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

Abstract

. (2016) 'Evaluating the eectiveness of restoring longitudinal connectivity for stream sh communities : towards a more holistic approach.', Science of the total environment., 569-570 . pp. 850-860. Further information on publisher's website: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractA more holistic approach towards testing longitudinal connectivity restoration is needed in order to establish that intended ecological functions 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. Radiotracking 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. Short-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 colonised. 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.

Does restoration work? It depends on how we measure success

“…These mixed results align with the few studies that have assessed fish passage restoration success (Pretty et al ; Noonan et al ; Evans et al ; Myers & Nieraeth ; Tummers et al ). Evans et al () found an increase in similarity in fish community composition upstream and downstream of a restored culvert 3 years after restoration, but a decrease in relative fish abundance (though biomass remained constant).…”

“…through insertion of baffles and adjusting culvert slope). In small passage structures such as culverts, resources are rarely put in place to evaluate the biological outcomes of these interventions (Bernhardt et al ; Tummers et al ; Rodeles et al ). This is unfortunate given that these structures are ubiquitous and studies of the impacts of restoration activities are critical to establishing best practices, setting expectations for restoration success and understanding the cost‐benefit analysis of different restoration approaches (see Neeson et al for an example of a return‐on‐investment framework for addressing barrier removal).…”

“…Additionally, observed “improvements” to biological metrics after restoration may simply be a result of natural spatiotemporal variation unless controlled for in the experimental design. The ideal scenario is to have a BACI (before‐after‐control‐impact) study design (Ogren & Huckins ; Tummers et al ) that controls for both spatial and temporal variation. However, few studies achieve this despite that it has been shown to be the overall superior method for monitoring (Smokorowski & Randall ).…”

Rainbow Trout Migration and Use of a Nature‐Like Fishway at a Great Lakes Tributary

“…; Tummers et al. ; Dodd et al. ); therefore, this species may be more adept at navigating the range of flows experienced within fishways with a nature‐like design.…”

“…; Calles and Greenberg , ; Tummers et al. ; Dodd et al. ), and 11 studies reported efficiency values for 43 nonsalmonid species at nature‐like fishways (Schmutz et al.…”