mediterranean species that winters in the southwest part of the Black Sea and the Bosphorus pre-strait area. In spring (May) it migrates for feeding and reproduction to the northwest part of the Black Sea. The autumn migration to the wintering areas takes place in September-October. The lifespan is about 10-12 years, though in catches the first four age classes dominate. The average length depends on the volume of the recruitment; the dominant generations in the age composition generally range between 11-15 cm. It is caught by trawler and trap net. The Bulgarian catch, which has ranged between 35 t (1968) and 2200 t (1974), includes only a small part of the stock. The larger part of the catch has been taken by Turkey (up to 65,000 t in 1979) and Russia (up to 22,000 t in 1972). The Romanian catch has reached a maximum of 2,200 tons. Assessments of utilization of the species come close to the values of the optimum allowable yield, corresponding to a total biomass of 100-400,000 tons Due to the seasonal character of the fishery (May-June and September-October) and peculiarities of the spring-autumn migration, Bulgaria utilizes about 1-2% of that stock. Over the last 5 years, the catch has sharply decreased due to the negative influence of Mnemia maccradyi (tons):

1988 1677  
1989 1101  
1990 164  
1991 55 (estimate)
1992 55 (estimate)

Anchovy (Engraulis encrasicholus)

A warm water, highly abundant species, it has a lifespan of 4-5 years and a mean length of 11-13 cm. It winters along the Anatolian coast and in spring (May) migrates to the northern regions of the Black Sea. A relatively small portion of the stock comes to the Bulgarian coast, even in years of high stock. Stock assessments are usually given separately for the two halves of the Black Sea and are determined by information obtained from experimental fishing with pelagic trawls (thousand tons):

West Black Sea: 40-300
East Black Sea: 36-264

In the last 5-6 years, the anchovy stocks have sharply declined, to the point that the species has now almost lost its commercial significance. The causes are the negative influence of Mnemiopsis and over fishing in the Turkish fishery in the winter.

Turbot (Scophthalmus maeoticus)

This carnivorous demersal (near bottom) species has a relatively long life-cycle (12-14 years), an average length of 55-58 cm, and an average weight of 3.7 kg. It migrates vertically in the winter to a depth of 80-90 m (November) and during its reproductive phase to a depth of 10-40 m (May). The Bulgarian annual catch over the last several decades has been as follows (tons):

1925-1934 39
1935-1954 110
1955-1977 294
1978-1980 93

The total biomass of the stock (VPA) ranges between 430 (1977) and 1710 (1962) tons The recruitment of the stock begins to decline if the commercial stock fall below 300 tons Such a decrease was registered in the late 1980s and led to a 5-year fishing moratorium put into effect by Bulgaria, Russia, and Romania. There were indications of a stock recovery in the first two years of the moratorium (1989-1990), but an invasion of Turkish fishing vessels into Bulgarian waters caused heavy damage that has been difficult to overcome. Information from a bottom trawling survey in January 1992 indicated a commercial biomass of 100 tons.

Black Sea shad (Alosa pontica pontica)

A bathypelagic anadromous fish, the Black Sea shad has a 7-year life span, an average length of 24-26 cm, and an average weight of about 220 g. Living in the Black Sea, it enters the Danube for spawning (April-May). The 3-4 age groups dominate. The Bulgarian annual catch from the Black Sea are in the range of 6-440 t and are determined by the fluctuations in abundance and by hydrometeorological conditions in April-May. The biomass of the species ranges between 1.8-11,000 tons (VPA). The main share of the catch is caught by Romania and Russia in the mouth of the Danube. In the last 5 years the stock has declined due to river pollution and the construction of dams and other hydrotechnical structures.

Pontic whiting (Odontogadus merlangus euxinus)

A boreal demersal species with a lifespan of 6-8 years, mean length of 16 cm, and mean weight of 25-30 g. It is an important link between benthic fauna and the larger predators. It has been only partially exploited as there is no tradition of marketing it. In the last 10 years the catch has reached 10-12,000 t, mainly by Russia and to a degree Romania. In the 1980s, the stock for the whole basin was assessed at 30-35,000 t, with 3-4,000 tons on the Bulgarian shelf.

Picked dogfish (Squalus acanthias)

Dogfish grow up to 150 cm in length and 3-7 kg in weight over a lifespan that reaches up to 20 years. The catches are taken primarily by trawl and bottom long-lines. There is no basis for a real assessment of the stock, though the catches in recent years have increased due to the market demand: 3-4,000 t for the basin as a whole and approximately 100-200 t for the Bulgarian shelf.

Gobies (Family Gobiidae)

The species of this family are not dominant in the annual catch. Annual changes of the latter are as follows (tons):

1940-1960 90-180
1961-1990 24-90

These figures reflect the substantial reduction of gobie populations in the coastal lakes. Until 1960, the catches in the Bourgas Lake were in the range of 30-115 tons per year. The situation was similar at Varna Lake, which was subsequently influenced by increases in pollution and salinity after the second canal between the sea and the lake was built.

In the sea the dominant species are Neogobius melanostomus and Mesogobius batracnocephalus (their local names are "strongil" and "lihnus"), which are caught by both commercial and recreational fishers. Approximately 80% of the sea catch (up to 30-40 tons annually) consists of strongil, a continuous-spawning species with a long reproductive cycle. Since 1990, a prohibition on spring fishing of gobies (45 days during their reproductive season) has been put into force. Assessments of the stocks (there are 21 species in the Bulgarian waters) have not been conducted. Recently, eutrophication and oxygen deficiency have continuously diminished the stocks of gobies. Other species important for the fishery are the mullets (Mugilidae), blue fish (Pomatomus saltatrix), silverside smelt (Atherina mochon pontica), and other fish of secondary importance. Bonito (Sarda sarda) and mackerel (Scomber scombrus), of utmost significance in the early 1970s, are now rarely caught.

The summarized data demonstrate that, since 1985, sprat has been the most important species for the Bulgarian fishery, accounting for up to 95% of the commercial catch. The Bulgarian catch also includes horse mackerel and Black Sea shad (about 2.5-3.0%) and other minor species. As a basis for comparison, the following are data for the species composition in the commercial fishery in the period 1931-1971 (the "clean sea" period)(%):

sprat 10.7-57.0
bonito 1.0-32.9
mackerel 10.4-27.3
horse mackerel 10.0-17.3

The differences are considerable and illustrate the substantial changes in the composition of catches, caused mainly by the eutrophication of the Black Sea.

In addition to national legislation, the Black Sea fishery is regulated by the International Commission for the Application of the Agreement for Fishing in the Black Sea, in which Bulgaria, Romania, and the Black Sea countries of the former Soviet Union participate. Every two years the Commission holds its meeting. It sets no quota limitations, but determines regulations for minimum allowable fish size for fishing of each commercial species, for bycatching at non-standard lengths, for minimum mesh size, etc. For the period 1 January 1989 to 31 December 1993, a moratorium on turbot fishing was established. The political changes in the Eastern European countries disrupted the functions of the Commission, and it now serves mainly as a means of exchanging fishery and scientific information. At present Bulgaria is trying to reestablish the previous relations so that a new text of the Convention can be elaborated. Turkey has been continuously invited to join the Commission and is expected to do so.

Bulgaria has taken measures to restrict the harmful effects of certain fishing activities on the fish resources and on marine ecosystems in general. In 1991, for the first time, a prohibition was put into place related to the use of bottom trawlers. In previous years trawlers caused irreversible damage not only to the fish stock but to the whole benthic biocoenosis. In 1992 all types of trawler fishing were forbidden within the 3-mile coastal zone along the north part of the Bulgarian coast and in the 1-mile zone south from Cape Emine. Authorities are expected to adopt other regulations for the protection of fish resources, and to carry out activities to compensate for the decrease in fish stocks by stimulating the development of mariculture. In general, the main issue in the protection and recovery of the Black Sea fishery resources remains protection of the marine environment from further pollution and the adoption of measures to improve the ecological state of the whole watershed basin.

Status and Assessment of Mariculture and Aquaculture Resources Along the Black Sea Coast

Along the Bulgarian Black Sea coast mariculture is still in a premature state of development. The Institute of Fish Resources at Varna and the Fisheries Institute at Bourgas planned and implemented biotechnologies (involving two options - with and without net sleeves) for the cultivation and processing, at sea and ashore, of mussels (Mytilus galloprovincialis Lmk). Two mussel farms were built: at Sozopol (IRP-25; planned annual production capacity 200-300 t live weight) and at Nessebar (the Black Sea Fishing Co. Ltd; planned annual capacity 300-400 t). Both farms are being used far below their actual potential.

In the 1970s the Fisheries Institute at Bourgas experimented with cage cultivation of steelhead trout (Salmo gairdneri) and kisutch (Oncorhynchus kisutch) at Sozopol. In the Experimental Station at Pomorie, the Fisheries Institute carried out research and development on hibernation (in a greenhouse) and fattening (in the Pomorie Lagoon from spring-autumn) of mullet fry (1+), capturing the 1-year fish in autumn (annual harvest 10-20 t; dominant species Mugil saliens and M. cephalus). In addition, the Experimental Station at Pomorie conducted tests on the propagation of Black Sea shrimp (Palaemon adspersus) and Black Sea flounder (Platychtys flesus). Phytoplankton and zooplankton were used for feed. In 1992, due to deficient state investments, research at the Pomorie Station ceased.

Private companies are interested in the development of commercial mussel culture. Mussels (Mytilus gallo-provincialis Lmk) are still the main species of interest to emerging farmers. In this respect, bi- and polyculture with algae or fish are also a tempting subject of research and development. Also worthy of attention are the combination of traditional fishing (trap nets, recreational fishing) and mussel culture, and the establishment and exploitation of artificial reefs.

