Fish passage

Channelised streams

Streams in urban environments are often converted into concrete-lined channels for flood and erosion control. These channels lack most of the ecological functions of natural streams and provide little habitat for native fish.

Issues

A channelised stream with no riparian margin or in-stream cover

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Lack of in-stream features – channels lack areas for fish to rest, feed and take refuge.

Lack of food – channels generally lack suitable surfaces for aquatic insects to live on or bankside vegetation for land invertebrates to fall into the water from, both of which are important food sources for fish.

Lack of shade – the absence of large trees and bushes to provide shading leads to increased water temperatures, which native fish are unable to tolerate.

Options

• Restoring channelised streams involves recreating natural stream patterns by reintroducing features such as meanders and flood plains, as well as adding large pieces of wood and rocks to provide habitat for aquatic animals.
  
  Restoring channelised streams (72.7 KB PDF)

Note: the pdf documents on this page are excerpts from ARC Technical Report 2009/084: “Fish Passage in the Auckland Region – a synthesis of current research".