Threats, distribution and abundance of
Yarra Pygmy Perch in Victoria during a
drought period
M.J. Jones, P. Tinkler, M. Lindeman, G. Hackett, A.
Pickworth
2008
Arthur Rylah Institute for Environmental Research
Technical Report Series No. 184
Arthur Rylah Institute for Environmental Research Technical Series No. 184
Threats, distribution and abundance of Yarra Pygmy
Perch in Victoria during a drought period
Matthew J Jones, Paul Tinkler, Michael Lindeman,
Graeme Hackett, Andrew Pickworth
Arthur Rylah Institute for Environmental Research
123 Brown Street, Heidelberg, Victoria 3084
October 2008
Arthur Rylah Institute for Environmental Research
Department of Sustainability and Environment
Heidelberg, Victoria
Report produced by:
Arthur Rylah Institute for Environmental Research
Department of Sustainability and Environment
PO Box 137
Heidelberg, Victoria 3084
Phone (03) 9450 8600
Website: www.dse.vic.gov.au/ari
© State of Victoria, Department of Sustainability and Environment 2008
This publication is copyright. Apart from fair dealing for the purposes of private study, research, criticism or review as
permitted under the Copyright Act 1968, no part may be reproduced, copied, transmitted in any form or by any means
(electronic, mechanical or graphic) without the prior written permission of the State of Victoria, Department of
Sustainability and Environment. All requests and enquires should be directed to the Customer Service Centre, 136 186
or email customer.service@dse.vic.gov.au
Citation: Jones, M., Tinkler, P., Lindeman, M., Hackett, G., and Pickworth, A. (2008) Threats, distribution and
abundance of Yarra Pygmy Perch in Victoria during a drought period. Arthur Rylah Institute for Environmental
Research Technical Report Series No. 184. Department of Sustainability and Environment, Heidelberg, Victoria
ISSN 1835-3827 (print)
ISSN 1835-3835 (online)
ISBN 978-1-74208-890-7 (print)
ISBN 978-1-74208-890-7 (online)
Disclaimer: This publication may be of assistance to you but the State of Victoria and its employees do not guarantee
that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore
disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in
this publication.
Front cover photo: Electrofishing in the Barwon River (left), the Curdies River (Right) (Matthew Jones).
Authorised by: Victorian Government, Melbourne
Printed by: Arthur Rylah Institute for Environmental Research. P.O. Box 137 Heidelberg, Victoria, 3084
2
Contents
List of tables and figures...................................................................................................................v
Acknowledgements ........................................................................................................................ vii
Summary ............................................................................................................................................1
1
Introduction.............................................................................................................................3
2
2.1
Methods....................................................................................................................................4
Survey Site ................................................................................................................................4
2.2
Sampling Methods ....................................................................................................................4
2.3
Water quality.............................................................................................................................5
2.4
Habitat Assessment ...................................................................................................................5
2.5
Threatening Processes...............................................................................................................5
3
3.1
Results ...................................................................................................................................10
Water quality ..........................................................................................................................10
3.2
Fish Fauna ..............................................................................................................................10
3.3
All sites combined ..................................................................................................................10
3.4
Individual Streams ..................................................................................................................17
3.4.1
Deep Creek .............................................................................................................17
3.4.2
Threatening Processes .............................................................................................18
3.4.3
Barwon River, Waurn Ponds and Pennyroyal Creek ..............................................20
3.4.4
Threatening Processes .............................................................................................22
3.4.5
Gnarkeet Chain of Ponds and Woady Yaloak River ...............................................23
3.4.6
Threatening processes .............................................................................................24
3.4.7
Thompson Creek, Curdies River and Merrigig Creek .............................................25
3.4.8
Threatening processes .............................................................................................26
4
4.1
Discussion ............................................................................................................................. 29
Species Diversity, Distribution and Abundance .....................................................................29
4.2
Status of Yarra pygmy perch ..................................................................................................31
4.3
4.2.1
Deep Creek .............................................................................................................31
4.2.2
Barwon River, Waurn Ponds and Pennyroyal Creek ..............................................31
4.2.3
Gnarkeet Chain of Ponds and Woady Yaloak River ...............................................32
4.2.4
Thompson Creek, Curdies River and Merrigig Creek .............................................32
Threatening processes ............................................................................................................32
4.3.1
Non-native fish .......................................................................................................32
4.3.2
Non-native vegetation .............................................................................................33
4.3.3
Loss of instream habitat ..........................................................................................33
4.3.4
Loss of riparian zone vegetation .............................................................................34
4.3.5
Presence of instream barriers ..................................................................................34
3
4.3.6
Modified flow regimes ........................................................................................... 35
4.3.7
High Salinity .......................................................................................................... 35
5
Conclusion ............................................................................................................................ 36
6
References ............................................................................................................................ 37
Appendix 1 ..................................................................................................................................... 40
4
List of tables and figures
List of tables
Table 1. Location of fish survey sites in the Barwon, Otway, Maribyrnong and Corangamite
Basins. .......................................................................................................................................6
Table 2. Prior records of Nannoperca obscura in the Barwon, Otway, Maribyrnong and
Corangamite Basins. .................................................................................................................8
Table 3. Water quality and depth of survey sites. .............................................................................11
Table 4. Size distribution of fish caught at all sites using all gear types. ..........................................12
Table 5. The size distribution of fish caught in Deep Creek using all gear types. ............................17
Table 6. Threatening processes identified in Deep Creek. ................................................................19
Table 7. Size distribution of fish caught in Barwon River, Pennyroyal Creek and Waurn Ponds
Creek using all gear types. ......................................................................................................21
Table 8. Threatening processes identified in Barwon River, Waurn Ponds Creek and Pennyroyal
Creek. ......................................................................................................................................23
Table 9. Size distribution of fish caught in Gnarkeet Chain of Ponds and Woady Yaloak River
using all gear types. ................................................................................................................24
Table 10. Threatening processes identified in the Gnarkeet Chain of Ponds and Woady Yaloak
River. ......................................................................................................................................25
Table 11. Size distribution of fish caught in the Curdies River, Merrigig Creek and Thompson
Creek using all gear types. ......................................................................................................26
Table 12. Threatening processes identified in Thompson Creek, Curdies River and Merrigig Creek.27
5
List of figures
Figure 1. Location of the four basins sampled. .................................................................................. 7
Figure 2. Size distribution of pygmy perches caught from all sites using all gear types: (a) Yarra
Pygmy Perch and (b) Southern Pygmy Perch. (Note that the x-axis scales differ in the two
graphs.) .................................................................................................................................. 13
Figure 3. Length–weight graphs for (a) Yarra Pygmy Perch and (b) Southern Pygmy Perch. ......... 14
Figure 4. Size distribution of three species of native fish caught from all sites using all gear types:
(a) Australian Smelt, (b) Common Galaxias and (c) Flat-headed Gudgeon. (Note that the xaxis scale is different in each graph.) ..................................................................................... 15
Figure 5. Size distribution of two non-native fish species caught from all sites using all gear types:
(a) Redfin Perch and (b) Eastern Gambusia (Note that the x-axis scale is different in each
graph.) ................................................................................................................................... 16
Figure 6. The size distribution of native fish caught in Deep Creek using all gear types: (a)
Southern Pygmy Perch and (b) Yarra Pygmy Perch. (Note that the x-axis scale is different in
each graph.) ........................................................................................................................... 18
Figure 7. Size distribution of Pygmy Perches caught in Barwon River, Pennyroyal Creek and
Waurn Ponds Creek using all gear types: (a) Southern Pygmy Perch and (b) Yarra Pygmy
Perch. (Note that the x-axis is different in each graph.) ......................................................... 22
Figure 8. Size distribution of pygmy perches caught in the Curdies River, Merrigig Creek and
Thompson Creek using all gear types: (a) Southern Pygmy Perch and (b) Yarra Pygmy
Perch. (Note that the x-axis scale is different in each graph.) ................................................ 28
6
Acknowledgements
We would like to thank Tim O’Brien and Tarmo Raadik for helping to write the project proposal,
and Tarmo Raadik for providing a list of previously surveyed sites, for discussing what sampling
methods could be used, and for commenting on a draft of the report. We would also like to thank
Stephen Saddlier for commenting on a draft of the report. The work was funded by the Natural
Heritage Trust and the Goulburn-Broken Catchment Management Authority. We also thank the
Corangamite, and Port Phillip and Westernport Catchment Management Authorities.
7
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Summary
Australia is one of the driest continents on Earth, and many stream discharges are highly variable
and intermittent. Drought occurs regularly and many small streams cease to flow, dry up
completely or revert to a series of pools. During dry periods, remnant pools act as refuges for
aquatic fauna such as native fish, supplying them with shelter, food and habitat. Under extreme
circumstances, remnant pools may contain a large percentage of the local fish population. With the
return of stream flows, fish in remnant waterholes are able to move and repopulate a reach of
stream, thus rebounding from a period of drought.
Since European settlement however, the flows of many of Australia’s freshwater streams have
been modified through extraction or damming further upstream, thereby reducing flow and
amplifying the effects of drought on aquatic biota. During such extreme periods, other
anthropogenic factors impact significantly on instream fauna, particularly threatened species.
In light of this, the Victorian Department of Sustainability and Environments Freshwater Ecology
section was commissioned to revisit a number of sites where Yarra Pygmy Perch have been
recorded. The aim of this survey is to determine the current status of the population during a
known drought period, documenting potential threats and identifying remedial actions.
A total of 25 sites were surveyed from which eleven native and five non-native fish species were
collected. A total of 7996 fish were sampled, 2030 (25%) of which were native fish. Southern
Pygmy Perch were the most commonly recorded species (691) followed by Yarra Pygmy Perch
(351), and Short-finned Eels (297), Common Galaxias (243), Australian Smelt (209), and Flathead Gudgeon (180). River Blackfish, Mountain Galaxias, Spotted Galaxias, Pouched Lamprey
and Tupong were found in low numbers. Eastern Gambusia (5703) were the most common nonnative followed by Redfin Perch (190), Goldfish (66), Tench (4) and Common Carp (3).
Yarra Pygmy Perch were recorded in all Basins where records existed, however they were absent
from a number of sites where they were previously found. A number of sites where prior records
exist were dry and the majority had reverted to a series of pools. Yarra Pygmy Perch ranged in size
from 21-71mm (mean 40.7), with length-frequency data indicating that the smaller size-classes are
more abundant than larger size-classes.
A number of threatening processes were identified including: the presence of non-native flora and
fauna species; the loss of instream habitat; loss/degradation of riparian zone vegetation; instream
barriers to fish movement; agricultural stock access; modified flows and increased salinity.
Importantly, the effects of these processes are likely to be exacerbated by the persistence of
drought conditions.
To reduce the impact of the threatening processes identified a number of recommendations have
been made, namely:
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
1
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period

Clearing non-native terrestrial plant species in the riparian zone, and reintroduction of
native species

Harvesting non-native fish species where possible. Similarly, the potential for drying
water bodies where non-native species prevail should be investigated.

