No abstract

108 years after Trgovčić (1908) authors made a revised list of fish species found in rivers and streams of the Lika region. Throughout the 8 years of investigation a total of 31 species of freshwater fish were recorded, of which only eight are indigenous for this area, for two species the origin is not known, and the remaining 21 species are introduced by anthropogenic activity over the last 100 years. This represents the over-domination of introduced species by the astonishing 300%. All of this increase in numbers causes significant increase in biomass and changes the naturally oligotrophic ecosystem, which might lead to rapid eutrophication and increase of water temperature. Furthermore, induced changes in the system make the habitat more suitable for introduced cyprinid fish, which again causes the increase of biomass production. Endemic fish species are retreating into upper parts of small tributaries and underground cave systems. The present research indicates species Delminichthys jadovensis, D. krbavensis, Telestes fontinalis and T. croaticus as real stygophiles, which makes them unique on the European continent.

At the beginning of the 20th century, the middle section of the Sava River in Croatia was unaffected by major human activities and rich in ichthyofauna. The Sava River was important for commercial and recreational fishing for the local population, which still remains today. However, the 1920s mining industry was established in Slovenia, which emitted carbon dust into the Sava River. At the same time, the construction of embankments to mitigate flooding started in the middle section. Furthermore, in the 1980s, the Krško nuclear power plant (NPP), and in the 2010s, the Krško hydropower plant (HPP) were built in Slovenia. These activities could have an impact on the composition of fish communities downstream from the major sources of disturbances. Therefore, the main aim of this paper were to analyze the changes in fish assemblages of the Sava River from 1978 to 2017, prior to and after the construction of Krško NPP and HPP at the Medsave site on the Sava River, 20 km downstream from the major construction operations. Collected data were divided into four sampling periods (SP): SP1, from 1978 to 1980; SP2, from 1991 to 1994; SP3, from 2001 to 2006, and SP4 from 2011 to 2017. Besides alien fish species, water quality and hydromorphological modifications were identified as significant stressors. In SP1 and SP2 limnophilic and eurytopic fish groups were predominant, and 26 different fish species were identified, but in SP3 and SP4 rheophilic fish groups become dominant, and the diversity has declined to 21 species. Threatened species blageon, Telestes souffia seems to be missing from the main course of the Sava River in last 20 years. It can be concluded that disturbances in the fish assemblage pattern have coincided with the presence of multiple stressors of human origin.

No abstract

Background. The molecular diversity of brown trout, Salmo trutta Linnaeus, 1758, has been poorly studied in Croatia. The control region of mitochondrial DNA (CR mtDNA) is in addition to other molecular markers a reliable for identifying phylogenetic lineages (haplogroups) and haplotypes of brown trout. Based on analyses of the control region of mitochondrial DNA several major brown trout phylogenetic lineages were identified of which the Danubian (DA) haplotypes, though not all, are considered native to Croatian rivers belonging to the Danube basin. The introduction of allochthonous haplotypes into natural streams seriously threatens the genetic diversity of this species. Therefore, the aim of this study was to map brown trout populations inhabiting Croatian rivers of the Danube River basin and to investigate their molecular diversity and phylogeographic patterns of the established haplotypes. Materials and methods. Anal fin tissue was taken from 141 specimens of brown trout in 14 localities in the protected areas of Croatia, situated in the mountainous regions of Gorski Kotar, Žumberak, as well as Mountain Papuk in the western Slavonia. The total DNA was extracted and then the amplification of the mtDNA control region was carried out using primers Trutta-mt-F and HN20. Amplification of the 440 bp long region of the LDH-C1 gene locus was done using primers Ldhxon3F and Ldhxon4R. Amplified LDH-C* fragments were used for Restriction Fragment Length Polymorphism (RFLP) analysis using BselI restriction enzyme. Results. Analysis of the CR mtDNA revealed the presence of two phylogenetic lineages, the DA and the Atlantic (AT). Haplotypes Da1, Da2, and Da22 were recorded within the DA lineage and At1 was recorded within the AT haplogroup. Two new haplotypes were described for the first time in this study and are named Da1f and Da1g. Restriction analysis of the lactate dehydrogenase gene locus revealed a high degree of hybridization between brown trout of DA and AT haplogroups. Conclusion. The results of this study confirmed the complex molecular diversity of brown trout and the high degree of the introduction of non-native haplogroups into rivers of the Danube basin in Croatia. Conservation of native brown trout populations has become evident, as introduced allochthonous DA and AT haplogroups severely disrupt the indigenous brown trout stock.