Sevan Trout Research Articles

Experimental Validation of Suitability of a River for Natural Reproduction of Trout of Lake Sevan Using Egg Incubation

The endangered endemic species Sevan trout (Salmo ischchan Kessler, 1877) is under the threat of extinction and its survival is dependent on restocking by smolts. Thus, there is an urgent need to find an effective solution for restocking wild populations. After developing a theoretical methodology to reveal the most suitable parts of spawning rivers for natural reproduction, we consider the incubation of eggs in the wild as an appropriate method for the validation of the results of the theoretical assessment. Thus, we estimate the eggs’ survival differences in the wild and microcosm conditions which found significant differences in the sac-fry emergence rate in the zones assessed as “partly suitable” and “unsuitable”. Also, the results show that the emergence of eggs in the wild was less than in the microcosm conditions and the success rate of emergence of eyed eggs in the wild was higher than that of the green eggs. The results of one-way ANOVA, correlation and general linear mixed model analyses have in general proven the theoretical assessment but raise some questions on the completeness of using a set of abiotic criteria as the range of success during different experiments varies significantly.

Fish Probiotics: Cell Surface Properties of Fish Intestinal Lactobacilli and Escherichia coli

The properties of intestinal bacteria/probiotics, such as cell surface hydrophobicity (CSH), auto-aggregation, and biofilm formation ability, play an important role in shaping the relationship between the bacteria and the host. The current study aimed to investigate the cell surface properties of fish intestinal bacteria and probiotics. Microbial adhesion to hydrocarbons was tested according to Kos and coauthors. The aggregation abilities of the investigated strains were studied as described by Collado and coauthors. The ability of bacterial isolates to form a biofilm was determined by performing a qualitative analysis using crystal violet staining based on the attachment of bacteria to polystyrene. These studies prove that bacterial cell surface hydrophobicity (CSH) is associated with the growth medium, and the effect of the growth medium on CSH is species-specific and likely also strain-specific. Isolates of intestinal lactobacilli from fish (Salmo ischchan) differed from isolates of non-fish/shrimp origin in the relationship between auto-aggregation and biofilm formation. Average CSH levels for fish lactobacilli and E. coli might were lower compared to those of non-fish origin, which may affect the efficiency of non-fish probiotics use in fisheries due to the peculiarities of the hosts' aquatic lifestyles.

STUDY OF PERMEABILITY OF FISH SKIN

Skin permeability of Sevan trout has been studied during 30 min in different solutions: in distilled water, in 70% ethanol, in solution of 0.125 M KCl. The permeability was measured by methylene blue. It was shown that the skin permeability for this dye changes depending in what solution these shreds of Sevan trout were kept and from which side the shred was tightened. It was also shown that distilled water, solution of 0.125 M KCl and ethanol cause structural changes in the skin layers of the Sevan trout, in particular the epidermis.

Caucasian treasure: Genomics sheds light on the evolution of half-extinct Sevan trout, Salmo ischchan, species flock

Five ecologically and phenotypically divergent ecomorphs of the genus Salmo are known from a landlocked alpine lake in the Caucasus, Lake Sevan. It is an example of sympatric diversification within a species-rich lineage with predominate mode of speciation being allopatric. The diversification of Sevan trouts was accompanied by spawning resource partitioning. Four lacustrine ecomorphs with different temporal-spatial spawning strategies and divergent morphology and coloration evolved along with a fifth ecomorph, brook trout, inhabiting the tributaries. Unfortunately, the Sevan trout diversity was almost destroyed by human activity, with two ecomorphs becoming extinct in the 1980s. We performed reconstruction of the evolutionary history of Sevan trouts based on high-throughput sequencing of both contemporary and historical DNA (∼ 50 y.o.) of all Sevan trout ecomorphs. Our study of complete mitogenomes along with genome-wide SNP data revealed the monophyly of four lacustrine ecomorphs and local brook trout, all derived from the anadromous form Caspian salmon, S. caspius. The species tree suggests a scenario of stepwise evolution from riverine to lacustrine spawning. Three genomic clusters were revealed, of which two refer to the riverine and lacustrine spawners within the flock of Sevan trouts (with FST value = 0.069). A few SNP outliers under selection were discovered that could be responsible for assortative mating based on visual recognition. The Holocene climatic oscillations and the desiccation of tributaries could have played an important role in the origin of lacustrine spawning. The relationships between lacustrine ecomorphs were not yet fully resolved. This radiation warrants further investigation.