Private companies are also interested in commercial cultivation of salmonid species such as Salmo salar, S. gairdneri, and O. kisutch. However, numerous problems - financing, legal aspects (e.g., permission for sea concessions), the environmental effects of introduced species, other risks from introductions, etc. - are still under discus-sion and remain to be solved. Turbot (Scophthalmus maeoticus) is also of utmost interest as a potential candidate for cultivation due to its high marketing demand and the damage that natural stocks have suffered. In 1991 Bulgaria joined the Mediterranean Regional Aquaculture Project (MEDRAP II) of the UNDP/FAO. The main activity of the project is to form networks for information, training, and research on aquaculture and the environment. The Fisheries Institute at Bourgas is the National Coordinator of MEDRAP. However, for Bulgaria to participate effectively in MEDRAP II, a number of organizational, technical, and financial problems need to be overcome.

Though promising results have been achieved and private mariculture initiatives have expanded, aqua/ mariculture development in Bulgaria is still influenced primarily by the general socioeconomic development of the country in the context of integrated coastal activities. Mariculture is a means for recovering and augmenting the fishery resources and for employing the coastal population through better use of the fish processing capacities that are available but currently under exploited. The mariculture facilities of Bulgaria that have already been established could serve as a stable, promising prerequisite for developing mariculture along the coast. The capacities and facilities of the IRP-25 (the former Fisheries Institute) include:

The Mussel Culture Farm at Sozopol (IRP-25 Co. Ltd., Bourgas, Bulgaria; the former Fisheries Institute)

The Mariculture Experimentation Station at Pomorie (IRP-25 Co. Ltd., Bourgas, Bulgaria; the former Fisheries Institute)

Status and Assessment of Reservoir, Specialized Fish Farm, and Danube River Resources

Bulgaria's water resources are relatively scarce, though in terms of area, the potential of the fresh waters is considerable. Their cadastral area is approximately 700 mil. m2; 300 mil. m2 of artificial water basins are in good condition for commercial fish exploitation, with natural and artificial breeding for industrial and recreational fishing. The area of specialized fish farms is approximately 37 mil. m2, with ponds for artificial breeding and rearing of freshwater fish. Good conditions exist for semi-intensive fish farming in some reservoirs - for artificial propagation, raising, fattening, and catching of valuable fish species. In some reservoirs, fish species have been introduced for commercial fishing and for specialized fish farms. These operations are still state or limited-ownership companies with state property. The decisions affecting privatization of the fish culture sector are still pending. Most reservoirs are not suitable for commercial fishery since they lack technical equipment. Those reservoirs are used for recreational fishing and their fish resources reproduce naturally. A few are artificially stocked from time to time.

The reservoirs that support fishing activity have various hydrographic, hydrochemical, hydrobiological, and fish farming peculiarities. They vary in area and volume and occupy different climatic zones. The forms of fish exploitation on them differ as well.

The share of reservoirs larger than 5 mil. m2 is the largest. These are classified as large reservoirs - 61.3% of the total reservoir area of the country. The average-sized reservoirs have an area of 2-5 mil. m2; their share of the total is 9.5%. Reservoirs smaller than 2 mil. m2 comprise 28.2% of the total dam lake area. Reservoirs suitable for intensive fishery activity include 37.6% of the total in the country. The remaining part of the reservoir potential is used for energy production, water supply, irrigation farming, hydromelioration, commercial and recreational fishery, and other activities.

In 1989, 12,455 t of fish were caught in these waters. The Danube catch added 360 tons The most important species were: carp (8011 tons; 64.36%); phytophages, mainly Hypophthalmichthys molitrix (Val) (2815 tons; 22.60%); trout (1099 tons; 8.82%); and other species (530 tons; 4.26%).

In the Danube catches, the following species were dominant: carp (Hypophthalmichthys molitrix), perch Carassius carassius (L.), Abramis brama L., Scardinius erythrophthalmus, the Danube barbel, and chub. Catches of sheetfish and sturgeons have declined. In the 1940s the Danube catch was several times larger; even in the 1950s and some later years the catch exceeded 1500 tons Several factors have contributed to the sharp decline of the fish stock and catch, including industrial pollution, sewage pollution, and destruction of the wetlands along the Danube (the last being sources for good catches and areas for natural fish reproduction and recruitment for the fish stock of the river. A large portion of the natural fish spawning areas have been destroyed. Commercial construction (especially hydrotechnical developments) along the riverbanks took away sand and other material from the river bottom, disturbing natural migration routes. Sturgeon (Fam. Acipenseridae) migrating from the Black Sea to breed in the Danube were heavily affected, as was the Black Sea shad (Alosa pontica pontica, also called "karagyoz").

As a result of the socioeconomic and political changes in the country after 1989, and in particular the disturbance of agricultural activity, production of fry and fingerlings and of fish for human consumption has sharply decreased. Last year fish production was 6-8000 tons A precise figure cannot be given, since the system for collecting statistical information has been disrupted. At the same time, production expenditures have quickly increased (i.e., prices of fodder, electricity, water, pharmaceuticals, etc.) and the market demand for fish has decreased. There are a number of difficult questions concerning the ownership and management of the fish ponds, the restoration of private land ownership, and the shift to a market economy that affect the processes of privatization in this sector.

The serious decrease in production of fry and fingerlings of basic commercial fish species also involves other factors: the labor-intensive nature of the operations, high risk factors (e.g., the water supply problem), quality demands, the heavy losses caused by the abundant fish-eating bird Phalacrocorax carbo (L. 1758). The status and potential (i.e., the availability of suitable fresh waters for propagation and cultivation) of the freshwater fish in Bulgaria are illustrated in the Tables 3, 4, and 5.

The present situation in the country is not favorable for building new fish farms. Fish production would considerably increase if better use were made of existing fish ponds and reservoir waters. The potential for developing existing resources is demonstrated by the following assessments:

a) The existing 37 mil. m2 of pond fish farms (average production 0.15-0.17 kg/m) could produce 5500-6000 t, and better management could produce more than 0.20 kg/m.

b) Small and average-sized reservoirs, with a total area of approximately 115 mil. m2 and an average production of 0.075-0.085 kg/m, could produce a total of 8500-10,000 tons of fish.

c) Larger reservoirs, with a total area of 190 mil. m2, could produce an average of 0.0065-0.0085 kg/m and 1250-1700 tons.

Under optimal conditions, then, the fresh waters of Bulgaria could potentially produce 15000-18000 tons Such quantities could satisfy consumer demand for freshwater fish while producing a share for export to the European market. Bulgarian trout is well appreciated in some Euro-pean countries and can compete in quality with the fish of many other countries. Carp is exported mainly to Greece, where the demand is higher than in other European countries.

To satisfy the need for freshwater farming production, 40-46 million fry and fingerlings are required. They could be obtained from the hatcheries, ponds, and fish farms of the country. In some of the large dams, fish cultivation in net cages could be carried out, although a lot of machinery is required to use this method. The quality of the pellet fodder remains one of the important issues in freshwater fish production. Bulgaria does not produce fodder of the required quality, and the high price of imported fodder is a barrier to the expansion of commercial farming activities.

Table 3. Specialized basin fisheries (fishbreeding basins/thousands of square meters)

District Total Including
Carp Trout
1. Bourgas 2,455 2,440 15
2. Haskovo 3,132 3,130 2
3. Plovdiv 6,746 6,530 216
4. Sofia 2,921 2,800 121
5. Varna 1,173 1,165 8
6. Lovech 7,269 7,240 29
7. Montana 2,855 2,825 30
8. Razgrad 10,855 10,855 -
Total 37,406 36,985 421

Table 4. Available water reservoir fund used for fishbreeding and fishing of freshwater fish - usable surface area of reservoirs (millions of square meters)

District Total Including
Small Medium Large
1. Bourgas 50.9 14.3 - 36.6
2. Haskovo 51.4 6.7 - 44.7
3. Plovdiv 43.4 13.9 4.6 24.9
4. Sofia 17.4 8.5 4.0 8.5
5. Varna 56.5 6.5 3.6 46.4
6. Lovech 38.3 12.2 8.9 17.2
7. Montana 31.6 15.7 3.3 12.6
8. Razgrad 16.5 11.7 4.8 -
Total 306.0 85.9 29.2 190.9

Table 5. Freshwater fish production in Bulgaria during 1989 (in tons)

District Total Including by species:
Carp Herbivorous Trout Other
1. Bourgas 2486 1792 432 112 150
2. Haskovo 1611 1331 250 - 30
3. Plovdiv 2850 1648 602 608 92
4. Sofia 812 316 209 254 33
5. Varna 283 156 80 - 47
6. Lovech 1674 1048 418 125 83
7. Montana 806 473 317 - 16
8. Razgrad 1833 1247 507 - 79
Total 12455 8011 2815 1099 5.30
Percent (%) 100.00 64.32 22.60 8.82 4.26

Status and Assessment of the River Fish Resources

The fish resources of the rivers in Bulgaria are of interest primarily for recreation. Some of the larger rivers - the Maritsa, Tundzha, Iskar, and Kamchia - supported commercial fisheries up until World War II. Commercial fishing then moved to the coastal fish populations, and the fish resources of the rivers are no longer of commercially significance.

Trout occupy the most important place among the river fish (Salmo trutta morpha fario, Salmo irideus Gbb.). They are found in the "trout zone" of the rivers over 800 m above sea level, where the average slope of the riverbed is over 28%. The findings presented below were obtained through an ichthyological survey of 26 rivers (Table 6). The ichthyologic material was collected according to methods described by Mahon et al. (1979), Penezak (1981), Penezak et al. (1981, 1982, 1984), Lobon-Cervia and Penezak (1984), and Zalewski (1983). The abundance was determined in accordance with the methods of Zipin (1956, 1958), Seber and Le Cren (1967), and Seber and Whole (1970). The biomass estimate was arrived at through the application of the formula of Mahon et al. (1978).

The beds of the rivers in these studies consist mainly of gravel and stones. The rivers are approximately 10-40 cm deep, reaching 60-80 cm in pools. The riverbanks are covered with coniferous and mixed forests and deciduous shrubs. In general, there are no large water plants.

