This study investigated long-term changes in zoobenthos in Lake Balkhash using data from 1975 to 2024. Lake Balkhash provides a suitable system for this analysis. Its hydrological regime is subject to fluctuations due to the combined use of its water for hydropower and irrigation. A total of 66 zoobenthic taxa were recorded. Boxplot analysis revealed substantial temporal variability in taxonomic richness over the study period. CONISS clustering identified temporal differences in zoobenthic taxonomic composition and distinguished different community states over time. However, the results should be interpreted with caution due to changes in sampling effort and improvements in taxonomic resolution over time, which may have influenced observed patterns in taxonomic richness. Water-level data for Lake Balkhash (1975–2022), representing the longest complete hydrological record available, were analyzed to assess relationships between water-level dynamics and zoobenthic taxonomic richness across two hydrological periods (≤1999 and ≥2000). Spearman correlation revealed a positive relationship between water level and taxonomic richness, which was slightly stronger with a one-year lag. However, the low explained variance suggests that additional environmental factors also influenced taxonomic richness.

Lake Balkhash is a large endorheic lake experiencing ongoing hydrological and climatic variability. This study aimed to evaluate the species composition and structure of the forage base across three trophic levels—phytoplankton, zooplankton, and zoobenthos—and to analyze trophic interactions of fish communities, including non-native species, in order to assess the functioning of the food web in the western and eastern basins of the lake. A 2025 assessment revealed a structurally reorganized yet relatively stable ecosystem. Phytoplankton showed an increase in taxonomic richness, while zooplankton and zoobenthos demonstrated compositional restructuring with a greater representation of ecologically tolerant taxa. The presence of certain invertebrate taxa in both Lake Balkhash basins indicates persistent spatial heterogeneity of the ecosystem. Despite moderate ecological resilience, biodiversity has not yet returned to historically recorded peak levels. Trophic analysis of fish communities showed generally moderate niche overlap among benthivorous species with localized differentiation of resource use. Predatory fishes also exhibited moderate overlap: pikeperch (Sander lucioperca) maintained stable dietary patterns with partial overlap with Volga pikeperch (Sander volgensis), whereas snakehead (Channa argus) and asp (Aspius aspius) demonstrated clearer trophic segregation. Non-native species displayed relatively narrow trophic niches (Bi < 0.30), indicating summer feeding specialization.

Мақалада 2024 жылы жүргізілген ихтиологиялық зерттеулердің деректері негізінде Қапшағай су қоймасында қаракөз популяциясының құрылымдық сипаттамалары, оның ішінде жастық құрамы, ұзындық-салмақтық көрсеткіштері және жыныстық құрылымы қарастырылған. Ауланған даралардың ұзындық мәндері 89-323 мм аралығында ауытқыса, популяциясы бойынша орташа ұзындығы 193 мм құрады. Үлкен салмағы бойынша 11-622 г аралығында ауытқып, орташа көрсеткіші 163 г сәйкес келді. Зерттеу нәтижелеріне сәйкес қаракөз балықтарының жастық қатары 2-8 жас аралығын құраса, олардың 4-6 жастағы дараларының үлесі басым болды. Ұзындық құрамы бойынша модальды класты 150-199 және 200-249 мм ұзындықтағы даралар құраса, салмақтық құрылымы тиісінше 120-179 және 180-239 г аралығындағы даралардың үлесіне тиесілі болды. Аталған сипаттамалар қаракөз балықтарының 30 мм ұяшықты ғылыми ауларға жиі түсуімен де расталады. Кейінгі жылдары аталған су қоймада қаракөз популяциясының құрылымдық көрсеткіштері жоғарылағаны байқалады. Ғылыми аулардың талдау нәтижесіне сәйкес көктемнен күзге қарай қаракөз балықтарының саны жоғарылайды. Интерполяциялық әдіс бойынша қаракөз популяциясының кеңістіктегі маусымдық таралу динамикасы анықталды. Көктем айларында қаракөз популяциясының кеңістіктегі таралуы Қапшағай су қоймасының оң жағалау акваториясында байқалса, ал жаз және күз мезгілдерінде олардың шоғырлануы сол жағалау акваториясының өзен сағалары маңында болатындығы анықталды. Балықтардың кеңістіктегі маусымдық таралу ерекшелігі де шоғырланған аймақтардағы қоректік базасының жоғары деңгейімен және де басқа да абиотикалық факторламен байланысты болуы ықтимал.

