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.

The improvement of water management calls for action in the Republic of Armenia. Nowadays, the development of the hydrobiological monitoring approaches and procedures is the main goal. However, a lack of knowledge on the background conditions prevents further activities of revaluating of the methods used for water monitoring in Armenia with the EU WFD principles. Following the results of baseline studies conducted in the Debed River system, it was concluded to investigate small tributaries in order to find the most relevant and the best available site in the drainage basin. The study aims to analyse the community of benthic macroinvertebrates of the Tandzut River. We suggest the Tandzut River as a relevant substitution for the recent best available site in the area due to the ecological status of the upper reaches of the Tandzut River, which is by one category higher than the recent best available site of the Pambak River system according to BMWP index.

Gammarus plays a central role in the detritus cycle and constitutes an important component in food webs. At the same time, taxonomy and morphological identification to species level is highly challenging in this genus. Thus, the freshwater gammarid diversity in the Caucasus biodiversity hotspot remains largely unstudied to date. We use DNA barcoding for the first time in assessing the biodiversity and taxonomy of gammarids within the amphipod genus Gammarus in the limnic ecosystems of Armenia. The results expand the knowledge on possible diversity and evolutionary lineages of Gammarus in the region. DNA barcodes obtained from our Armenian specimens consistently indicate four to six well-defined molecular operational taxonomic units (MOTUs) within three distinct morphospecies clusters. One to three MOTUs correspond to the Gammarus balcanicus species complex, two MOTUs to the G. komareki complex, and one MOTU to the G. lacustris complex. Five BINs out of six were unique and new to BOLD.

The caddisfly fauna of Armenia is poorly known, and the country has been largely absent from recent faunistic and taxonomic research in the Caucasus region. In May 2025, a short field survey in the Dilijan National Park, northeastern Armenia, resulted in the discovery of a new species of Wormaldia McLachlan, 1865 from a tributary of the Aghstev River. Wormaldia dilijanica sp. nov. is described and illustrated based on male genital morphology. The species is distinguished by the combination of the following characters: slender, digitate apex of segment X; S-shaped, tapering superior appendages; second segment of inferior appendages nearly parallel-sided and as long as the first; broad anteromesal projection of segment IX; and a phallic organ bearing one large spine, one smaller spine, and a cluster of short basal spines. The new species is compared with Wormaldia kera Oláh, 2019 from Georgia and W. hoska Oláh, 2020 from Azerbaijan. Finding of the new species from Dilijan National Park in Armenia despite a very limited sampling efforts, suggests that the country harbors a rich but still undocumented fauna of caddisflies.

Freshwater ecosystems are increasingly affected by anthropogenic stressors, necessitating the assessment of sensitive biomarkers of sublethal impact. This study assessed the seasonal variability of oxidative stress parameters in the amphipod Gammarus lacustris from three tributaries of Lake Sevan (Armenia)—the Gavaraget, Karchagbyur, and Argichi Rivers—with contrasting hydrophysical and hydrochemical conditions. During 2022–2024, lipid peroxidation (MDA), antioxidant enzymes (CAT, SOD, GR, and GST), and glutathione (GSH) were measured in specimens collected in May, July, and October and related to temperature, dissolved oxygen, nutrients, major ions, and trace elements. Biomarker levels generally increased from spring to summer and declined in autumn, following temperature and photoperiod patterns. Statistically significant seasonal dynamics were most consistent in the Karchaghbyur River, while, in the Gavaraget and Argichi Rivers, they varied by biomarker and year. Amphipods from the Gavaraget River exhibited consistently elevated levels of oxidative stress biomarkers, consistent with elevated nutrient concentrations and stronger anthropogenic impacts. A short-term increase in all biomarkers in the Argichi River in 2023 indicated episodic acute stress. Overall, the response of oxidative stress biomarkers in G. lacustris reflected both the natural seasonal variability and spatial differences in environmental pressure, confirming their potential as a tool for monitoring Lake Sevan’s tributaries.