DOI: 10.5061/dryad.2778n3g
title: Data from: Flow restoration and the impacts of multiple stressors on fish communities in regulated rivers

description: River regulation for hydropower is undertaken worldwide, causing profound
 alterations to hydrological regimes and running water habitats. Regulated
 catchments are often subjected to additional stressors, arising inter alia
 from agriculture, forestry and industry, which are likely to interact with
 impacts of river regulation on fish and other biota. Such interactions are
 poorly understood, hindering planning of effective mitigation and
 restoration. We investigated fish responses to increased discharge (as a
 restoration measure) in regulated rivers in Sweden. We compiled
 electrofishing data from river channels downstream of hydropower dams,
 each of which either has or lacks a mandated minimum discharge
 corresponding to c. 5% of pre‐regulation discharge. We further analysed
 interactions between flow restoration and co‐occurring local and regional
 stressors. River channels without a mandated minimum discharge were
 characterised by a low diversity of fish species with traits favouring
 persistence under unpredictable environmental conditions, including
 omnivory, short life cycles and small size. Additional stressors further
 reduced diversity, and increased dominance by broad niched, opportunistic
 species. Both the presence and magnitude of a mandated minimum discharge
 were positively related to fish diversity and density, and the relative
 density of three economically and recreationally valuable species.
 However, the size of these relationships frequently varied with the
 presence of additional stressors. Increasing levels of hydrological
 degradation and reduced connectivity at the catchment scale reduced
 positive flow‐ecology relationships and hindered restoration of fish
 communities towards reference conditions. However, application of a
 mandated minimum discharge also assisted in mitigating impacts of some
 co‐occurring stressors, especially reduced riparian integrity. Synthesis
 and applications. Additional stressors can strongly influence the outcomes
 of flow restoration for fish community diversity and composition. Our
 approach combining fish species and trait data from multiple flow
 restoration projects with information on additional stressors yielded
 valuable insights into factors affecting flow restoration success, useful
 for (i) identifying the systems most likely to benefit from mandated
 minimum flows, (ii) modelling influences of multiple stressors on
 flow‐ecology relationships, (iii) prioritising additional measures to
 manage co‐occurring stressors and enhance outcomes from flow restoration.
description: Fish communities and
 traits from bypassed river reaches with and without a mandated minimum
 flowThe file contains data
 on fish communities sampled as part of Swedish national monitoring from 68
 stations situated in bypassed river reaches downstream of hydropower dams
 in Sweden. The file includes basic information on the reaches, species
 abundances and diversity, and species trait data scored based on the
 www.freshwaterecology.info database. For more information, see the README
 fileGöthe
 et al for Dryad.xlsx