The study is devoted to the assessment of the role of Cyprinid fish (gaster, bream, etc. species) in the formation of a spawning herd and the structure of the ichthyocenosis of the Promyslovaya River (Kaliningrad region), one of the key watercourses of the Curonian Lagoon basin of the Baltic Sea. Based on six years of monitoring (2017, 2018, 2021-2024) using the NetCor sonar system and control fishing nets, the transformation of the fishing community was revealed, divided into two phases. In the period 2017-2021, bream, bream and roach were mined, but in 2022-2024. Galera has become an absolute dominant (76% of the population, 75% of the biomass). The increase in its share is associated with a decrease in the number of bream due to the bar at the mouth, which restricts its migration. The Palia–Kownatski Index confirmed the transformation of the community: In the second phase, gaster prevailed in all sections of the river, including spawning grounds. Spatial analysis showed a decrease in the proportion of gaster from the mouth (89%) to the upper reaches (50%), and temporal distribution revealed a prolonged spawning season of this species (April–June). In 2024, a general decrease in the number of fish was recorded, probably due to land reclamation work to clean the riverbed, which affected the hydrological regime and the food supply of this river. The comparison of hydroacoustics data and net catches confirmed a high correlation of methods and the effectiveness of hydroacoustics in the conditions of small rivers in the Kaliningrad region. The work highlights the key role of the gustera in maintaining the stability of the ichthyocene under anthropogenic impact and the need to take such species into account when managing the aquatic ecosystems of the Baltic Sea basin.
Aldushin et al. (Fri,) studied this question.