Geomorphological alterations, hydrological disconnectivity and water pollution are among
the dominant pressures affecting ecological integrity in urban streams. River restoration approaches
often involve utilising in-stream structures to encourage flow heterogeneity and promote habitat
diversity. However, few studies examine the success of such projects. In this study, fish density,
biomass and community structure at paired restored and unrestored reaches across five tributaries of
the River Thames were examined. Fish density varied among rivers and reaches but was generally
higher at restored sites. Restored sites also exhibited higher overall fish biomass, attributed mainly
to the presence of brown trout (Salmo trutta L.) at the River Wandle. Despite higher density and
biomass values at restored sites, the community structure analysis did not identify strong links
between either river or restoration status using either species-specific density or biomass. Our results
highlight that although reach-scale restoration can lead to localised increases in species density
and biomass, this may chiefly be due to aggregation owing to preferential habitats created through
restoration activities at these sites. Over larger spatial scales, significant improvements to species
richness and diversity are likely to be limited due to the poor water quality and disconnected nature
of these urban streams. Whilst reach-scale restoration clearly has the potential to provide preferential
habitats for fish species, future efforts should focus on improving connectivity for fish across the
wider Thames basin network by removing barriers to passage, improving water quality, restoring
watershed processes and creating well-connected, diverse habitats which can facilitate the survival
of a wide array of fish species throughout their life cycle.