Fencing off the riparian zone to minimise stock damage and encourage recovery of native
species in the area - native vegetation can also be reintroduced to the riparian zone.
Restoring the riparian zone should also promote instream habitat in the form of wood and
coarse particulate organic matter (i.e. leaves, branches, bark, grass etc).

Aquatic vegetation should be protected/encouraged where possible

Where possible, restore flow seasonality (i.e. stream flows mimic historical records) and
flooding, which will help to reduce the adverse impacts of flow modification on native fish
(i.e. uncoupling of flow/temperature spawning cycles for native fish) and ensure natural
stream forming processes continue to occur.

Try to minimise pumping (stock and domestic) from remnant water bodies (i.e. Deep
Creek at Lancefield–Kilmore road). This may involve contacting farmers and conducting
an inspection of the pump site.

Identify point and diffuse sources of saline intrusion with an attempt to minimise entry
into the waterway. Restoring the riparian zone may help to; prevent saline surface water
from entering the stream; lower saline watertable.
Importantly, with another dry winter-spring period likely in 2009, it is recommended that a
number of sites be monitored throughout the spring - summer period to prevent remnant
waterholes from drying-up. Sites most at risk include;

Gnarkeet Chain of Ponds (at Hamilton Highway, west of Berrybank)

Deep Creek at ford on Baynton Road, at Lancefield–Kilmore road and at Lancefield–
Tooborac Road

Thompson Creek at Willowite Road, at Rices reserve and upstream of Torquay road

Pennyroyal creek off Bush’s lane.
Adding water to the above mentioned sites in the event that they are likely to dry-up may help to
sustain the local population.
2
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
1 Introduction
Australia is one of the driest continents on Earth, and many stream discharges are highly variable
and intermittent. Drought occurs regularly and many small streams cease to flow, drying up
completely or reverting to a series of pools. This variable nature of our freshwater systems has
resulted in whole ecosystem and species adaptations (McMahon and Finlayson 2003). Some native
fish, for example, have a higher recruitment rate in periods of flood (Roberts et al. 2008), taking
advantage of the increased food and habitat availability that flooding offers, while others (e.g.
Tasmanian Mudfish, Eastern Little Galaxias) aestivate in crayfish burrows or under rocks, and
burrow during periods of drought (Allen et al. 2002).
During dry periods, remnant pools act as safe havens for aquatic fauna such as native fish,
supplying them with shelter, food and habitat. In extreme circumstances remnant pools may
contain a large percentage of the local fish population. With a return of stream flows, fish in
remnant waterholes are able to move and repopulate a stream reach, thus rebounding from a period
of drought.
However, since European settlement the flows of many of Australia’s freshwater streams have
been modified through extraction or damming, thereby reducing flows (Walker 1985) and
amplifying the effects of drought, on aquatic biota. During dry spells other anthropogenic factors
(loss or degradation of riparian zone vegetation or instream habitat, stream bank erosion, channel
modification, instream barriers, non-native fish species and their associated diseases and parasites,
reduced water quality including elevated salinity levels, sedimentation and siltation), may impact
significantly on instream fauna, particularly threatened species (Koehn and O'Connor 1990).
One species particularly at risk is the Yarra Pygmy Perch Nannoperca obscura, a member of the
Nannopercidae family (Allen et al. 2002). Athough its distribution is patchy and highly
fragmented, it inhabits southern flowing systems from West Gippsland to Lake Alexandrina and
the Finniss River in South Australia (Saddlier and Hammer 2007). Yarra Pygmy Perch are thought
to spawn demersal, non-adhesive eggs over vegetation during the spring–summer months, when
water temperatures exceed approximately 16°C. Their diet consists primarily of insects, insect
larvae, and crustaceans (Saddlier and Hammer 2007). Yarra Pygmy Perch typically occur in slowflowing water with an abundance of aquatic vegetation, and their distribution often overlaps with
Southern Pygmy Perch (Woodward and Malone 2003). The species is classified as ‘near
threatened’ in Victoria (DSE 2007) and is listed as threatened in Victoria under the Flora and
Fauna Guarantee Act 1998 (Vic.) and vulnerable nationally under the Environment Protection and
Biodiversity Conservation Act 1999 (Cwlth).
The Freshwater Ecology section of the Victorian Department of Sustainability and Environment
was commissioned to revisit a number of sites where Yarra Pygmy Perch has been recorded, with
the aim of determining the current state of the population during a known drought period,
documenting potential threats and identifying remedial actions.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
2 Methods
2.1 Survey Site
Sites were sampled in four basins; Barwon, Otway, Maribyrnong and Corangamite (Figure 1). Site
numbers were coded numerically, with the prefix B, O, M or C according to their respective basin
(Table 1). Sites were selected where prior records of Yarra Pygmy Perch existed (DSE database)
and where current river conditions still allowed fishing. These sites are additionally referenced (†).
Particular attention was paid to the Barwon River, Thompson Creek, Deep Creek and Woady
Yaloak Creek, given the short time available for field work. If a site with a prior record was not
suitable for sampling because of a low availability of water, shallow depth or high salinity, another
site was chosen (Table 2). A digital photograph was taken at most sites (Appendix 1).
Seven sites were fished in the Barwon River and its tributaries (labelled B-1 to B-7), eight sites in
the Otway Basin, particularly Thomson Creek and some tributaries (O-1 to O-8), seven sites in the
Maribyrnong basin, all in Deep Creek (M-1 to M-7), and three sites in the Corangamite basin (C-1
to C-3), two of which were in the Woady Yaloak Creek (Table 1). A number of sites on Waurn
Ponds Creek where prior recorded existed were not assessed due to the limited time-frame of the
study (Table 2).
2.2 Sampling Methods
Fish surveys were conducted during daylight from 14–24 April 2008 using a Smith–Root 7.5 GPP
bank-mounted electrofishing unit or, in the case of small isolated pools where the electrical
conductivity was too high for electrofishing, a fine-mesh dip net. At each site all available habitat
types were surveyed where possible, but areas with good vegetative or other instream cover were
targeted to increase the capture efficiency of the target species.
Where electrofishing was used, the operator fished reaches in an upstream direction, fishing all
habitat types along the edges and in the middle of the stream where possible, stunning and
retrieving fish. An assistant used a fine-mesh dip net to collect any stunned fish missed by the
operator. Isolated pools were fished around the perimeter and in the middle of the pools where
possible. Stream lengths up to 100 m long were sampled where stream conditions permitted; where
streams were reduced to isolated pools, entire pools were fished. Where numbers of Yarra Pygmy
Perch were high, sampled sections may have been less than the 100 m maximum.
All fish captured were identified and counted, and their lengths were measured (mm). Where
lengths were measured, either caudal fork length (LCF) or total length (TL) was recorded. Any
Southern or Yarra Pygmy Perch captured were also weighed to the nearest 0.1 g. Where both
Yarra Pygmy Perch and Southern Pygmy Perch occurred at the same site, individuals of each
species were retained for later verification. All Yarra Pygmy Perch were examined for disease,
deformity or damage. At each site, counts were made of fish observed and confidently identified,
but not captured.
4
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
2.3 Water quality
The following water quality parameters were recorded at each sample site, including:

dissolved oxygen (mg/L)

oxygen saturation (%)

electrical conductivity (µS/cm)

turbidity (NTU)

temperature (ºC)

