fish spawning in the lower river murray icon sites, south australia: with reference … ·...

FISH SPAWNING IN THE LOWER RIVER MURRAY ICON SITES, SOUTH AUSTRALIA: WITH

REFERENCE TO DROUGHT INTERVENTION MONITORING

SARDI Aquatic Sciences Publication Number: F2009/000360-1 SARDI Research Report Series Number: 377

Luciana Bucater, Katherine Cheshire and Qifeng Ye

SARDI Aquatic Sciences PO Box 120 Henley Beach SA 5022

2009

FISH SPAWNING IN THE LOWER RIVER MURRAY ICON SITES, SOUTH AUSTRALIA:

WITH REFERENCE TO DROUGHT INTERVENTION MONITORING

SARDI Aquatic Sciences Publication Number: F2009/000360-1 SARDI Research Report Series Number: 377

Luciana Bucater, Katherine Cheshire and Qifeng Ye

2009

This Publication may be cited as:

Bucater, L., Cheshire, K. and Ye, Q. (2009) Fish spawning in the lower River Murray icon sites, South Australia: with reference to drought intervention. SARDI research

report series number: 377, SARDI Aquatic Sciences Publication Number F2009/000360-1, SARDI Aquatic Sciences, Adelaide, pp 53.

South Australian Research and Development Institute

SARDI Aquatic Sciences

2 Hamra Avenue

West Beach SA 5024

Telephone: (08) 8207 5400

Facsimile: (08) 8207 5406

www.sardi.sa.gov.au

Bucater et al. 2009

DISCLAIMER © 2009 Murray-Darling Basin Authority and SARDI Aquatic Sciences

The authors warrant that they have taken all reasonable care in producing this report. The report has been through the SARDI Aquatic Sciences internal review process, and has been formally approved for release by the Editorial Board. Although all reasonable efforts have been made to ensure quality, SARDI does not warrant that the information in this report is free from errors or omissions. SARDI does not accept any liability for the contents of this report or for any consequences arising from its use or any reliance placed upon it.

This work is copyright Murray-Darling Basin Authority and South Australian Research and Development Institute – Aquatic Sciences. Photographs cover artwork and logos are not to be reproduced, copied or stored by any process without the written permission of the copyright holders or owners. All commercial rights are reserved and no part of this publication covered by copyright may be reproduced, copied or stored in any form or by any means for the purpose of acquiring profit or generating monies through commercially exploiting (including but not limited to sales) any part of or the whole of this publication except with the written permission of the copyright holders.

However, the copyright holders permit any person to reproduce or copy the text and other graphics in this publication or any part of it for the purposes of research, scientific advancement, academic discussion, record-keeping, free distribution, educational use or for any other public use or benefit provided that any such reproduction or copy (in part or in whole) acknowledges the permission of the copyright holders and its source (‘insert title of publication’) is clearly acknowledged.

To the extent permitted by law, the copyright holders (including its employees and consultants) exclude all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this report (in part or in whole) and any information or material contained in it.

The contents of this publication do not purport to represent the position of Murray-Darling Basin Authority/South Australian Research and Development Institute – Aquatic Sciences in any way and are presented for the purpose of informing and stimulating discussion for improved management of Basin's natural resources.

SARDI Research Report Series Number: 377

SARDI Aquatic Sciences Publication Number: F2009/000360-1

Authors: Luciana Bucater, Katherine Cheshire and Qifeng Ye Reviewers: Sandra Leigh & Lachie McLeay (SARDI), David Hohnberg & Stuart Little (MDBA) Glynn Ricketts (SA MDB NRM Board) Approved by: Jason Tanner

Signed: Date: 7 October 2009 Distribution: SA Murray-Darling Basin Natural Resource Management Board, Murray-Darling Basin Authority and SARDI Aquatic Sciences Library Circulation: Public Domain

Bucater et al. 2009

1

TABLE OF CONTENTS

TABLE OF CONTENTS............................................................................................................................... 1 LIST OF TABLES ........................................................................................................................................ 2 LIST OF FIGURES....................................................................................................................................... 3 ACKNOWLEDGEMENTS............................................................................................................................ 4 EXECUTIVE SUMMARY.............................................................................................................................. 5 1 INTRODUCTION ................................................................................................................................. 7 2 OBJECTIVES ...................................................................................................................................... 8 3 METHODS........................................................................................................................................... 8

