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Keywords:

  • river;
  • recolonization;
  • taxon richness;
  • fish;
  • urban development;
  • engineering

ABSTRACT

  1. Restoring longitudinal connectivity is a key river restoration goal. This study tested the efficacy of a fish ramp and spoiler baffles for restoring indigenous fish communities upstream of a culvert.
  2. Before–after monitoring showed that installation of the ramp and spoiler baffles increased species richness (mean increase 80%) and total fish density (mean increase 45%) upstream of the culvert.
  3. Passage trials on the ramp and baffled culvert were carried out using inanga, Galaxias maculatus (Jenyns), a commonly occurring weak-swimming migratory fish. The trials showed that inanga were capable of successfully ascending both the ramp (overall 27.1% success) and culvert with baffles (overall 6.2% success) under the conditions tested (cf. 0% success for this species before retrofitting), but passage efficiency was still relatively low in both cases.
  4. Retrofitting of culverts can therefore be effective for restoring upstream fish passage. However, to maximize effectiveness it is essential that restoration goals are well defined and retrofitting solutions are designed appropriately for the target species. Copyright © 2012 John Wiley & Sons, Ltd.