pH.
The water quality meter (TPS 90FL-T) was calibrated according to the manufacturer’s
specifications.
2.4 Habitat Assessment
At each of the sampled sites, physical waterbody characteristics were observed and recorded,
including the waterbody type, flow type and level of flow. Instream characteristics were also
observed, including the percentage composition of waterbody substrate, instream cover and
aquatic vegetation. The percentage composition of riparian vegetation was also assessed, along
with the land use around the site. Finally, the atmospheric conditions at each site during the survey
were observed.
2.5 Threatening Processes
At each site the presence or absence of threats, both instream and surrounding the site, was
observed and recorded, along with a rating of the severity of these threats to fish populations at the
site. Alien fish species that were captured during the survey were removed from the system to
reduce predation pressure and the risk of disease transmission.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Table 1. Location of fish survey sites in the Barwon, Otway, Maribyrnong and
Corangamite Basins.
Site
Waterbody
B-1 (†)
Location
o
Waurn Ponds
38 12’3.7”
o
Barwon R
Upstream of Pollocksford Rd, at weir, west of
Stonehaven
38 8’39.7”
Barwon R
Private property opposite Murgheboluc Cricket
Ground
38 6’40.4”
Barwon R
Opposite Hopes Plains Rd, off Hamilton Highway,
Inverleigh
38 6’28.4”
o
B-3
o
B-4 (†)
(†) Barwon R
B-5
6 (†) Pennyroyal Ck
(†)
Longitude (E)
o
144 19’16.1”
Downstream of Pioneer Rd bridge, Grovedale
Ck
B-2 (†)
Latitude (S)
Barwon R
o
144 11’13.4”
o
144 8’28.2”
o
144 5’34.6”
At bridge on Kildean Rd, Southwest of Winchelsea
38o17’57.8”
143o56’14.7” B-
Downstream of weir off Bushs Lane, Deans Marsh
38o24’35.8”
143o51’30.7” B-7
Bridge at Deepdene Rd, South of Whoorel
38o23’29.5”
o
143o48’9.7”
o
1km upstream of weir, at end of Minya Lane, North
of Breamlea
38 16’30.1”
144 22’57.2”
(†) Thompson Ck
O-2
O-3 Thompson Ck
Upstream of Horseshoe Bend Rd, Rices Reserve
38o16’13.8”
144o21’0.1”
Upstream of Torquay Rd, South of Mount Duneed
38o16’27.1”
144o19’29.1”
O-4 (†)
Thompson Ck
Downstream of Pettavel Rd, north-east of Paraparap
38o15’49”
144o14’17.8”
O-5 (†)
Thompson Ck
At Willowite Bridge Rd, north-east of Paraparap
38o15’45.1”
144o13’6.7”
O-6 (†)
Thompson Ck
Downstream of Nobles Rd, south of Modewarre
38o17’27”
144o8’14.7”
O-7 Merrygig Ck
Upstream of Blackgate Rd, south of Freshwater Ck
38o16’49.6”
144o16’17.5”
O-8 (†)
Downstream of Curdies River Rd, Curdie
38o26’49.7”
142o57’35”
M-1 Deep Ck
Upstream of Chintin Rd, west of Monegeetta North
37o23’55.4"
144o47’56.6”
M-2 Deep Ck
Upstream of Joyces Rd, east of Romsey
37o21’42”
144o48’8.9”
M-3 Deep Ck
At bridge on Barry St / Romsey Rd, east of Romsey
37o20’53.8”
144o46’51”
O-1
Thompson Ck
Curdies R
o
o
Deep Ck
Upstream of Barnes Lane/Sheehans Road, east of
Romsey
37 19’49.8”
M-5
Deep Ck
Private property downstream of Lancefield–Kilmore
Rd
37 17’13.7”
144 46’44.8”
(†)
M-6
M-7 (†)
Deep Ck
At Lancefield/Toobarac Rd, north of Lancefield
37o15’38.7”
144o44’9.7”
Deep Ck
At Ford on Baynton Rd, north-west of Lancefield
37o15’26.3”
144o42’46.4”
M-4
o
C-1 (†)
C-2 (†)
C-3 (†)
o
Woady Yaloak
Ck
Gnarkeet Ponds
o
38 1’26.5”
143 37’43.9”
At Hamilton Hwy bridge, West of Berrybank
37o58’14.9”
143o28’2.9”
o
37 47’24.8”
At end of Cemetery Rd, west of Cape Clear
† indicates prior records of Yarra pygmy perch.
6
o
At bridge on Hamilton Hwy, Cressy
Woady Yaloak
Ck
144 47’4.7”
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
o
143 34’53”
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
70
0
70
140
N
Km
W
E
S
Maribyrnong
Corangamite
Otway
Barwon
Figure 1. Location of the four basins sampled.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Table 2. Prior records of Nannoperca obscura in the Barwon, Otway, Maribyrnong and Corangamite Basins.
Basin and
Waterbody
Site
Date
Gear
Type
Collector
Fished
2008
Site
ID (†)
Dry
YPP
present
Comments
Maribyrnong
Deep Ck
At Lancefield–Toobarac Rd bridge
1/9/1998
BT
Woodward & Malone
Y
M-6
Y
Deep Ck
Baynton Rd, NW of Lancefield
1/9/1998
BT
Woodward & Malone
Y
M-7
Y
Deep Ck
Baynton Rd, NW of Lancefield
27/12/2003
DN
Unmack
Y
M-7
Y
Barwon R
End of lane, West of Murghebolac
14/09/1999
EF/BM
Zampatti
Y
B-4
Y
Barwon R
Kildean Road, SW of Winchelsea
14/12/2000
EF/BM
Zampatti
Y
B-5
N
Barwon R
Pollocksford Rd weir
12/12/2000
EF/BM
Zampatti
Y
B-2
Y
Barwon R
Bridge at Deepdene Rd
11/12/2000
EF/BM
Zampatti
Y
B-7
N
Barwon R
At weir d’stream of Inverleigh
28/11/2000
LN
Zampatti
N
–
–
Too deep to EF/BM
Hospital Swamp
In dam on south shore, Lake Rd
6/12/2002
BT
Billows & Baldwyn
N
–
–
No access to EF/BM
Pennyroyal Ck
D’stream of weir, off Bushs La
22/09/1999
EF/BP
Raadik
Y
B-6
Y
Reedy L
Fitzgerald Rd, Leopold
22/11/2002
DN
Billows & Harding
N
–
Y
–
Reedy L
Fitzgerald Rd, Leopold
22/11/2002
BT
Billows & Harding
N
–
Y
–
Reedy L
Woods Road, Moolap
22/11/2002
DN
Billows & Harding
N
–
Y
–
Waurn Ponds Ck
D’stream of Pioneer Rd
16/12/2002
DN
Unmack
Y
B-1
Waurn Ponds Ck
D’stream of Cockrans Rd crossing
19/2/2002
EF/BM
Close, Webb & Koster
N
–
–
–
Waurn Ponds Ck
Javis Oval
19/2/2002
EF/BM
Close, Webb & Koster
N
–
–
–
Waurn Ponds Ck
D’stream of Grovedale Rd
crossing
19/2/2002
EF/BM
Close, Webb & Koster
N
–
–
–
Waurn Ponds Ck
Rotary Peace Park
19/2/2002
EF/BM
Close, Webb & Koster
N
–
–
–
Barwon
8
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Y
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Waurn Ponds Ck
Camdell Court
19/2/2002
EF/BM
Close, Webb & Koster
N
–
–
–
Waurn Ponds Ck
D’stream of Barwon Heads Rd
19/2/2002
EF/BM
Close, Webb & Koster
N
–
–
–
Floating Islands L
Princes Hwy, W of Pirron Yaloak
17/07/1990
EF/BP
McKenzie
N
–
Y
–
Gnarkeet Ponds
Hamilton Hwy, West of Cressy
19/06/1974
–
–
Y
C-2
Y
Woady Yaloak Rr
Hamilton Hwy, Cressy
11/01/2003
SN
Unmack
Y
C-1
Y
Woady Yaloak R
Power Line Reserve, Cape Clear
17/07/1990
EF
McKenzie
Y
C-3
N
Curdies R
Curdies River Rd, Curdie
17/12/2002
SN
Unmack
Y
O-8
Y
Thompson Ck
Ghazeepore Rd, Freshwater Ck
27/12/2002
SN
Unmack
N
–
Thompson Ck
Upstream of weir
09/03/2001
EF/BM
Zampatti
N
–
–
Thompson Ck
Rices Reserve
09/03/2001
EF/BM
Zampatti
Y
O-2
Y
Thompson Ck
Upstream of Horseshoe Bend Rd
09/03/2001
EF/BM
Zampatti
N
–
–
Thompson Ck
D’stream of Ghazeepore Rd
09/03/2001
EF/BM
Zampatti
N
–
Thompson Ck
D’stream of Pettavel Rd
09/03/2001
EF/BM
Zampatti
Y
O-4
Y
Thompson Ck
D’stream of Willowite Rd
09/03/2001
EF/BM
Zampatti
Y
O-5
Y
Thompson Ck
D’stream of Nobles Rd
09/03/2001
EF/BM
Zampatti
Y
O-6
N
Hindaugh Ck
D’stream of Willowite Rd
09/03/2001
EF/BM
Zampatti
N
–
Corangamite
Otway
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
9
Y
Y
Y
–
–
–
Too deep to EF/BM
No access to EF/BM
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
3 Results
3.1 Water quality
Throughout the survey, water quality — most notably electrical conductivity (EC) — was variable
(Table 3). Of all the sites surveyed, Merrigig Creek recorded the highest EC reading. The EC of
Lake Connewarre was higher (49 000 µS/cm), but this was outside the operating range of the
electrofishing equipment and so was not surveyed. The Barwon River (B-7) had the lowest EC
reading. Thompson Creek (O-6) had the lowest dissolved oxygen content, although this was still
above the level at which fish may be adversely affected. Thompson Creek also recorded the
highest pH (O-2), and Deep Creek the lowest (M-7). Turbidity was highly variable and appeared to
depend on factors such as flow, aquatic vegetation and the presence of European Carp. Maximum
and average depths of the sample area also varied considerably.
3.2 Fish Fauna
3.3 All sites combined
Eleven native and five non-native fish species were recorded, along with two crustacean species
(Table 4). A total of 7996 fish were collected, 2030 (25%) of which were native fish. Southern
Pygmy Perch were the most commonly recorded species (691) followed by Yarra Pygmy Perch
(351), Short-finned Eels (297), Common Galaxias (243), Australian Smelt (209), and Flat-head
Gudgeon (180). River Blackfish, Mountain Galaxias, Spotted Galaxias, Pouched Lamprey and
Tupong were found in low numbers. Eastern Gambusia (5703) was the most common non-native
species, followed by Redfin Perch (190), Goldfish (66), Tench (4) and Common Carp (3).
Yarra Pygmy Perch ranged in size from 21 to 71 mm (mean 40.7, Table 4), but the length–
frequency graph has a slightly elongated right ‘tail’, indicating that smaller size-classes (i.e. 2646 mm) are more common than predicted by a normal distribution (Figure 2). This result is in
contrast to Southern Pygmy Perch, which has a bimodal length–frequency distribution. The
smaller size-classes of this species were also more abundant.
Figure 3 indicates a positive relationship between length and weight for both Yarra Pygmy Perch
and Southern Pygmy Perch (i.e. as length increases, weight increases). There is a flattening of the
curve in the upper size-classes for Southern Pygmy Perch, but this is not as evident for the Yarra
Pygmy Perch. Weights ranged from 0.1 to 4.9 g (mean 1.13 g, SD ±0.93) for Yarra Pygmy Perch
and 0.1 to 6.5 g (mean 1.27 g, SD ±1.18) for Southern Pygmy Perch.
The length–frequency graphs for other native species with a similar size ranges to that of Yarra
Pygmy Perch are shown in Figure 4. The graphs for Fleathead Gudgeon have a normal
distribution, while common galaxias have a slightly elongated right tail indicating that smaller
size-classes are more common than predicted under a normal distribution. The length-frequency
of Australian Smelt varied, however fish 36-56 mm log were most commonly observed.
10
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
The length-frequency distribution of both Eastern Gambusia and Redfin Perch possessed elongated
right tails indicating that smaller size-classes (22-30 mm for Eastern Gambusia and 42-80 mm for
Redfin Perch respectively) were observed more than expected for a normal distribution (Figure 5).
Table 3. Water quality and depth of survey sites.
Site
EC
Water
Temp
.
D.O.
D.O.
(mg/L)
(%
sat.)
pH
Turbidity
(NTU)
Max.
depth
(m)*
Ave depth
(m)*
B-1
2530
17.8
8.30
71.4
8.02
16.7
1.4
0.5
B-2
2680
17.9
9.14
96.1
8.36
1.7
1.3
0.7
B-3
2250
15.3
10.06
102.9
8.03
0.63
0.9
0.4
B-4
2150
14.1
12.65
111.1
8.11
2.5
–
–
B-5
1100
13.3
7.24
73.0
7.69
–
1.1
0.5
B-6
873
15.6
6.51
62.2
7.39
6.13
1.4
0.4
B-7
314
16.5
5.90
64.6
7.23
2.03
1.6
0.5
O-1
9320
16.6
8.95
99.1
8.40
14.0
0.5
–
O-2
8440
17.3
7.03
71.9
8.91
4.2
–
0.5
O-3
14220 17.0
5.03
50.8
8.55
27.2
1.6
1.2
O-4
13330 14.6
6.62
59.3
8.06
6.4
1.5
1.0
O-5
12630 15.8
5.84
54.7
8.29
4.7
2.0
0.5
O-6
6160
14.6
1.72
13.9
7.31
71.3
–
–
O-7
21150 16.1
4.53
48.3
7.92
11.97
1.8
0.5
O-8
1295
14.7
8.84
84.1
7.89
1.13
1.8
0.4
M-1
977
12.9
3.25
24.8
7.60
2.9