Table 6. Mean numbers and biomass of river trout (Salmo trutta fario L.) in the major water basins

Water basin of river Rivers where sport fishing is permitted Rivers where sport fishing is banned
Numbers/ha Biomass (kg/ha) Numbers/ha Biomass (kg/ha)
1. Vucha 831 72.527 3051 185.738
2. Chaya 270 28.167 1185 70.980
3. Mesta 1382 56.236 2290 91.211
4. Strouma 981 34.737 1490 41.297
5. Vit 1180 40.465 2413 89.280
6. Iskar 199 7.617 463 14.537
Total 807 39.958 1815 82.174

The oxygen content of the water is usually over 8 mg/l; pH is 6.8-7.4; total hardness is 1.53-6.30 German degrees; oxidation is 1.8-2.5 mg/l. The mean annual temperature of the water is 4-8°C. With few exceptions, trout is the sole fish species living in rivers in these zones. In some of the rivers under investigation, individual specimens of the mountain barbel (Barbus meridionalis petenyi Henkel), leshanka (Phoxinus phoxinus L.), and glavoch (Cottus gobio L.) could be caught, but they are very scarce and do not influence the trout populations. There is little or no industrial or sewage pollution in the trout zone.

The state of the stock depends primarily on the recreational fishery. The populations investigated in most of the rivers are natural and self-reproducing. The influence of artificial breeding is very small and is felt mainly in limited parts of the rivers. In many river sections, the conditions for natural reproduction, conservation, and recovery of the populations remain good. Table 6 illustrates that the abundance and biomass of trout in the rivers where recreational fishing is permitted are about half that of the rivers where fishing is prohibited. An indirect conclusion can be made that the fishery rivers can potentially accommodate at least twice as many fish, but that their complete exploitation will damage natural reproduction; fish populations would have to be artificially cultivated to allow them to increase in abundance up to the optimum.

In addition to trout, many other native species live in the Bulgarian rivers. Dominant species include chub, mountain barbel, Maritsa barbel, and Krim barbel.

The abundance and biomass of the ichthyofauna in the Bulgarian rivers (3 main fishing areas) are shown in Table 7.

The share (%) of valuable species in the rivers (3 fishing areas) also is presented in Table 7.

The abundance and biomass of the dominant valuable species living in those fishing areas are shown in Table 8.

Table 7. Abundance (#/ha) and biomass (kg/ha) of ichthyofauna and percentage of abundance and biomass represented by valuable fish species in the internal rivers of the three major water basins

Water basin Abundance
(#/ha) 		Biomass
(kg/ha) 		% represented by valuable species
Abundance Biomass
1. River Danube 33,000 295 61 75
2. Black Sea 78,250 271 19 55
3. Aegean Sea 1,344 139 49 80

Table 8. Abundance (#/ha) and biomass (kg/ha) of dominant valuable species in the internal rivers of the three major water basins

Water basin River mullet
(Leucicus oephalus)		 Black barbel
(Barbus meridionalis petenyl)		 Maritea barbel
(Barbus cyclolepia)		 Crimean barbel
(Barbus tauricus)
Abundance / Biomass
1. River Danube 4,600/77 6,830/96 - -
2. Black Sea 79,700/125 - - 4,020/13
3. Aegean Sea 1,780/51 - 3,280/67 -

Table 9. Abundance (#/ha) and biomass (kg/ha) of ichthyofauna and percentage of abundance and biomass represented by valuable fish species in the internal rivers of Bulgaria

River Abundance
(#/ha) 		Biomass
(kg/ha) 		% represented by valuable species:
Abundance Biomass
1. Mesta 6,640 142 40.28 83.42
2. Strouma 24,904 278 61.50 82.78
3. Arda 8,785 117 45.52 73.00
4. Vit 26,724 258 68.00 88.00
5. Palakaria 39,288 332 51.00 65.00
6. Zlatna Panega 2,339 50 63.49 72.38
7. Fakiyska 51,057 223 20.38 55.16
8. Sredetska 157,537 392 17.12 45.20

The abundance and biomass of the fish populations in some of the major Bulgarian rivers are indicated in Table 9.

Table 10 shows the abundance and biomass of the dominant fish species in the same rivers.

(Note: in Tables 8 and 10 the abundance (individuals/ha) is indicated in the numerator, and biomass (kg/ha) in the denominator).

It must be stressed that the Zlatna Panega River is heavily polluted along its whole length. The Strouma River is contaminated in different parts of its course; along 60 km there are no fish. The Vit River, in the sector below Pleven, has no fish for 70 km. Such is also the state of the Sredetzka River below the town of Grudovo (Sredetz).

Conclusion

As a conclusion to this report it should be pointed out that there is no complete, well defined, and precise evidence about the present state of the fish resources of the freshwater basins and along the Bulgarian Black Sea coast. This is due to the lack of systematic, coordinated research about the status and dynamics of the ichthyofauna as a resource. Much systematic research is carried out by the Institute of Fish Resources at Varna (for the Black Sea), the former Fisheries Institute (now IRP-25 Co. Ltd, for mariculture), the Institute of Freshwater Fish Culture at Plovdiv (mainly regarding freshwater commercial culture, including state fish farms), and certain centers for applied research within the Council of Hunters and Fishermen (regarding water basins for recreational fishing, mainly rivers and reservoirs). Some scientific data are also available through the Institute of Zoology and the Institute of Oceanography of the Bulgarian Academy of Sciences and the Biological Faculty of the University of Sofia, though their research is more biologically than resource (i.e., stock) oriented.

Table 10. Abundance (#/ha) and biomass (kg/ha) of dominant valuable species in the internal rivers of Bulgaria

River River mullet
(Leucicus oephalus)		 Black barbel
(Barbus meridionalis petenyl)		 Maritea barbel
(Barbus cyclolepia)		 Crimean barbel
(Barbus tauricus)
Abundance / Biomass
1. Mesta 690/79 - 2,290/66 -
2. Strouma 4,055/63 - 3,900/61 -
3. Arda 590/12 - 3,640/75 -
4. Vit 2,660/56 12,670/156 - -
5. Palakaria 11,000/154 6,665/96 - -
6. Zlatna Panega 150/20 1,160/37 - -
7. Fakiyska 9,400/98 - - 1,540/12
8. Sredetska 15,000/153 - - 6,500/14

The main problem is a lack of linkages and a coordinating unit to harmonize the efforts of the many highly specialized and competent scientists, to stimulate and encourage their activities, and to summarize scientific results in a useful and applicable form for commercial conclusions and recommendations. This need is even more urgent now than in the past, due to the long-term effects on fishing and fish culture of the former state monopoly, which caused heavy exploitation of the resources while not caring about their protection, reproduction, and recovery.

Despite the high levels of pollution found in most water basins of Bulgaria, the freshwaters provide large volumes of food with high nutritive, dietary, and pharmaceutical value. The society and the state need to pay attention to the potential noted above, and to create favorable conditions for the development, reproduction, recovery, augmentation, and rational exploitation of the fish resources of Bulgaria.

Recommendations

As a result of the analysis in this report it can be concluded that the state of Bulgarian fishery resources is critical (unsafe), and that serious measures are required to improve their natural and artificial rearing, conservation, and monitoring. On this basis, some recommendations can be identified, the accomplishment of which will contribute to the reinforcement of the resource base as a whole and to improvements in the present state of fish resources as well.

1. Improve the laws and other legislative acts affecting the fisheries in order to retain the fish resources:

1.1. Elaborate a new Fishery Law and convey it to the Prime Ministry (Cabinet Council) and also to the Parliament by the end of 1993.

1.2. Improve the operating laws and other legislative acts for commercial utilization, protection, reproduction, and control of fish resources through statements of the Cabinet Council and the other responsible institutions by the end of 1993.

1.3. Prohibit all types and kinds of trawling and dragged fishing equipment and installations in the 3-mile coastal zone of the Black Sea to avoid disturbance of the sea-bottom benthic biocoenses at the productive depths.

1.4. Prohibit in stages all types of fishing activity in individual sections of the rivers and at the same time take measures to improve the conditions of natural fish reproduction, artificial fish rearing, protection, and control.

1.5. Introduce a system of licenses for persons engaged in commercial fishing on the Black Sea, the Danube, and inland water basins.

1.6. Prepare quota limitations for the commercial fishery and a system to enforce them.

1.7. Pursue international agreements for fishing on the Danube and Black Sea by attracting the attention of Bulgarian and international non-governmental organizations. Re-examine the Agreement for the Fishery in the Black Sea and involve all the Black Sea countries in it.

2. Other measures and actions connected with the protection and reproduction of fish resources:

2.1. Stimulate development of mariculture along the Black Sea coast by creating and building up installations for the rearing of mussels, mullets, salmon, and other species.

2.2. Stimulate private fish farming during the privatization process by creating private and cooperative fish farms, and effective exploitation of the reservoir waters for fish production.

2.3. Conduct an inventory and classification of the freshwater resources suitable for fish farm exploitation (for commercial and recreational fishing and for fish-farming). Each water basin should be divided into commercial and recreational fishing zones, and zones should also be established to protect fish reproduction through legislative regulation of their utilization, management, and conservation.

2.4. Create a register of all permanent fishing grounds along the Black Sea coast and the Danube, and provide for their rational exploitation through regulation, legal protection, conservation, and control.

2.5. Stimulate selection activities (genetic breeding) in fish farms, to ensure that all fish producers receive acceptable fry and fingerlings.

2.6. Exploit all possibilities for the acclimatization of some new fish species to the Bulgarian climate, and determine the suitability of corresponding water basins, with the aim of increasing fish production, diversifying the assortment of fish in the country, and achieving positive ecological effects.

2.7. Carry out activities to limit the harmful effects of the invasive Mnemiopsis ctenophore on Black Sea resources.

2.8. Take measures to re-establish procedures for gathering fishery statistics, with a view toward ensuring full and exact information on the state of the fish resources by species and their present degree of commercial exploitation.

