Abstract

Sevan trout is an endemic fish species, registered in the Red Data Book of Armenian Animals as a ‘Critically Endangered’ species (IUCN category: CR A2cd) and is one of the most valuable fish of the Armenian ichthyofauna. For the purpose of preservation of this endangered fish species, rivers in the South-West part of Lake Sevan have been studied and their potential for spawning has been assessed through a relatively ‘cheap’ and ‘time-saving’ approach developed on the basis of hydrophysical, hydrochemical and hydrobiological studies. The results have shown that the highest potential to support natural reproduction of Sevan trout is in the middlestream part of Lichq river, as well as in the downstream part of Bakhtak river and the part of Bakhtak-Tsakqar system near the connection of the Bakhtak and Tsakqar rivers; however, all these areas need some remediation to achieve ‘high potential’.

INTRODUCTION

Sevan trout (Salmo ischchan) is an endemic fish species, registered in the Red Data Book of Armenian Animals as a ‘Critically Endangered’ species (IUCN category: CR A2cd). Being one of the most valuable fish species of Armenian ichthyofauna, it's encountered only in the drainage basin of Lake Sevan, which is the biggest reservoir of freshwater in the South Caucasus region. Originally there were four races of Sevan trout – summer ishkhan (Salmo ischchan aestivalis, Fortunatov), Gegharquni (Salmo ischchan gegarkuni, Kessler), winter ishkhan (Salmo ischchan ischchan, Kessler) and bojak (Salmo ischchan danilewskii, Iakowlev), which differed by their reproductive ecology and growth rates. Particularly, unlike the summer ishkhan and gegarquni, winter ishkhan and bojak were lacustrine forms and spawn only in the littoral zone of the lake. Sevan trout is endangered today, due to the mismanagement of Lake Sevan water- and bio-resources, as well as the anthropogenic impact on the rivers inflowing to the lake. As a result of the consumption of its water for irrigation and production of electricity, the level of the lake periodically decreased from the 1930s to the 1990s, thus many sites in the shore zone of Lake Sevan became dry and lacustrine forms were eliminated after losing their spawning sites (Gabrielyan 2010). Currently only two races of Sevan trout, summer ishkhan and Gegharquni, spawning in the Lake Sevan drainage basin rivers, have survived, but have become rare. Thereby, the significance of studying the current state of their spawning sites, aimed at revealing the areas most appropriate for their natural reproduction, as well as at finding out natural and artificial constraints for their spawning migration in the rivers, is really high. Not less important, the global concern regarding the declining efficiency of spawning of salmonids has produced a huge amount of information on their reproductive ecology (Elliott 1994; Fleming 1998; Armstrong et al. 2003; Esteve 2005; Louhi et al. 2008; Nika et al. 2011), which mainly refers to the brown trout (Salmo trutta) and, particularly, to its stream-dwelling forms (morpha fario). This allows filling the knowledge gap about the specific habitat and real conditions of Sevan trout. Generally it can be stated that Sevan trout have selected slightly shallower spawning sites (15–45 cm) with the dominancy of gravel and cobble (16–256 mm), as well as with the presence of sand and flow velocity of 15–55 cm s−1 (Gabrielyan 2010).

STUDY AREA

Aimed at the assessment of the rivers' potential for supporting natural reproduction of Sevan trout, the pilot project was carried out in the South-West part of Lake Sevan (40°06′–40°11′N, 45°7′–45°15′E, Figure 1). The rivers Lichq, Bakhtak and Tsakqar were chosen based on the results of the most recent study on Sevan trout reproductive ecology, implemented in the 1980s (Smoley 1987).

Figure 1

Location of study area and sampling sites.

Figure 1

Location of study area and sampling sites.

Lake Sevan is one the biggest high mountain lakes in the world, with an altitude of 1,900 m a.s.l. All its tributaries are formed in the surrounding mountain ranges and flow through the territory of different climate zones, which influences the rivers' hydrophysical, hydromorphological and some hydrochemical parameters. Particularly, the main parts of the studied reaches are located in areas with a moderate climate type with relatively dry, warm summers and cold winters. A few of the sampling sites (T3, B4) are located in areas with a moderate climate type with short, cool summers and cold winters.