–
–
M-2
2266
11.4
1.76
25.2
7.44
4.2
–
–
M-3
1250
13.6
3.40
33.4
7.26
4.2
–
–
M-4
980
10.2
4.20
45.0
7.20
14.0
–
–
M-5
1246
16.2
9.77
89.1
7.42
10.8
1.5
0.5
M-6
1021
19.1
12.25
136.9
7.41
5.0
1.5
0.5
M-7
1028
13.4
5.13
46.1
6.78
12.93
1.6
1.0
C-1
9460
17.8
7.42
86.1
7.93
3.5
–
1.7
C-2
5600
17.0
11.75
123
8.65
101
2.5
–
C-3
3310
15.3
6.45
77
7.93
1.1
–
2
* sampled area only
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Table 4. Size distribution of fish caught at all sites using all gear types.
Species
Total
Number
Mean length
and SD
(mm)
SD
Minimum
Maximum
Number
Measured
(mm)
(mm)
Short-finned Eel
297
10
481.3
102.4
215
580
River Blackfish
4
3
188.3
97.2
80
268
Common Galaxias
243
103
88.6
19.7
55
153
Mountain Galaxias
32
22
48.5
6.9
42
74
Spotted Galaxias
6
6
89.3
3.9
83
92
Pouched Lamprey
12
2
232.5
159.1
120
345
Southern Pygmy Perch
691
469
41.4
12.7
17
83
Yarra Pygmy Perch
351
337
40.7
9.7
21
71
Flat-headed Gudgeon
180
148
62.6
16.1
30
106
Tupong
5
4
283.0
17.6
263
303
Australian Smelt
209
94
46.1
8.9
26
67
Yarra Spiny Cray
8
8
25.0
14.7
13
50
Freshwater Shrimp
1820
Native species
Non-native species
Eastern Gambusia
5703
640
27.5
6.9
10
57
Eurpoean Carp
3
3
224.3
31.5
190
252
Goldfish
66
36
80.6
25.0
44
179
Redfin Perch
190
104
74.7
53.4
38
327
Tench
4
4
255.0
103.1
150
394
Total no. fish
7996
1993
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Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
a)
40
Yarra pygmy perch
35
n=337
30
25
20
15
10
Frequency
5
b)
0
0
8
16
24
32
40
48
56
64
72
80
45
Southern pygmy perch
40
n=469
35
30
25
20
15
10
5
0
0
8
16
24
32
40
48
56
64
72
80
88
Length (mm)
Figure 2. Size distribution of pygmy perches caught from all sites using all gear
types: (a) Yarra Pygmy Perch and (b) Southern Pygmy Perch. (Note that the x-axis
scales differ in the two graphs.)
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
a)6
Yarra pygmy perch
n=334
5
4
3
2
1
Weight (g)
0
7
Southern pygmy perch
n=466
b)6
5
4
3
2
1
0
0
10
20
30
40
50
60
70
80
90
Length (mm)
Figure 3. Length–weight graphs for (a) Yarra Pygmy Perch and (b) Southern Pygmy
Perch.
14
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
14
Australian Smelt
n=94
12
10
8
6
4
2
0
0
8
16
24
32
40
48
56
64
16
Common galaxias
n=103
14
Frequency
12
10
8
6
4
2
0
0
20
40
60
80
100
120
140
160
20
Flathead gudgeon
18
n=148
16
14
12
10
8
6
4
2
0
0
20
40
60
80
100
120
Length (mm)
Figure 4. Size distribution of three species of native fish caught from all sites using
all gear types: (a) Australian Smelt, (b) Common Galaxias and (c) Flat-headed
Gudgeon. (Note that the x-axis scale is different in each graph.)
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
15
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
a)
40
Redfin Perch
35
n=104
30
25
20
15
10
Frequency
5
b)
0
0
40
80
120
160
200
240
280
320
120
Eastern Gambusia
n=640
100
80
60
40
20
0
0
8
16
24
32
40
48
56
Length (mm)
Figure 5. Size distribution of two non-native fish species caught from all sites
using all gear types: (a) Redfin Perch and (b) Eastern Gambusia (Note that the xaxis scale is different in each graph.)
16
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
3.4 Individual Streams
3.4.1
Deep Creek
Nine fish species totalling 2882 fish were collected from the seven sites surveyed in Deep Creek
(Table 5). Of these, 463 (16.1%) were native fish. Southern Pygmy Perch (293) was the most
abundant species, followed by Yarra Pygmy Perch (70), Short-finned Eels (65), Australian Smelt
(32) and Flat-head Gudgeon (3). Of the non-native fish species, Eastern Gambusia (2164) were the
most common followed by Redfin Perch (187), Goldfish (66), and Tench (2). One species of
native crustacean, Parataya australiensis, was also sampled.
Yarra Pygmy Perch ranged in size from 26 to 63 mm (mean 41 mm) (Table 5). The length–
frequency graph has a slightly elongated right ‘tail’, possibly as a result of an underlying bimodal
(adults and juvenile/immature) length–frequency distribution (Figure 6). The presence of a
bimodal length–frequency distribution is more obvious in the data for Southern Pygmy Perch, in
which small size-classes were most abundant.
Table 5. The size distribution of fish caught in Deep Creek using all gear types.
Total
Number
Mean
Number
length
Measured (mm)
Short-finned Eel
65
2
Australian Smelt
32
Southern Pygmy
Perch
SD
Minimum
(mm)
Maximum
(mm)
366.5
214.3
215
518
2
43.5
0.7
43
44
293
164
39.3
20
70
Yarra Pygmy Perch
70
70
41.0
8.8
26
63
Flat-headed Gudgeon
3
3
73.3
14.8
57
86
Freshwater Shrimp
250
–
–
–
–
–
Redfin Perch
187
101
69.7
44.2
38
287
Goldfish
66
36
80.6
25.0
44
179
Eastern Gambusia
2164
294
29.0
7.6
10
55
Tench
2
2
327
94.8
260
394
Total no. fish
2882
674
Species
Native species
11.5
Non-native species
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
a)20
18
Southern pygmy perch
n=164
16
14
12
10
8
6
4
Frequency
2
0
0
8
16
24
32
40
48
56
64
72
80
10
Yarra pygmy perch
9
n=70
b)8
7
6
5
4
3
2
1
0
0
8
16
24
32
40
48
56
64
Length (mm)
Figure 6. The size distribution of native fish caught in Deep Creek using all gear
types: (a) Southern Pygmy Perch and (b) Yarra Pygmy Perch. (Note that the x-axis
scale is different in each graph.)
3.4.2
Threatening Processes
Yarra Pygmy Perch inhabiting Deep Creek are subject to a number of threatening process (Table
6). Predation and harassment by non-native fish was observed. Loss of instream habitat and
changes in various aspects of the riparian zone are potentially increasing predation and
erosion/sedimentation respectively. Other obvious threats identified include a lack of water as a
result of drought and the pumping of water from remnant waterholes. At some sites stock had
unrestricted access to the stream, resulting in stream bank erosion, loss of instream habitat and
increased sedimentation. Instream barriers to fish movement were also present.
18
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Table 6. Threatening processes identified in Deep Creek.
Threatening process
Observed
Predation by redfin perch
Y
Increased predation from low water
levels/instream habitat
Eastern gambusia harassment (i.e. fin
nipping)
Unlikely
Unknown
Y
Y
Y
Y
Y*
Y
Y
Disease/parasites from non-native fish
Barriers to movement (i.e. ford, culvert,
bridge)
Likely
Y
High salinity
Lack of water/flow
Y
Water extraction (from remnant waterholes)
Y
Low dissolved oxygen levels
Y
Riparian zone cleared (i.e. roads,
agriculture)
Y
Stream bank erosion
Y
Sedimentation from riparian zone
erosion/clearing
Y
Loss of instream habitat
Y
Urban rubbish
Y
Livestock access
Y
Elevated nutrients from livestock access
(which may lead to algal blooms)
Destruction of instream habitat and
increased sedimentation due to livestock
access
Y
Y
Y
Common carp uprooting instream habitat
Y
Urbanisation/parkland
Y
Non-native vegetation (i.e. willows)
Y
* The Yarra pygmy perch can inhabit salinities much higher than recorded in this system.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
3.4.3
Barwon River, Waurn Ponds and Pennyroyal Creek
Fifteen different species of fish were collected from seven sites surveyed in Barwon River basin
totalling 1124 fish (Table 7). These comprised of 911 (81%) native and four non-native species.
Two native species of crustacean were also recorded.
Southern Pygmy Perch (201) were the most common species recorded followed by Australian
Smelt (177), Common Galaxias (151), Yarra Pygmy Perch (124), Short-finned Eel (89), Flatheaded Gudgeon (80), Mountain Galaxias (32), and low numbers of Spotted Galaxias, River
Blackfish and Tupong (Table 7). In addition, 45 Nannoperca spp. (Yarra or Southern Pygmy
Perch) were recorded but not measured. Of the non-native fish species, Eastern Gambusia (206)
were the most abundant followed by Common Carp, Redfin Perch and Tench.
Yarra Pygmy Perch ranged in size from 25 to 71 mm (mean 41.8 mm, Table 7). The length–
frequency graph has a slightly elongated right tail, indicating that smaller size-classes were
observed more than would be expected under a normal distribution; fish around 38-40 mm also
appeared to be in low abundances (Figure 7). The length–frequency relationship of Southern
Pygmy Perch appears to reflect that of a normal distribution.
20
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Table 7. Size distribution of fish caught in Barwon River, Pennyroyal Creek and
Waurn Ponds Creek using all gear types.
Total
Number
Number
Measured
Mean length
(mm)
SD
Minimum
(mm)
Maximu
m (mm)
Short-finned Eel
89
5
520
52.4
450
580
River Blackfish
4
3
188.3
97.2
80
268
Common Galaxias
151
51
90.3
15.3
61
132
Mountain Galaxias
32
22
48.5
6.9
42
74
Spotted Galaxias
6
6
89.3
3.9
83
92
Southern Pygmy Perch
201
137
47
10.5
21
69
Yarra Pygmy Perch
124
110
41.8
11
25
71
Nannoperca spp.
45
Flat-headed Gudgeon
80
65
60.9
16.1
30
98
Tupong
2
2
297
8.5
291
303
Australian Smelt
177
92
46.1
9
26
67
Freshwater Shrimp
1000+
Euastacus yarraensis
8
8
25
14.7
13
50
European Carp
3
3
224.3
31.5
190
252
Eastern Gambusia
206
111
25.6
5.3
15
51
Redfin Perch
2
2
201
19.8
187
215
Tench
2
2
183
46.7
150
216
Total no. fish
1124
619
Species
Native species
Non-native species
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
16
a)
Southern pygmy perch
14
n=137
12
10
8
6
4
Frequency
2
b)
0
0
8
16
24
32
40
48
56
64
72
80
16
Yarra pygmy perch
n=110
14
12
10
8
6
4
2
0
0
8
16
24
32
40
48
56
64
72
80
Length (mm)
Figure 7. Size distribution of Pygmy Perches caught in Barwon River, Pennyroyal
Creek and Waurn Ponds Creek using all gear types: (a) Southern Pygmy Perch and
(b) Yarra Pygmy Perch. (Note that the x-axis is different in each graph.)
3.4.4
Threatening Processes
A number of threatening processes were identified in the Barwon basin, including fin nipping by
Eastern Gambusia, high salinity, barriers to fish movement, clearing of the riparian zone, stream
bank erosion and sedimentation (Table 8). Threatening processes were also observed within each
stream. In the Barwon River urbanisation and the presence of urban rubbish were clearly evident,
and also in particular the ability for livestock to access the stream, destroying instream habitat and
increasing sedimentation. Threats in Waurn Ponds Creek include a lack of water or stream flow,
urbanisation and the presence of urban rubbish. Observed threats in Pennyroyal Creek include lack
of water or stream flow, loss of instream habitat, and the destruction of instream habitat coupled
with increased sedimentation as a result of livestock access.
22
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Table 8. Threatening processes identified in Barwon River, Waurn Ponds Creek and
Pennyroyal Creek.
Threatening process
Observed
Predation by redfin perch
Increased predation from low water levels/instream habitat
Eastern gambusia harassment (i.e. fin nipping)
