Капшагайское водохранилище – это один из крупных рыбохозяйственных водоемов Казахстана. В настоящее время в водохранилище основную долю в уловах соствляют карповые виды рыб, среди которых доминирует лещ (Abramis brama L.). Известно, что характер формирования биопродукционного потенциала экосистем водоемов во многом определяется питанием и формированием пищевых взаимоотношений рыб на разных этапах развития. Поскольку лещ (Abramis brama L.), сазан (Cyprinus carpio L.) и вобла (Rutilus rutilus caspicus J.) имеют сходные спектры питания, были изучены их особенности и характер конкуренции за пищевые ресурсы. Приводятся данные мониторинговых исследований по питанию рыб, проведенных в весенний период 2018-2021 гг. Для характеристики особенностей питания вычислялся процент встречаемости, относительная масса кормовых компонентов и индекс наполнения желудочно-кишечных трактов рыб. На основании приводимых данных выявлены пищевые взаимоотношения между исследованными видами.

Sturgeon stock enhancement is one of the key approaches for the conservation of sturgeon species and the restoration of aquatic biological resources. In Kazakhstan, these activities are mainly concentrated in the Caspian and Irtysh river basins, where broodstocks are formed from natural populations for artificial reproduction and annual replenishment of natural stocks. Such programs also provide an opportunity to assess the biological status of populations and evaluate the level of differentiation between sterlet populations inhabiting the Irtysh and Caspian basins. This study analyzed morphological similarities and differences between sterlet (Acipenser ruthenus) populations from the Irtysh and Zhayik rivers. Morphometric analysis revealed clear morphological differentiation between the studied populations. The most pronounced differences were observed in head width parameters (HC and BC), as well as in the SO and R indices, whereas measurements related to total body length showed minimal variation between samples (about 1%). Statistically significant differences (t-test, p ≤ 0.05) were identified for several morphometric indices, including the length-to-height ratio (L/H), head size index (C/L), and relative body height index (H/L). Considering these differences is important when planning stocking activities to ensure successful adaptation, maintain genetic diversity, and minimize the risk of degradation of local sterlet populations.

В 2024 году на рыбоводном хозяйстве ИП «АК балык» были отработаны комбинированные технологии выращивания молоди форели бассейновым и бассейново-садковым методами, для целесообразного использования производственных площадей и увеличение выхода продукции с единицы площади. Были проанализированы данные гидрохимических показателей водоема и бассейнов, оценено их влияние на рыбоводно-биологические показатели молоди форели, был проведен сравнительный анализ полученных данных по рыбоводно-биологическим показателям, таким как темп роста, выживаемость. При выполнении работ использовались гидрохимические, рыбоводные и ихтиологические методы. Выращивание молоди форели от навески 1 г проходилось в мальковых бассейнах на протяжении 27 суток. В результате проведения работ абсолютный прирост молоди составил 14,1 г, среднесуточный прирост составил 0,52 г. Выживаемость молоди составила 96%. При достижении навески 15,1 г., молодь была разделена и рассажена при одинаковой плотности посадки в бассейновые и садковые условия. Период выращивания составил 30 суток. По результатам проведенных работ установлено, что абсолютный и среднесуточный приросты форели в садке был выше чем в рыбоводном бассейне: 34,5 г и 1,15 г в садке, против 25 г и 0,83 г в бассейне. Выживаемость в обоих случаях составила 96%. Более высокий прирост в садке может быть обусловлен наличием в водоеме естественной кормовой базы и дополнительным питанием форели за счет поедания насекомых, упавших в воду.

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.

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.