The rivers Tsakqar and Bakhtak are typical mountainous streams in the upper and middlestream parts with a high average channel slope (from 1.2% to 16%) and velocity (25–57 cm s−1). The river Lichq, as well as downstream parts of the Bakhtak and Tsakqar rivers are closer to lowland river type with low average channel slope (from 0.06% to 0.82%) and velocity (5–19 cm s−1). The river Bakhtak is the longest (30 km) among the studied rivers, with a catchment area of 148 km2 and mean annual discharge at the river mouth of 0.65 m3/s. It has a very unstable flow regime due to snowmelt (79% of flow is in April-July). The river Tsakqar has a length of 12 km and a catchment area of 66 km2. Mean annual discharge at the river mouth is 0.46 m3/s and flow is distributed almost equally during all seasons due to groundwater feeds. The shortest river among those studied is the Lichq (8 km) with a catchment area of 34 km2 and mean annual discharge at the river mouth of 2.1 m3/s. It also has stable flow distribution during all seasons due to groundwater feeds (Pavlov et al. 2010).

Eight complex field trips to the rivers Lichq, Bakhtak and Tsakqar were carried out in May-June and October-November of 2015, which coincided with the spawning seasons of summer ishkhan and Gegharquni respectively. All field trips in May-June were carried out before the irrigation season launch and in October-November coincided with the end of the irrigation season in the Lake Sevan basin. Additionally, all three rivers are impacted by domestic wastewater from small villages located in the catchment basins, because there is no wastewater treatment plant in that part of the region and all wastewater flow into the rivers. Thus, all three rivers are mainly affected by biogens and organic matter.

MATERIALS AND METHOD

During the field trips the following hydrophysical and hydrochemical parameters, vital for the assessment of rivers' appropriateness as spawning areas for Sevan trout, were investigated: ground type, temperature regime, hydrologic peculiarities, as well as the pH and oxygen regime, the presence of fish lurking for fry and obstacles for fish migration. Measurements of temperature, pH and dissolved oxygen (DO) were made by Hanna HI9813-5N pH/EC/TDS and Hanna HI9147-10 DO meters respectively. Ground types in each studied reach were revealed by empiric observation. The benthic macroinvertebrates composition in different parts of the rivers was studied as a food base for fry, as well as for the assessment of water quality. Sampling of macrozoobenthos, its further processing and determination were made according to AQEM methodology (Manual 2002) by using keys (Bestimmungshilfen 2010; Waringer & Graf 2011). Water quality was assessed according to the BMWP index (Semenchenko & Razluckiy 2010). The presence and projective coverage of macrophytes was observed empirically. Potential obstacles for fish spawning migration were registered and some physical measurements (height, length, slope) were taken. Additionally, the average annual and monthly hydrologic and hydrophysical data for the rivers of Lake Sevan drainage basin were used for comparison with the current measurements (Pavlov et al. 2010). Statistical analyses of the collected data were made by IBM SPSS 22 software. Spatial information for further mapping was collected by a Garmin eTrex20 GPS receiver. Spatial analysis of the collected data for the assessment of the rivers' potential was made by ArcGIS 10.1 software. The main principle of the developed assessment technique is the construction of logical chains, where the factors influencing the potential of the rivers to support natural reproduction of Sevan trout are classified according to their strength. For example, insurmountable obstacles, critically inappropriate ground types and temperatures have the highest weight in the chain and food base has the lowest weight. The main merit of such an assessment technique used around the world is the preliminary substitution of the vast variety of factors (e.g., specific conductance, nitrate, nitrite, ammonium and redox potential etc.) (Pander et al. 2009; Nika et al. 2011; Sternecker et al. 2013) in the study of the benthic macroinvertebrate community. This allows assessing water quality by simple bioindication methods and having more reliable results than with the use of more hydrochemical parameters, because unlike hydrochemical parameters, assessment of water quality based on benthic macroinvertebrates gives the opportunity to estimate the long-lasting anthropogenic effect and avoid the regular replications necessary in hydrochemical studies. Sternecker et al. 2013 have also stressed the use of benthic macroinvertebrates in the studies of salmonids' spawning habitats, but only in aspect of food base. The main demerit of such a technique is the limited application for other regions, where different sources of pollution (industrial, toxic, etc.) may play a significant role.