Background/Objectives: The genetic structure and phylogeographic history of nelma (Stenodus leucichthys) populations across Eurasia remain incompletely understood. This study aimed to investigate genome-wide genetic differentiation among populations from seven Eurasian localities, with particular attention to the genetic distinctiveness and conservation significance of the middle Irtysh population. Methods: Genome-wide single nucleotide polymorphism (SNP) data from 41 specimens representing seven Eurasian localities, including 11 specimens from the middle reaches of the Irtysh River, were analysed. Genetic structure and admixture were assessed using ADMIXTURE with leave-one-out cross-validation (LOOCV), principal component analysis (PCA), discriminant principal component analysis (DPCA), and f₂-statistics. Phylogeographic relationships and divergence times were also investigated. Results: ADMIXTURE analysis indicated the lowest LOOCV error at K = 2–4. Across all K values, the Irtysh population remained genetically homogeneous and distinct, whereas other populations exhibited varying degrees of admixture. The Volga population clustered with Arctic Ocean basin populations at K = 2 but formed a separate genetic cluster at K = 3–4; the Indigirka population was also distinguished at K = 4. PCA, DPCA, ancestry estimation, and f₂-statistics consistently supported genetic differentiation among populations. The Volga, Irtysh, and Ob populations were approximately equidistant from one another, while the remaining populations showed closer genetic relationships to the Ob lineage, with increasing differentiation towards the east. The three major lineages (Volga, Irtysh, and Ob) diverged between the penultimate and last glacial periods. The Volga population was estimated to have diverged approximately 108–84 thousand years ago (MIS 5c–MIS 5a), while the Ob semi-anadromous population diverged approximately 90–60 thousand years ago (late MIS 5–MIS 4). Eastern populations subsequently diverged from the Ob lineage during MIS 4–3, whereas the Kubena population diverged during MIS 2. Conclusions: The Irtysh population represents a genetically distinct and homogeneous lineage of Stenodus leucichthys. Its pronounced genetic differentiation highlights its conservation importance and suggests that population decline associated with river regulation may have serious consequences for the preservation of its unique genetic diversity.

ThearticlepresentstheresultsofresearchonthecommunityofplanktonicmicroalgaeofsmallreservoirsintheWestKazakhstanregion. These are the reservoirs Kirovskoye, Dongelekskoye, Pyatimarskoye and the Kushum River. The species composition of algae is a reflection of all the processes occurring in the ecosystem of the reservoir. 70 taxa have been recorded in the phytoplankton community of four reservoirs in the West Kazakhstan region, including diatom -40, green –16, euglen –10, miazoa –2 and one each of blue–green and golden algae. The species diversity of microalgae varied by body of water. The minimum number of species of planktonic microalgae was recorded in the Pyatimar reservoir, the maximum in the Dongelek reservoir. Diatoms Cocconeis placentula, Brebissonia lanceolata, Epithemia sorex, Navicula radiosa, Ulnaria asus, Ulnaria ulna, and green Eudorina elegans, Hyaloraphidium contortum, and Scenedesmus quadricaudawere widespread and were found in all the surveyed reservoirs. The character of quantitative development of planktonic microalgae in reservoirs was similar. In most of them, diatoms and green algae formed the basis of biomass and community size. The Shannon-Weaver diversity index, calculated from phytoplankton biomass, was in therange of 2.96-3.9 bits/mg. The values of the index indicated the stability of the structure of the community of planktonic microalgae.

The Markakol lenok, Brachymystax savinovi, is an endemic salmonid inhabiting Lake Markakol and its tributaries in eastern Kazakhstan. Over the past century, both abundance and population structure of this taxon have been influenced by natural and anthropogenic factors, highlighting the need for updated assessments of its conservation status. This study evaluated the current population condition, habitat characteristics, and conservation prospects during 2020–2024. Results indicated that Lake Markakol maintained favourable hydrochemical and hydrological conditions during 2020–2024, with no evidence of substantial ecological degradation. The Markakol lenok population was characterised by the predominance of intermediate age classes, positive allometric growth, satisfactory condition factors, and a substantial proportion of mature individuals, indicating relatively stable population status and preserved reproductive potential. In addition, broodstock and replacement populations established under aquaculture conditions showed high survival and successful adaptation to different rearing technologies, confirming the feasibility of artificial propagation programmes for the conservation and sustainable management of the species. Wild brood fish from the Uidene River were successfully adapted to captive conditions, enabling establishment of broodstock and production of viable offspring under controlled conditions. These findings provide a scientific basis for conservation and restoration measures.