This article reviews the status of fisheries in the western parts of the North and Middle Caspian Sea in the territory of Dagestan Republic, the Russian Federation. Commercial fish stocks are greatly influenced by changes in the Caspian environment induced by natural (sea level fluctuations, water advection, seabed seismicity) and anthropogenic (regulation of major rivers, pollution, invasive species, etc.) factors, as well as fishery management. Fisheries development in Dagestan is reviewed by: (1) summarizing data on the biological and eco-geographical context of biological productivity; (2) evaluating the current status of stocks of the major commercial fish species in this region and assessing the prospects for their commercial use; (3) analyzing the responses of aquatic biological resources to natural and anthropogenic impacts. A number of recommendations are suggested for establishing sustainable fisheries management in the Western Caspian Region.
The Caspian Sea continues to attract the attention of researchers, due to it being a unique fisheries waterbody and, in recent decades, one of the world's most prolific oil and gas areas. Currently, the global community is well aware of the Caspian Sea issues, particularly, the dramatic decline in its biological resources, especially Sturgeons.
The Dagestan coast of the Caspian Sea (Figure 1) can be considered as a specific mixing zone of waters coming from the Volga River and the Caspian Sea proper, with additional freshening impacts from Dagestan rivers; e.g. an interaction zone between the North and Middle Caspian. In general, the western Caspian coastal zone differs from the other Middle Caspian areas in its high trophic capacity (mass of the substances involved in biological cycle), which is conditional on the advection of nutrient-rich North Caspian waters. This contribution to the phosphorus and nitrogen inputs is considerably greater than those discharged from the land surface of Dagestan.
Dagestan shelf zone is crossed by the coastal migration routes (northward and southward) of Sturgeons (Acipenser and Huso), Salmonids (Salmo), Shads (Alosa), Mullets (Chelon), and other commercially important fish species. Feeding, wintering and spawning grounds of these fishes are also located there. Prior to the 1990s, it was used as the all-year-round feeding ground for approximately 40% of the Caspian Sturgeons (Abdusamadov, 2004a,b).
Western Caspian fisheries region includes the Caspian coastal zone adjacent to the marine border of the Dagestan Republic, the Russian Federation, and the watersheds of the Terek, Sulak and Samur, together with the inland fresh waterbodies. Traditionally, the fishing industry of Dagestan was based on coastal, offshore, and inland fisheries (including aquaculture) and formed a part of Russian fisheries complex in the Caspian.
Development of the Western Caspian fisheries during the 20th−early 21st Centuries was complex, involving a large number of interconnected factors—of natural origin (e.g. sea level fluctuations, hydrology, and water chemistry), human-induced impacts (e.g. damming of the rivers, pollution, invasions – targeted and accidental introductions), and fishery policies. It should also be noted that the natural factors may well have been affected by the anthropogenic interventions, which are largely unexplored. Another consideration is the rapid and large-scale response of the Caspian ecosystem to changes in conditions, which is most vividly demonstrated by the Comb-Jelly, Mnemiopsis leidyi Agassiz, 1865, invasion in the early 2000s. This situation urgently calls for the development of tools in support of an ecosystem-based approach to fishery management, which can only be successful if implemented at the regional level by all five Caspian states.
The goal of this article is to assess the current status and define feasible areas of fisheries development in the Western Caspian region of the Russian Federation. This involves the following interrelated objectives: (1) to summarize data on eco-geographical and biological background of biological productivity; (2) to assess the current stocks status of the major commercial fish species in this region and demonstrate the prospects for their commercial use; (3) to analyze response action of aquatic biological resources to the natural and anthropogenic impacts; (4) to provide recommendations for sustainable fisheries management in the Western Caspian region.
