Managed flooding as a tool for supporting natural fish reproduction in man‐made lentic water bodies

In 2001, fish diversity and abundance were investigated in six man‐made borrow pits in the flood plain of the River Dyje (Danube basin). All borrow pits had uniform habitats without shelter, and with limited spawning and nursery areas. Spawning and nursery habitat conditions in three borrow pits were experimentally improved by managed flooding during spring and summer, while the other three borrow pits were not flooded. Adult (>1 year) fish were surveyed in spring and autumn by beach seining and 0+ fish were monitored monthly by dipnetting and fry beach seine nets. Flooded borrow pits had slightly higher adult species richness, considerably higher adult fish abundance and considerably higher 0+ fish species richness and abundance. The seasonal decline in 0+ fish abundance varied between flooded and non‐flooded borrow pits, with a faster decline in 0+ abundance at non‐flooded sites. Management implications for floodplain lentic water bodies are discussed.