Sava River System Research Articles

Conservation genetics study of huchen in Slovenia recommends river system‐based management and indicates self‐sustainability of the middle Sava population

Abstract The middle part of the Sava River in Slovenia provides one of the longest free‐flowing habitats for huchen, a threatened species that is also protected by the European Habitats Directive. However, there are plans for the construction of a chain of hydropower plants along this stretch of river. It has previously been assumed that huchen is no longer self‐sustainable here, but dependent upon stocking with hatchery‐reared fish. Using microsatellite and mitochondrial DNA, the genetic structure of huchen in its entire range in Slovenia was analysed with the particular aim of assessing the self‐sustainability of the species in the middle Sava. Using factorial correspondence analysis and assignment tests, a distinct genetic cluster was identified for each of the three main river systems in the country (Sava, Kolpa and Mura–Drava). In the middle Sava, a genetic admixture between stocked and local individuals, observed beyond F1, and a unique genetic substructure not corresponding to the stocking sources, were found. These results indicate the self‐sustainability of the middle Sava population and justify its protection. The estimated effective population size in the middle Sava is below the accepted minimum, and additional fragmentation arising from dam construction would cause the genetic breakdown of this huchen population. To preserve local genetic pools and possible inter‐population adaptive differentiation, we recommend that the three, historically isolated, river system‐bound populations (from the Sava, Kolpa and Mura–Drava) are managed separately. However, separate management of the small, isolated populations in the once free‐flowing Sava river system is not encouraged as it may cause their genetic impoverishment. The potential impact of this study on the conservation management of huchen more widely is discussed, with emphasis on the Balkans, where large populations still exist and their management is just beginning.

Genetic characterisation of European mudminnow (Umbra krameri) populations from the Sava River system

Two new populations of the European mudminnow (Umbra krameriWalbaum, 1792) were discovered in the Sava River system, one in its middle part (Bosnia and Herzegovina) and the other in a tributary to the Kupa River (Croatia). The Croatian population is the most upstream mudminnow discovery in the Sava River system known to date. The genetic structure of the newly recorded mudminnow populations was examined using mitochondrial DNA and microsatellite loci. By adding these new populations to the analysis of the population genetic structure of mudminnow from the Sava River system, previously unresolved relationships between the populations from the upper and the lower Sava were clarified: the middle Sava populations were shown to be well outside the hybridisation zone with the Danubian clade, meaning the upstream boundary of this zone is confined to the lower Sava. The results also suggest that mudminnow populations in the Sava River system are less isolated than previously believed. Namely, intermediate gene-flow was detected when comparing the uppermost Sava population with the lower Sava populations. Taking these results into account, appropriate guidelines are proposed to preserve mudminnow populations from the Sava River system.

The study of the interactions between Sava River and Zagreb aquifer system (Croatia) using water stable isotopes

Water stable isotopes were used to investigate hydrological pathways and interactions between surface water and groundwater in the Zagreb aquifer system (Croatia). δ2H and δ18O values indicate a spatial variability of the influence of individual groundwater sources inside the aquifer – local precipitation and the Sava River water. Fractions of surface water in groundwater strongly depend on fluctuations of the river water level and less on the distance from the Sava River. These data extend our understanding of groundwater flow in the Zagreb aquifer system, interactions between Sava River water, local precipitation and groundwater. The results of the research allow more precise monitoring plans and definition of the sanitary protection zones of the well fields in the future.

Description of a new species of Alburnus Rafinesque, 1820 (Actinopterygii, Cyprinidae, Leuciscinae) from the Kolpa River in the Sava River system (upper Danube drainage), with remarks on the geographical distribution of shemayas in the Danube.

Alburnus sava, new species, is described from the Kolpa River. The Kolpa is a tributary of the Sava, a major tributary of the Danube River, in the Black Sea basin. Alburnus sava is distinguished from its congeners in the Danube drainage, A. mento and A. sarmaticus, by having 23−27, usually 24−26, gill rakers; the ventral keel usually completely covered by scales (scaleless part maximum 15% of the keel length); 15−16, mode 15, branched pectoral-fin rays; the length of the gill raker at the junction of the arch limbs 65−70% of the length of the opposite outer gill filament; and a relatively long lower jaw (37−40% HL or 112−130% interorbital width). Alburnus sava is a large-sized potamadromous shemaya known to occur in the entire Sava drainage. The taxonomic status of A. mento and A. sarmaticus is confirmed. Alburnus danubicus is discussed and as there are no new arguments, it is kept as a valid species. New details on the distribution of shemayas in the Danube drainage are presented.

Genetic and morphological variability of the European mudminnow Umbra krameri (Teleostei, Umbridae) in Serbia and in Bosnia and Herzegovina, a basis for future conservation activities.

As a basis for future conservation activities, the genetic and external body morphology variability of the European mudminnow Umbra krameri, a highly endangered fish species in Serbia and in Bosnia and Herzegovina, was determined for existing populations with the use of molecular markers (mitochondrial and microsatellite DNA) and geometric morphometric methods. Mitochondrial DNA cytochrome b gene analysis revealed two previously undescribed haplotypes: Da1 (the Lugomir population from the Danube River basin) and Sa1 (the Bakreni Batar and the Gromiželj populations from the Sava River system), with a corresponding genetic distance of 0·7%. Paired values of FST and DAS distances for microsatellite marker data show that the difference between the Danube and the Sava populations is seven to nine times higher than the difference between the populations within the Sava River system. Geometric morphometric analyses also support a clear separation of the Lugomir population from the Bakreni Batar and the Gromiželj populations. The analysis of the body shape variation, however, indicates a significant difference between the two genetically indistinguishable Sava populations. The observed genetic and phenetic relationships of the analysed mudminnow populations most probably represent a consequence of historical, geographical and ecological factors. These results will offer guidelines for future protection, conservation and sustainable management of this species in the region.

Origin and cycling of riverine inorganic carbon in the Sava River watershed (Slovenia) inferred from major solutes and stable carbon isotopes

The Sava River and its tributaries in Slovenia represent waters strongly influenced by chemical weathering of limestone and dolomite. The carbon isotopic compositions of dissolved inorganic carbon (DIC) and suspended organic carbon (POC) fractions as well as major solute concentrations yielded insights into the origin and fluxes of carbon in the upper Sava River system. The major solute composition was dominated by carbonic acid dissolution of calcite and dolomite. Waters were generally supersaturated with respect to calcite, and dissolved CO2 was about fivefold supersaturated relative to the atmosphere. The δ13C of DIC ranged from −13.5 to −3.3‰. Mass balances for riverine inorganic carbon suggest that carbonate dissolution contributes up to 26%, degradation of organic matter ∼17% and exchange with atmospheric CO2 up to 5%. The concentration and stable isotope diffusion models indicated that atmospheric exchange of CO2 predominates in streams draining impermeable shales and clays while in the carbonate-dominated watersheds dissolution of the Mesozoic carbonates predominates.