Bibliography

Boyadjiev At. and P. Petrov, 1964. Regarding the issue about introduction of complementary valuable fish species into carp farms. Ribno stopanstvo, No. 8-9, 11-13. (in Bulgarian).

Boyadjiev A. and P. Petrov, 1972. Ergebnisse der kombinierten Aufzucht von Karpfen (Cyprinus carpoi L.) mit zwei und dreisomerigen Amurkarpfen (Ctenopharingodon idella Val.) Zeitschrift fur die Binnenfischerei der DDR, 9, 274-283. (in Deutsch).

Boyadjiev At.and Gr. Grozev, 1972. Cultivation of complementary fish in carp farms. Izv. CNIRPD, Commercial Fish Farm Station, Plovdiv, vol. IX, 3-13. (in Bulgarian).

Boyadjiev At. and P. Petrov, 1972. Trial to harmonize feeding with growth rate of carp. Izv. CNIRPD, Comm. Fish Culture Station, Plovdiv, vol. IX, 25-34. (in Bulgarian).

Boyadjiev At. and P. Petrov, 1977. Trial to define optimum density of silver carp in carp polyculture. Izv. IRP, Freshwater Culture Station, Plovdiv, vol. XII, 115-138. (in Bulgarian).

Boyadjiev At. and P. Petrov, 1977. Experimentation of methodology for carp cultivation in larger density of polyculture. Izv. IRP, Fresh Water Culture Station, Plovdiv, vol. XII, 139-152. (in Bulgarian).

Boyadjiev At., 1977. Regarding certain issues of fish fry production. Ribno Stopanstvo, No. 8.

Boyadjiev At., 1983. First results of breeding and cultivation of bufalo in Bulgaria. Izv. ISR, Plovdiv, vol. XII (Jubilee Volume). (in Bulgarian).

Georgiev Z. and P. Kolarov, 1962. On the migrations and distribution of the horse mackerel (Trachurus mediterraneus ponticus) in the western half of the Black Sea. Izv. IRR, Varna, 2, 147-172. (in Bulgarian).

Grozev Gr. and At. Boyadjiev, 1970. How to raise 1+ phytophague carps. Ribno Stopanstvo, 7, 4-5. (in Bulgarian).

Grozev Gr. and At. Boyadjiev, 1971. Reproduction and cultivation of phytophages (Ctenopharingodon idella Val., Hypophthalmichtys molitrix Val., Aristichthys nobilis Rich) in the climatic environment of Bulgaria. Proceedings of the XIII meeting of the Danube Fishing Commission, Beograd. (in Russian).

Grozev Gr. and At. Boyadjiev, 1972. Cultivation of phytophague carps up to 1+. Izv. CNIRPD, Comm. Fish Culture Station, Plovdiv, vol. IX, 15-22. (in Bulgarian).

Grozev Gr.and At. Boyadjiev, P. Nachev, 1969. Results of phytophague carps reproduction in Bulgaria. Ribno Stop., No. 6, 7-9. (in Bulgarian).

Ivanov L., 1964. Dynamics of the Black Sea mackerel (Scomber scomber) resources of migrating along the Bulgarian Black Sea coast. Izv. NIRSO, Varna, 5, 65-91. (in Bulgarian).

Ivanov L., 1966. On the biology of the Black Sea mackerel (Scomber scombrus) Izv. NIRSO, Varna, 7, 97-134. (in Bulgarian).

Ivanov L., 1970. An attempt to determine the mortality of the Black Sea mackerel (Scomber scombrus) caused by fishing and natural prerequisites. Izv. NIRSO, Varna, 10, 75-90. (in Bulgarian).

Ivanov L., 1973. On the reproduction od the Black Sea mackerel (Scomber scombrus). Acta Biol. Jugosl. (E Ichthiol.), 5 (1), 35-45. (in Russian).

Ivanov L., 1977. Fluctuations of the catches of bonito in the Black Sea and in the Mediterranean. Ribno Stop., 6, 1-3. (in Bulgarian).

Ivanov L., 1979. Dynamics and rational stock exploitation of natural and artificial reproduced fish population. Dr. Sci. Thesis, 256pp. (in Bulgarian).

Ivanov L., 1979a. Possibilities for substantial increase in the fish catches from the Black Sea. Ribno Stop., 5, 21-23. (in Bulgarian).

Ivanov L., 1979b. Method for retrospective determination of the quantity of the newly and earlier recruitment in the fish populations. Izv. IRR, Varna, 17, 7-15. (in Bulgarian).

Ivanov L., 1979d. Dynamics of the resources of turbot (Scophthalmus maeoticus) of the Bulgarian shelf, and action to be taken for their rational exploitation. 1. Growth and mortality. 2. Resources and reproduction. Hydrobiologia, Sofia, 9, 3-28. (in Bulgarian).

Ivanov L., 1979e. Mise a jour de l'evaluation du stock de turbot (Scophthalmus maeoticus) devant la cote Bulgare de la Mer Noire. FAO Fish. Rep., 226, 7-13.

Ivanov L., 1980. Potential sources of error in applying methods of virtual population analysis to short-life fish of underfished stocks. Proc.IRR, Varna, vol. XVIII, 71-84. (in Bulgarian).

Ivanov L., 1982. Effect of fish weight and recruitment on estimated stocks by using the method of virtual population analysis. Proc. IRR, Varna, vol. XIX, 7-18. (in Bulgarian).

Ivanov L., 1982. Predictable models of catches from artificially reared fish stocks by year-long and density dependant formation of fish populations in undrained water bodies. Proc. IRR., Varna, vol. XIX, 19-34. (in Bulgarian).

Ivanov L., 1983. Population parameters and limiting methods of sprat (Sprattus sprattus L.) catches in the Western Black Sea. Proc. IRR, Varna, vol. XX, 7-46. (in Bulgarian).

Ivanov L., 1989. On the ratio between the catchment, stock and production of the Black Sea (Sprattus sprattus L.). Hydrobiology, Bulg. Acad. Sci., vol. 34, 68-78. (in Bulgarian).

Ivanov L. and M. Karapetkova, 1978. Evaluation des resources en turbot (Scophthalmus maeoticus Pallas) devant la cote bulgare de la Mer Noire et mesures de surveillance. FAO Fish. Rep., 224, 83-104.

Ivanov L. and P. Kolarov, 1979. On the relation between the catches of the Danube shad (Alosa kessleri pontica) and the solar activity. Soc. Intern. Limnol., XIX Jubilaumstangung Donausforsch. Bulg. Akad.Wiss., 389-95. (in Bulgarian).

Ivanov L. and Karapetkova M., 1981. The effect of fishing on the population of the Black Sea turbot (Scophthalmus maeoticus Pallas) of the Bulgarian Black Sea shelf. Hydrobiology, Bulg. Acad. Sci., Sofia, vol. 15, 81-93. (in Bulg).

Ivanov L. and Beverton R., 1985. The fisheries resources of the Mediterranean. Part two: Black Sea Etude Rev. GFCM/ Stud. Rev. GFCM, 60, 135pp. (in English).

Ivanov L. and Mihailov K., 1987. On the relation between catch, stock and production of the Black Sea anchovy (Engraulis encrasicholus ponticus Aleks.). Oceanology, Bulg. Acad.Sci., vol. 20, 16-25. (in Bulgarian).

Karapetkova M., 1980. Dynamics of the stocks of turbot Scophthalmus maeoticus (Pallas) of the Bulgarian shelf. Rh.D. Thesis, 116pp. (in Bulgarian).

Kissiov N., 1979. Basic issues of commercial fishing. Sofia, Techn. Publ. House, 186pp. (in Bulgarian).

Kissiov N., 1979. Geography of the fishing grounds. Sofia, Techn. Publ. House, 85pp.

Kolarov P., 1964. Size and age composition of the bluefish (Pomatomus saltatrix) of the Bulgarian Black Sea coast. Izv. IRR, Varna, 4, 207-220. (in Bulgarian).

Kolarov P., 1964a. Certain peculiarities in the variation of the age composition of the Black Sea herring (Alosa kessleri pontica Eichiv.). Izv. IRR, Varna, 5, 93-116. (in Bulgarian).

Kolarov P., 1978. On certain changes in the population of Alosa kessleri pontica during its migration towards its reproduction areas. Limnology of the Bulgarian sector of the Danube. Sofia, Bulg. Acad. Naukite, 238-249. (in Bulgarian).

Kolarov P., 1982. On the dynamics of the Black Sea shad (Alosa kessleri pontica Eichv.). Proc. Inst. fish, Varma, vol. XIX, 35-57. (in Bulgarian).

Kolarov P., 1985. Biological peculiarities and population dynamics of anadromous fishes. Dr. Sci. Thesis, 419pp. (in Bulgarian).

Konsulov A., 1980. Storm-resistant installation for mussel and oyster cultivation. Izv. IRR, Varna, vol. 18, 113-119. (in Bulgarian).

Konsulova Ts., 1974. First results in trials for mussel cultivation along the Bulgarian Black Sea coast. Izv. NIORS, Varna, vol. 13, 93-105. (in Bulgarian).

Konsulova Ts., 1979. Trials for cultivation of Mytilus galloprovincialis Lam ("long-lines") in the aquatoria of the Bulgarian Black Sea coast. Izv.IRR, Varna, vol. 17, 55-66. (in Bulgarian).

Konsulova Ts., 1979. Growth rate of cultivated mussels (Mytilus galloprovincialis Lam) in the conditions of the Bulgarian Black Sea coast. Ribno Stop., 6, 12-14. (in Bulgarian).

Konsulova Ts., 1981. Growth of cultivated mussels related to attachment density. Ribno Stop., 1981, 14-18. (in Bulgarian).

Marinov B. and At. Boyadjiev, 1970. Nutritive value and orgaloptic peculiarities of grass carp. Izv. Fresh Water Culture Station, Plovdiv, vol. VII, 99-105. (in Bulgarian).