General characteristics of fish fauna in the Western Caspian region
Fish fauna of the Western Caspian region (western parts of both North and Middle Caspian and their basin) is represented by over 80 species and subspecies (native and introduced, both permanent dwellers and occasional migrants from the south Caspian) belonging to 50 genera in 16 families (Bogutskaya et al., 2013). Of those, 63 species and subspecies in 14 families occur in the shelf zone. The Dagestan Caspian coast represents a mixing zone of freshened North Caspian waters moving southward with brackish-saline Middle Caspian waters. In general, the hydrochemical regime is favorable for fish and their food organisms. These environmental conditions contributed to formation of an euryhaline and eurythermic fish fauna, which features both Arctic representatives (Terek Trout Salmo ciscaucasicus Dorofeyeva, 1967 and Inconnu Stenodus leucichthys (Gueldenstaedt, 1772)), thermophilic species of Ponto-Mediterranean origin (Atherina caspia Eichwald, 1831 and Syngnathus caspius Eichwald, 1831), marine relicts (Kilkas and Shads), and species of freshwater origin (Sturgeons, Cyprinids, and Percids). The modern composition of the fish fauna in the Dagestan coastal zone was enriched in 1930s, during the Caspian Sea regression, which caused shifts in fish migration routes and feeding grounds towards the western part of the North Caspian.
The most common species in the shelf zone are Clupeidae – Caspian Marine Shad, or Brazhnikov's Shad, or Dolginka (Alosa braschnikowi (Borodin, 1904) species complex), North Caspian Shad (Alosa caspia (Eichwald, 1838)), and Big-eyed Shad (Alosa saposchnikowii (Grimm, 1885)), and Caspian Kilka (Clupeonella caspia (Svetovidov, 1941)); Cyprinidae – Wild Carp (Cyprinus carpio (Linnaeus, 1758)), Bream (Abramis brama (Linnaeus, 1758)), Kutum (Rutilus kutum (Kamensky, 1901)), and Caspian Roach, or Vobla (Rutilus caspicus (Jakovlev, 1870)); Mugilidae – Golden Grey Mullet (Chelon auratus (Risso, 1810)) and Leaping Mullet (Chelon saliens (Risso, 1810)). Agrakhan Puzanok Shad (Alosa sphaerocephala) and Black-backed Shad (Alosa kessleri (Grimm, 1887)), as well as Big-eyed Kilka (Clupeonella grimmi (Kessler, 1877)), and Anchovy Kilka (Clupeonella engrauliformis (Borodin, 1904)) are less abundant; the Kilkas are mostly confined to the deeper areas of the shelf slope. Other species are relatively rare in this area, including all sturgeon species, Terek Trout, and Inconnu.
In slightly brackish coastal areas, semi-anadromous and non-migratory (fluvio-lacustrine) fishes dominate the species diversity and anadromous species (North Caspian Trout, Inconnu, and sturgeons) occur less frequently. The most abundant semi-anadromous fish species are: Caspian Roach and Bream followed by Wild Carp and Pike-Perch (Sander lucioperca (Linnaeus, 1758)). Fluvio-lacustrine freshwater fishes are represented by numerous predatory species including Perch (Perca fluviatilis (Linnaeus, 1758)), Pike (Esox lucius (Linnaeus, 1758)), Wels (Silurus glanis (Linnaeus, 1758)), and Pike-Perch, and by a group of cyprinids including Rudd (Scardinius erythrophthalmus (Linnaeus, 1758)), two species of the genus Carassius, White Bream (Blicca bjoerkna (Linnaeus, 1758)), and Tench (Tinca tinca (Linnaeus, 1758)). Species diversity in the middle sections of the Terek, Sulak, and Samur rivers is approximately half the number of species in their lower reaches and estuarine areas; in mountainous sections it is composed of 6 to 8 species and decreases to 1 or 2 species in the uppermost reaches. Virtually all the species listed above are exploited by commercial fisheries.
Hydrobiological features of the study area: Long-term dynamics and relation to fish stocks
In the western shelf zones of the North and Middle Caspian, zooplankton species richness is about 112 species. The North Caspian is inhabited mainly by euryhaline and eurythermic representatives of the Mediterranean fauna; the copepod Calanipeda aquaedulcis Kritchagin, 1873 and the cladoceran Podon polyphaemoides (Leuckart, 1859) are the typical species in this group. No significant changes in species composition in the Middle Caspian were registered during the periods preceding and following the recent sea transgression.