Likely
Barriers to movement (i.e. ford, culvert, bridge)
Y
High salinity
Y
Lack of water/flow
Y2,3
Water extraction (from waterholes)
Y1
Y
Y
Y
Y
Y1
Y
Low dissolved oxygen levels
Y
Riparian zone cleared (i.e. roads, agriculture)
Y
Stream bank erosion
Y
Sedimentation from riparian zone erosion/clearing
Y
Loss of instream habitat
Y3
Urban rubbish
Y1,2
Livestock access
Y1,3
Y1,2
Y1,3
Elevated nutrients from livestock access (which may lead to
algal blooms)
Y13
Y1,3
Y1,2
Urbanisation/parkland
Non-native vegetation (i.e. willows)
3.4.5
Y1,3
Y1
Common carp uprooting instream habitat
1 Barwon River
Unknown
Y
Disease/parasites from non-native fish
Destruction of instream habitat and increased sedimentation
due to livestock access
Unlikely
2 Waurn Ponds Creek
Y
3 Pennyroyal Creek
Gnarkeet Chain of Ponds and Woady Yaloak River
Four native and one non-native fish species were recorded from the three sites surveyed in
Gnarkeet Chain of Ponds and Woady Yaloak River (Table 9). One crustacean was also recorded.
Of 2085 fish, 61 were native fish, Flat-headed Gudgeon being the most common (37), followed by
Yarra Pygmy Perch (13), Southern Pygmy Perch (7), and Short-finned Eel (4). Yarra Pygmy Perch
ranged in size from 26 to 63 mm (mean 40.6 mm), while Southern Pygmy Perch ranged in size
from 37 to 83 mm (mean 53.3 mm). Eastern Gambusia (2024) were the only recorded non-native
fish species, but they were very abundant.
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Table 9. Size distribution of fish caught in Gnarkeet Chain of Ponds and Woady
Yaloak River using all gear types.
Total
Number
Number
Measured
Mean
length
(mm)
Short-finned Eel
4
0
Southern Pygmy Perch
7
Yarra Pygmy Perch
Species
SD
Min.
(mm
)
Max.
(mm
)
–
–
–
–
7
53.3
17.7
37
83
13
13
40.6
12.0
26
63
Flat-headed Gudgeon
37
30
70.6
15.1
34
106
Freshwater Shrimp
500
0
–
–
–
–
Eastern Gambusia
2024
24
22.9
7.9
14
40
Total No. fish
2085
74
Native species
Non-native species
3.4.6
Threatening processes
Both the Gnarkeet Chain of Ponds and Woady Yaloak River were highly saline and had cleared
riparian zones, and stream bank erosion was obvious (Table 10). Gnarkeet Chain of Ponds also
lacked water or stream flow, and as a result of livestock access to the stream had instream habitat
loss and increased sedimentation. Woady Yaloak River was also likely to have these threats,
although they were not observed at the survey site.
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Table 10. Threatening processes identified in the Gnarkeet Chain of Ponds and
Woady Yaloak River.
Threatening process
Observed
Likely
Unlikely
Predation by redfin perch
Unknown
Y
Increased predation from low water
levels/instream habitat
Y
Y
Eastern gambusia harassment (i.e. fin nipping)
Y2
Y2
Disease/parasites from non-native fish
Y
Y
Barriers to movement (i.e. ford, culvert,
bridge)
Y
Y
High salinity
Y
Lack of water/flow
Y1
Water extraction (from waterholes)
Y2
Y
Low dissolved oxygen levels
Riparian zone cleared (i.e. roads, agriculture)
Y
Stream bank erosion
Y
Sedimentation from riparian zone
erosion/clearing
Y
Loss of instream habitat
Y1
Y
Y1
Y2
Y
Urban rubbish
Livestock access
Elevated nutrients from livestock access
(which may lead to algal blooms)
Destruction of instream habitat and increased
sedimentation due to livestock access
Y1
Y
Y
Y2
Y
European carp uprooting instream habitat
Urbanisation/parkland
Non-native vegetation (i.e. willows)
1 Gnarkeet Chain of Ponds only
3.4.7
Y
Y
Y
2 Woady Yaloak River only
Thompson Creek, Curdies River and Merrigig Creek
Nine fish species were collected from the eight sites surveyed in the Otway basin, including seven
native and two non-native species (Table 11). One crustacean species was also recorded. A total of
1904 fish were collected, 640 (33.6%) were native species, the most common being Southern
Pygmy Perch (190), followed by Yarra Pygmy Perch (144), Short-finned Eel, Common Galaxias,
Flat-headed Gudgeon, Pouched Lamprey and Tupong. Of the non-native fish species, Eastern
Gambusia was the most abundant (1263), while only one Redfin Perch was found. Yarra Pygmy
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Perch ranged in size from 21 to 67mm (mean 39.7mm, Table 11). The length–frequency graph
(Figure 8) indicates that the sample population of Yarra Pygmy Perch had a normal distribution
but Southern Pygmy Perch had a bimodal distribution.
Table 11. Size distribution of fish caught in the Curdies River, Merrigig Creek and
Thompson Creek using all gear types.
Total
number
Number
measured
Mean
length
(mm)
Short-finned Eel
139
3
493.3
40.4
450
530
Common Galaxias
92
52
87.0
23.4
55
153
Pouched Lamprey
12
2
232.5
159.1
120
345
Southern Pygmy Perch
190
161
38.2
13.6
17
78
Yarra Pygmy Perch
144
144
39.7
8.9
21
67
Flat-headed Gudgeon
60
50
59.5
15.4
33
95
Tupong
3
2
269.0
8.5
263
275
Freshwater Shrimp
70
0
–
–
–
–
Eastern Gambusia
1263
211
27.0
6.1
12
57
Redfin Perch
1
1
327
–
327
327
Total No. fish
1904
626
Species
SD
Min.
(mm)
Max.
(mm
)
Native species
Non-native species
3.4.8
Threatening processes
Threatening processes common to all sites surveyed in the Otway basin included riparian zone
clearing causing sedimentation and erosion, and loss of instream habitat (Table 12). Threatening
processes shared by both Thompson Creek and the Curdies River included the presence of nonnative vegetation, stream bank erosion and livestock access which is destroying instream habitat
and increasing sedimentation. In both Thompson Creek and Merrigig Creek high salinities and
lack of water/flow were evident. Eastern Gambusia harassment and barriers to fish movement
were identified solely in Thompson Creek, as was predation from redfin perch in the Curdies
River.
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Table 12. Threatening processes identified in Thompson Creek, Curdies River and
Merrigig Creek.
Threatening process
Observed
Likely
Predation by redfin perch
Y2
Y1,3
Y1,3
Y1,3
Y1,3
Y1
Y3
Y3
Y1,3
Y1,3
Y2,3
Y2,3
Y
Y
Y3
Y3
Increased predation pressure with low water
level
Eastern gambusia harassment (i.e. fin nipping)
Disease/parasites from non-native fish
Barriers to movement (i.e. ford, culvert,
bridge, weir)
Y1
High salinity
Y1,3
Lack of water/flow
Y1,3
Water extraction (from waterholes)
Unlikely
Unknown
Low dissolved oxygen levels
Riparian zone cleared (i.e. roads, agriculture)
Y1,2,3
Stream bank erosion
Y1,2
Sedimentation from riparian zone
erosion/clearing
Y1,2,3
Loss of instream habitat
Y1,2,3
Y1,3
Urban rubbish
Y1,2
Livestock access
Elevated nutrients from livestock access
(which may lead to algal blooms)
Destruction of instream habitat and increased
sedimentation due to livestock access
Y1,2
Y3
Y3
Y1,2,3
Y1,2,3
Y3
Y3
European carp uprooting instream habitat
Y
Urbanisation/parkland
Y
Non-native vegetation (i.e. willows)
1 Thompson Creek
2 Curdies River
Y1,2
Y3
Y3
3 Merrigig Creek
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
a)
20
Southern pygmy perch
18
n=161
16
14
12
10
8
6
4
Frequency
2
b)
0
0
8
16
24
32
40
48
56
64
72
80
88
20
Yarra pygmy perch
18
n=144
16
14
12
10
8
6
4
2
0
0
8
16
24
32
40
48
56
64
72
80
Length (mm)
Figure 8. Size distribution of pygmy perches caught in the Curdies River, Merrigig
Creek and Thompson Creek using all gear types: (a) Southern Pygmy Perch and (b)
Yarra Pygmy Perch. (Note that the x-axis scale is different in each graph.)
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
4 Discussion
4.1 Species Diversity, Distribution and Abundance
In Victoria the number of migratory species present in south-flowing streams (i.e. streams
connected to the ocean) is impacted by the presence of instream barriers. Under natural conditions
and with the absence of barriers, streams connected to the ocean should contain a number of
obligatory migratory species; that is, species that need to migrate from freshwater to the
estuary/ocean, or vice versa, as a necessary part of their life-cycle. However, with the presence of
instream barriers, migratory species will be less abundant, or absent altogether, so that the number
of fish species present is often greatly reduced. Unfortunately the presence of instream barriers is
rarely the only threatening process that native fish face in Victoria; other threatening processes are
elaborated later in this discussion.
Barwon River, Pennyroyal Creek and Waurn Ponds Creek were found to have four obligatory
migratory native fish species (Short-finned Eel, Common Galaxias, Spotted Galaxias and Tupong)
and six non-migratory native species. Relative to the other basins sampled, this basin has a high
species diversity, even though the number of migratory species in Pennyroyal Creek is relatively
low.
Pennyroyal Creek contained only short-finned eels in addition to the three non-migratory species
collected, and therefore may be regarded as depauperate. Short-finned Eels are not necessarily a
good indication of a stream’s ability to support migratory species because they are good climbers
and are able to move over land and thus bypass instream barriers (Sloane 1984). Short-finned Eels
are often seen migrating over the sandbar at high tide when estuaries are closed to the sea (M.
Jones pers. obs.).
In Barwon River eight native fish species were found, three of which are obligatory migratory
native species (Short-finned Eel, Common Galaxias and Tupong). River Blackfish, although
present in Barwon River, were found in low numbers, possibly a result of the lack of instream
habitat. Their preference for instream habitat has been well documented (Khan et al. 2004; Koster
and Crook 2007).
Five native fish species, three of which were migratory, were collected from Waurn Ponds Creek.
A recent study also found the same three obligatory migratory species (Short-finned Eel, Common
Galaxias and Spotted Galaxias) during a non-drought period (Close et al. 2002). These results
indicate that the current drought conditions may not be impacting the migratory fish assemblages
in this stream, but further investigation is required to substantiate this.
No native fish species were collected from Merrigig Creek. The creek was completely dry with the
exception of one dam on an agricultural property, which was highly saline and contained a large
number of Eastern Gambusia (see site photo in Appendix 1). Native fish within this creek are
likely to be adversely affected by the high salinity, but this needs to be validated during a normal
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
flow period. The fish assemblage found in Merrigig Creek will be affected by its intermittent
nature and high densities of Eastern Gambusia.
Three obligatory migratory native fish species (Common Galaxias, Pouched Lamprey, and
Tupong) and three non-migratory species were collected from Curdies River. The presence of
