Criteria of sustainable management of large river systems-ecological aspects and challenges of the 21 st century

River systems maintain unique biotic resources and provide essential renewable water supplies for humankind. Flood pulses are the key natural drivers of species richness and productivity of the large river-floodplain ecosystems, but traditional water management has sought to reduce the natural variability of river flows to achieve more stable water supplies for socio-economic water needs. The increasing human pressure on river systems directly threatens the biodiversity of fluvial ecosystems across the world. Ecologically sustainable river management is aimed at maintaining the ecological integrity of the affected ecosystems while meeting the intergenerational human needs and sustaining the full array of other goods and services provided by natural river ecosystems. Several criteria of ecologically sustainable water management are outlined, such as the assessment of the reference status, the documentation of the deficiencies of the baseline conditions, the identification of the causes of ecosystem degradation using the DPSIR framework, the analysis of the compatibility of water needs, the definition of the target vision, etc

Abundant prey or optimal microhabitat? Natrix tessellata stays hidden in safe areas in a diverse floodplain along the Danube at Göd, Hungary

Natrix tessellata (Laurenti, 1768) is a diurnal piscivorous Eurasian snake species with a large distribution area. Along the River Danube it is present in the floodplain and along the lower stretch of tributaries. The distribution of N. tessellata among the different microhabitats along the River Danube at Göd (1669-1671 rkm) and its relationship with environmental parameters and fish presence/absence, species composition, size distribution and abundance was studied at eight selected sections. Samples were collected twice a month from March to October in 2008-2009; N. tessellata was found between May and early October. Altogether 26 N. tessellata sightings were recorded together with 497 individuals of 21 fish species along the same sections, while another 5,547 individuals belonging to 28 fish species were caught in snake-free areas. Microhabitat characteristics were more important than the presence of fish in determining along which section N. tessellata stays. It favoured slow-flowing sections with aquatic macrophytes and a sandy or muddy bottom. In spite of their suitability, artificial habitats were not much used maybe due to increased risk of disturbance and predation/persecution. The habitat preference of N. tessellata changed less between the two studied years with different water level fluctuations than those of fishes and it was not identical with that of any of the fish species caught. However, fish 15-30 mm and longer may influence the distribution of N. tessellata

Elektromos halászattal gyűjtött minták napszakos változásai a Duna Budapest feletti szakaszán és egyes mellékvízfolyásaiban = Diurnal changes in samples of electrofishing in Danube section upstream of Budapest and its tributaries

Consideration  of  diurnal  changes  of  fish  distribution  is  a  basic  requirement  in  development  of  sampling  strategy for fish monitoring in large rivers. In present study, sampling results of day and night electrofishing  were compared in two sections of the Danube (at Szob and Sződliget), and two tributaries (the Ipel river at  Szob and the Sződrákosi stream at Sződliget). Samples contained 3895 individuals of 35 fish species in 2012.  Some  species  (Romanogobio  vladykovi,  Zingel  zingel,  Sander  volgensis,  etc.)  were  observed  only  in  night  samples,  furthermore species richness and abundance in  the night samples was significantly higher  than in  the day samples in  the Danube. Evaluation  of diurnal  variability in electrofishing catches, can contribute  to  development of standard fish sampling methods in large rivers. | A  folyami  halállományok  reprezentatív  felmérését  elősegítő  mintavételi  stratégia  kidolgozásakor  fontos  kérdés  a  halak  eloszlásában  megfigyelhető  napszakos  változások  figyelembevétele.  Tanulmányunkban  elektromos  halászattal  végzett  nappali  és  éjszakai  felmérések  eredményeit  hasonlítottuk  össze.  A  mintavételeket két dunai helyszínen (a szobi és sződligeti folyószakasz), valamint két mellékvízfolyásban, az  Ipoly szobi szakaszán és a Sződrákosi‐patak sződligeti torkolatánál hajtottuk végre, 2012‐ben. Felméréseink  során  összesen  35  halfaj  3895  egyedét  határoztuk  meg.  Egyes  halfajok  (pl. Romanogobio vladykovi, Zingel  zingel, Sander volgensis) csak az éjjeli mintákban voltak megfigyelhetőek,  továbbá az éjszakai halászatokkal  általában  több  halfaj  volt  gyűjthető  és  nagyobb  egyedszámban,  mint  a  nappali  időszakban.  Az  elektromos  halászat  fogási  eredményében  megfigyelhető  napszakos  változékonyság  elemzésével  a  standard  folyami  monitorozási eljárások fejlesztéséhez kívánunk hozzájárulni

A brief overview of the long-term changes of fish fauna in the Slovak-Hungarian section of the Danube River

Description of the fish fauna was completed by way of literary review, field experience, and some rare species have been found in the catches of commercial fishermen. Suitable publications and reports are available from the 18th century. The upper part of the Slovak-Hungarian section of the Danube is aggrading and anabranching, while its lower part is a wandering sinuous channel. The native fish fauna includes 54 species, while the alien fish fauna contains 23 species, 11 of which are exotic in Europe. Two species, Huso huso and Acipenser stellatus are practically extinct from the Middle Danube region. This river stretch is heavily modified, and the historical changes of the fish fauna were evaluated in conjunction with human impacts

Az emberi tevékenység hatása a halfauna alakulására az Ipoly alsó (magyarországi) szakaszán

Az Ipoly magyarországi szakaszának hosszúidejű halfauna változását a 19. századtól megjelent halfaunisztikai publikációk és közvetlen halbiológiai felméréseink alapján jellemeztük. A vizsgált alsó folyó-szakaszon 56 halfaj előfordulása igazolható. Áttekintést adtunk a folyó antropogén hatásokkal összefüggő változásairól, valamint meghatároztuk a folyó natív halfaunáját és adventív faunaelemeit. A halfauna térbeli eloszlását és összetételének alakulását folyószabályozási beavatkozásokkal összefüggően ismertettük

Hucho hucho (Linnaeus, 1758): last natural viable population in the Eastern Carpathians - conservation elements

There is great variation in the conservation status of the last habitats with long-term natural viable populations of the salmon species Hucho hucho in Maramureş Mountains Nature Park, Eastern Carpathians (Romania). According to the specific guidelines for Natura 2000, 42.11% are in good conservation status, 31.57% are of average status, and 26.32% are in a partially degraded condition. In this study area, 6 main risk elements were identified related to human impact on the environment: poaching, minor riverbed morphodynamic changes, liquid and solid natural flow disruption, habitat fragmentation leading to isolation of fish populations, organic and mining pollution, and destruction of riparian tree and shrub vegetation. All of them have contributed to the decrease of H. hucho distribution in the study area to about 50% of the previous local range. Individuals of this species were recorded in only 21 of the 370 sampling stations