Prior to the early 1980s, C. aquaedulcis dominated the coastal zooplankton of the Middle Caspian. Since its invasion into the Caspian Sea (recorded in 1981), the Mediterranean copepod Acartia clausi Giesbrecht, 1889, has become the most common (dominating in number and biomass) zooplankton species in Dagestan coastal waters, superseding C. aquaedulcis. According to the recent winter plankton survey conducted by CaspNIRKh Dagestan Branch, the zooplankton biomass along the Dagestan coast typically ranges from 100 to 300 mg m−3 with some areas ranging from 300 to 500 mg m−3.
In the early 2000s, invasion of the Comb-Jelly into the Caspian led to large-scale changes throughout the food chain (Karpyuk, 2003; Karpyuk et al., 2004). High zooplankton consumption by the Comb-Jelly resulted in decreased plankton diversity. In certain sea areas, plankton composition was reduced to 9 species, mostly at the expense of important fish food items. Comparisons for the periods 1991−1993 and 2000−2002 showed that following the Comb-Jelly invasion, the abundance and biomass of the Caspian zooplankton decreased by more than 80%, from 17.3 to 3.2 thousand ind. m-3 and from 116 to 18.5 mg m−3, respectively (Polyaninova et al., 2003).
The distribution of the Comb-Jelly across the Caspian correlates with the seasonal migrations of zooplankton, as confirmed by seasonal distribution mapping (Sokolsky et al., 2002; Shiganova, 2009). The number and biomass of zooplankton in the Middle Caspian have decreased by 75−80% (autumn 2003), compared with similar data for 1994. Concurrently, the number of zooplankton species in the Middle Caspian has dropped by about 50%, in the South Caspian – by 67%. Moreover, two Caspian native species—Eurytemora grimmi (Sars, 1897) and E. minor Behning, 1938 —the main food items of planktivorous fishes, have disappeared completely and the current number and biomass of zooplankton in the Middle Caspian is formed by only one species, the non-indigenous Acartia tonsa Dana, 1846.
Planktivorous fishes (Kilkas and Shads) represent the next link in the food chain. The influence of the invader was clearly detectable in the long-term catch data for Anchovy Kilka yearlings. In 2001, this most numerous Caspian species showed the lowest yield for the entire observation period (Abdusamadov, 2001). Russian catches of Kilka decreased from 150.5 thousand tonnes in 1999 to 17.0 thousand tonnes in 2003 and to 7.9 thousand tonnes in 2014. Currently, the Caspian populations of Caspian Kilka are still below pre-invasion levels.
Of a total of 234 benthic invertebrate species, only 30 species have appreciable abundance. Among those are some native Caspian and Ponto-Caspian species: mollusks Didacna trigonoides (Pallas, 1771) and Adacna polymorpha (Litvinenko et Starobogatov, 1967), and crustaceans Stenogammarus similis (Sars, 1894), Pterocuma pectinata (Sowinsky, 1893), and Stenocuma gracilis (Sars, 1894).
Over the past 30 years, significant changes have been observed in benthic communities. Each group of benthic animals featured certain predominant species in different periods. Among the annelids, polychaete Hediste diversicolor (Müller, 1776) dominated throughout the 1970s, the Mediterranean invaders Mytilaster lineatus (Gmelin, 1791) and Abra segmenta (Recluz, 1843) (commonly as Abra ovata in non-taxonomic literature), the latter predominating over the former – from 1970 to 1985, and native species of Hypanis – in all the subsequent years. Within crustaceans, the most diverse group, Amphipoda, dominated from 1970 to 1985, whereas from 1986 to 2002, both Amphipoda and Cumacea species dominated. Rising sea level had a positive effect on the trophic capacity of the waterbody. The total average biomass of benthic animals was 59.8 g m−2 in the early 1970s, and, in 1978−2002, during the sea transgression, it increased to 70.9 g m−2.
