Programme: Scientific Research Fund

The project aims to investigate the current status, ecological characteristics, and phylogeographic relationships of so-called “muddy fishes”, a group of freshwater species closely associated with marshes and floodplain habitats along the Middle and Lower Danube. These fishes inhabit relatively shallow water bodies with low flow velocity, fine sediments, and high organic matter content, and exhibit specific adaptations to periodically unfavorable environmental conditions. Over the past century, large-scale drainage, river channel modification, and hydrotechnical regulation within the Danube River basin have led to a drastic reduction and fragmentation of riparian wetlands. This has had a strong negative impact on this ecologically specialized group of species, many of which are now rare and persist in small, isolated populations, particularly in the Bulgarian section of the Danube basin.
The main objective of the project is to conduct up-to-date mapping and a comprehensive assessment of remnant populations of key marsh fish species, including Carassius carassius, Leucaspius delineatus, Scardinius erythrophthalmus, Misgurnus fossilis, and Umbra krameri. Detailed data will be collected on their biology, ecology, and population structure, including diet composition, fecundity, growth, abundance, biomass, and age structure. The results will be compared with available data from the Middle Danube basin, allowing an evaluation of longitudinal spatial differences in population status and habitat quality along the river continuum.
In parallel, the project will analyze the genetic structure and phylogenetic relationships among populations from the Middle and Lower Danube using DNA barcoding and complementary population-genetic approaches based on mitochondrial genes. The aim is to determine whether the studied populations constitute a single evolutionary unit or represent genetically differentiated lineages shaped by historical fragmentation and hydrological dynamics.