RESULTS AND DISCUSSION

Hydrophysical and hydrochemical characteristics

The start of Sevan trout spawning migration depends on water temperature. Studies show, that spawning migration of summer ishkhan and Gegharquni start when daily average water temperature in the rivers reaches +7.5 °C and drops below +5.8 °C, respectively (Savvaitova et al. 1989). Water temperature measurements have shown that, starting from the second half of May, all downstream parts of the studied rivers' are appropriate for summer bakhtak spawning migration (Table 1). During May, the average morning temperature was the lowest in the Bakhtak river (+5.5 °C), whereas in the other two studied rivers it was higher (+7 °C in the Lichq river and +8.5 °C in the Tsakqar). Due to the small amplitude of elevations in its drainage basin and groundwater feed, lower daily and seasonal temperature fluctuations have been registered in the Lichq river. Literature data analyses for these rivers also show that the average water temperatures in May are optimal for the spawning migration of summer ishkhan (Pavlov et al. 2010). The data provided in Table 1 prove that water temperature in June was appropriate for the spawning migration to all studied areas. Similar studies in October-November seasons showed that average temperatures in the first half of October were not appropriate for the spawning migration of Gegharquni. However, at the end of October the registered temperatures regularly dropped below +5.8 °C. According to temperature analyses the most appropriate river for Gegharquni's natural reproduction is the Bakhtak.

Table 1

Hydrophysical and hydrochemical parameters of some studied parts of the rivers

Sampling siteAverage DO (mg/l)Average oxygen saturation (%)Average daily temperature (°C)Average value of pH
May 
 Lichq downstream 8.8 78 +8.7 7.8 
 Tsakqar downstream 8.5 80 +9.1 7.87 
 Bakhtak downstream 96 +8.1 8.07 
 Bakhtak-Tsakqar 72 +10.5 8.01 
June 
 Lichq upperstream 10.8 89 + 7.6 6.92 
 Lichq middlestream 11.72 100.5 + 8.6 7.07 
 Lichq near the dam 11 99 + 10.7 7.26 
 Lichq downstream 10.5 85 + 14.6 7.52 
 Bakhtak upperstream 10.2 92 + 7.9 7.15 
 Bakhtak middlestream 11.85 103 + 9.4 7.58 
 Bakhtak downstream 8.15 90 + 13.5 9.01 
 Bakhtak-Tsakqar 9.8 95 + 13 8.56 
October 
 Lichq downstream 10.65 96.5 + 8.3 7.67 
 Lichq middlestream 10.35 92 + 7.8 7.25 
 Lichq upperstream 9.96 83.3 + 7.4 7.17 
 Bakhtak-Tsakqar 9.43 85 + 6.1 7.75 
 Bakhtak middlestream 9.71 89 + 5.4 7.3 
November 
 Lichq downstream 11.9 98.5 + 6.9 7.62 
 Lichq middlestream 11.82 98 + 6.5 7.1 
 Lichq upperstream 11.2 93 + 6.3 6.98 
 Tsakqar downstream 13.4 110.4 + 5.7 8.1 
 Bakhtak-Tsakqar 13.33 110 + 5.5 8.18 
 Bakhtak downstream 12.3 104.3 + 5.1 8.23 
 Lichq near the dam 12.51 104.7 + 6.5 7.4 
Sampling siteAverage DO (mg/l)Average oxygen saturation (%)Average daily temperature (°C)Average value of pH
May 
 Lichq downstream 8.8 78 +8.7 7.8 
 Tsakqar downstream 8.5 80 +9.1 7.87 
 Bakhtak downstream 96 +8.1 8.07 
 Bakhtak-Tsakqar 72 +10.5 8.01 
June 
 Lichq upperstream 10.8 89 + 7.6 6.92 
 Lichq middlestream 11.72 100.5 + 8.6 7.07 
 Lichq near the dam 11 99 + 10.7 7.26 
 Lichq downstream 10.5 85 + 14.6 7.52 
 Bakhtak upperstream 10.2 92 + 7.9 7.15 
 Bakhtak middlestream 11.85 103 + 9.4 7.58 
 Bakhtak downstream 8.15 90 + 13.5 9.01 
 Bakhtak-Tsakqar 9.8 95 + 13 8.56 
October 
 Lichq downstream 10.65 96.5 + 8.3 7.67 
 Lichq middlestream 10.35 92 + 7.8 7.25 
 Lichq upperstream 9.96 83.3 + 7.4 7.17 
 Bakhtak-Tsakqar 9.43 85 + 6.1 7.75 
 Bakhtak middlestream 9.71 89 + 5.4 7.3 
November 
 Lichq downstream 11.9 98.5 + 6.9 7.62 
 Lichq middlestream 11.82 98 + 6.5 7.1 
 Lichq upperstream 11.2 93 + 6.3 6.98 
 Tsakqar downstream 13.4 110.4 + 5.7 8.1 
 Bakhtak-Tsakqar 13.33 110 + 5.5 8.18 
 Bakhtak downstream 12.3 104.3 + 5.1 8.23 
 Lichq near the dam 12.51 104.7 + 6.5 7.4 

