Do we know enough to save European riverine fish?-A systematic review on autecological requirements during critical life stages of 10 rheophilic species at risk

Modeling of fish population developments in the context of hydropower impacts and restoration planning requires autecological information on critical life stages (especially on juvenile stages and reproduction). We compiled and examined the current data availability in peer-reviewed and grey literature on autecological requirements of ten rheophilic fish species at risk, belonging to the salmonid, cyprinid, and cottid families. In total, 1725 data points from 223 sources were included. Economically important salmonids and the common nase were the most studied species. Grey and peer-reviewed data showed similar dispersion and variance and contributed nearly equally to the data pool of the specific species. An in-depth analysis on seven ecological parameters revealed no significant differences between both sources in terms of data availability and quality. We found substantial deficits in the data for about a quarter of the reviewed ecological parameters, in particular on individual densities in the habitats, egg development and information about juvenile stages despite the necessity of such data for more advanced population analyses. To secure fish populations in the long term, more data on basic autecological parameters is needed and grey literature might add valuable information, particularly if it relies on standardized methodologies.