Biology of rudd (Scardinius erythrophthalmus, Cyprinidae) of the Uglich reservoir

This work presents for the first time a comprehensive analysis of the population structure and growth of the rudd Scardinius erythrophthalmus (L., 1758) in the Uglich reservoir. Despite the widespread occurrence of the species, its population in the Uglich reservoir had not previously been the subject of a special study, which determined the purpose of this work. The material was data for 2019–2024, collected using mobile networks as part of the monitoring of aquatic bioresources conducted by the Branch for Freshwater Fisheries of the VNIRO Federal State Budgetary Institution (VNIIPRH). The studied part of the population is represented by age groups from 3+ to 8+ years old, with a predominance of 4+ and 5+ individuals (67.3%), with an average length of 21.8 cm and a weight of 273 g. The sex ratio was 1:0.3 towards females, and the Fulton fatness coefficient ranged from 2.12 to 2.91 (average 2.51). The increase in mass relative to length is described by a positive allometric equation (W = 0.013694L3.197, R2 = 0.96), which indicates favorable trophic conditions. The parameters of the Bertalanffy equation (Linf = 34.32 cm, K = 0.12) characterize moderate growth rates typical for the middle latitudes. From 2012 to 2016, there was a decrease in redfin biomass from 11 tons to 5 tons, and its stabilization at the achieved level within 4 years. From 2020 to 2023, biomas increased to 9.4 tons. In 2024, the reserves of rudd are estimated at 6.4 tons, which corresponds to the long-term average values. The data obtained indicate a stable state of the rudd population in the conditions of the Uglich reservoir, which is not experiencing significant commercial and amateur pressure.