This study aims to analyze the biotopic factors affecting the EPT assemblage diversity in the rivers of the Târnava Watershed. Our research revealed that the high diversity of the Plecoptera communities is associated with river reaches with boulder and cobble lithological substrate, accentuated slope and natural bank dynamics, and also it is directly correlated with dissolved oxygen and inversely correlated with chemical and biochemical oxygen demand, total hardness, nitrates and total nitrogen in the water. The high diversity of the Trichoptera communities is associated with water which presents moderate quantities of nutrients (total phosphorus, phosphates) and with river reaches with heterogeneous structures (where runs and bends were present). The diversity of the Ephemeroptera communities is positively correlated with the multiannual average flow and riverbed width.
The paper presents the structure of the benthonic macro-invertebrates communities in the Berzasca, Sirinia, Liubcova, and Mraconia rivers. The results are based on quantitative benthos samples (95 samples), collected in July 2014 from 19 sampling stations within the study area. In longitudinal profile, the benthonic macro-invertebrate communities of the Sirinia, Liubcova and Berzasca rivers displays relatively large structural variability, while the communities of the Mraconia River displays smaller structural variability. The structure of the benthonic macro-invertebrate communities correlated with the biotope characteristics indicates the good ecological status of the analysed rivers, with the exception of the Berzasca River sector downstream of the town of Berzasca and immediately upstream of the Danube junction, a sector with moderate ecological status due to negative effects from man-made modifications in the lotic biotope of the sector.
The action framework at the European Union level for the protection of biodiversity was established based on the Habitats Directive (92/43/EEC) and the Birds Directive (79/409/EEC). One main element of the future implementation of these Directives in Croatia is the establishment of a Natura 2000 network of special protection sites, a network which should rely on a specific monitoring plan at national level for each species of community interest. In this context, the present study proposes a set of monitoring elements for Barbus meridionalis for the Croatian Continental Biogeographical Region. The proposal is based on seven main criteria: proximity of national border, high quality populations, habitats which should be ecologically reconstructed, key habitats/sectors with high importance for connectivity, point sources of industrial pollution, areas/sectors influenced by diffuse sources of agricultural pollution, and areas/sectors influenced by habitat modifications.
Thymallus thymallus is considered a species of significant protective importance within the Vişeu Watershed. The state of habitats characteristically inhabited by Thymallus thymallus within the Maramureş Mountains Nature Park is balanced between reduced (one third of the lotic sectors where the species was identified), average (one third) and good (one third). The excellent conservation status is currently missing for populations of this fish in the Vișeu Basin.
Human impact types identified as contributing towards the decreasing state of Thymallus thymallus habitats and therefore populations in the studied area in comparison with its natural potential are: poaching, minor riverbeds morphodynamic changings, solid and liquid natural flow changes, destruction of riparian trees and bush vegetation, habitat fragmentation/isolation of population, organic and mining pollution, and displaced fish that are washed away during flood periods in the lotic sectors uniformized by humans.
The condition of aquatic habitats typically occupied by Romanogobio uranoscopus within the Maramureş Mountains Natural Park fluctuates, in the best cases, between reduced to average. Good or excellent conservation status is now absent for populations of this species in the researched area. The identified human impact types (poaching, minor riverbeds morphodynamic changes, solid and liquid natural flow changes, destruction of the riparian vegetation and bush vegetation, habitat fragmentation/isolation of population, organic and mining pollution and displaced fish that are washed away during the periodic flooding in the lotic sectors uniformized by humans) are contributing to the diminished ecological state of Romanogobio uranoscopus habitats and for that reason populations. Romanogobio uranoscopus is now considered a rare species in the studied basin but where this species was specified as missing, it has been registered with a restorative potential.
The ecological state of lotic ecosystems occupied naturally by Barbus meridionalis, in the Vişeu Basin within the Maramureş Mountains Natural Park, vary among good to reduced. The inventoried human activities which negatively influence the ecologic state of the Barbus meridionalis species habitats and populations are the organic and mining pollution, and poaching. The habitats with low and inadequate conditions created a reduced status of the Barbus meridionalis populations; the status of Barbus meridionalis populations is not so much affected in the cases of habitats of average to good condition. Barbus meridionalis is considered a relatively common fish species in the researched watershed despite the fact that its populations ecological status has decreased from 2007-2015, but the restoration potential in the area for improving this species status is high.
The action framework at the European Union level for the conservation of biodiversity was set up based on the Birds Directive (79/409/EEC) and Habitats Directive (92/43/EEC). One principal element of the implementation of these two significant Directives in Croatia is the set up of a Natura 2000 network of protected areas, a network which should be based on a specific monitoring plan at Croatian national level for each species which is considered of community interest. In this general context, this study suggests a set of monitoring elements for Rhodeus sericeus amarus for the Croatian Continental Biogeographical Region. The suggestions are based on eight selected criteria: Croatian national borders proximity sectors overlay; very good quality populations of Rhodeus sericeus amarus in terms of population density and structure (e.g. protected areas) in characteristic good habitats; habitats which need ecological reconstruction to allow this fish species populations structure ameliorate or natural repopulation; key sectors with importance for connectivity (e.g. lotic sectors between different important sectors, rivers confluence areas, etc.); sectors influenced by human impact like: industrial pollution point sources, sectors influenced by agricultural diffuse sources of pollution, sectors influenced by habitats modifications (watercourses remodeling, watercourses regulation, etc.), geographically extreme monitoring sections in the most-upstream and mostdownstream sections of the rivers, in this species range and in the near outer proximities of these extremes
The relative larger size of the Berzasca River, respectively the relatively constant environmental conditions, with relatively stenotopic ichthyocenosis, suffered small qualitative and quantitative fish fauna modifications in time, compared to the smaller rivers such as Sirinia, Liubcova/Oreviţa and Mraconia. The Danube “Iron Gates” I Lake influences the lower sectors of the studied rivers in term of fish species exchange. The accidental droughts in the karstic zones of the studied lotic sectors have a negative influence on the spatial continuity of the local fish fauna, and the climate change can increase these influence in the future. All the studied rivers play an important role for the near Danube “Iron Gates” I Lake lotic fish species of small-medium size, as reproduction and shelter habitats.
Following the accession of Croatia to the EU, a study was carried out on a Croatian Natura 2000 site which includes habitats used by the following fish species of conservation interest: Eudontomyzon vladykovi, Rhodeus sericeus amarus, Gobio uranoscopus, Romanogobio kesslerii, Barbus meridionalis, Zingel streber and Cottus gobio. Harmful effects on fish fauna were found due to: poorly-integrated water management, over-extraction of water for irrigation, fragmentation of riparian vegetation, low cooperation between environment institutions in Croatia and Slovenia, abuse of pesticides, uncontrolled waste water, sources of chemicals and heavy metals, leakage of nitrogen, habitats fragmentation due to dams and canals, non-native fish species, invasive species and gravel extraction. Specific management actions are proposed that take account of the different fish species of conservation interest and their specific biological and ecological requirements.
The ADONIS: CE was used to design a specific management model for the Sabanejewia aurata (De Filippi, 1863) populations. The proposed model is based on this species, in situ identified biological/ecological necessities in relation to the habitats, the conservation status indicators and appropriate management actions and the pressures and threats founded in the study area. Such on species, on habitats and on site based management system was done to complete this approach for ROSCI0132, the other fish species which are living there being treated already in this respect.