ԿԱԴՄԻՈՒՄԻ ԵՎ ՊՂՆՁԻ ՌԻՍԿԻ ԳՆԱՀԱՏՈՒՄԸ ՁԿՆԱՄՍԻ ՍՊԱՌՄԱՆ ԴԵՊՔՈՒՄ

The aim of the study is to assess the non-carcinogenic risk of heavy metals (Cd, Cu) through fish consumption by the population of Yerevan. The method of K-means cluster analyses has been applied. The amount of the average daily intake of cadmium and copper detected in the fish samples of Sevan Trout, Sterlet and Sazan didn᾿t exceed the standards of International Health Regulation (IHR). Non-carcinogenic risks related to their effect haven’t been recorded. The results of cluster analyses can serve as a base for conducting general dietary investigations.

Checklist of the freshwater fishes of Armenia, Azerbaijan and Georgia

We present a critical checklist of freshwater fish species found so far in the countries of Armenia, Azerbaijan and Georgia. In total 119 freshwater fishes are recorded. There are 40, 86 and 96 species currently known for Armenia, Azerbaijan and Georgia respectively. From these 119 species, seven are endemic and seven species are alien. From the alien species, only three (Carassius gibelio, Gambusia holbrooki and Pseudorasbora parva) can be considered as widespread and invasive. There are four species (Gasterosteus aculeatus, Gobio artvinicus, Perca fluviatilis and Salmo gegarkuni) that are translocated within the region. Seven species are confirmed or recorded for the first time including G. artvinicus and Oxynoemacheilus veyselorum for Armenia, Azerbaijan and Georgia, Capoeta kaput and Rhinogobius lindbergi for Azerbaijan and Georgia, Capoeta razii for Azebaijan, Oxynoemacheilus cemali and Squalius agdamicus for Georgia. In this checklist, Acipenser colchicus is treated as a synonym of Acipenser persicus. Sand smelts of the Black and Caspian Sea basin are identified as Atherina caspia and Clupeonella caspia is treated as a synonym of Clupeonella cultriventris. Coregonus sevanicus is listed as Coregonus sp. until the situation of Sevan whitefish is better understood. Capoeta sevangi and Capoeta ekmekciae are synonyms of Capoeta capoeta. The fish often identified as Capoeta capoeta gracilis from rivers south of the Kura most likely belong to C. razii. The Black and Caspian Sea Rutilus populations are treated as conspecific, therefore R. kutum is a junior synonym of R. frisii. Oxynoemacheilus veyseli is valid as O. veyselorum. We list the alien Rhinogobius species as R. lindbergi, however the name is provisional and needs further confirmation. All Squalius species from the Kura River drainage are identified as S. agdamicus, however in the Aras, it is replaced by S. turcicus. Squalius orientalis is treated as a valid species restricted to the eastern Black Sea basin. The four forms of Lake Sevan trout (Salmo ischchan, S. gegarkuni, S. danilewskii and S. aestivalis) are treated as valid species, two of them (S. ischchan and S. danilewskii) are extinct. Rutilus sojuchbulagi from Azerbaijan is also extinct.

ПРИМЕНЕНИЕ НОВОГО МЕТОДА ИСКУССТВЕННОЙ ИНКУБАЦИИ ИКРИНОК СЕВАНСКОЙ ФОРЕЛИ (SALMO ISCHCHAN, KESSLER) В ЕСТЕСТВЕННЫХ УСЛОВИЯХ ПРИТОКОВ ОЗ. СЕВАН (АРМЕНИЯ)

Endemic fish species of Armenian ichthyofauna – the Sevan trout (Salmo ischchan, Kessler, 1877) is registered in the Red Book of Animals of the Republic of Armenia as critically endangered (corresponds to IUCN category: CR A2cd). Its natural reproduction hardly occurs as a result of numerous problems related to the use and management of water and bio-resources in the drainage basin of Lake Sevan. The Lichq River is formerly known as a spawning river for two ecological races of Sevan trout, but because of different factors there are no more wild populations of Sevan trout spawning. The aim of the study was checking the efficiency of two methods of egg incubation in the Lichq River for restoration of Gegarkuni population. The experiments were carried out with newly fertilized and eyed eggs of Gegarkuni in the same periods and in the same areas to avoid the unforeseen effects of environmental factors on assessment. The results showed that the mortality rate of green eggs in the natural conditions is quite high before reaching eyed egg stage (65-68%), while the mortality rate of eyed eggs planted in the natural conditions is only 9-17%. This means that the effectiveness of planting eyed eggs is higher for the artificial restoration of Gegarkuni stocks in the nature.