Specific studies on DO requirements for Sevan trout has not been carried out, thus the appropriate data for other freshwater forms of salmonids were used for comparisons and analysis. Particularly, studies on rainbow and brown trout have shown that the optimal DO conditions for egg development vary from 8 mg/l to 15 mg/l, and for juveniles and adults from 7 mg/l to 15 mg/l, with the average temperatures below +15 °C (Chapman 1986). The parameter of DO of water in all seasons was satisfactory to support Sevan trout natural reproduction and further life cycles of fry and juveniles in all three rivers (Table 1). Due to the drop of temperatures in October-November compared to May-June, the value of DO increased. The most optimal DO conditions were registered in November.

The first complete study of salmonids' requirements on pH was made in the 1960s by FAO (Water quality 1968). As stated in that report ‘the pH range which is not directly lethal to fish is 5–9. However, where high pH values are caused by the vigorous photosynthetic activity of aquatic plants, accompanying high temperatures and supersaturation of dissolved gases (together with other factors) may also contribute to a greater or lesser extent to fish mortality, making it difficult to correlate mortality with laboratory data on pH value alone’. However, specific tests on brown trout have shown that the level of pH of 6.2 can be lethal for this fish. Further studies only prove that freshwater salmonids are more sensitive to acidic water (Kocovsky & Carline 2005). Statistical data on hydrochemical parameters in spawning rivers of Sevan trout reveal the absence of significant concentrations of toxic elements in the rivers of the Lake Sevan basin, but, at the same time, there is no information indicating that Sevan trout have ever spawned in acidic or near acidic water conditions. Typically, pH level in all spawning rivers of Sevan trout varies from 7.2 to 9.3 (Asatryan 2013). Thereby, the pH parameter can also be a constraining factor for the Sevan trout spawning migration, if the values drop below 7. The studies have not revealed serious seasonal fluctuations of this parameter, despite values below 7 being registered in some cases. According to this parameter, the upperstream part of the Lichq river is quite inappropriate for Sevan trout spawning. In all studied parts of the Bakhtak and Tsakqar rivers, the pH parameter was suitable.

One more important factor for trout spawning is ground type. Sevan trout as well as brown trout prefer spawning in riffle and run type habitats (Pedersen et al. 2009; Gabrielyan 2010; Sternecker & Geist 2010; Nika et al. 2011). Suitable ground types for the spawning of Sevan trout have been revealed in the middle and, in some cases, in the upperstream and downstream parts of the rivers where strong dominancy of gravel and cobble has been observed. Particularly gravel was dominant (>50%) in almost all studied reaches of middlestream part of the Bakhtak and Tsakqar rivers as well as the upper part of the Lichq river. Cobble was dominant (>40%) in the middlestream part of the Lichq river. The dominancy of sand and mud (>85%) was registered at the L1, B2 and BT1 sampling sites (Figure 1), which critically decreases the potential of these parts to support natural reproduction of Sevan trout. Artificial ground (river channelized in the territory of Lichq village) covered by sand and mud was registered in the main part of the L4 sampling site, which also decreases the potential of that part to support natural reproduction. Formally, the ground types of downstream parts of the Tsakqar and Bakhtak rivers are also mostly suitable for Sevan trout spawning, but in reality the stones in those parts are covered by periphyton and organic matter, which decreases the possibility of spawning there. Thus, there is a necessity for water quality improvement in the downstream parts of the rivers and creation of an artificial ground suitable for Sevan trout spawning. Typically, the ground of the downstream parts consists of sand and mud, accumulated in those parts due to decreased flow velocity.

