Brown Trout Abundance in Boreal Streams With Large Wood

ABSTRACT Large wood has been found to be a crucial component in riverine ecosystems. However, due to the heavy channelization of rivers and intensive forestry practices over the past few decades, the amount of large wood in these ecosystems has decreased worldwide. River restoration aims to mitigate the effects of channelization and restore the channel closer to its original, pre‐channelized form, but large wood has been an overlooked component in restoration. In this study, we investigated the effect of large wood on the density of brown trout ( Salmo trutta L.) parr in several natural rivers in southern Finland and Sweden. The density of 0‐year‐old parr was higher in areas with a high concentration of large wood, but no difference was found in the densities of 1‐year‐old or ≥ 2‐year‐old parr or other fish species. Other microenvironmental factors did not influence parr density. Due to the apparent positive impact of large wood on 0‐year‐old parr density, it is recommended as a part of river restoration.