An integrative evaluation of suitability of a river for natural reproduction of trout of Lake Sevan (Armenia).

Endemic fish species of Armenian ichthyofauna-Sevan trout (Salmo ischchan Kessler, 1877)-is registered in the Red Book of Animals of the Republic of Armenia as "Critically Endangered" (corresponds to IUCN category: CR A2cd). Its natural reproduction hardly occurs as a result of numerous problems related to the use and management of water and bio-resources in the Lake Sevan drainage basin. Masrik River is formerly known as a spawning river for two ecological races of the Sevan trout, but there is no up-to-date and in-depth studies of its potential to support natural reproduction. Thus, a set of spawning criteria was arranged as matrix and state of Masrik River as spawning area for the Sevan trout was assessed. The results showed that the potential of different parts of Masrik River to support natural reproduction of Sevan trout varied from quite appropriate to inappropriate. The main limiting factors revealed were water temperature, velocity and substrate conditions.

High-throughput sequencing of the mitochondrial genomes from archived fish scales: an example of the endangered putative species flock of Sevan trout Salmo ischchan

Sevan trout, Salmo ischchan, dwelling in the mountain Lake Sevan (Caucasus) is a unique species complex. Four sympatric forms of Sevan trout were divergent in both their phenotypes and ecologies. Three forms were lacustrine spawners but were unique in their spawning times and the type of substrate. The fish community of Lake Sevan was strongly impacted by human activity in twentieth century. Two forms of Sevan trout went extinct in the 1980s and the other two forms are at the brink of extinction. The present study demonstrated that archived/historical scales of extinct forms stored at room temperature for up to 44 years are a suitable source of DNA for high-throughput sequencing and for the reconstruction of mitochondrial genomes. In addition, we obtained the mitochondrial genomes of the extant forms for comparison to the extinct forms and reconstruction of a mitogenomic phylogeny of all forms of Sevan trout. The mitogenome gene arrangement was identical in all individuals studied with structure similar to other Salmo spp. The nucleotide sequence divergence between sympatric forms was shallow (P-distance = 0.0003–0.0012). A phylogenetic tree based on mitogenomes confirmed sister position of Sevan trout to the Caspian trout, Salmo trutta caspius (P-distance = 0.0049).

Sequencing of two mitochondrial genomes of endangered form of the Sevan trout Salmo ischchan aestivalis

The two complete mitochondrial genomes of endangered form of the Sevan trout Salmo ischchan aestivalis are published in this paper. The mitochondrial DNA (mtDNA) is 16,677 base pairs (bp) in length and contained 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. The overall base composition of the genome in descending order was 29.4% – C, 27.9% – A, 26.0% – T, 16.7% – G, without a significant AT bias of 53.9%.

Two complete mitochondrial genomes of extinct form of the Sevan trout Salmo ischchan danilewskii

The mitochondrial genomes from two individuals of the extinct subspecies of the Sevan trout Salmo ischchan danilewskii are published in this paper. The mitochondrial DNA (mtDNA) is 16,665 base pairs (bp) in length and contained 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. The overall base composition of the genome in descending order was 27.9% of A, 29.4% of C, 16.7% of G, and 26.0% of T without a significant AT bias of 53.9%.

Fish introductions in the former Soviet Union: The Sevan trout (Salmo ischchan) - 80 years later.

