Title: Ecological evaluation of newly established bank structures on the Danube Canal (Vienna, Austria) and comparison with other habitats in the Danube system

Author: Brigitta Boda

Supervising Institution: BOKU University

Year: 2025

 

Abstract:

This study investigated the fish communities associated with different bank habitats and navigation
intensities on the Donaukanal in Vienna, Austria. In fall 2024 and spring 2025, two boat electrofishing
surveys were carried out at three biologically engineered habitats (pile wall, stone throw and short
groynes), as well as six riprap sections subjected to different intensities of boat traffic. Results were
compared with pre-existing surveys from the Donaukanal and two nearby rivers (Viennese Danube,
Traisen), as well as the adapted fish ecological leitbild of the Donaukanal. Combined with the
preceding Danube and Traisen surveys, 10.369 individuals of 43 species were included in the study.
Fish abundance was significantly lower (p<0,01) in the Donaukanal than in reference rivers. In the
canal, S. cephalus had the highest relative abundance (64%), followed by N. melanostomus (9%) and
P. phoxinus (7%). Community composition was skewed towards adult individuals. Species diversity
was lower in the Donaukanal than in the reference rivers, even in bio-engineered habitats and
especially at riprap affected by heavy traffic. Compared with 3-4 Gobiidae species in the reference
rivers, only N. melanostomus was found in the Donaukanal. Native C. gobio, absent from the other
rivers, coexisted with round goby in four of the sampled strips, and two vulnerable leitbild species
B. sapa and R. amarus were also caught. The abundance of P. phoxinus was notably higher than in
previous studies, indicating a potential shift in community composition since recent monitorings.
Both bank morphology and navigation had significantly negative effects on fish length, abundance
and biomass (p<0,01-0,02), but the impact of navigation was generally stronger than of the
morphological differences. Findings of this study suggest that bio-engineered habitats are
moderately more suitable than riprap for the fish, but they do not compensate for the general
morphological deficits or the wave impact.

 

Keywords: Donaukanal, restoration ecology, morphological mitigation, urban canal, ship-induced
waves, riverine fish