Marinov B. and At. Boyadjiev, 1973. Method for determination of standards for control catches in fish culture. Ribno Stop., 4, 23-25. (in Bulgarian).

Marinov B. and A.Boyadjiev, 1974. Methode fur objective Bestimmung von Kriterien bei Kontrol-fangen in der Fischzucht. Zeitschrift fur die Bin-nenfischerei der DDR, Band XXI, Mai 1974, 5, 137-146.

Moncheva S. and Ts. Konsulova, 1983. Phytoplankton in the nutrition of cultivated mussels in the area of Cape Kaliakra. Izv. IRR, Varna, 145-152. (in Bulgarian).

Popov V. and S. Zlatanova, 1986. Development of mussel culture along the Bulgarian Black Sea coast. FAO Fish Rep (GFCM/FAO Techn. Con-sultation on Open Sea Shellfish Culture), 74-77. (in English).

Prodanov K., 1982. An approximate estimation of the optimum level of exploitation of whiting stock. Proc. Inst. fish, Varna, vol. XIX, 59-65. (in Bul-garian).

Prodanov K.and P. Kolarov, 1983. On the problem of the rational exploitation of fish populations. Proc. Inst. fish, Varna, vol. XX, 47-70. (in Bulgarian).

Prodanov K., 1984. Biology and exploitation parameters of the whiting from the Bulgarian Black Sea coast. Ph.D.Thesis. (in Bulgarian).

Prodanov K., 1986. Condition of Whiting stock of the Western Black Sea area and off the Bulgarian coast in 1976-1982. Hydrobiology Bulg.Acad.Sci., vol.27, 50-55. (in Bulgarian).

Prodanov K., 1991. An attempt for an approximate evaluation of the average stocks of Merlangus euxinus in the western part of the Black Sea during the 1976-1984 period. Hydrobiology, Bulg. Acad. Sci., Sofia, vol. 36, 76-83. (in Bulgarian).

Stamov St. and S. Zlatanova, 1988. Trace elements in Mytilus galloprovincialis Lmk from Sozopol area (Bulgarian Black Sea coast). Rapp. Comm. Int. Mer Medit., (31)2, p. 160.

Stamov St., I. Slavcheva, and S. Zlatanova, 1990. Trace elements in Mytilus galloprovincialis Lmk from Sozopol and Nessebar areas, Bulgaria. Rapp. Comm. Int. Mer Medit., (32)1, p. 56.

Stoyanov S., 1960 The state of the stocks of the anchovy caught along the Bulgarian coast in the period 1945-1950 and 1955-1959. Tr. NIRR, Varna, 3, 63-75. (in Bulgarian).

Stoyanov S., 1963. The state of the stocks of pontic sprat caught along the Bulgarian coast in 1952-1960 Izv., NIRR, 1, 1-58. (in Bulgarian).

Stoyanov S., 1965. Dynamics of the resources of the pontic sprat (Sprattus sprattus sulinus). Izv. NIRSO, Varna, 6, 21-48. (in Bulgarian).

Stoyanov S., 1966. Reproduction and preparation of a resource model of the pontic sprat (Sprattus sprattus sulinus). Izvv. NIRSO, Varna, 7, 135-157. (in Bulgarian).

Stoyanov S., 1975. Long-term trends in the Black Sea catches. Ribno Stop., 7, 17-18. (in Bulgarian).

Stoyanov S., 1980. Stock-recruitment relationships in Black Sea sprat (Sprattus sprattus sulinus Antipa). Comptes rendus l'Acad. Bulg. Sci. (33)8, 1107-1109. (in English).

Stoyanov S., 1980. On the long-term prognosis of Black Seas sprat reproduction. Compte rendu l'Acad. Bul Sci., (33)9, 1223-1225. (in Eng).

Zlatanova S., 1985. Regarding spring-summer spat attachment and options for cultivation of mussels (Mytilus galloprovincialis Lmk.) Hran prom. nauka, 4, 43-51. (in Bulgarian).

Zlatanova S., 1984. Cultivation of mussels without application of net sleeves. Ribno Stopanstvo, 7, 21-23. (in Bulgarian).

Zlatanova S., Iv. Lahnev, and D. Anev, 1986. Biological and technical problems in cultivation of mussels (Mytilus galloprovincialis Lmk.) along the south Bulgarian Black Sea coast. Probleme de Maricultura, Constanta, 47-48. (in Russian).

Zlatanova S. and M. Mihov, 1989. Technological and sanitary problems in commercial mussel culture. Rep.Int. Symp. mariculture, Anapa, 13pp. (in Russian).

Zlatanova S. and K. Prodanov, 1989. Characteristics of growth in different regimes for cultivation of mussels (Mytilus galloprovincalis Lmk), Hran. prom, 8, 19-26. (in Bulgarian).

Zlatanova S. and G. Goergieva, 1990. Mussels (Mytilus galloprovincialis Lmk) as a source of biological active substances. Morski svyat, 2, 12.

Zlatanova S. and V. Petrova-Karadjova, 1988. Monitoring on phytoplankton in mussel culture along the Bulgarian Black Sea coast. Rapp. Comm. Int. Mer Medit., (31)2, p. 223.

Zlatanova S., 1989. Bulgarian open-sea mussel culture. Int. Symp., Kerch, USSR, 5pp. (in English).

Soil Cover, Land Use, and Soil Degradation in Bulgaria

Pencho P. Konishev, Alexander V. Koulikov, and Hachadur D. Tchuldjian

Bulgaria's Soil Cover Structure

Soils are classified and mapped on the basis of a number of properties - the kind, thickness, and arrangement of the soil horizons (or layers), and their color, texture, structure, reaction, consistency, and mineralogical and chemical composition - as well as moisture and temperature regimes. Soils tend to form a continuum on the earth's surface, as one usually grades gradually into others. The boundaries or limits of the range of one kind of soil define that soil. Soils are defined and classified in this way so that we can remember their significant properties, organize our knowledge of them, and show relationships among them and between them and their environment.

The factors influencing soil formation - parent material, biota, climate, topography, - vary in space and over time. At any one moment we observe a complex mosaic of soils on the earth's surface. Interactions among the factors are constrained in space, resulting in intricacies far beyond simple descriptions of cause and effect (Arnold and Wilding, 1991).

The structure of the Bulgaria's soil cover is very complicated. An adequate explanation of its evolution requires an understanding of factors beyond those presently affecting its formation. Current soil formations are the result of natural changes from the Pliocene up to the present, of neotectonic processes, and of human land use practices.

Soils can be grouped in different ways, depending on the soil characteristics used in classifying them and on the scale of the map on which the soil cover is shown.

Eleven orders of soils are designated in the Soil Taxonomy (Soil Survey Staff, 1975). They are believed to include all existing soils of the Earth. Eight soil orders - Alfisols, Aridisols, Entisols, Histosols, Inceptisols, Mollisols, Spodosols, and Vertisols - have been recognized within the relatively small territory of Bulgaria. The variations in soil cover structure are complicated by the spatial variability of today's climatic conditions. Five pedoclimatic regimes are recognized in the country's territory: Frigid-Udic, Mesic-Udic, Mesic-Ustic, Mesic-Xeric, and Thermic-Xeric (Boyadjiev, 1989).

Combinations of the most significant properties of the whole soil and of the soil moisture regimes define 32 great groups of soils (the third level of the Soil Taxonomy) - a sixth of those found in the whole territory of the United States. Ninety subgroups (the fourth level of the Soil Taxonomy) are currently recognized in Bulgaria - about a tenth of those found in the United States.

The soil associations shown in the 1:1,000,000 scale map are composed of several related soil subgroups and similar soil temperature regimes. More than 60 types of soil associations can be shown at this scale. To describe each type of soil association would require more time and space than is possible here; we shall describe only the principal soil cover characteristics of the major physiographic provinces of Bulgaria.

Soil associations 1, 2, 3, 5, 6, 7, 8, 9, 10, 15, 26, 27, and 28 are located in the northern part of the Danubian Plain. Typic and Entic Calcixerolls, Calcic, Typic, and Entic Haploxerolls, Typic and Entic Haplustolls, Typic Argixerolls, and Mollic Haplustalfs are the predominant soils in these associations. They form mainly on loess and loess-like deposits on nearly level to gently sloped areas. Alluvial terraces and bottomlands are occupied by Aquic and Fluvaquentic Haploxerolls and Haplustolls, and Fluva-quentic and Typic Haplaquolls. Mollic Halaquepts and Terric, Sapric-Terric, and Fluvaquentic Medihemists occur on nearly level or depressional parts of the floodplain. Ruptic-Alfic and Rendollic Eutrochrepts, and Typic, Lithic, and Entic Rendolls are formed on clayey residuum weathered from limestone on the low hills in the eastern part of the Danubian Plain.

Soil associations 4, 13, 14, 16, 17, 18, 20, 21, 24, 25, and 29 occupy the southern part of the Danubian Plain and the Ludogorsko Plateau in the eastern part of the Danubian Plain. Vertic, Typic, and Entic Hapludolls, Typic Agriudolls, Typic, Mollic and Albaquic Hapludalfs, and Entic and Typic Chromuderts and Pelluderts are the predominant soils in these associations. These soils are formed on silty and clayey continental deposits on the hilly plain. In the river valleys these soils are found in combination with Aquic, Mollic, or Typic Udifluvents. Dystric, Ruptic-Alfic, and Rendollic Eutrochrepts and Entic, Typic, and Lithic Rendolls are formed in silty and clayey residuum weathered from limestone and siltstone.

Soil associations 11, 12, 19, 30, and 66, including Calcic and Typic Haploxerolls, Typic Calcixerolls, are formed on loess deposits on the Danubian Plain, and Typic Haploxeralfs are formed on clayey continental deposits on the Avren Plateau. Typic, Entic, and Lithic Rendolls are formed in clayey limestone regoliths. The river valleys are occupied by Aquic, Mollic, and Typic Xerofluvents, and sometimes by Mollic Halaquepts. These associations cover the Black Sea coastal plain.

