title: Evaluating the effectiveness of restoring longitudinal connectivity for stream fish communities: towards a more holistic approach.
abstract: A more holistic approach towards testing longitudinal connectivity restoration is needed in order to establish that intended ecological functions of such restoration are achieved. We illustrate the use of a multi-method scheme to evaluate the effectiveness of 'nature-like' connectivity restoration for stream fish communities in the River Deerness, NE England. Electric-fishing, capture-mark-recapture, PIT telemetry and radio-telemetry were used to measure fish community composition, dispersal, fishway efficiency and upstream migration respectively. For measuring passage and dispersal, our rationale was to evaluate a wide size range of strong swimmers (exemplified by brown trout Salmo trutta) and weak swimmers (exemplified by bullhead Cottus perifretum) in situ in the stream ecosystem. Radio-tracking of adult trout during the spawning migration showed that passage efficiency at each of five connectivity-restored sites was 81.3-100%. Unaltered (experimental control) structures on the migration route had a bottle-neck effect on upstream migration, especially during low flows. However, even during low flows, displaced PIT tagged juvenile trout (total n=153) exhibited a passage efficiency of 70.1-93.1% at two nature-like passes. In mark-recapture experiments juvenile brown trout and bullhead tagged (total n=5303) succeeded in dispersing upstream more often at most structures following obstacle modification, but not at the two control sites, based on a Laplace kernel modelling approach of observed dispersal distance and barrier traverses. Medium-term post-restoration data (2-3years) showed that the fish assemblage remained similar at five of six connectivity-restored sites and two control sites, but at one connectivity-restored headwater site previously inhabited by trout only, three native non-salmonid species colonized. We conclude that stream habitat reconnection should support free movement of a wide range of species and life stages, wherever retention of such obstacles is not needed to manage non-native invasive species. Evaluation of the effectiveness of fish community restoration in degraded streams benefits from a similarly holistic approach.
authors.affiliation: School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK. Electronic address: j.s.tummers@durham.ac.uk.
authors.forename: Jeroen S
authors.initials: JS
authors.lastname: Tummers
authors.affiliation: Wear Rivers Trust, Low Barns Nature Reserve, Witton-le-Wear, County Durham DL14 0AG, UK.
authors.forename: Steve
authors.initials: S
authors.lastname: Hudson
authors.affiliation: School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK.
authors.forename: Martyn C
authors.initials: MC
authors.lastname: Lucas
mesh_terms: D063147:Animal Distribution; D000818:Animals; D003247:Conservation of Natural Resources / Q000379:methods*; D004739:England; D052918:Environmental Restoration and Remediation / Q000379:methods; D005399:Fishes / Q000502:physiology*; D010473:Perciformes / Q000502:physiology; D014337:Trout / Q000502:physiology
keywords: Fish assemblages; Habitat fragmentation; PIT; Passage efficiency; Telemetry; VIE