migratory species indicates that instream barriers in Curdies River may not be limiting upstream
movement, and therefore the river could be considered to be in reasonable health, despite species
diversity being slightly lower than the Barwon River system. River Blackfish, Spotted Galaxias,
and Mountain Galaxias — all present in the Barwon Basin — were notably absent from Curdies
River, but juvenile Pouched Lampreys were collected. Pouched Lampreys spend up to four years
inhabiting the mud of freshwater streams before metamorphosing and migrating downstream to
mature as adults in the ocean. This species, while not commonly captured, is not uncommon, and it
is not unlike the Short-finned Eel in that it can bypass significant instream barriers by moving
short distances overland (Allen et al. 2002). Importantly, increased sedimentation/siltation loads
(through erosion, stock access to creek, etc.) may also provide suitable conditions for lampreys, so
further investigation is required before it can be determined whether their distribution is natural or
aided by increased sediment/silt loads.
Despite Thompson Creek being heavily sampled relative to other streams (six sites on the
Thompson were surveyed for this study), only two obligatory migratory native fish species (Shortfinned Eel and Common Galaxias) were collected, indicating that the system is degraded in terms
of the presence of migratory species. Three non-migratory native fish species were also recorded
(Flat-headed Gudgeon, Southern Pygmy Perch and Yarra Pygmy Perch). However, a recent study
of Thompson Creek collected eight native freshwater fish species, four of which were migratory:
Short-finned Eel, Spotted Galaxias, Common Galaxias and Tupong (Zampatti 2001). Spotted
Galaxias and Common Galaxias were two migratory species not recorded during our study.
The absence of the migratory species suggests that the barrier immediately downstream of the
lowest sampling site may be affecting fish movement. This barrier has had a rock-ramp fishway
installed, and was working during the previous study (Zampatti 2001), however it was overgrown
with terrestrial vegetation at the time of this study, evidence that the fishway has not operated for
an extended period of time. The absence of a number of migratory and non-migratory species is a
result of the threatening processes identified in this study, and these processes are elaborated on
later in this discussion.
Only one obligatory migratory native fish species (Short-finned Eels) were found in each of Deep
Creek, Gnarkeet Chain of Ponds and Woady Yaloak River. In addition, Deep Creek contained four
non-migratory native species, and three were collected in Gnarkeet Chain of Ponds and Woady
Yaloak River. The ability of Short-finned Eels to negotiate instream barriers has already been
mentioned, and the low number of migratory native species in conjunction with the low number of
non-migratory native species indicates that these three creeks are depauperate. These three streams
should support other migratory and non-migratory native species (see the Barwon River and
Waurn Ponds Creek data), and their absence is likely to be a result of threatening processes
identified and discussed later in this report.
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Sampling inefficiencies inherent in electrofishing procedures are likely to have contributed to
some species not being collected. The lower reaches of larger streams, such as Thompson Creek,
are more difficult to sample thoroughly when compared with small streams, or streams reduced to
a series of pools, such as Pennyroyal Creek.
4.2 Status of Yarra pygmy perch
4.2.1
Deep Creek
The length–frequency graph of Yarra Pygmy Perch indicates that spawning and recruitment
occurred during the spring–summer (2007–08) months in Deep Creek; fish as small as 26 mm
were recorded in May 2008. The data also indicates that the fish population in Deep Creek is
dominated by smaller size-classes (i.e. younger fish), as larger size-classes were less abundant, but
bimodal length–frequency distributions for Pygmy Perch are not uncommon (Humphries 1995;
Woodward and Malone 2003). Recent data indicates that Southern Pygmy Perch (a closely related
species) around 30 mm long are around 70 days old (Tonkin et al. in review), and it is known that
a 45 mm long Southern Pygmy Perch is approximately one year old and that a 52 mm fish
approximately 1.5 years old (Humphries 1995). The largest fish captured was a 76 mm fish and
was aged at 3+ years. Such results would suggest that some Yarra Pygmy Perch collected during
this survey maybe more than two years old.
Yarra Pygmy Perch were collected from three of the seven sites surveyed; one site (M-5) was not a
historical record. The 70 fish collected from the three sites (M-5, M-6, M-7) were locally
abundant (28, 22, 20, respectively). This suggests that these latter sites provide more suitable
conditions for the survival of the species, or that threatening process may be less severe than at the
other sites. Numerous threatening processes are likely to have contributed to this result (refer to
Table 6) — loss of instream habitat, loss of riparian zone, modified flow regime, presence of nonnative species, salinity, instream barriers and modified flow regimes. These are discussed later in
this section.
4.2.2
Barwon River, Waurn Ponds and Pennyroyal Creek
As for Deep Creek, the length–frequency graph of Yarra Pygmy Perch collected from Barwon
River, Pennyroyal Creek and Waurn Ponds Creek indicates that spawning occurred during the
spring–summer of 2007–08, and fish as small as 25 mm were recorded (Figure 7). The 40 mm and
50 mm size-classes appear to be under-represented, but this may be the result of a number of
factors acting together (i.e. predation, low recruitment, sampling error, etc.). The population
sampled appeared to consist predominantly of younger individuals, with few larger, older
individuals (long right tail, Figure 7). This appears to be common for Yarra Pygmy Perch at all
sample sites (Figure 2). Estimated ages are likely to be similar to those in Deep Creek, but otoliths
would need to be extracted and aged for confirmation.
Although only one site was surveyed in Pennyroyal Creek and in Waurn Ponds Creeks, these two
sites yielded the highest abundances of Yarra Pygmy Perch. This is despite Pennyroyal Creek’s
habitat being classified as degraded. In contrast, Yarra Pygmy Perch were found at only two of the
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
five sites surveyed in Barwon River. This suggests that the Barwon River fish assemblage is
depauperate and that the distribution of Yarra Pygmy Perch is relatively fragmented.
Fragmentation is likely to be a result of numerous threatening processes (see Table 8), which are
discussed later in this section. However, sampling error is likely have a substantial influence on the
number of fish and species collected, as Barwon River is substantially larger than Pennyroyal
Creek, and Pennyroyal Creek’s fish assemblage was concentrated because of low flows (Appendix
1).
4.2.3
Gnarkeet Chain of Ponds and Woady Yaloak River
Very few Yarra Pygmy Perch were captured in either Gnarkeet Chain of Ponds or Woady Yaloak
Creek. However, their sizes ranged from 26 to 63 mm, indicating that spawning and recruitment
had occurred during the previous season. The sample site at Gnarkeet Chain of Ponds was highly
degraded and saline, yet Yarra Pygmy Perch were still present (see site photos in Appendix 1).
Threatening processes at this site (Table 10) are discussed in the following section. The site in
Woady Yaloak Creek at the end of Cemetery Road, west of Cape Clear, was thought to contain the
best and most undisturbed habitat in the survey, but none were collected there. However, this site
is too wide and deep to survey effectively with the portable electrofisher; and surveys need to be
conducted there using a boat.
4.2.4
Thompson Creek, Curdies River and Merrigig Creek
No native fish were found in Merrigig Creek, which was not surprising given that the creek had
dried up and the only site with water was a highly degraded, highly saline farm dam in the creek
bed where a large number of Eastern Gambusia were present. The majority of Yarra Pygmy Perch
in this system were collected from Thompson Creek, where 166 individuals were recorded.
A total of 28 Yarra Pygmy Perch were collected from the Curdies River. The length-frequency
graph suggests that spawning and recruitment was likely to have occurred over the previous
spring–summer, as fish lengths ranged from 21 to 67 mm. The length–frequency graph has a
slightly elongated right tail, indicating that larger size-classes were less common than smaller sizeclasses (Figure 8).
A number of threatening processes were identified at the survey sites in this basin including;
riparian zone clearing, sedimentation from erosion (due to riparian zone clearing), loss of instream
habitat, instream barriers to fish movement, increased salinity, the presence of non-native species,
etc. (Table 12). These are discussed in the following section.
4.3 Threatening processes
4.3.1
Non-native fish
Eastern Gambusia are known to have a negative affect on Australian native fish (Howe et al.
1997), attacking the fins of fish (i.e. fin nipping) (Rowe et al. 2007), and are tolerant of a wide
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
range of environmental conditions, including high salinities and high water temperatures (> 38°C)
(McDowall 1996). Physical removal of Eastern Gambusia is impractical because of their
widespread distribution and ability to reproduce rapidly. Predation by piscivorous native fish may
help to control their abundance, but allowing temporary waterbodies to dry completely may be the
best solution. The movement behaviour of Eastern Gambusia from areas of refuge is neither well
documented nor well understood.
It is generally agreed that Redfin Perch's predatory nature and prolific breeding habits have an
adverse effect on native fish (Cadwallader and Backhouse 1983). Redfin perch are believed to
compete with large native fish for food and habitat, and in doing so potentially affecting their
abundance and distribution (T Raadik pers. comm.). Furthermore, Cadwallader and Backhouse
(1983) suggest that, because of Redfin Perch's piscivorous nature, it could significantly reduce the
abundance of smaller native fish species such as Pygmy Perch, Rainbow Fish and Carp Gudgeon
in enclosed systems. In Western Australia, the once common Western Pygmy Perch are
fragmented, having little overlap with Redfin's distribution (Hutchison 1991). In addition, Redfin
