Macro- and microhabitats used by 0+ fish in a side-arm of the River Danube
Kurmayer, R.; Keckeis, H.; Schrutka, S.; Zweimüller, I.
Use of macro- and microhabitats by fish larvae and juveniles was studied during 1992 in a floodplain side-channel of the River Danube, 40 km downstream of Vienna, using a modified form of point abundance sampling. Twenty-nine sampling points were defined within four habitat components (shallow bank, gravel-bank, steep bank and riprap), at which several biotic and abiotic variables were measured. Species richness was highest during July due to seasonal turnover of species, when early spawners such as Chondrostoma nasus and Vimba vimba were migrating from nursery grounds and later spawners such as Gobio gobio and G. albipinnatus were immigrating to new nursery areas. The shallow bank had the highest species diversity and was most important for older larvae and juveniles. The steep bank had the greatest number of young larvae, mainly Abramis brama, Rhodeus sericeus and Blicca bjoerkna, but species richness decreased considerably during the summer. In the riprap, fish associations were characterised by varying abundance of eurytopic species. Ontogenetic shifts in habitat were observed. Larvae and juveniles of rheophilic species (C. nasus, Leuciscus leuciscus, G. albipinnatus, G. gobio) were restricted to shallow banks and gravel-banks. Our results provide important information on the autecological requirements of floodplain fishes,useful for the development of criteria for river restoration and/or enhancement.