Evaluating the effectiveness of restoring longitudinal connectivity for stream fish communities: towards a more holistic approach

Tummers, J.S.; Hudson, S.; Lucas, M.C.

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 (2–3 years) 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.

Citation

Tummers, J., Hudson, S., & Lucas, M. (2016). Evaluating the effectiveness of restoring longitudinal connectivity for stream fish communities: towards a more holistic approach. Science of the Total Environment, 569-570, 850-860. https://doi.org/10.1016/j.scitotenv.2016.06.207

• Journal Article Type: Article
• Acceptance Date: Jun 26, 2016
• Online Publication Date: Jul 14, 2016
• Publication Date: Nov 1, 2016
• Deposit Date: Aug 16, 2016
• Publicly Available Date: Jul 14, 2017
• Journal: Science of the Total Environment
• Print ISSN: 0048-9697
• Electronic ISSN: 1879-1026
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 569-570
• Pages: 850-860
• DOI: https://doi.org/10.1016/j.scitotenv.2016.06.207
• Public URL: https://durham-repository.worktribe.com/output/1399165