The study was conducted on the Obedska Bara Ramsar site at two localities, Krstonošića okno and canal Vok, to provide insight into fish community status by analysing fish biomass, biodiversity, and changes after restoration measures. A total of 685 fish samples were examined across four periods, from 2011 to 2023. Biodiversity index, relative biomass, and non-native species were analysed to evaluate the restoration measures’ influence. All parameters showed a negative trend until the restoration works were implemented, after which they increased. This study also provides recommendations to improve the site considering the Mission Restore our Ocean and Waters by 2030.

The article presents the results obtained within the DaWetRest project, which focuses on wetlands preservation and restoration along the Danube River, ranging on three demonstrator sites: the Middle Danube Demo (MD DEMO located in Croatia), the Lower Danube Demo (LD DEMO, located in Bulgaria) and the Danube Delta Demo (DD DEMO-located in Romania). The project aims to provide insight into nature-based solutions, ecological characteristics, hydrology, water quality, vegetation, wildlife, soil, land use and other factors that represent a relevant contribution to the restoration efforts and it contributes to the wetland restoration using concreate hydro-technical measures for ecosystem improvement. This study presents the initial results from in situ applied geophysics, where Electric Resistivity Tomographies (ERT) were applied on the MD Demo (main pilot site in the Municipality of Draž, Croatia) which represents the flood area, located east of the Danube River embankment of the State border. This geophysical surveys represents an exploratory approach that aims to contribute for a better understanding and knowledge on groundwater resources and quality through the determination of potential aquifer areas from main geological features of the area of interest and also as a potential contribution to establish carbon sequestration areas.

Bioeconomy is becoming a more interesting field for investments in the Republic of Croatia, especially in its small regions and local administrative units. Vukovar-Srijem county is one such unit in eastern Croatia with noticeable potential for development in a circular, carbon-neutral, and sustainable bioeconomy. Due to the nature potential represented by one of the largest forest reservoirs in Europe-Spačva basin, forestry is one of the most important county branches. Aiming to provide more inputs on the wood biomass management, the study on the biomass flow of Vukovar -Srijem c ounty was conducted in 2020 by collecting data from local stakeholders and official reports. The study results have shown that Vukovar-Srijem county has the potential to increase the efficiency level of biomass use, but specific actions on the value-chain strengthening, finalisation of wood products, and innovative ecosystem establishment are still needed. The results highlight the predominant use of sawdust for heating purposes in the VSC region, suggesting potential for optimizing its utilization towards a circular, carbon-neutral, and sustainable bioeconomy, thus offering novel insights for future research and initiatives aiming to maximize economic and environmental benefits from wood biomass residues.

Over the last 14 years, ichthyological and ecological parameters have been monitored in the Labudovo okno Ramsar site. This area is important for its biodiversity as it is home to many rare and endangered plants and animal species. A total of 3861 fish specimens were sampled and measured at six sampling sites four times during the sampling period. An analysis of biodiversity indexes, relative biomass (kg/ha), and relative annual production (kg/ha) was carried out to assess the effectiveness of existing conservation measures. The results obtained show a trend decline in biodiversity, relative biomass, and relative annual production. This indicates a biodiversity conservation problem that should be addressed through other mechanisms in addition to the principles of the Ramsar Convention.

Abstract The investigation of fish parasites in Bosnia and Herzegovina in recent years became significant, and therefore new records of parasitic trematodes and their hosts are important for better understanding of fish parasitology and pathology. In this study 41 parasitic specimens were collected and the basic taxonomical characters were measured (body length and width, diameter of oral and ventral sucker, length and width of pharynx, ovary length and width, testes length and width and eggs length and width). After the sampling of the parasites, they were collected and conserved in 70% ethanol. After that procedure the aforementioned characters were measured using Digimizer Image Analyzer Version 4.1. After all measurements, the trematode parasite Azygia robusta was confirmed for the first time on brown trout Salmo trutta. This first record was found in the Vrbas River near Banja Luka, Bosnia and Herzegovina (Sava River Basin). Former records of this parasite in Europe were observed on other salmonid fish species, as huchen Hucho hucho. This new record should be very important part of data of fish parasitology in Bosnia and Herzegovina.

The scientific investigation of aquatic ecosystems in Bosnia and Herzegovina has become increasingly intense in recent years. Due to a deficit in studies regarding parasitology and biological control of diseases, two important fish ectoparasites (Chilodonella cyprini and Ichthyophthirius multifiliis) were investigated in 22 fish species (400 individuals) during 2017 from the middle flow of the Sava River. The prevalence of infection and infection intensity were analyzed and signs of ichthyophthiriasis were also documented. The study gives recommendations for the development of aquatic ecosystem management.

Condition factor of fish species is very important parameter for understanding fish biology and pathology. For that purpose, we sampled 120 fish individuals from the Sava River at four locations (Posavina region), where most of them belongs to the Cyprinidae family while the others belonging to the families: Percidae, Siluridae, Ameiuridae, Esocidae and Gobiidae. In total fish sample we found that 49 fish individuals were infected by different types of skin ectoparasitic protozoa species (Ichtyobodo necator, Chilodonella cyprini, Trichodina sp., Ichthyophthirius multifiliis and Apiosoma sp.). The values of condition factor were in interval of 0,520 to 1,834.

Istraživanjem ektoparazitskih trematoda na vrsti Scardinius erythrophthalmus donjeg toka rijeke Save ustanovljene su tri vrste trematoda koje parazitiraju na skrgama ili koži riba. Tokom istraživanog perioda uzrkovali smo 120 jedinki vrste Scardinius erythrophthalmus. Ukupno 85 jedinki ili vise od 70% pokazalo je prisustvo jedne tri ustanovljene ektoparazitske trematode. Determinacija trematoda provedena je do nivoa vrste za jednu trematodu (Posthodiplostomum cuticola) i do nivoa roda za dvije (Dactylogyrus i Gyrodactylus). Kljucne rijeci: rijeka Sava, donji tok Orasje, ektoparazitske trematode