Subject: Carp and Wetlands: #introduction
Status: R
CARP AND WETLANDS:
A RESEARCH PROJECT
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By University of Adelaide students Frances Marsh (Honours in
Environmental Management) and Scotte Wedderburn, Catherine Miles, Troy
Horn, and Julie Pfitzner (Bachelor of Environmental Management)
Please email us with your comments!
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Contents
[INLINE] Introduction
[INLINE] Some background to the project
[INLINE] Carp in Australia
[INLINE] Field sites
[INLINE] Building on previous research
[INLINE] Industry support
[INLINE] Our research
[INLINE] Team Pilby in action!
[INLINE] Future research - a PhD study
[INLINE] Acknowledgements
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Introduction
We are students in the Department of Environmental Science and
Management at the University of Adelaide's Roseworthy Campus (South
Australia). Having completed a Bachelor of Applied Science in Natural
Resource Management here last year, Fran is now continuing with
Honours in Environmental Management, while Scotte, Catherine, Troy,
and Julie are enthusiastic second years who are doing projects for a
subject called Field Studies II. Under the supervision of Dr Friedrich
Recknagel, we are sampling a range of parameters in two wetlands, one
of which is managed to exclude mature fish, along the lower River
Murray. This page has been set up to describe the project and discuss
some results so far. If anyone who stumbles onto here has any
questions or comments, we would love to hear them. (And please bear in
mind that we are only humble students and have no pretensions to
research expertise!)
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Some background to the project
The River Murray and its associated tributaries in the Murray-Darling
Basin comprise an extremely important water resource for much of
south-eastern Australia. However, since white settlement, this
resource has become degraded by natural and artificial forms of
pollution, massive water removal for human uses, and regulation by a
series of locks and weirs. Cyanobacteria, or blue-green algae, are a
natural component of the river water, but eutrophication, the
introduction of exotic fish species, and regulation have all played a
part in making large numbers of cyanobacteria, called a "bloom", a
common occurrence in the warm summer months. Apart from the taste and
odour problems this causes, several species of cyanobacteria are
commonly toxic, so the presence of cyanobacterial blooms is a water
quality problem for all who use the river and its water. In addition,
changes to the river system have led to massive degradation and
decimation of habitats, both along the river and in the associated
lakes and wetlands. The River Murray is a floodplain river, and its
wetlands are vital to the health of the river. Among the many
functions of wetlands are floodwater storage, removal of nutrients,
sediment filtering and immobilisation, and provision of habitats for
fish and wildlife to nest, breed, and feed. The rehabilitation or
restoration of wetlands is crucial to the the health of the river and
the survival of its species, and ultimately its sustainability as a
resource.
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Carp in Australia
Although introduced to Australia as an ornamental pond fish in the
1870s, carp (Cyprinus carpio) did not enter the Murray-Darling Basin
until the 1960s, and apparently took less than five years to become
dominant. Carp have the attributes of a typical pest species - they
tolerate a wide range of environmental conditions, are opportunistic,
and have high fecundity, all of which have contributed to their
success. In addition, native fish species have declined in abundance
since river regulation, while the regulated conditions are eminently
suitable for carp. Hence the decrease of native species has occurred
concurrently with the increase in carp numbers, and despite much
speculation and anecdotal evidence, there is no real evidence to link
the two. Scientific research in Australia on the effects of carp has
been limited, although there is some evidence to indicate that carp
increase turbidity and can uproot fragile water plants, decreasing
abundance and diversity. Some commonly perceived effects of carp are
increased turbidity and nutrients, declining abundance and diversity
of water plants, macroinvertebrates, and native fish, and collapsing
banks. However, there are many other human impacts on the waterways
which could be responsible for these effects. In a field situation, it
is difficult to isolate the effects of various other impacts,
particularly those caused by changes in hydrology since the regulation
of the river, but owing to the complexity of natural systems,
laboratory experiments are somewhat inadequate because they can never
exactly simulate real conditions. Hence carp are perceived to be a big
problem in Australia, and certainly there is much anecdotal evidence
and the declaration of carp as a noxious species across the country to
support this, but much further research is needed to confirm or deny
any impacts.
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Field sites
Pilby Creek
Pilby Creek is a small creek on the Chowilla floodplain, near Renmark,
South Australia. A backwater wetland extends off the creek, upstream
and downstream of which regulatory structures have been constructed.
Upstream, a 4 bay inlet fitted with metal 1 cm mesh screens and
drop-down log grooves has been installed to prevent the entry of
mature common carp, Cyprinus carpio. This barrier naturally prevents
the entry of other mature fish, but the exclusion of carp was seen as
a priority, for reasons which will be discussed below. Downstream of
the wetland, a valve and large culvert allow release of the water from
the wetland, but there is no mesh. Hence, the wetland is usually
drained at the beginning of summer by closing the inlet with planks
and opening the outlet valve, and is then refilled after being left
dry for a month or two. The wetland has very few dead trees and logs
in it and along the banks, the dominant macrophyte or waterplant
species is Typha orientalis, or cumbungi, with Phragmites australis
the second most abundant species. Other macrophytes, such as
Vallisneria gigantea (ribbonweed), Persicaria decipiens (slender
knotweed), and Lemna and Azolla species (duckweed) are also present.