The northern cuesta-like foothills of the Balkan Mountains (Stara Planina) are occupied by soil associations 22, 23, and 31. Lithic, Albaquic, and Aquic Hapludalfs, and Lithic, Dystric, and Ruptic-Alfic Eutrochrepts are the dominant soils in these associations. Typic and Aquic Udifluvents can be found in the river valleys.

Soil associations 32, 33, 34 and 36 occupy the highest parts of the Balkan, Rila, Rhodope, Pirin and other mountains. Lithic, Lithic Ruptic-Alfic, Ruptic- Alfic, and Umbric Dystrocrepts, Entic, Lithic Haplumbrepts, Entic, Lithic and Cryic Rendolls, Entic and Lithic Haplorthods can be found in these mountain regions. Typic and Aquic Udifluvents, and Cumulic and Fluventic Haplumbrepts occur in the river valleys.

Soil associations 37, 38, and 44 occur in the former Pliocene lake basins in the western part of the country. The soil cover of these areas consists of Typic and Entic Chromuderts and Pelluderts, Aquic, Albaquic, Lithic, and Vertic Hapludalfs.

The mountain foothills of the country's southern part are occupied by soil associations 35, 40, 60, 61, and 62, which consist of Typic, Lithic, Ruptic-Alfic, and Rendollic Eutrochrepts, Typic, Vertic, and Lithic Hapludalfs as dominant components, and Typic and Aquic Udifluvents as soils in the river valleys.

Soil associations 39 and 41 occur in the Strouma River valley. The dominant soils of these associations are Typic, Udic, Vertic, and Lithic Haplustalfs in the middle part of valley, and Lithic Haploxeralfs in the southern part of the valley.

The major components of soil associations 47, 48, 49, and 50, which occur in the Thracian Lowland, are Typic and Entic Chromoxererts and Pelloxererts on the flat areas; Vertic, Typic, and Albaquic Haploxeralfs on the nearly level and gently sloped areas; and Typic and Aquic Xero-fluvents, and Fluventic and Fluvaquentic Haploxerolls in the bottomlands. In the central part of the Lowland can be found Aquic and Typic Natrixeralfs and Aeric Halaquepts.

Soil Associations 57, 58, and 59 occur in the basin-and-range structures at the southern foot of the Balkan Mountains. The soil cover of these basins consists of Typic Udifluvets and Ustifluvents, Fluventic Ustochrepts, and Typic and Lithic Haplustalfs in the western basins, and Typic and Aquic Xerofluvents and Aeric Halaquepts in the eastern basins.

Typic, Albaquic, and Lithic Hapludalfs, and Typic, Vertic, and Lithic Haploxeralfs are dominant components of soil associations 46 and 55, which occur in the foot-hills in the northern and eastern parts of the Thracian Lowland.

Soil associations 51, 52, 63, 64, and 65, which occupy both the southern part of the Black Sea coastal plain and the southern part of the Maritsa River valley, have similar soil cover structures. Differentiating these associations is the presence of Aquolic and Typic Salorthids near the salty lakes (lagoons) of the Black Sea beach plain.

The eastern Rhodope and Strandzha Mountains, the Sakhar rolling mountains and hills, and the foothills of these low mountain systems are occupied by soil associa-tions 54, 55, and 67. The dominant soils of these associations are Typic, Vertic, Albaquic, Lithic, and Lithic-Ruptic-Xerochreptic Haploxeralfs, and Lithic, Ruptic-Alfic, and Rendollic Eutrochrepts. Typic and Aquic Xerofluvents and Ustifluvents can be found in the river valleys.

The southeastern part of Strandzha Mountain is covered by soil association 68. The special components of this association are Ultic and Aqultic Haploxeralfs, which correspond closely to peculiarities of the native vegetation in this area.

The highly diverse mosaic of these soil associations in Bulgaria provide the best evidence and basis for understanding the natural development and future conservation of biodiversity and genetic resources. Soils are not simply a rooting medium for plants and a source of bioproduction. The main features of the environments that existed during the formation and subsequent evolution of soils are reflected and recorded in the properties of the current soil cover. Another way of saying this is that soil cover is the product and "memory-bank" of biospheric and lithospheric interactions. In short, soil cover records and remembers human activities on the earth's surface (Arnold et al., 1990).

Land Use and Soil Conservation Problems

This section of our report discusses the main agricultural activities within Bulgaria.

Statistical data and 1990 evaluations show that Bulgaria's total territory of 11.1 million ha is divided among agricultural land (6.85 million ha; 61.6%), woodland (3.85 million ha; 34.7%), and built-up areas (0.4 million ha.; 3.7%). Industrial enterprises, open mines, settlements, infrastructural systems, and other developments occupy 6.6% of the country's total territory. Inland waters, rivers, ravines, and degraded lands cover 1.5%.

The area of cultivated land is 4.6 million ha, or 41.8 % of the country's territory. Pasture land occupies 1.5 million ha (13.7%). The cultivated lands are grouped as follows: cropland - 3.85 million ha (83.1% of the cultivated area); grassland - 0.49 million ha (10.5% of the cultivated area); and vineyards and orchards - 0.3 million ha (just over 6% of the cultivated area).

The largest areas of cultivated land areas are located in northern Bulgaria (59.01%). The area of cultivated land in the Lovech and Varna regions are 0.77 and 0.71 million ha respectively; in the Russe region - 0.65 million ha; and in Montana - 0.65 million ha. The Sofia region, notwithstanding its large total territory, contains the least cultivated land (0.41 million ha).

The area of arable land in 1990 was 217,000 ha below that of 1950, despite the fact that 406,000 ha were added to the arable land fund in the interim. The expan-sion of arable land was due mostly to the plowing of pasture land, deforestation, and drainage of the Danubian floodplain. During the same period, 290,000 ha of arable land were afforested or turned into pastures, 88,200 ha were occupied by reservoirs and canals, and 91,100 ha were disturbed by construction works. A large area of arable land was displaced by open-pit coal mining in the eastern part of the Thracian Lowland, and only 3,160 ha were reclaimed.

Before the land reform measures of 1946 were adopted, most landowners in Bulgaria possessed small-sized properties. Landowners with properties smaller than 10 ha held over 2.9 million ha, or more than 50% of the total agricultural land area. In the 1950s, when the cooperative farms were established, fields were reconstructed to accommodate large-scale cultivation, disturbing the naturally established field boundary strips that delimited the former properties. As a result, the natural habitats of many species were disturbed and the corridors connecting agricultural and forest territories broken. The accelerated specialization and concentration of agricultural production led to a sudden restriction of species diversity in large territories, reducing the stability of the agroecosystems. This led to accelerated soil degradation. Intensive fertilization and the neglect of manures in the agroecosystem increased soil acidification. About 7.5% of the arable land area is highly acidic, and there is proof that the rate of acidification has accelerated.

Soil erosion is the most serious problem in terms of both its significance and its rate. Estimates show that 78.3% of the arable land and 15% of the forest land are highly susceptible to water erosion, and 38.9% to wind erosion. The total average annual soil loss from all types of land use is estimated at 135.9 million tons. Irrigated land requires special measures to reduce erosion rates; 25.3% of the arable lands are under irrigation, and 20% are located on slopes with little or no protection against soil erosion.

Soil conservation practices are not new for agriculture in Bulgaria. From time immemorial, contour cropping and drainage furrowing after sowing have been practiced on sloping lands. There still exist old terraces, reinforced by stone and field boundary strips and overgrown with bushes and trees, in the mountainous and semi-mountainous regions, where grapes and tobacco have been grown over the generations. Afforestation to control soil erosion on eroded slopes and reinforcement projects along the banks of torrential streams date in Bulgaria from the beginning of the 20th century.

When large-scale agriculture was first organized in the late 1940s and 1950s, the field boundary strips were plowed up, most of the trees and bushes uprooted, and large fields for cultivation formed. As a result, water and wind erosion began to do unimpeded damage to agricultural land. This process was accelerated by the communist ideology's philosophical thesis - that land, being a natural resource, cannot be held privately, but only as public property. For the majority of people, this meant that everybody could exploit the land but none were obliged to take care of it.

The effects of that unwise agrarian policy arose soon afterwards. In less than 25 years, about 10% of the arable land eroded completely and became unsuitable for cropping or afforestation. Siltation in the reservoirs occurred at a rate 5-6 times faster than project expectations. Some small ponds built by the cooperative farms completely silted up in 2-3 years. About 20% of field crops were swept away periodically by dust storms. Rainstorms formed deep gullies on sloped lands and muddy torrents destroyed not only the field crops but highways, railroads, bridges, and residential and utility buildings as well.

In the early 1970s, soil erosion was recognized as a national problem of primary significance for the damage it caused to the national economy. Government decrees, seeking to organize a campaign for soil conservation, were issued. The Designing Bureaus, in methodological collaboration with research teams, planned many erosion control projects for separate watersheds and cooperative farm territories: terracing of vineyards and orchards, hydrological and biological reinforcement of torrential streams, construction of pasture complexes, and additional measures to improve and increase soil productivity.

In general, these soil conservation projects were planned with a high level of proficiency. Research information on expected rates of soil loss and the effects of soil conservation measures was used when erosion control projects were designed. However, most of these projects were never completely carried out. The Specialized Enterprises that were supposed to execute the projects preferred to undertake only those erosion control projects that were best funded, or that the cooperative farms preferred.. For example, measures designed to partition and orient large fields according to the local relief in the land - strip cropping, buffer strip cropping, crop rotations, conservation tillage practices - were neglected. The state funds for soil conservation were devoted mainly to hydrotechnical reinforcement of torrential streams, terrace construction, riverbed correction, small dam construction, planting of grasses, afforestation, and improvements of pasture land (fencing, clearing of stones and bushes, the filling of small gullies, ditch construction, sod improvement, fertilization, etc.).

