Danube Flood Research Articles

Dominance and change in the numbers of mosquito larvae of the biting mosquitoes sub-family (Culicinae) in the Szigetköz region

In the region of Szigetkoz (North-West Hungary) mosquito larvae were regularly collected at 64 sites in 16 villages of 4 districts every week between 1-30 September, 1999. As a result we identified the larvae of 19 mosquito species, among them 93.68% were Aedes vexans Meig. and 5.11% were Culex pipiens pipiens L. The numbers of the mosquito larvae to be collected at site proves the heterogenity of the biotops in the districts. We collected 5718 larvae in district I, 2401 larvae in district II, 1170 in district III, 232 344 in district IV. District IV reflects the effect of the Danube floods i.e. the flood area was overflown with perched water and the water temperatures often rose above 30 °C. These factors contributed to the dominance of Aedes vexans. Regular inspections, the knowledge of the species and the identification of the larvae development enabled us to set the date of optimal biological protection.

Hidden biodiversity in the groundwater of the Danube Flood Plain National Park (Austria)

A high number of stygobites (35 taxa) was recorded within a protected area, the Lobau in Vienna. It is shown that within National Parks, the identification of biodiversity hotspots of stygobites represents an attractive scientific activity, which increases the cultural value of protected landscapes.

Changes in juvenile fish assemblages in two backwaters of the Szigetköz floodplain after river diversion by the Gabcikovo Dam

The braided hydrosystem of the Szigetköz floodplain played a prominent part in the structure of the fish communities in the upper section of the middle river Danube Regulations and flood control measures have modified the natural resources of the area since the 19th century. At the end of 1992, the River Danube was diverted to the by‐pass canal of the Gabcikovo Hydroelectric Power Plant and most of the small tributaries to the river became dry in the floodplain. The juvenile fish assemblages have been monitored since the completion of the Dam of the River Gabcikovo. The monitoring results of parapotamic and plesiopotamic backwaters demonstrate the importance of hydrological connectivity of the floodplain tributaries.

Multi-scale analysis of habitat use during late summer for 0+ fishes in the River Garonne (France)

Relationships between environmental variables and 0+fish in the upper River Garonne (France) were studied at different habitat scales during late August 1995. In total, 3911 0+ fish representing 21 species were sampled using point abundance sampling by electrofishing. Fish reproductive function of floodplain channels was evaluated using principal components analysis of 0+ fish distributions (in absence/presence), with distinction of the three main channel types (flowing, partially abandoned and abandoned channels). A descriptive model of microhabitat use and microhabitat profiles of 0+ fish was developed for the more frequently encountered species using canonical correspondence analysis and an electivity index combined with chi-square analysis. Water velocity, water depth and distance from the bank were the most important microhabitat variables, followed by bank gradient and bottom composition. Partially-abandoned channels provide conditions particularly suitable to 0+ fish, with submerged vegetation in these side-channels serving many of the fishes as refuge and feeding areas. Similarities in microhabitat use were found with respect to 0+ juvenile fish in the Danube flood plain (Slovakia/Hungary), the upper River Rhone (France) and the River Great Ouse catchment (England).

Comparative Analysis of Feeding and Schooling Behaviour of the Cyprinidae Alburnus alburnus (L., 1758), Rutilus rutilus (L., 1758), and Scardinius erythrophthalmus (L., 1758) in a Backwater of the Danube near Vienna

AbstractUnderwater observations of the three common fish species Alburnus alburnus (L., 1758), Rutilus rutilus (L., 1758) and Scardinius erythrophthalmus (L., 1758) in a small part of the Danube flood area near Vienna have been made from June to October 1985 and 1986. Particular emphasis has been laid on the partitioning of feeding resources and habitat. It has been established that these species prefer different water zones. Alburnus a. and Scardinius e. are “obligate” schoolers (BREDER, 1967) whereas Rutilus r. is a facultative schooler. While feeding Rutilus r. and Scardinius e. form “aggregations” (BREDER, 1959) and both adopt equivalent feeding techniques. Furthermore Alburnus a. is a quick moving species living near the surface and chasing mostly in schools. While inter‐ and intraspecific aggression is rarely observed for Rutilus r. and Scardinius e., Alburnus a. often show interspecific actions.