Around the perimeter, Pilby is flanked by Eucalyptus largiflorens
(black box) and Eucalyptus camaldulensis(river red gum). At the
deepest point, the wetland is 1.8 metres deep.
Pilby Creek: one of the inlet bays showing mesh (and an algal bloom trapped
on the wetland side)
Pilby Creek inlet bay
Pilby Creek wetland: the top end
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Enlargement
Lock 6 wetland
Lock 6 wetland is adjacent to Pilby Creek wetland, but is fed directly
from the River Murray. Like many wetlands along the river, it was
ephemeral before regulation, but has been permanently inundated since
nearby Lock 6 was built in the 1920s. As a result, there is a large
number of dead trees in the wetland, and it consequently supports many
water birds. Lock 6 wetland is shallower and covers a larger area than
Pilby, but the actual volume of water in both is very similar. The
macrophyte population mainly consists of large beds of Typha
orientalis with some Phragmites australis along the bank, while the
same species form occasional reed islands in the open water. E.
largiflorens and E. camaldulensis are the main trees around the
wetland, but where there is only a thin strip of land between the
lagoon and the river, a thick stand of Salix babylonica, or willow
trees, grows.
Lock 6 wetland
Lock 6 wetland
Enlargement
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Building on previous research
In 1996, Nadene Schiller conducted a comparative study of Pilby Creek
and Lock 6 wetlands for her Honours project, in order to both obtain
some baseline data about the differences between the two, and draw
some preliminary conclusions regarding the carp exclusion management
of Pilby. She monitored macroinvertebrates, fish, and macrophytes,
assisted by Scott Matthews who studied water quality, and found some
strong differences between the two wetlands. As part of a long term
monitoring program, we have continued to sample these and other
parameters.
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Industry support
We receive financial support from the Murray-Darling Association, and
interest and advice from:
* Mike Harper from Bookmark Biosphere (which encompasses the
Chowilla floodplain)
* Peter Baker at the Australian Water Quality Centre/South
Australian Water Corporation (SA Water)
* Anne Jensen at the South Australian Department of Environment and
Natural Resources (DENR)
* Bryan Pierce at the South Australian Research and Development
Institute (SARDI)
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Our research
We have sampled a wide range of wetland components because we hope to
assess as many parameters as we can which may indicate changes or
aberrations due to the presence of carp, a different hydrological
regime, or other causes. While it is difficult to assign definite
reasons or explanations for the results we have, at least we are
building up a database of information about the two wetlands. This is
important, because despite widespread recognition of the value of
wetlands, very little sampling or monitoring has actually been carried
out on natural wetlands, particularly over an extended time frame. For
Pilby Creek and Lock 6 wetlands, this is the second year of sampling,
and we have learnt a lot about the ecosystem components, but this is
still a minimal amount of knowledge in the face of management
considerations. Perhaps after ten years of sampling, some definite
assertions can be made about the wetlands and their behaviour under
certain conditions, but thus far the most we can conclude from our
study are that things "might be", "could indicate that", or "may
influence" something, and our major recommendation will be for further
research.
[LINK]Phytoplankton, water quality, nutrients, and chlorophyll - Fran
[LINK]Fish - Scotte
[LINK]Macroinvertebrates - Catherine
[INLINE] Frogs - Troy
[LINK]Macrophytes - Julie
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Team Pilby in action!
If you want to see us out and about, click here!
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Future research - a real postgraduate study!
Mardi van der Wielen will be carrying out a Masters or PhD project
(depending on funding) at Pilby Creek wetland (among others) over the
next two or three years, beginning in October 1997. She will be
continuing along the lines of our work, but will probably drop some
areas of study in favour of concentrating on hydrology, carp, and
cyanobacteria, particularly as she will most likely have several
wetlands along the river to study. Mardi completed a science degree at
Flinders University (Adelaide, South Australia), continued with
Honours, and then came to Roseworthy Campus in 1996 to undertake a
Graduate Diploma in Natural Resource Management. You can look out for
her web page soon (I guess!) but in the mean time if anyone has any
suggestions, questions, or ideas about the next three years at Pilby,
please let us know. One of the more immediate changes that may be
happening there is the introduction of spawn-cued Murray cod. This is
an idea that has been tossed around for a while by Bryan Pierce and
others but whether anything will come of it we don't know.
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Thanks to:
Project-wise
Peter Baker at SA Water/Australian Water Quality Centre
Bryan Pierce at SARDI
Anne Jensen at DENR/Wetland Care Australia
Mike Harper at Bookmark Biosphere(and formerly at DENR)
Leon Broster at the Murray-Darling Association
Jim Marsh at SA Water (Fran's Dad!)
Page-wise
Gary Starr, a knowledgeable, helpful person who also knows a lot about
population genetics and Hakea carinata!
Desktop Publishing for the links, Badger's Animated GIF Gallery for
the animated gifs, and for the backgrounds, Albino Frog Software and
Bob Waldock's Carp Safari Page
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