The distribution pattern of benthic biomass within the coastal waters of the western Middle Caspian was characterized by persistent areas of concentration associated primarily with sand-bottomed deep slopes around the Chechen Island. The biomass of benthos in this area was depth-dependent, increased in successive depth layers (from 50 to 200 g m−2), and consisted mainly (90%) of mollusks Abra segmenta and Hypanis plicata (Eichwald, 1829). Reduced biomass of benthic organisms, food items important to Sturgeon, was observed in the Middle Caspian.
Gross phytoplankton primary production in the Caspian Sea was estimated at 143.4 million tonnes carbon (Salmanov, 1987); the percentage contributions for the North, Middle, and South Caspian were 19.9%, 44.4%, and 35.0%, respectively. When the sea-level rose (up to −27.75 m asl), primary production in the North Caspian increased by a factor of 1.68 i.e. up to 47.7 million tonnes of carbon, changing the percentage contributions to 29.3% (North), 39.2% (Middle), and 31.5% (South Caspian).
Our recent data have revealed a dramatic decrease in Caspian productivity, compared to previous years. In 2002, the total biomass of phytoplankton in the North Caspian declined almost three-fold, compared to the years 1936−1940. Changes in the productivity rate of the Middle and South Caspian were accompanied by structural changes in the phytocoenoses. Thus, the most consumed phytoplankton dinoflagellate Exuviella cordata decreased to 1/85 of its biomass in the Middle Caspian during the past 70 years. Some instances of algal blooms, particularly, of minute algae, were due to their low consumption by plankton and benthic invertebrates (Abdusamadov, 2004a).
Negative changes at the primary production level caused subsequent results at the primary consumers’ level (zooplankton and mollusks) that were evident in the Middle and even South Caspian. Over the last 70 years, the food supply of semi-anadromous fishes in the North Caspian has decreased by ca. 40%, i.e. down to 1732 thousand tonnes compared to 2679 thousand tonnes in 1930s. Annual catches of these fishes have dropped from 299,000 tonnes in 1930s to 8 000 tonnes in 2012.
It should be noted that in recent years, the food supply of semi-anadromous fishes has increased; however, the sharp downward trend in catches has persisted. This clearly indicates that accumulated impacts on these populations have reached a critical point and further adverse effects may lead to irreversible changes in their status.
The impact of sea-level fluctuations on fishes in the shallow coastal zone
Changes in the level of the Caspian Sea represent its intrinsic characteristic. This phenomenon is well known and studied; however, no definitive conclusion on its root causes or agreed forecasts have been developed. Changes of the sea level, both long-term on a global-scale fluctuations and local short-term surges in the coastal zone produce significant effect on fish habitats and their life cycle.
Wind-induced surges in the Dagestan coastal zone contribute to instability in the salinity regime. According to the Dagestan Hydrometeorological Center, the magnitudes of synoptic, seasonal, and interannual salinity fluctuations in the coastal waters are significant and correlate with frequency of prevailing north-west and south-east winds. Freshening of the coastal water occurs in months when northern-western winds prevail, whereas salinization increases with south-east winds. For instance, in the Makhachkala area, the difference between the extreme recorded salinity values can exceed 8 ppm (Monakhov et al., 1997).
During the recent Caspian transgression, the sea level rise resulted in expansion of feeding and spawning areas. On the other hand, this process led to increased contamination in the coastal zone through pollutant washout from flooded territories. Another resultant factor of economic importance was the change in coastal fishery practices due to significant increases in depth at fishing sites.
The influence of large-scale sea level rise and tidal phenomena on fish fauna, fish habitats and behavior patterns is demonstrated by the case study of Kizlyar Bay, the highly productive fish feeding and spawning area, harvested for semi-anadromous and freshwater species. During the last Caspian regression (1971−1977), the Kizlyar Bay water area was reduced to 1000 km2, the average depth decreased to 1.5 m, the average salinity equaled 2.5 ppm and its value often reached 6−8 ppm in some sites (Abdusamadov, 1989). Thus, the feeding and spawning habitats in the bay used by semi-anadromous and freshwater fish species as well as migration routes of sturgeons, shads, and Caspian Kilka were considerably reduced and restricted mostly to the most freshened areas. The following sea transgression resulted in considerable changes in Kizlyar Bay. The bay area increased by 150%, up to 1500 km2, expanding the feeding grounds for all resident species in the bay and adjacent waters and the spawning grounds for semi-anadromous and, particularly, non-migratory fluvio-lacustrine fishes. The area of the coastal spawning grounds increased from 20 km2 in 1977 to 200 km2 in 1991. This led to dramatic, up to three-four-fold increases in the numbers of Wild carp, Pike, Prussian Carp, Rudd, Perch, and Tench; their annual reproduction level was rising since 1986 until 2000 (Figure 2). Later, during the period of stabilization and some decline of the sea level (by 0.5 m), the yield of fish juveniles in the bay declined in about two times and reached 560−600 million individuals (young-of-the-year) by 2003 (Abdusamadov, 2004a).
