Biological features and population dynamics of roach Rutilus rutilus (Cyprinidae) in the Uglich Reservoir

In the Uglich Reservoir, the roach Rutilus rutilus (Linnaeus, 1758) is a fairly common species of the carp family, occupying the second position in terms of abundance (36.3%) and biomass (11.5%) after the bream Abramis brama (Linnaeus, 1758). A study of the biological features and population dynamics of roaches in the Uglich Reservoir (2012-2024) revealed a difference in the average size of individuals (length 20.3 cm, weight 211 g) caught using trawl and net fishing compared with historical data from 1976-1977 (13.2–14.1 cm, 50-57 g). Every year, the 5+ age group was present in catches, and in the period from 2012 to 2019 and in 2024 it prevailed. At the same age, the largest absolute and relative increase in fish was noted. The age structure (3+-13+) was characterized by female dominance (87.2%). In length, the females were significantly larger than the males. For the roach of the Uglich reservoir, a growth graph was constructed using the Bertalanfi equation (growth coefficient K = 0.17, theoretical age coefficient t0= –1.159), and the theoretical maximum length (Linf = 33.022 cm) was calculated. The size-mass dependence (LWR) for roach is given, which indicates a positive allometric growth. The application of the LBI (Length based indicators) indicator method confirmed the rational use of the population: the conservation of juveniles and large individuals, in accordance with the MSY concept. The biomass ranged from 474 tons (2012) to 577 tons (in 2023-2024). A low concentration of roach was detected in the bottom layers of the riverbed, probably due to hypoxia. The results update data for fisheries management and biodiversity conservation.