2003. Barriers to Fish Passage in the streams of the North Shore, Auckland, NZ. Conference Paper.
Authors
Damian Young, Environmental Engineer (BE Env), North Shore City Council
Wendy Symmans, Environmental Scientist (MSC Hons), North Shore City Council
Ian Boothroyd (DPhil, MBA, MLBiol, MRSNZ), Kingett Mitchell and Associates
Abstract
As we look to protect our environment, there is a growing recognition of the importance of natural stream habitats. Many of our native fish migrate to and from the sea as part of their lifecycle. Structures such as culverts, dams and piped sections can form impassable barriers, which effectively deny many species from accessing important life sustaining habitats. More emphasis is now being placed on ensuring that migratory pathways of native fish are maintained or reinstated where appropriate.
More than 120 km of streams on the North Shore have been surveyed to determine the effects of the stormwater infrastructure on the aquatic environment. Entire stream networks have been walked. Information regarding the influence of structures on instream hydraulics and fish passage has been collected. All potential barriers, both man-made and natural, have been classified based on their locations in the stream network and their anticipated effect on fish passage. Structures generally considered to prevent fish migration have been proven to be surmountable. Native fish species were found to have navigated major piped sections in excess of 700 m in length and drops greater than 3 metres to access important upstream habitats.
Fish experts might be in no doubt as to the extraordinary abilities of native fish. Yet ultimately they are not the managers of the stormwater systems in New Zealand. For this reason it is important that a common ground of understanding is created for all, experts, stormwater managers and also, importantly, the community. It is imperative that wherever possible our engineered works in stream systems are fish friendly while still catering for the traditional needs of providing effective stormwater management. On going studies both in the laboratory and in the field will be necessary to consolidate our understanding of the requirements that stormwater design should include.
KEYWORDS
Diadromous, Perched Culvert, Fish Passage, Migratory, Hydraulics
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