The impact of river runoff and water resources on biological productivity in the Terek River
During the period of 1978–2007, average annual water runoff from the Terek and Sulak rivers was 9.4 km3. Water runoff from the Terek River basin plays a significant role in generating biological productivity in the Caspian-Terek fisheries. Changes in the aquatic ecosystem that have occurred there in the past fifty years have resulted mainly from regulation of the river flow, implementation of fisheries projects, pollution, and other anthropogenic impacts (Abdurakhmanov et al., 2002).
Damming of various Terek sections in the mid-2000s, diking in its lower reaches, and opening of the drainage “proryv” (so-called “cut”) via Agrakhan Peninsula (Uch-Kosa) have led to formation of a new main branch called the New Terek, shallowing and swamping of wetlands in the Terek River old delta and Agrakhan Bay regions, breaking their connection with the sea, distorting historical fish migration routes and downstream migrations of fish larvae and juveniles, causing losses of spawning and wintering grounds (Mikhailov and Mikhailova, 2010).
The deficit of the Terek water budget has caused negative impacts on fishes in the region, especially during their upstream migration and spawning periods. For instance, the seasonal water deficit during April and May can reach 500 million m3 in the outlet section of Kargalinskaya Dam (105 km upstream from the Terek mouth). The estimated river water resources and inter-annual flow distributions required for fisheries under a secured annual water supply plan are presented in Table 1.
Middle reaches of the Terek River are still used for natural Sturgeon reproduction. The boundaries of Sturgeon spawning area in this river were discovered through field surveys; the pebble bar site opposite Razdolnoye settlement marks the upper limit, and the lower limit is near the Naurskaya village. The total length of the spawning section is 104 km; the most distant site is situated 359 km upstream the Terek River mouth. The total area of the eight surveyed spawning sites amounts to 132 ha, of which the channel spawning grounds account for 46.5 ha, and flooded (wetland) spawning grounds for 85.5 ha. However, spawning success is limited by the Kargalinskaya Dam (hindering access to the spawning sites) and depends on water availability (deficit) at Kubyakinsky bank and the Cut sections. According to long-term observations, the number of sturgeon spawners and spawning efficiency in the Terek depend primarily on their sea stocks and hydrological conditions in the river in a given year.
Stellate Sturgeon spawning season in the Terek lasts about four months (May–August), generally starting in early May, at water temperatures of 14–16°C. Mass spawning is observed during the highest water levels, in the second half of June to early July, at 21–23°C. The Terek spawning population of Russian Sturgeon is represented mostly by a hiemal (winter) race; the proportion of vernal (spring) spawners in the brood stock is insignificant. The winter race of Russian Sturgeon spawns in early spring, at water temperatures of 8–13°C. Russian Sturgeon of the early spring run spawn in the second half of April and May, at water temperatures of 16−18°C (Belyaeva et al., 1989).
Drifting sturgeon larvae in the Terek consist mostly of Stellate Sturgeon. The proportion of Russian Sturgeon is very low, varying from 0.5% to 13%, between years. Beluga larvae have never been seen in test catches. Before the opening of the Cut via Agrakhan Peninsula, migrating sturgeon larvae entered the North Agrakhan, where feeding conditions were favorable for growth and survival. Currently, the majority of the early larvae are carried out directly into the saline (up to 12 ppm) waters of the Middle Caspian, which negatively affects their survival rate, since salinity tolerance has not yet developed at this stage (Khodorevskaya, 2011).
