Abstract As an endemic species, Dalmatian barbelgudgeon was introduced into Šatorsko Lake, but it was insufficiently explored at this locality. The aim of this study was to determine seasonal variations of physicochemical parameters of the water in relation to morphometric and hematological parameters of Dalmatian barbelgudgeon from Šatorsko Lake. Physicochemical analysis of the water recorded lower values of temperature, O2 concentration, O2 saturation, electrolytic conductivity and suspended matter in autumn, while other analyzed parameters indicated lower values in spring. The analysis of morphometric parameters (weight, standard length, total length and Fulton’s condition factor) determined higher values of all the parameters during spring, while a significant difference was noted only for Fulton’s condition factor. A statistically significant difference was observed for all erythrocyte lineage parameters (RBC-red blood cells, HB-hemoglobin concentration, HCT-hematocrit, MCV-mean corpuscular volume, MCH-mean corpuscular hemoglobin, MCHC-mean corpuscular hemoglobin concentrations). In white blood cells, a statistically significant difference was recorded for lymphocytes, non-segmented neutrophils and monocytes, while the proportion of segmented neutrophils and basophils was slightly increased in spring. Furthermore, the recorded values of pseudo-eosinophils were equal in spring and autumn. The results of these studies indicate a significant influence of exogenous and endogenous factors on the variability of morphometric and hematological parameters of Dalmatian barbelgudgeon from Šatorsko Lake.

Abstract. Alongside climate change, the introduction of non-native species (NNS) is widely recognized as one of the main threats to aquatic biodiversity and human wellbeing. Non-native species and biodiversity are generally low priority issues on the political agendas of many countries, particularly in European countries outside the European Union (EU). The objectives and tasks of this study were to address the policy regulation, education level, education practices, and socioeconomic perceptions of NNS in the Balkans. A questionnaire-based survey was conducted in Albania, Bosnia and Herzegovina, Montenegro, North Macedonia and Turkey (Balkan EU candidate and potential candidate members), in Croatia and Greece (Balkan EU Member States) and Italy (non-Balkan EU Member State). The EU Alien Regulation (1143/2014) concerning NNS is implemented in EU Member States and Montenegro, whereas Albania, Bosnia and Herzegovina and Turkey have not reported specific policy regulations for NNS. Permanent monitoring programmes specifically designed for NNS have not yet been established in the EU Member States. Most countries tackle the issue of NNS through educational activities as part of specific projects. Education level is indicative of the implementation of NNS policy regulation, and efforts are needed for the proper development of relative study programmes. Public awareness and educational preparedness concerning NNS in the Balkans were identified as poor. Strong programmes for management and education should be developed to increase public awareness to prevent further biodiversity losses in the Balkan region.

Heavy metals belong to a group of substances, which, after reaching a natural habitat, can manifest various negative effects. This paper analyses heavy metals (Cu, Cd, and Pb) in the Una river and fish samples, whereby individuals of grayling (Thymallus thymallus) were used for analysis. The samples were taken at three locations at the Una river: Ripac, Hatinac, and Grmusa. Alongside with the examination of the content of heavy metals, quality of water was tracked, including the following parameters: temperature, pH, electrical conductivity, dissolved oxygen, suspended matter, BPK5, KPK – Cr, total nitrogen – N, total phosphorus P, sulphates, chlorides, nitrites – NO2, nitrates – NO3, fluoride, and heavy metals (Cu, Cd, and Pb). Besides the content of heavy metals, proteins, fats, water, carbohydrates, and mineral matter were found in the grayling fillets. Amount of heavy metals (Pb, Cu, and Cd) were under maximum allowed concentration (MAC).             Key words: heavy metals, water, fish.

Coefficients of organs, along with haematological characteristics, represent an important means of monitoring the health and condition of fish. Organosomatic indices show the state of organ systems and individual organs. They manifest as changes in size, which are reflected through a decrease or increase, under the influence of environmental factors. Chub individuals from the Suturlija River were used for analysis. The paper analyses the Fulton's condition factor, heart, liver, and spleen coefficients as a condition factor. Furthermore, the values of total length, standard length, and body weight were determined for all individuals. Also, certain haematological parameters were analysed in the paper: total leukocyte count and differential blood count. A total of 19 chubs caught from the Suturlija River were analysed. The obtained result of Fulton's condition factor (1.53) indicates favourable habitats for chub individuals in the Suturlija River. The results of organosomatic indices are without major variations between individuals (CSI = 0.184, SSI = 0.992, HSI = 0.133). The mean leukocyte count was 45.857x109/l, with the highest proportion of lymphocytes in the differential