Hydraulic microdistribution patterns of larval fire salamanders (Salamandra salamandra salamandra) in the Weidlingbach near Vienna, Austria

1. This study examined the longitudinal distribution of larval fire salamanders (Salamandra salamandra salamandra L.) in the Weidlingbach system, a first‐ to fourth‐order tributary of the Danube near Vienna, Austria. On the microhabitat scale, actual current velocities, Reynolds numbers and Froude numbers at larval locations were measured and larval positions mapped. 2. Larval densities were highest in shallow first‐ and second‐order tributaries where mean current speeds were less than 20 cm s−1, mean Reynolds numbers were less than 12 000 and mean Froude numbers were less than 0.30. Young larvae appeared on 26 April, fully grown larvae were observed from 11 May and larvae started metamorphosis from 27 June. Young adults left the brook between 26 August and 8 September. A severe flood on 25 May significantly reduced larval density, especially at sites near the source. 3. At a given sampling station young larvae favoured microhabitats exposed to only minor hydraulic stress. As larvae grew, they also colonized microhabitats with moderate current velocity (4–15 cm s−1). At sites with generally low discharge, larvae were distributed over a wider range of current velocities than at sites with higher discharge; at the latter, larvae were constricted to sheltered microhabitats.