Prior to the regulation of the upper sections of the Terek, this river was important for natural reproduction of the Terek Trout; its commercial stocks provided annual catches up to 0.45 tonnes. The Trout spawning grounds were located in the upper reaches of the Terek and its tributaries: the Baksan, Malka, Urukh, Ardon, Sunzha, Ass, Argun, and other rivers. As mentioned above, hydraulic construction resulted in a total loss of Terek Trout spawning in the Terek and depletion of the once large stocks. Artificial breeding of this species is conducted at Ardon, Chegem, and Maysky fish hatcheries. However, the restocking numbers are insignificant (250–300 thousand fry per year) allowing only a minimal sustained population of Terek Trout.
Regulation of the Terek flow caused the decline in the total wetland area, in the abundance of semi-anadromous and fluvio-lacustrine fishes, as well as changes in the ecological equilibrium, i.e. proportions of different ecological groups in the ecosystem (Abdusamadov, 2004a). The proportion of non-migratory freshwater fish increased at the expense of valuable semi-anadromous species. This trend was reinforced through intentional introduction of so-called Chinese carps (Silver Carp, Bighead and Grass Carp), which established self-sustained populations in the Terek River drainage long ago (Abdusamadov, 1986). The process of species’ substitution is vividly demonstrated by the drop in stocks and catches of Wels and Caspian Roach, the main fishery items until the mid-1950s (Demin, 1962). Pike, Rudd, Tench, Perch, and Crucian Carp dominate the modern catches, while these species were not previously specified in fisheries statistics. Concurrently, fish productivity of the waterbodies dropped from 34.9 kg ha−1 to 1.9 kg ha−1, i.e. by 95% (Table 2).
Thus, a sharp drop in the catches of valuable semi-anadromous and anadromous fish species, along with the almost complete depletion of their stocks in the Terek drainage resulted from human-induced impacts (hydraulic construction) on fish reproduction, feeding and migration. This situation confirms the need for urgent development of novel integrated approaches to cope with emerging challenges. The status of commercially important fish stocks in the Terek River and its tributary systems could be improved through rationally managed use of water resources that provides for the fishery needs with regard to spawning and migration.
Other abiotic impact factors: Advection, seabed seismicity and pollution
In the Middle Caspian, the annual summer vertical advection of deep waters represents an abiotic impact to the marine ecosystem. In general, this phenomenon stimulates productivity processes in the Western Caspian region via nutrient transport into the coastal zone (Abdurakhmanov et al., 2002). However, the other factors accompanying this advection may produce adverse effects on fish life cycles. During advection period (usually, late June and July), cold low-oxygen water (12–14°C, 1–3 mg O2 l-1) enters the coastal zone. Due to the sharp gradients of water temperature and dissolved oxygen, foraging fishes (e.g. Sturgeon, Caspian Roach, Mullets, Gobies) are forced to shift to the warmer waters for 2–3 weeks (Shikhshabekov et al., 2009). If another environmental factor, the calm, is added, the situation becomes worse, resulting in fish suffocation in the area of impact.
An example of the synergy of natural and human-induced factors is demonstrated by the mass fish mortality in the Caspian Sea in April–July, 2001. The total fish loss amounted to 166 thousand tonnes of which 99% were Anchovy Kilka and 1% consisted of Big-eyed Kilka, Caspian Shad, and Caspian Pipefish (Sedov et al., 2001). In the opinion of fishery scientists, two major factors contributed to this unprecedented phenomenon: deteriorated status of Kilka stocks and the seabed seismic activity. The invasive zooplankton-feeder Comb Jelly became a primary food competitor of Caspian Kilkas. The Comb Jelly explosive rise in the second half of 2000 impaired the physiological fitness of the Caspian Kilka populations. Further, the mass mortality itself was triggered by gas emissions (radon, methane) from seabed fractures, as evidenced by the records (including archival data) of crustal movements in the Caspian Sea (Katunin et al., 2002).