The Soviet Union played the leading role in fish introductions in Eurasia. However, only 3% of all introductions prior to 1978 gave a commercial benefit. One of the noteworthy examples appears to be the Sevan trout (Salmo ischchan Kessler, 1877)—an endemic salmonid of Lake Sevan in Armenia. This species has been introduced to Kirghizstan, Kazakhstan, and Uzbekistan, however, only the Kirghiz population has persisted in relatively high numbers. In this paper we provide the first extensive molecular study of S. ischchan using samples from the native population from Lake Sevan and three hatcheries in Armenia, as well as from the population introduced to Lake Issyk Kul in Kirghizstan. The Kirghiz population has been isolated since the introductions took place in 1930 and 1936. Our results, based on 11 nuclear microsatellites and a 905 bp fragment of the mitochondrial control region suggest that hatcheries have maintained genetic variability by way of ongoing translocations of individuals from Lake Sevan. Simultaneously, significant Garza-Williamson M-values suggest that bottlenecks could have reduced the genetic variability of the wild populations in the past. This hypothesis is supported by historical data, indicating highly manipulated water-level regulations and poaching as two main factors that dramatically impact fish abundance in the lake. On the other hand, a similar situation has been observed in Kirghizstan, but this population likely rebounded from small population size faster than the other populations examined. The Kirghiz population is significantly genetically differentiated from the other groups and have morphological features and biological attributes not observed in the source population. Genetic data imply that the effective population size in the native population is lower than that found in the introduced population, suggesting that some active protection of the Lake Sevan population may be needed urgently.

Prompt assessment of the potential spawning areas of Sevan trout in the South-West part of Lake Sevan

AbstractSevan 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’.

A description of Echinorhynchus baeri Kostylew, 1928 (Acanthocephala: Echinorhynchidae) from Salmo trutta in Turkey, with notes on synonymy, geographical origins, geological history, molecular profile, and X-ray microanalysis.

A population of Echinorhynchus baeri Kostylew, 1928 with 18–24 rows of 8–10 proboscis hooks each and long fusiform eggs measuring 95–110 × 18–22 μm collected from Salmo trutta (Salmonidae) in a branch of the Murat River in Turkey is described and specimens are designated as neotype. Specimens of two similar populations of E. baeri (E. baeri Kostylew, 1928 and E. sevani Dinnik, 1932) were previously described from Salmo ischchan in Lake Sevan, Armenia. Waters of Lake Sevan and the Murat River were previously joined during the Middle Miocene-Pliocene. The two populations from Lake Sevan and ours from Turkey had identical morphology and size eggs. The proboscis armature and eggs, among other features of our Turkish specimens, proved intermediate between E. baeri and E. sevani, thus eliminating the significance of the described differences between these two species and confirming their synonymy with priority to Echinorhynchus baeri (junior synonym: Echinorhynchus sevani Dinnik, 1932). Echinorhynchus baeri is apparently a highly variable species. The two descriptions from Lake Sevan did not include features or illustrations of females, except for references to trunk and egg size but the eggs were illustrated. Complete morphometric comparisons are made and females of the Turkish material are described for the first time. DNA sequencing (mitochondrial cytochrome oxidase subunit I gene; nuclear 18S rRNA gene) results from two available E. baeri individuals were equivocal. New features to the Acanthocephala include the presence of rootless uncalcified apical proboscis hooks studied with X-ray microanalysis.

Morphological characters of lake forms of salmonid fishes of the genera Salmo and Oncorhynchus (Pisces: Salmonidae)

Based on a study of the morphological characteristics of the Sevang trout Salmo ischchan Kessler, 1877 acclimatized in Lake Issyk Kul (Kirghizia) and the lake form of the masu salmon Oncorhynchus masou (Brevoort, 1856) in Lake Biwa (Japan) their unique characteristics were defined. These characters allow to consider these forms as subspecies. The main directions and the rate of change of the characters with the forming of trouts and salmons in Atlantic and Pacific species in lake conditions are considered.

Hepatocyte ultrastructure of the Sevan trout (Salmo ishchan gegarkuni Kessel) during ontogeny

Hepatocytes of Lake Sevan Salmo were examined at several stages in their life cycles which are different from the point of view of the manner of feeding. Salmo were reared at the fish farm, they were fed with the yolk of the chick eggs. It was revealed that hepatocytes of larva, which was sampled immediately after hatching (endogenous feeding) intensively synthesized the proteins; accumulated and secreted the bile product stored glycogen and lipids. The ultrastructure of larva hepatocytes changed on the 5th and 10th day after larva began to accept food (mixed feeding--endogenous and exogenous). Golgi complex became bigger, glycogen disappeared, lipid droplets became smaller (on the 5th day) and disappeared completely (on the 10th day). Morphological differentiation finishes during the fingerling period (exogenous feeding). Cisternae of granular endoplasmic reticulum (GER) and mitochondria are arranged around nucleus, near bile canaliculus and sinusoids. Big areas of glycogen lie between the organelles. Relative volumes of GER, mitochondria, glycogen increased, but the relative volume of Golgi complex diminished.