Analysis of water quality of a reservoir on a small river and the status of ichthyofauna in anthropogenic conditions

The surface waters of the estuaries of the estuary are mostly characterized by low quality, which was formed as a result of considerable anthropogenic loading and transformation of the catchment area. The monitoring data of the ecological and sanitary status of the surface waters of the Basov Kut reservoir are presented, as well as the results of accounting for dead fish due to the frosts that occurred in the mouth of the Ustye River during 2011–2017. It is established that the Bas Basin is not suitable for recreational use. Amateur fisheries are also a danger to the population, as lactose-positive E. coli, the Staphylococcus aureus index, the Enterococcus microorganism index, Lamblia intestinalis cysts and eggs are detected in this reservoir annually. In 2017, cholera vibrios (Vibrio cholera non O1) were detected. Hydrochemical indicators, in particular in 2018, revealed inconsistency with the following indicators: odor – 2 points; color 3; BOD5 – 6.5–7.5 mgO2/dm³; COD 40–50 mgO2/dm³. In samples tested for sanitary – microbiological and parasitological parameters, cholera – like vibrio (non O1) was detected. The deterioration of water quality by the content of biogenic elements, in particular, compounds of Nitrogen and Phosphorus, which leads to increased eutrophication of the reservoir. The “flowering” of water in 2018 began in the third decade of June and lasted until October. This process harms not only hydrobionts, but also humans, as blue-green algae toxins can accumulate in fish tissues and cause poisoning when consumed by such products. In addition, there was a significant percentage of fish that did not meet the requirements of DSTU 2284: 2010 in terms of organoleptic characteristics. The greatest damage to the populations of fish that inhabit the Estuary during the fatalities was caused in 2012. When the estimated loss of fishery resources amounted to 377.4 thousand individuals, according to scientists and control bodies. Annual fatalities have led to quite significant losses of populations of industrially valuable fauna. A significant loss of fishery resources was noted in 2017 – about 10.32 thousand. It was noted that the following populations of fish were most affected by the frost in the estuary: Rutilus rutilus, Scardinius erythrophthalmus, Leucaspius delineatus, Perca fluviatilis, Carassius gibelio, Tinca tinca, Esox lucius, Sander luciocaper, Abracerperis This poses a significant threat to the further reproduction of ichthyofauna in the mouth of the Ustya River, and also calls into question the possibility of amateur fishing in these sites.