These two examples demonstrate that the impact of natural abiotic factors on the sea ecosystem may negatively interact with concurrent human-induced impacts, such as climate change, pollution, or seismic activity triggered by seabed drilling, underwater pipeline construction, etc. This area of research is gaining importance, particularly with respect to intensified oil and gas production activities in the Caspian region (Abdurakhmanov et al., 2002).
The majority of pollutants enter the Dagestan coastal zone with the North Caspian waters, i.e. from the Volga River and the contribution of the Caucasian rivers is small. The annual total discharge of petroleum products equalled 1430 t y−1, phenols –30 t y−1, and synthetic surfactants –20 t y−1. Among the Dagestan rivers entering the Caspian; the major contributor to the pollutant discharges is the Terek River (60−70%) (Abdusamadov et al., 2003).
Major sources of pollution in the Caspian Sea are pollutants flowing in with river waters; the disposal of untreated industrial and agricultural waste waters and municipal and domestic effluents from settlements in the coastal zone; and oil extraction in the coastal and shelf zones (Zonn, 2001). In Dagestan, the same is true especially the role of rivers as the main pollutant “suppliers,” where the nutrient input is significant, representing a feasible source of the sea eutrophication. Given current conditions, the optimal conservation strategy in the Caspian Sea, under integrated natural and human-induced impacts, should be minimization of the pollution loads to the Caspian ecosystems and implementation of effective monitoring actions. One of the main reasons for deteriorating quality of the fisheries’ waters is the increased domestic discharges from developing coastal cities and settlements, with an almost complete absence of sewage treatment facilities (Abdusamadov et al., 2003; Abdusamadov, 2004a).
Trends in fishery policy and current situation in Dagestan fishery
For a long period, the Western Caspian coast was an important fishing area. Fishing in Dagestan waters dates back to the late 16th –early 17th Century, when sturgeons, Terek Trout, and other valuable fish species were harvested from the Terek and Samur rivers. Extensive fishery development on the Dagestan Caspian coast started in the late 19th–early 20th Century. At that time, the number of coastal fishing grounds located between Makhachkala and Derbent increased from 45 (1896) to 54 (1914) and the annual catches of marine and anadromous Shads, the major fishery items, reached 45.6 thousand tonnes (Knipovich, 1923).
Dagestan fishery reached its peak in the 1930s, when annual catches exceeded 60 thousand tonnes and were composed almost exclusively of valuable commercial species including 2–3 thousand tonnes of sturgeons. Compared with the earlier period, the catch composition shifted towards prevalence of semi-anadromous species and the introduction of a new fishery item – Caspian Kilkas. However, the fishery practices at that time were characterized by large volumes of by-catch (juveniles of valuable fish species – Sturgeons, Salmonids, Clupeids, and others) (Abdusamadov, 2001).
Introduction of new fishery rules in the Caspian Sea, in the early 1960s, resulted in the exclusion of major commercial fish species, such as Sturgeons, anadromous Shads and Salmonids from the catches and considerable reduction in catches of marine Shads, Caspian Kilka, Caspian Roach, Bream, Pike-Perch, Wild Carp, and other species.
However, total Dagestan catches decreased insignificantly through 1961−1999, mainly, due to the fishery transition to harvesting Kilkas in the South Caspian using specialized vessels and advanced technology. By early 1970s, annual Kilka catches exceeded 400,000 tonnes and in the subsequent years Anchovy Kilka became the major object of the Caspian Sea fisheries (Panin et al., 2005).
The collapse of the Caspian Kilka fishery in 2001 resulted in a sharp four-fold drop in their catches from 2000 to 2003, despite sustained fishing efforts (number of vessels per fishing day) at around the level of the year 2000. The stocks of Anchovy Kilka were severely depleted; its current contribution to the overall species composition is 15% (data for 2010). Therefore the total sea catches of all Kilka species still remain at low levels (Figure 3).