According to a 1987 Agricultural Ministry report, the funds laid out at that time for the National Long- Term Erosion Control Program protected about 20% of the lands exposed to erosion. Though not very high, even that percentage is suspicious because the whole program of erosion prevention was never completely fulfilled. Moreover, erosion control structures, once completed, were not main-tained and began quickly to deteriorate: many terraces have been damaged, water collection ditches have broken, grassed land has not been protected from excessive grazing, and so forth.

As previously mentioned, a large part of the country's best land suffers periodically from wind erosion. The significance of the problem has been established and is generally acknowledged, but nothing has been done to protect soils except to research and design projects. Lately, shelterbelts to protect fields have not been planted due to funding shortages. On irrigated land, lack of interest has been the main factor preventing the application of erosion control tillage, crop rotations, and other agronomic techniques for erosion control (Rousseva et al., 1992).

With the radical changes taking place in the country's economy, it is difficult to predict how soil conservation will progress in the future. It is logical to expect that soil conservation problems will decrease after land reprivatization occurs. It is also logical to hope that these land use changes will have a favorable impact on biodiversity.

Industrial Pollution of Soils

The chronicle of industrial soil pollution begins in the early 1960s, when large-scale industrialization became more evident in Bulgaria. This period saw the construction of plants for ferrous and non-ferrous metallurgy, lignite coal power production, crude oil processing, large-scale chemical synthesis, metal processing, and cement production.

The first signs of environmental disturbance appeared at this time (Raikov, 1984). They became more concretely and dramatically apparent in several locations during the 1970s (MOE, 1991; Raikov et al., 1988; Dilov and Petrov, 1987). However, definite and precise data on these effects were classified as so-called "state secrets" during the 1980s.

A system for routine soil pollution monitoring has now been organized. It is based on a limited number of indicators that describe the typical pollutants emitted within the country's territory. Heavy metal and arsenic emissions from several production activities, fly ash from power plants, and dust from cement production undoubtedly have negative effects on both soil productivity and the quality of agricultural products. Other phenomena being monitored include: secondary soil acidification due to acid precipitation, fluorine dust pollution, secondary soil salinization, and pollution of soils near oil refineries. Acute damage to vegetation shortly after irrigation with waste water containing organic chemicals and acids, and single incidents involving chlorine, sulphur oxides, and nitrogen oxides have been recorded accidentally.

Heavy Metal Pollution of Soils

The soil chemical and agronomic aspects of heavy metal pollution have been studied at some length. The most regularly occurring metals are copper, zinc, lead, and cadmium. Other heavy metals - nickel, chromium, mercury - have been found at significant levels only rarely. Their heavy concentrations are usually related to ore mining or are concomitant emissions of the main pollutant (copper, zinc, and lead).

Almost all heavy metals accumulate primarily in the surface soil layer and slightly in the lower soil horizons. This is due to the high reactibility of humic matter and the clay colloids. This is illustrated by data from Tchuldjian (1989).

Bulgarian soils are low in organic matter and relatively high in clay. Clay minerals are highly reactive with different pollutants, and the heavy metals in particular. Their behavior in the soil is controlled by soil acidity. Consequently, different forms of heavy metals occur according to their availability to plants across the whole range of soils, from slightly alkaline calcareous to strongly acid podzolic soils. Likewise, industrial emissions and deposits range from alkaline to strongly acid. Thus, pyrometallurgical lead-zinc emissions of dust contribute to soil alkalinity. But copper pyrometallurgy emits excessive sulphur oxides that acidify the soil. The most mobile forms of the heavy metals, which retain their toxicity in the soil solution, occur in relatively high concentrations in the acid soils and in lower concentrations in the calcareous soils.

Depth (cm) 0-28 41-51 71-81 94-104 122-132 161-171
Copper (ppm) 456 36 30 29 38 42

Although the amount of heavy metals available to the plants provide a more precise definition of the upper limit of phytotoxicity and/or of the permissible levels of occurrence in food and forages, the total metal content level is still accepted as a measure of risk. In Bulgaria, this depends on soil acidity (pH). In accordance with that, limits for Ac, Pb, Zn, and As soil content have been established and accepted (State Gazette 36, 1979). They are presented in Table 1.

Limits on permissible levels in food (State Gazette 39, 1984) and recommended limits for forages (Dilov and Petrov, 1987) have also been accepted. The characteristic amounts of background concentrations suggest that soils in Bulgaria contain forms of metal microelements at safe levels. When additional soil acidification occurs, the permissible levels decline, and metal concentrations may allow phytotoxicity to occur.

Table 1. Permissible levels for lead, copper, and zinc recommended for Bulgarian soils

Permissible level in soil (ppm) pH of soil in a water suspension (1:2:5)
3.5 4.0 4.5 5.0 5.5 5.7 6.0 6.2 6.5 7.0 7.5 8.0
Pb 20 25 30 40 50 60 70 75 80 80 80 80
Cu 15 20 25 40 60 80 120 230 250 260 270 280
Zn 20 30 40 60 90 110 200 300 300 340 360 370

Notes: The permissible level for As is 25 ppm.

  Recommended levels according to various literature sources
Cd Ni Co Cr Se Sb W Ti Zr Sn Mo F
ppm 3 50 50 100 10 5 50 5000 300 50 5 800

The total accumulations of heavy metals in the soil are evaluated in accordance with the natural background and/or permissible pollution limit levels. Commonly, slight pollution of the soil - i.e., when the content is less then the doubled background level - is acceptable. The permissible pollution level defines higher degrees of pollution risk and imposes respective forms of land use limitations, due to the non-degradable nature of heavy metal pollutants. Detoxification is difficult, and has rarely been undertaken at the time the pollution occurs.

Sources of Pollution and the State of Their Technologies

a) Metallurgy

b) Irrigation with polluted surface waters

Nearly all the country's rivers are affected, particularly in their middle and lower reaches. The rivers receive effluents from mining, ore-processing, and metallurgy. Typically this results in high rates of heavy metal accumulation in irrigated lands. The affected area is estimated at between 8,000 and 10,000 hectares. The most significantly affected rivers are the Topolnitsa, Teamok, Ogosta, and Arda.

c) Sewage sludge from town water purification stations

Sewage sludge contains high levels of heavy metal, but considerably less than sludges from the large cities in the western countries. As a rule, Cd, Ni, Cr, and Pb occur in amounts above the permissible limits for sludge applications in soils. Bulgaria still experiences problems with sludge processing practices.

d) Fly ash pollution from steam power plants

The importance of this source lies in its abundance - 7 million t/year - and in the chemical composition of the deposition. Many microelements and heavy metals occur. Ashes poor in CaO often contain heavy metals, radioactive elements, As, and B in much higher levels than the soils (Minkov, 1984; Ministry of Energetics, 1985). Some detailed studies have shown that the composition of ash deposits varies greatly depending on the origin of the material (domestic vs. import):

  Metal
  Mo As Ni Cr
Content (ppm) 14-206 8-1112 27-110 20-105
Mean 55 55 55 71
  Metal
  Sb Zn U Th
Content (ppm) 1-15 40-149 6-21 14-24
Mean 11 81 12 18

A large amount of ash has already accumulated - 150 million tons. Local ash local problems are very serious. The dumps occupy hundreds of hectares of agricultural land and are mostly filled up. Some estimates indicate that Bulgaria is the leading country in terms of ash per capita (760 kg) (Ministry of Energetics, 1985).

It has not yet been shown that fly ash deposition rate reduces soil productivity, even in areas close to steam power plants with high power production levels (600-800 MW). Soils are heavily polluted only in close proximity to the dumps. There are no definite data of the airborne effects on soil acidity. However, the direct effects on vegetation have been established, and are appreciable at the relatively short distance of 3-4 km. The most typical effect has been documented in tobacco fields, where the quality of the leaves is severely affected. Soot pollution has also been established in close proximity to the power plants.

There are about 15 steam power plants (200-800 MW) in Bulgaria. Most were built between 1958 and 1965, primarily in regions producing a range of agricultural products - grain, forage, tobacco, and vines.

e) Cement dust pollution

The cement industry is a large polluter of the envir-onment. In 1976, Bulgaria's 6 cement plants emitted a total of 400,000 t of cement dust (Skopina et al., 1982). In addition, this production accounts for 15% of the ash, 10% of the phosphogypsum, and the total amount of lead slag (Christo et al., 1982). In areas near cement plants, extremely important sanitary and hygienic problems appear. However, cement dust does not always affect the soils in such a way as to reduce soil productivity. Results on strongly acid soils are similar to those obtained after the purposeful application of lime. For example, in a region of light grey forest soils (Typic Albaqualfs), the pH level is 5.3, exchangeable Ca 9 meq/100 g, and cation exchange capacity 18 meq/100 g; these change, respectively, to 7.8, 25 meq/100 g, and 27 meq/100 g. The soil physical and mechanical-technological properties improved. In addition, free carbonates amounting to 3.1% appeared. However, similar cement dust deposition on calcareous soils contributed to the deterioration of the plant nutrition regime. In one example, the free carbonate content reached 17% (Kolchakov and Faitondjiev, 1981).

Cement dust directly affects vegetation. A thick deposition crust, combined with alkaline toxicity, was observed in the Zlatna Panega region. Even more complicated situations can be observed when airborne pollutants from different sources are mixed together (as has occurred as Devnya-Povelyanovo, Dimitrovgrad, and Pernik).

f) Fluoride dust pollution

Though incidental, fluoride dust pollution has been established near the phosphate producing plants at Devnia-Povelyanovo and Dimitrovgrad. Fluoride toxemia symptoms were described in ruminants allowed close to the plant near Dimitrovgrad in the early 1970s. Increased fluorine concentrations have been established in the forage grasses there - enough to induce chronic poisoning. Studies of other sources, such as the glasswork plants, have not yet been conducted.

g) Soil salinization

Soil salinization is an indirect effect of industrial pollution. Unpurified waste waters emitted in production processes are widely used in irrigation systems. Irrigation using waters from the Tundzha, Maritsa, and Danube Rivers creates a risk of secondary salinization in many localities. At the same time, the risk of using underground waters for irrigation can be considerably higher.