Benthic macroinvertebrates community and water quality assessment

Barseghyan & Vardanyan (2015) have shown that Sevan trout fry prefer to feed on the Diptera of Chironomidae and Simuliidae families in the early months of their life, and on mayflies (Ephemeroptera) and caddisflies (Trichoptera) as well as Gammaridae crustaceans later. This fish starts eating all kinds of benthic macroinvertebrates from the age 1+. Analyses of benthic macroinvertebrate biomass (Figures 25) reveal that the dominant and subdominant groups of zoobenthos correspond to taxa preferable by trout in all seasons. Studies have also shown that the highest diversity of macroinvertebrates was mainly in the downstream part of the Bakhtak-Tsakqar system (from 13 to 17 families), except for November, where the absolute maximum from all studied periods was registered in the Tsakqar river' downstream part. Generally, the lowest diversity of macroinvertebrates during all field trips was revealed in the Lichq river, especially in the downstream part. Due to the morphological and geological features of the Lichq river drainage basin, the flow velocity is too low and ground types are very poor in the downstream part to support the diversity of macroinvertebrates. On the other hand, conditions created there promote the development of appropriate habitats for the Diptera and mollusks. Thus, this part is becoming one of the main areas for fish feeding. The highest biomass in 1 m2 in May was registered in the Bakhtak-Tsakqar system (47 g/m2) and the lowest – in the Lichq river downstream (1.1 g/m2). Water quality assessed by BMWP index has shown that the most polluted part in May is the downstream of the Lichq river (BMWP score – 17) and the least polluted is the Bakhtak-Tsakqar system (BMWP score – 54). Due to water stagnation, the self purification potential of the Lichq river is very low in the downstream part and organic matter accumulates there, creating inappropriate conditions for Sevan trout.

Figure 2

Benthic macroinvertebrate composition, biomass and studied rivers' water quality in May.

Figure 2

Benthic macroinvertebrate composition, biomass and studied rivers' water quality in May.

Figure 3

Benthic macroinvertebrate composition, biomass and studied rivers' water quality in June.

Figure 3

Benthic macroinvertebrate composition, biomass and studied rivers' water quality in June.

Figure 4

Benthic macroinvertebrate composition, biomass and studied rivers' water quality in October.

Figure 4

Benthic macroinvertebrate composition, biomass and studied rivers' water quality in October.

Figure 5

Benthic macroinvertebrate composition, biomass and studied rivers' water quality in November.

Figure 5

Benthic macroinvertebrate composition, biomass and studied rivers' water quality in November.

Studies implemented in June (Figure 3) have shown that the diversity of macrozoobenthos became higher due to lower water turbidity compared with May, as well as increased transparency and aeration of water. The highest biomass of macroinvertebrates was recorded in the upperstream part of the Lichq (22.4 g/m2). Assessment of water quality has shown that, compared to May, the BMWP score increased in all studied parts due to physical changes in water flow, but changes in water quality class were registered only in the Bakhtak river. The most polluted part was the downstream of the Lichq river (BMWP score – 21) and the least polluted – the Bakhtak-Tsakqar system (BMWP score – 65).

The diversity of macrozoobenthos, as well as biomass mainly decreased in October due to the impact of water consumption in the summer period (Figure 4). Only the Bakhtak-Tsakqar system experienced significant changes in the structure of benthic macroinvertebrates compared to June. The highest total biomass was registered in the upperstream part of the Lichq (18.6 g/m2). Although the organic pollution increased in the downstream part of the Lichq, it's also suitable for summer bakhtak fry due to The presence of macrophytes as well as Diptera lurking as food. Results of water quality assessment have shown that, compared to June, only the water quality of the Tsakqar was improved and assessed as ‘good’ (BMWP score – 57). It's probably the consequence of low water consumption from dwellers of Tsakqar village, which prefer to consume water from the more saturated Bakhtak river, which also flows through the village. The highest water quality was registered in the Bakhtak-Tsakqar system part (BMWP score – 61) and, like in May and June, the worst water quality was registered in the Lichq downstream part (BMWP score – 21).

Due to serious weather changes influencing hydrophysical and hydrochemical parameters of water, obvious changes were registered in November. Increase in the number of macrozoobenthos groups was registered in all studied parts of the Bakhtak and Tsakqar rivers. Particularly, the highest diversity within all investigations was registered in the downstream part of the Tsakqar (18 families). The biomass of macrozoobenthos in the Tsakqar and Lichq rivers was also highly increased. Unlike October, the highest biomass was registered in the middlestream part of the Lichq river (37.1 g/m2). There were no changes in the Lichq rivers' macrozoobenthos qualitative structure due to a relatively stable flow regime and water quality. As a result of the macrozoobenthos' high diversity, the highest value of water quality (75, which referred to ‘good’ water quality) from all was also registered in the downstream part of the Tsakqar river. Water quality in the Bakhtak worsened, which possibly was the result of the additional organic matter provided to water by leaves and debris.

