Impact of anthropogenic factors on the population structure of non-fish seafood in reservoirs of Azerbaijan

The aim of the study was to establish the impact of anthropogenic factors on population size and structure. The article presented the results of a comprehensive empirical study aimed at assessing the influence of anthropogenic factors on the structure and abundance of shrimp (Palaemon elegans, Palaemon adspersus) and freshwater crayfish (Astacus leptodactylus, Pontastacus eichwaldi) populations in the conditions of Shamkir and Mingachevir reservoirs of Azerbaijan. In the period from June to August 2024, field surveys were conducted at sites with different degrees of pollution. The assessment included analyses of the density of individuals, age and sex composition, juvenile abundance and mortality, and spatial distribution of populations. For freshwater crayfish, the average density of Astacus leptodactylus ranged from 12 individuals/m2 (clean zones of the Shamkir reservoir) to 5 individuals/m2 (polluted zones of the Mingachevir reservoir). The number of Pontastacus eichwaldi varied from 7 to 2 individuals/m2 . The share of juveniles in the population structure in clean areas reached 42% (Palaemon elegans) and 40% (Astacus leptodactylus), while in polluted areas it decreased to 15-20%. Mortality of juveniles up to 40% was recorded in sites with organic pollution. An imbalance in the sex composition was observed in areas with high levels of pollution: in Palaemon adspersus and Pontastacus eichwaldi the proportion of males exceeded 55%, while in clean areas females predominated or an equal ratio was maintained. The greatest decrease in the abundance of all species was observed in the Mingachevir reservoir – up to 60% for Pontastacus eichwaldi, which indicates the high sensitivity of the species to complex anthropogenic impact. The results showed that chemical pollution, recreational load and poaching are the determining factors of population degradation. A direct correlation between the level of anthropogenic impact and the decrease in abundance, disturbance of age and sex structure was established. Indicator indicators for monitoring the state of freshwater ecosystems were proposed. The obtained results can be used for development of monitoring programmes and ecological-restoration measures in aquatic ecosystems of Azerbaijan