Soil salinization in connection with brine production is typical in the industrial region of Provadiya-Devnya in northeastern Bulgaria. In this region, the incidence of phytotoxicity is readily apparent, affecting a total area of 600 hectares. The soils of the region - Typic and Calcic Haploxerolls - are transformed to Aeric Halaquepts (3-4% salts, exchangeable Na = 40-70% of the cation exchange capacity of soils) (Kavarjiev, 1985).

Low Productivity Soils

Low soil productivity can result from several causes: heavy metal accumulations from different sources; secondary acidification from acid deposition and nitrogen fertilizers (which results in the increased availability of heavy metals to plants); phytotoxicity, as observed markedly in copper-arsenic polluted soils. Instances of 100% crop losses have even been observed. Significant cases of loss of soil fertility have been observed after eradication of vineyards and the sowing of shallow-rooted crops.

Health problems have resulted from the ingestion of foods and forages containing toxic elements. This is one of the most serious problems facing Bulgarian agriculture, especially in areas where soils are polluted with lead and even low levels of cadmium. Some regions of the country have high background levels of heavy metals.

There have been cases of acute poisoning of ruminants that ingested fodder grasses and silages polluted by airborne deposits. Contamination is a particularly large problem on lands used to grow leafy vegetables, leafy forages, and tobacco.

Responding to Soil Pollution Problems

It is the general aim of pollution response activities to decrease or modify the consequent effects of pollution on soils and plants in a manner compatible with normal land uses and other forms of human activity. To meet this general goal, a number of measures are required.

Control

A program to control current heavy metal pollution of soils is already in progress. Land use restrictions and adaptations of farming practices have also been initiated in several localities that face high pollution risks.

Assessment

Some of the measures recommended and/or applied in the past need to be evaluated and modified (by adopting new rules and higher penalties, additional prohibitions, technical improvements, new devices, decreased allowable outputs of lead, zinc, and copper, and so forth). At present, there is no significant change for the worse in heavy metal pollution of the environment in Bulgaria due to the general decrease in production.

Inventory and mapping

Inventory and mapping have been taking place for more than ten years, with set purposes according to the sources of pollution. At this point, 22 districts out of a total of 28 administrative subdivisions of the country have been mapped at a 1:25,000 scale. In addition, a monitoring network has been established to measure trends in heavy metal pollution of soils (Table 2).

Amelioration

The goal of amelioration activities is to respond to pollution problems through an optimal regime of cultivation, fertilization, crop rotation, plant protection, and other agricultural practices. Improvements in soil properties through chemical melioration, enrichment with organic matter, and other means are undertaken with a view toward decreasing the availability of heavy metals to plants.

Health and emission standards

Health risks and emission standards are checked in particular cases to ensure that they are adequately coordi-nated.

Education and extension materials

As far as we know, there are no widely available publications or handbooks on this issue in Bulgaria. A small monograph entitled "Some Problems of the Pollution of Soils" was edited by L. Raikov (1984) and published by Zemizdat. At present, some development projects involving this issue use literature from abroad.

Policy

The goal of policy reforms should be to establish a financial and taxation system that addresses the problems that farmers and others face from pollution sources, that builds in effective market mechanisms, and that leads to restraints on and/or total cessation of soil pollution.

Table 2. Heavy metal pollution of soils

By District Cu Zn Pb Cd Ni Co Cr Hg Mn As Total
Plovdiv + + 7200 + - - - - - - 7200
Sofia District 4700 + + + - - - - 0 4700 4700
Kurdjali 0 < 3400 3400 + + 0 + - - - 3400
Pazardjik 2300 - 300 - - - - - - 400 2300
Montana 260 240 1600 - - - - - - - 1600
Sofia City 0 < 1200 1200 + - - - - < 1200 + 1200
Vidin 500 80 90 - - - - - - - 500
Pernik 0 < 300 300 0 - 0 0 0 0 < 300 300
Haskovo 200* 100 0 0 0 0 0 - 0 - 200*
Bourgas 200* 0 0 - 0 0 0 0 0 + 200*
Targovishte - + 170 0 - - - - - - 170
Vratsa 130 + + + - - - - - < 130 130
Stara Zagora 100* < 100* < 100* 0 0 0 0 - - 0 100*
Sliven 100* < 100* < 100* 0 0 0 0 0 0 0 100*
Yambol - < 100* 100* 0 + 0 + 0 0 0 100*
Pleven 0 + 100* 0 0 0 0 0 0 0 100*
Razgrad 0 + 100* - 0 0 0 - - - 100*
Shumen 0 + 100* - 0 0 0 - - - 100*
Gabrovo < 100* 100* < 100* - 0 0 0 - - - 100*
Veliko < 100* 100* 0 - 0 0 0 - - - 100*
Kyustendil + < 100* 100* 0 0 0 - - - - 100*
Varna 100* + + 0 0 0 0 0 0 + 100*
Russe + + 100* - 0 0 0 - - - 100*

Notes:
* = expected polluted area
- = no data available
+ = data for pollutant concomitant with major pollution
0 = established levels below the admissible limit.

Bibliography

Arnold R. W. and Wilding L. P., 1991. The Need to Quantify Spatial Variabilities of Soils and Landfarms. SSSA Special Publication No 28.

Boyadziev T., 1989. Temperatouren i voden rezim na pochvite v Bulgariya. V Problemi na pochvoznanieto pri ousloviyata na intenzivno zemedelie, Sofiya, str. 207-214.

Dilov P., I. Petrov i dr., 1987, Ekotoksologichni problemi na promishlenoto zivotnovudstvo pri zamursyavane s tezki metali, V sb. Mezd. simpozioum po proekt 9 na MAV", t. 1, Yambol.

Global Soil Change, 1990. Editors: Arnold R. W., Szabolcs I., Tarqulian V. O., International Institute for Applied Systems Analysis, Laxenburg, Austria.

Godishnik za sustoyanieto na prirodnata sreda v Bulgariya, Ministerstvo na okolnata sreda, 1991. Sofiya, str. 177-208.

Higienni normi za predelno dopoustimi kolichestva tezki metali v hranitelni prodoukti v mg/kg svezo teglo, 1984. Prilozenie No. 1 ot Haredba na MH3, Vol. 39.

Hristov H., V. Angelova, and N. Daneva, 1982. Otsenka na vuzmoznostite za izpolzvane na nyakoi kroupnotonazni otpadutsi ot promishlenostta, V sb. Haouchno-teoretichna konferentsiya po opazvane i vuzproizvodstvo na prirodnata sreda, 1-5.II.1982, Slunchev bryag, t. 2, str. 224-228.

Iolevski M., R. Kaloyanova, V. Koinov, and H. Trashliev, 1973. Pochvena karta. Atlas na HRB. GOUGK, Sofiya.

Katalog za kolichestvoto i kachestvoto na pepelta i sgouriyata ot TETS v sistemata na SO "Energetika" prez 1985g. Ministerstvo na energetikata, Energoproekt, HIPPIES.

Kavurdziev Ya. Vliyanie na antropogennata deinost za zasolyavane na pochvite v porechieto na r. Provadiiska, V sb. "IV nats. konferentsiya po pochvoznanie", 28-30 mai 1985, Sofiya.

Kolyakov I. and L. Faitondziev, 1982. Aspekti na izmeneniyata na pochvenite svoistva pod vuzdeistvieto na tsimenten prah v raionite na tsimentenite zavodi, V sb. "Haouchno-teoretichna konferentsiya po opazvane i vuzproizvodstvo na prirodnata sreda", Slunchev bryag, t. 1, str. 172-175.

Kolyakov I. and L. Faitondziev, 1982, Promeni na nyakoi himichni i morfologichni svoistva na svetlosiva /psevdopodzolista/ gorska pochva, gleevidna, pod vuzdeistvieto na tsimentov prah, V sb. "III natsionalna konferentsiya po pochvoznanie", 21-23.II. 1981, Sofiya, ch. I.

Minkov M., K. Todorov, and D. Evstatiev. Ekologichen efekt ot izpolzvaneto na sgouropepelni smesi ot ou-tainitsite na TETS, V sb. "Haouchno-teoretichna kon-ferentsiya po opazvane i vuzproizvodstvo na prirodnata sreda", 1-5.II.1982, Slunchev bryag, t. 2, str. 220-224.

Naredba No. 3, 1979, DV No. 36.

Problemi na zamursyavaneto na pochvata, ed. L. Raikov, 1984, Zemizdat, Sofiya.

Raikov L., H. Dancheva, M. Mihailov and D. Iotov, 1988. Tezkometalno zamursyavane na pochvite v HRB, V sb. "Aktoualni problemi po opazvane na prirodnata sreda v Razgradska oblast", I naouchna konferentsiya, Rouse, 28-29.I.1988, t. 2.

Rousseva S. S., Koulikov A. V. and Lazarov A. L., 1992. Soil Erosion and Conservation in Bulgaria, Prevention and Remediation Workshop, Budapest, pp. 38-54.

Skopina H., S. Tsekova, E. Vasileva, V sb. "Yobileina naouchna sesicha na HTSOPSVR pri KOPS", 11 mai 1982, Sofiya, KOPS.

Soil Survey Staff, 1975. Soil Taxonomy. A basic system of soil Classification for Making and Interpreting Soil Surveys. USDA - SCS Agric. Handbk., p. 436, U.S. Cov. Print. Office, Washington, DC.

Tchuldjian H., 1989, Heavy Metal Pollution of Soils, in "Lectures on soil science" (edit. T. Boyadjiev, Project FAO/Bul/TCP/Bul, 4502-T), pp. 315-324.

Back | Table of Contents | Next