Conference 2003
Greening the City:
Bringing Biodiversity Back
into the Urban Environment
Abstract:
Restoring
In-stream Values and Habitat for Canterbury Mudfish in Okeover Stream,
Christchurch
Leanne O'Brien (Department of Zoology, University of Canterbury)
& Rachel Barker (Parks & Waterways Unit, Christchurch City Council)
Since the 1990s there
has been a changed approach to managing streams throughout Christchurch
city. The focus has moved away from managing drainage channels
to restoring streams for the plants, fish, invertebrates and birds
they support — and to make streams an enjoyable part of our
daily lives. At the Okeover Stream, Christchurch City Council and
the University of Canterbury have gone a step further and created
a special project that is the first of its kind in Christchurch.
The Okeover Stream has
changed considerably over the past few years; this project is the
latest in a series of focused habitat restorations. Previously,
the upper section of the stream was often dry, due to reduced flow
from the ground water springs that once fed this stream. This reach
was looking doomed until the Maths and Computer Science building
was constructed. This building is air-conditioned using aquifer
water which is pumped round the building and the piped into the
stream at its upper end. This produces an adequate flow of good
quality water. However, the air-conditioning is not always on,
and when it is turned off, such as in University holidays, little
water is left. This restoration project was designed to mediate
the impacts of these fluctuating water levels on the aquatic community.
One species which thrives
in such fluctuating spring-fed streams is the Canterbury mudfish.
Mudfish habitats often dry up, but mudfish are quite amphibious,
if pools go stagnant they can breathe air at the water surface,
or leave the water. If the whole area dries they can survive for
months, as long as they are moist. So mudfish appear perfectly
suited to this type of waterway. When establishing a species it
is important to consider food resources and habitat requirements,
particularly for vulnerable stages of development. Extensive habitat
development has been conducted with the site excavated to construct
deep pools to retain water during low flow. An innovative feature
of this restoration is the creative use of engineering structures
such as gabions (wire baskets filled with river stones) to line
pools and direct flow, creating refuge and backwaters within the
stream. Backwater areas are important for mudfish as they provide
a still habitat for the vulnerable fry stages. Native aquatic
vegetation, which is important to mudfish for spawning, will also
be established in these backwaters. Our vision is to have a thriving
population of Canterbury Mudfish located here on the University
campus, where their progress can be monitored and researched over
the long-term. We hope that lessons learned from establishing this
population can be used to direct conservation initiative in other
habitats where mudfish could gain a stronghold.
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