Though the analysis of natural factors allows conclusions to be made about the suitability and potential of the studied rivers for spawning of Sevan trout, in some cases artificial obstacles have bigger importance in decision making than the natural factors (Figure 6). During the field trips, five obstacles for Sevan trout spawning migration were revealed. Today, one of them is insurmountable for fish, two others are hard to surmount or, in some cases, insurmountable (e.g. during low water periods). The last two obstacles are surmountable, but their presence has negative impact on fish.

Figure 6

Distribution of Sevan trout spawning migration obstacles and assessment of studied rivers' potential as spawning areas for Sevan trout.

Figure 6

Distribution of Sevan trout spawning migration obstacles and assessment of studied rivers' potential as spawning areas for Sevan trout.

Assessment of potential spawning areas of Sevan trout

GIS analysis of the collected data and qualitative assessment of the studied rivers' potential to support natural reproduction of Sevan trout was made (Figure 6).

Under the methodology, the possibility of river parts supporting the natural reproduction of Sevan trout was classified into five classes. The first two classes (Inappropriate by natural or by artificial reasons) mainly refer to the parts of the rivers with unsuited ground types like sand and mud (L1) or temperature regimes (B6 – parts of the rivers above 2,500 m a.s.l.), as well as to the parts after insurmountable obstacles (T2) or the territories of settlements, where fishing is not regulated and the use of forbidden devices for fishing is out of control (B4, B5). There may also be some additional factors like unsuitability of hydrophysical or hydrochemical parameters, as well as river bed conditions (L4) influencing such assessment. The parts called ‘low potential or unwanted’ refer to the places after hard surmountable obstacles (L3) and with open access for dwellers and livestock (T1, B2, B3). Some specific parameters like water level (T1) and ground types (B2) also had impact on classification. The other parts (B1, BT2, L2) mainly have appropriate conditions to support natural reproduction of Sevan trout and further growth of fry in those areas, but today there is no place which can be ideally suitable for this fish. Even the parts assessed as appropriate need some improvement of several parameters, like clearing of the river beds from waste (BT2), improvement of water quality (B1, L2), regulation of marginal poaching (L2) etc. To be assessed as ‘high potential’, the reach has to meet the following requirements simultaneously: habitats should offer a series of flow types to include pools, runs, riffles and glides, complex substrate diversity must also be exhibited throughout the reach. Ample cover on both banks needs to be present to provide refuge for both juvenile and adult fish, and the instream and marginal vegetation must be incorporated. There needs to be suitable ground type without obvious signs of pollution or marginal poaching and without migration barriers.

CONCLUSION

Based on a ‘cheap’ and ‘time-saving’ approach, hydrophysical, hydrochemical and hydrobiological investigations for the assessment of several rivers' potential to support natural reproduction of Sevan trout were developed. Implemented studies have shown that the Lichq, Bakhtak and Tsakqar rivers consist of different habitats suitable for Sevan trout natural reproduction. By hydrophysical and hydrochemical parameters, the river Bakhtak has the highest potential as a spawning river for Sevan trout. The highest potential to support natural reproduction of Sevan trout was revealed to be in the middlestream part of the Lichq river, as well as in the downstream part of the Bakhtak river and the part of the Bakhtak-Tsakqar system near the connection of the Bakhtak and Tsakqar rivers; however, all these areas need some remediation to achieve ‘high potential’. Based on the best international practice (Louhi et al. 2008; Pedersen et al. 2009; Hauer et al. 2011; Sternecker et al. 2013; Hauer et al. 2015), the following mitigation measures are proposed:

  • To limit river access by livestock and the local population in the middlestream part of the Lichq river, as well as downstream parts of the Bakhtak and Tsakqar rivers. Also some artificial gravel dumping is recommended in these parts.

  • To ban water consumption from the Bakhtak and Tsakqar rivers starting from September and up to the end of January, which will stabilize the discharge and ensure the availability of the depth preferable for trout, as well as increase the self-purification potential of the rivers.

  • To restore the fluvial processes by removal of accumulated fine sediments in the downstream part of the Tsakqar river.

Due to the artificial constraints for spawning migration and some hydrophysical parameters, the upperstream parts of the rivers are inappropriate for Sevan trout reproduction. Although the different parts of the studied rivers have potential for being spawning areas of this endemic fish, there is no ideal place for that at present.

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