Since the mid-2000s, priority has been given to fishery development of Caspian Kilka, Shads, and Mullets which had been under-exploited. Fishing for Caspian Kilka and Shads had been degraded previously, due to inappropriate fishery organization and adverse hydrometeorological conditions at the fishing grounds. A number of anomalous warm winters in recent years have introduced another impact factor that caused changes in the timing of spring spawning migration and migration routes of Shads and, consequently, their entry into the coastal fishing zone (Abdusamadov et al., 2004a).
In Dagestan, according to our data, fish catches of Caspian Kilka with shore stationary nets were stable in 2007–2009, ca. 3.0 tonnes daily per unit of fishing gear. Considering steady trends in individual fish parameters (age, weight and length) and stable dynamics of age-and size-weighted indexes, it may be concluded that commercial stocks of Caspian Kilka are sufficient to justify its fishery exploitation now and in the future.
In general, catches of sea fishes increased, from 426.8 tonnes in 2006 to 953 tonnes in 2010 (Table 3) over the past 5 years, mainly as a result of intensified Mullet fishing (Figure 4). However, the lack of a specialized seiner fleet hampers development of coastal fisheries.
According to official statistics, 1487.2 tonnes of semi-anadromous and fluvio-lacustrine fishes were harvested in the Terek-Caspian region in 2010. At the same time, the actual fishery capture was considerably higher; it corresponded to the approved TAC-2010 (total allowable catch), i.e. of the total 2242 tonnes, 755 tonnes were attributed to illegal, unreported, and unregulated (IUU) catches.
The measures suggested for preservation, rehabilitation, and sustainable management of fisheries resources in the Western Caspian region are aimed at:
Improving the protection of marine biological resources and their habitats, ensuring effective state control over the use and protection of aquatic biological resources to curb poaching and fishery violations and illegal export of fishery products;
Developing aquatic biological resources management by adoption of an ecosystem-based approach including monitoring, green technology, and other related measures.
The measures suggested to enhance conditions for natural reproduction of valuable fish species include:
Reclaiming spawning grounds in Kizlyar and Agrakhan bays;
Improving fish access to natural spawning grounds;
Equipping water intakes at the Terek, Sulak, and Samur rivers with fish protection structures;
Improving the hydrological regimes of regulated water courses allowing for reproduction of aquatic bioresources in this region.
Measures suggested to increase fisheries’ efficiency are aimed at maintaining a balance between environmental and economic priorities:
Extended fisheries research and development (improved TAC estimation methods, recommendations for fisheries regime and selective fishing, forecasts of the status of the marine ecosystem);
Economic instruments to promote sustainable fisheries (incentives for multi-purpose utilization of catches, credit financing for underexploited resources) and the development of new fishing areas, e.g. for Anchovy Kilka in the Middle Caspian;
International cooperation between all littoral states and harmonization of national fishery policies including development and adoption of unified fishery rules for the Caspian Sea basin, which is especially important for conservation of such species as Sturgeons, Trouts, Inconnu, Shads, Mullets, and Kutum.
A comprehensive analysis of current status of Dagestan fisheries and the major obstacles to its effective development was conducted for the Ministry of Agriculture, Dagestan Republic.
The main factors that contributed to the critical status of fishing industry in Dagestan Republic were identified as follows:
The lack of an integrated state approach to fisheries management, the legal framework and mechanisms for sustainable long-term management of aquatic bioresources.
The unified regional system for protection, reproduction and use of fisheries resources was disrupted.
Inefficient conservation measures and deteriorating economic situation in the coastal areas led to the rampant fish poaching, especially on Sturgeons, which declined to a critical level.
The impacts of natural and anthropogenic factors: sea level fluctuations, river regulation, biological pollution, and others played a negative role in reduction of fish stocks.
Development of marine and freshwater aquaculture would significantly reduce the pressures on over-exploited fish stocks and address the socio-economic problems in the Caspian coastal areas. The favourable climatic conditions, extensive hydrographic network, sufficient land and aquatic resources including seawater and geothermal sources provide the basis for regional aquaculture development in three ways: market production of pond fish, pasture fisheries, and mariculture. Sturgeons and Trouts are suggested as the main species for seawater commercial cultivation and artificial breeding (for restocking purposes) in deepwater storm-protected cages and in tanks at the coastal fish farms.