Transformation of the morphometric channel characteristics of the Promyslovaya River (Curonian Lagoon basin) following land reclamation works

Abstract

The article presents the results of a comprehensive assessment of the transformation of the morphometric characteristics of the Promyslovaya River channel (Curonian Lagoon basin) following reclamation works conducted in 2023-2025. The study is based on a comparative analysis of bathymetric survey data from before (2021) and after (2025) the interventions, as well as data from control fishing surveys of the watercourse’s fish fauna during the periods of 2018-2022 and 2025. It was found that the reclamation works led to pronounced changes in channel morphometry. At six representative cross-sections, an increase in average depth by 30-40%, channel width by 1.8-2.9 times, and an average increase in cross-sectional area by 176% were recorded, which radically improved the watercourse’s capacity. The most substantial transformations occurred in the previously silted mouth and transition zones. Analysis of the ichthyological data revealed certain changes in the structure of the fish community. After the works, the European smelt, a valuable migratory species and an indicator of improved migration conditions, was recorded in the river for the first time. A redistribution of the proportions of dominant species and changes in the size and species structure of the river’s fish community were also documented. The obtained results indicate the successful achievement of the reclamation works’ goal – improving conditions for spawning migrations of fish. The necessity of establishing long-term monitoring to consolidate the positive effect is substantiated.