In order to better understand the complex geologic history of the Mediterranean area, we have analysed evolutionary history, phylogeographic structure and molecular diversity of freshwater fishes belonging to the genus Telestes. As primary freshwater fishes distributed largely in the Mediterranean basin, this genus represents a suitable model system for investigating the historical biogeography of freshwater drainage systems in southern Europe. In this investigation we have included samples representing all Telestes species and based our analyses on one mitochondrial and one nuclear gene. We have investigated phylogenetic structure inside the genus Telestes, estimated divergence times, reconstructed ancestral distribution ranges and described intraspecific molecular diversity. Diversification of Telestes started in the Early Miocene, when the ancestors of T. souffia, lineage comprising T. croaticus and T. fontinalis, and the one comprising T. pleurobipunctatus and T. beoticus got isolated. The remaining species are genetically more closely related and form a common cluster in the recovered phylogenetic trees. Complex geological history of southern Europe, including formation of continental bridges, fragmentation of landmass, closing of the sea corridor, local tectonic activities, led to complicated biogeographical pattern of this genus, caused by multiple colonization events and passovers between ancient rivers and water basins. Especially pronounced diversity of Telestes found in the Adriatic watershed in Croatia and Bosnia and Herzegovina is a consequence of a triple colonization of this area by different lineages, which led to an existence of genetically distinct species in neighboring areas. Significant intraspecific structuring is present in T. souffia, T. muticellus, T. croaticus and T. pleurobipunctatus. Besides in well-structured species, elevated levels of genetic polymorphism were found inside T. turskyi and T. ukliva, as a consequence of their old origin and unconstrained evolutionary history.

Saprolegnia parasitica causes saprolegniosis, a disease responsible for significant economic losses in aquaculture and declines of fish populations in the wild, but the knowledge of its distribution and prevalence in the environment is limited. We developed a fast, sensitive and specific S. parasitica droplet digital PCR (ddPCR) assay and demonstrated its applicability for the detection and quantification of the pathogen in environmental samples: swab DNA collected from the host (trout skin, surface of eggs) and environmental DNA extracted from water. The developed assay was used to assess how abiotic (i.e. physico-chemical parameters of the water) and biotic (health status of the host) factors influence the S. parasitica load in the environment. The pathogen load in water samples was positively correlated with some site-specific abiotic parameters such as electrical conductivity (EC) and calcium, while fluorides were negatively correlated, suggesting that physico-chemical parameters are important for determining S. parasitica load in natural waters. Furthermore, skin swabs of injured trout had significantly higher pathogen load than swabs collected from healthy fish, confirming that S. parasitica is a widespread opportunistic pathogen. Our results provide new insights into various environmental factors that influence the distribution and abundance of S. parasitica.

The genus Telestes primarily comprises freshwater fish distributed mostly in the Mediterranean area. Recent investigation of the evolutionary history of this genus revealed that it originated in southern Europe, where the most ancient Telestes species are still present. The isolation of rivers in the karstic region facilitated allopatric speciation, resulting in a high number of Telestes species and a great portion of endemic species in freshwater systems of Croatia and Bosnia and Herzegovina. Most of the endemic Telestes species have very small distribution areas, inhabiting a single river or a few water bodies in a single karstic field, making them extremely vulnerable to anthropogenic changes. In order to contribute to practical conservation of the endemic Telestes species through the design of conservational measures that are likely to be the most effective in ensuring the future viability and undisturbed evolutionary course of those species, we have investigated their population genetic structure and estimated their viabilities. Population viability analyses were carried out based on the current state of populations and their habitats, as well as recognized threats. Several scenarios also included potential threats. Our results show that invasive species pose the biggest threat to the future survival of the endemic Telestes species. Contrary to previous opinions that a reduced genetic diversity is characteristic for small populations, high intraspecific genetic diversity was revealed inside most of the investigated species, which might enable most of the populations to cope with future changes and mitigate negative effects.

The general status of lampreys (family Petromyzontidae) in Bosnia and Herzegovina was reviewed to determine the species composition and geographical distribution of this group in the region. This paper reviews the available literature to provide a critical analysis of the current status of lamprey species. According to the available data, their status can be considered as indeterminate, largely due to limited published records. While eight species are recorded as present in the region (Eudontomyzon danfordi, E. mariae, E. vladykovi, Lampetra fluviatilis, L. planeri, L. soljani, Lethenteron zanandreai, Petromyzon marinus), only three species (E. vladykovi, L. soljani, P. marinus) are confirmed to occur. Their distribution is recorded in waters of both the Danube and the Adriatic Sea catchments. Given the deficiencies in our understanding of the taxonomic status of some populations and knowledge of the geographical distribution of lampreys inhabiting both catchments, research focused on improving understanding of the phylogenetic, morphological and phenotypic traits of lampreys in Bosnia and Herzegovina is warranted to resolve these uncertainties. Problems related to threats and conservation, and future perspectives for protective management strategies are discussed. This paper provides the context for future biodiversity conservation and management with regard to lamprey species in Bosnia and Herzegovina.

This is the first report of the early development for the endemic Krbava minnow Delminichthys krbavensis from a karstic field in Croatia, and the first report of any species of the genus Delminichthys. The description is based on basic morphometric measures and meristic counts during a 48-day observation of embryos and larvae acquired from successful spawning and rearing in an aquarium. The mean total length of larvae at the time of hatching was 3.12 mm. Mouth opening and independent feeding and intestinal function were observed after day 11 post-hatching (PH) at which time the yolk sac was completely absorbed in all individuals. Flexion of the urostyle began after day 18 PH and was completed by day 23 PH. Pectoral fins developed on day 7 PH, pelvic fins begin to develop by day 44 PH and the formation of caudal, dorsal and anal fin was complete by day 48 PH, when individuals presented the full set of soft rays. Understanding its early development is particularly valuable in assessing the environmental impacts on this endangered species and is essential for its effective monitoring and conservation.