predation are said to have adverse affects on Dwarf Galaxias (Galaxiella pusilla), Yarra Pygmy
Perch, Ewen's Pygmy Perch (Nannoperca variegata) and juvenile Macquarie Perch (Macquaria
australasica) (Wager and Jackson 1993). Redfin Perch have also been blamed for the decline of
Trout Cod (Maccullochella macquariensis) through competition for food and predation (Wager
and Jackson 1993). Redfin have the potential to affect native fish through the introduction of
pathogens, particularly epizootic haematopoietic necrosis virus (EHNV), which is pathogenic for
Silver Perch, Mountain Galaxias, Macquarie Perch, Murray Cod and other native fish (Arthington
and Bluhdorn 1995) and caused a major decline in Macquarie Perch in the Australian Capital
Territory (Lintermans 1991).
4.3.2
Non-native vegetation
The replacement of native riparian vegetation with non-native vegetation is a worldwide
phenomenon (Read and Barmuta 1999). Willows, for example, are found in the riparian zone of
many stream reaches in cleared agricultural areas throughout Australia. Australian native trees
drop their leaves continuously throughout the year, possibly peaking in late summer, supplying
macroinvertebrates (which are the prey of most fish species) with a steady supply of food (Read
and Barmuta 1999). In contrast, willows drop their leaves over a short period in autumn, and the
leaves break down faster than those of native species. Consequently the food supply for
macroinvertebrates is abundant for only a short period of time, and does not supporting
macroinvertebrate assemblages continuously throughout the year (Read and Barmuta 1999). Fish
species dependant on a continuous supply of macroinvertebrates are therefore likely to be
adversely affected by the presence of non-native vegetation. In fact, changes in riparian zone from
trees and shrubs to grasses, and from vegetated riparian zones to degraded banks, result in changes
to the instream fish assemblage (Growns et al. 1998; Growns et al. 2003). Restoring the riparian
zone with indigenous vegetation will increase the useable instream food supply for
macroinvertebrates, and therefore the fish fauna assemblage.
4.3.3
Loss of instream habitat
Instream structure provides a refuge for native fish (including Yarra Pygmy Perch) during high
discharge events, as well as helping to reduce predation by other fish. Instream structure also helps
to reduce competition for food and improve the carrying capacity of the stream by increasing
habitat complexity. With higher levels of habitat complexity, macroinvertebrate colonisation (and
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
therefore food availability for native fish) increases. Instream habitat such as aquatic vegetation
also provides the structure that Yarra Pygmy Perch require for spawning. Additionally, instream
structure helps to maintain the natural stream-forming processes (e.g. channel migration), and
reduces scouring and erosion.
The majority of instream habitat is provided by aquatic vegetation and woody debris. Because
woody debris originates from the riparian zone, restoring the vegetation in this zone will help to
reduce the negative impacts that the loss of instream habitat has on Yarra Pygmy Perch. Similarly,
promoting the growth of remnant aquatic vegetation or seeding areas where aquatic vegetation
once grew will help restore the instream habitat for Yarra Pygmy Perch and other native fish.
Limiting stock access to streams will mitigate the impacts of trampling and foraging on instream
vegetation and help to minimise stream bank erosion, sedimentation, and nutrient inputs from
stock faeces.
4.3.4
Loss of riparian zone vegetation
The riparian zone is the transitional zone between the terrestrial and aquatic environments. The
riparian zone provides a buffer when run-off occurs during heavy rainfall, filtering the water of
sediment and minimising the transfer of diffuse source pollutants such as nutrients, salts and
chemicals. The riparian zone also provides organic (fine, medium and coarse particulate organic
matter) and inorganic matter, which are important drivers of the biological functioning of aquatic
systems. The riparian zone also stabilises the stream bank, preventing erosion during high flow
events.
The riparian zone is often degraded or damaged as a result of agricultural practices. In the past,
landholders have grazed/ or cropped to the water’s edge, allowing stock to graze and damage the
riparian zone, and in upstream reaches riparian vegetation is often non-existent. The removal of
riparian vegetation increases sedimentation and erosion, reduces instream habitat, allows diffuse
sources of pollutants to enter the stream, and interrupts important biological functions. Fencing off
and revegetating the riparian zone will help to reverse these negative effects. Fencing the riparian
zone will also prevent stock from gaining access to the stream, therefore preventing instream
damage, i.e. damaging aquatic vegetation, increasing siltation and erosion, and elevated nutrients
levels as a result of faecal contamination.
4.3.5
Presence of instream barriers
Fish movement is important for dispersal, spawning, colonisation, predator avoidance, and
obtaining suitable resources such as food and habitat. Up to 70% of native freshwater fish species
migrate between freshwater and estuarine or marine environments at some stage of their life-cycle
(Harris 1984). However, in Victoria nearly 2200 artificial structures, such as gauging stations,
dams, weirs, fords and culverts, restrict fish movement (McGuckin and Bennett 1999). Fish
movement and migration are protected under a number of Acts (Water Act 1999, Fisheries Act
1995, Flora and Fauna Guarantee Act 1998 and Conservation, Forests and Lands Act 1987). This
protection has resulted in the construction of rock-ramp and vertical-slot fishways (designed to
promote fish passage) at many of the major instream barriers.
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Unfortunately, with the persistence of drought conditions, water levels in many Victorian streams
have fallen, exposing barriers to fish movement that would otherwise be submerged. Fish
restricted by barriers are likely to experience reduced water quality, increased predation pressure,
more competition for available food and habitat, increased exposure to disease, and possibly
higher mortality rates. Restoring natural flow regimes may help reduce the impact of instream
barriers during extended drought periods.
4.3.6
Modified flow regimes
The demand for water from agriculture, horticulture and urbanisation has greatly increased the
stress on Australian riverine systems. Flows in many systems are now controlled by dams, weirs,
regulators and irrigation channels, and water extraction for irrigation, stock and domestic use also
occurs. Such development has altered the magnitude, seasonality and variability of flows, and
river–floodplain exchanges (which are important for driving biological functioning within streams)
have been reduced.
Altered flow regimes are known to affect fish communities and vegetation types (Cadwallader
1978; Chesterfield 1986; Gehrke et al. 1995). Gehrke et al. (1995) found that Common Carp
dominated the highly regulated systems such as the Murray and Murrumbidgee Rivers, while there
was a significant trend for reduced species diversity in increasingly regulated systems. It was
suggested that the balance between native and non-native fish species has been changed by
desynchronising the environmental and reproductive cycles of native species (Gehrke et al. 1995).
The result is that the timing of water releases suits the spawning and recruitment cycles of nonnative fish.
Similarly, in many smaller streams flow modification through over-extraction may have a
significant impact on native fish, particularly when the effects are exacerbated during drought.
Fish generally retreat to deeper waterholes during periods of low flow, as these areas provide more
suitable resources (food, habitat and shelter from predation). Deep waterholes are also likely to be
where water extraction typically occurs, as they will be the last parts of a stream to dry up.
Minimising water extraction at remnant waterholes will therefore help to preserve native fish fauna
during extended drought periods, thus providing a remnant population able to recolonise streams
when flows return.
4.3.7
High Salinity
Salt is a natural part of the Australian landscape, and biota inhabiting rivers and wetlands have
adapted to variable salinities (Nielsen et al. 2003). Under natural conditions, salinity rises during
low flow periods and falls during high flow periods as salinity is flushed from the system. During
periods of low flow, organisms survive by tolerating extreme conditions or avoiding them (Nielsen
et al. 2003). In fact, many taxa posses morphological, physiological and life-history characteristics
that provide some capacity for tolerance, acclimatisation or avoidance (James et al. 2003).
However, riverine systems are becoming increasingly saline because of a decrease in the
magnitude and frequency of flushing flows (Nielsen et al. 2003). Unfortunately, little is known
about the salinity thresholds of freshwater biota (egg survival, sperm survival, larval deformation,
recruitment, and effects on algae and macroinvertebrate assemblages). The effects of increased
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
salinity on complex ecosystem processes, or thresholds which prevent semi-aquatic and terrestrial
species from using aquatic resources (James et al. 2003), are also unknown. Until conclusive
evidence is gathered on the effects that saline environments have on freshwater biota, riverine
systems should be managed so that salinities do not become excessively high. Management may
include minimising point sources of salinity, storing enough water to flush saline water from the
system (which will also increase dissolved oxygen levels), ensuring that the environment has
enough water by managing water allocations, monitoring groundwater, and planting trees where
groundwater intrusion may be occurring.
5 Conclusion
The distribution of Yarra Pygmy Perch was found to be fragmented. The low water levels
experienced as a result of the current drought, combined with numerous anthropogenic induced
changes, are likely to be contributing to this fragmentation. A number of threatening processes
have been identified, including the presence of non-native species (fish, willows, grasses), loss of
instream habitat and riparian vegetation, the presence of instream barriers, modified flows, stock
access and increased salinity.
To reduce the impact of the threatening processes identified, the following actions are
recommended to be undertaken where possible:
36

Clear non-native terrestrial plants in the riparian zone and reintroduce native species.

Remove non-native fish and investigate the potential for drying water bodies where nonnative species are dominant.

Fence off the riparian zone to minimise stock damage and encourage recovery of native
species in the area; native vegetation can also be reintroduced to the riparian zone.
Restoring the riparian zone should also promote instream habitat in the form of wood and
coarse particulate organic matter (i.e. leaves, branches, bark, grass, etc.).

Protect and encourage the growth of aquatic native vegetation.

Restore flow seasonality (i.e. stream flows that accord with historical records) and
flooding, which will help to reduce the adverse impacts of flow modification on native fish
(i.e. uncoupling of flow/temperature spawning cycles for native fish) and ensure that
natural stream forming processes continue to occur.

Minimise pumping of water for stock and domestic use from remnant water bodies
(particularly Deep Creek at Lancefield–Kilmore Road). This may involve contacting
farmers and conducting an inspection of the pump site.

Identify point and diffuse sources of saline intrusion with the aim of minimising the entry
of salt into the waterway. Restoring the riparian zone may help to prevent saline surface
water from entering the stream, and lower the saline watertable.
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Because another dry winter–spring period is likely in 2009, it is important that a number of sites
are monitored throughout the preceding spring–summer period and that action is taken if necessary
to prevent remnant waterholes from drying up. Sites most at risk include:

Gnarkeet Chain of Ponds at Hamilton Highway, west of Berrybank

Deep Creek at the ford on Baynton Road, at Lancefield–Kilmore Road and at Lancefield–
Tooborac Road

Thompson Creek at Willowite Road, at Rices Reserve and upstream of Torquay Road

Pennyroyal Creek off Bushs Lane.
Adding water to the above mentioned sites in the event that they are likely to dry up may help to
sustain the local population.
6 References
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Saddlier, S. & Hammer, M.P. 2007. National Recovery Plan for the Yarra Pygmy Perch
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Appendix 1
Barwon River (at weir, off Pollocksford Road, Stonehaven).
40
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Barwon River near Inverleigh.
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Barwon River at Kildean Road.
42
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Pennyroyal Creek (off Bushs Lane).
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Barwon River (at Deepdene Road).
44
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Thompson Creek (1 km upstream of weir, north of Breamlea).
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Thompson Creek (at Rices Reserve).
Thompson Creek (upstream of Geelong–Torquay Road).
46
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Thompson Creek (downstream of Pettavel Road).
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Thompson Creek (at Willowite Road bridge).
48
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Thompson Creek (downstream of Nobles Road).
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Merrygig Creek (upstream of Blackgate Road, south of Freshwater Creek).
50
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Curdies River (downstream of Curdies River Road, Curdie).
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Deep Creek (at Joyces Road).
52
Arthur Rylah Institute for Environmental Research Technical Report Series No. 184
Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Deep Creek (Barry Street, Romsey).
Deep Creek (Sheehans Road).
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Deep Creek (Lancefield–Kilmore Road).
54
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Deep Creek (Lancefield–Toobarac Road).
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Deep Creek (at ford on Baynton Road).
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Woady Yallock Creek (at bridge on Hamilton Highway, Cressy).
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Threats, distribution and abundance of Yarra pygmy perch in Victoria during a drought period
Gnarkeet Chain of Ponds (at Hamilton Highway bridge, west of Berrybank).
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Woady Yallock Creek (at end of Cemetery Road, west of Cape Clear).
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ISBN 978-1-74208-890-7 (print)
ISBN 978-1-74208-890-7 (online)