3.1 STUDY SITE................................................................................................................................... 8 3.2 HYDROLOGY ............................................................................................................................... 10 3.3 SAMPLING REGIME....................................................................................................................... 10 3.4 SAMPLING EQUIPMENT AND METHODOLOGY .................................................................................. 11 3.5 SORTING AND IDENTIFICATION ...................................................................................................... 11 3.6 MEASUREMENT OF ENVIRONMENTAL VARIABLES............................................................................ 12 3.7 DATA ANALYSIS ........................................................................................................................... 12

3.7.1 Assemblage descriptors ....................................................................................................... 12 3.7.2 Statistical analyses ............................................................................................................... 12

4 RESULTS .......................................................................................................................................... 14 4.1 SPATIAL VARIATION IN 2008 DOWNSTREAM OF WELLINGTON, LOCK 1 AND LOCK 6.......................... 14

4.1.1 Environmental variables (from TDS field measurements).................................................... 14 4.1.2 Larval assemblage in 2008................................................................................................... 16

4.1.2.1 Catch summary .......................................................................................................................... 16 4.1.2.2 Spatial variation in total larval abundance and species richness................................................ 19 4.1.2.3 Spatial variation in larval assemblage structure with reference to environmental variables ....... 21

4.2 INTER-ANNUAL AND SPATIAL VARIATION DOWNSTREAM OF LOCK 1 AND LOCK 6 FROM 2005 TO 200825 4.2.1 Environmental variables 2005-2008 (from DWLBC data) .................................................... 25 4.2.2 Larval assemblage 2005-2008 ............................................................................................. 27

4.2.2.1 Catch summary .......................................................................................................................... 27 4.2.2.2 Inter-annual and spatial variation in total larval abundance and species richness ..................... 32 4.2.2.3 Inter-annual and spatial variation in larval assemblage structure with reference to environmental variables 34

4.3 LOWER LAKES LARVAL ASSEMBLAGE ............................................................................................ 40 4.3.1 Environmental variables (from TDS field measurements).................................................... 40 4.3.2 Catch summary..................................................................................................................... 40 4.3.3 Spatial variation .................................................................................................................... 41

5 DISCUSSION..................................................................................................................................... 43 5.1 SPATIAL VARIATION...................................................................................................................... 43 5.2 INTERANNUAL VARIATION DOWNSTREAM OF LOCKS 1 AND 6, FROM 2005-2008 .............................. 45

6 KEY FINDINGS ................................................................................................................................. 48 7 MANAGEMENT IMPLICATIONS...................................................................................................... 50 8 RECOMMENDATIONS FOR FUTURE RESEARCH........................................................................ 52 9 REFERENCES .................................................................................................................................. 53 10 PERSONAL COMMUNICATION ...................................................................................................... 57

Bucater et al. 2009

2

LIST OF TABLES

Table 1. Sampling sites with corresponding river section and coordinates. ............................... 10 Table 2. Two-way univariate PERMANOVA for differences among sites and trips for dissolved

oxygen, conductivity, temperature and pH. Bold text indicates significant value........ 14 Table 3. Total number of fish larvae collected downstream of Wellington and Lock 1 and Lock 6,

in 2008. ........................................................................................................................ 16 Table 4. Two-way univariate PERMANOVA for total larval abundance and species richness in

2008, amongst site and trip. Bold text indicates significant value............................... 20 Table 5. Two-way multivariate PERMANOVA for assemblage structure in 2008, amongst site

and trip. Bold text indicates significant value. ............................................................. 21 Table 6. SIMPER analysis for the comparison of assemblage structure between Wellington,

Lock 1 and Lock 6, collected in 2008. ......................................................................... 22 Table 7. Pearson (r) and Kendall (τ) correlation coefficients between each NMS axis and the

environmental variables and species. (Critical τ value for significance at 0.05 = 0.205). Bold text indicates significant correlations. .................................................................. 24

Table 8. Three-way univariate PERMANOVA for differences among years, sites and trips for discharge, water level, temperature and salinity. Bold text indicates significant value...................................................................................................................................... 25

Table 9. Total number of freshwater fish larvae collected downstream of Locks 1 and 6 in 2005, 2006, 2007 and 2008................................................................................................... 28

Table 10. Three-way univariate PERMANOVA for total larval abundance and species richness among years, site and trip. Bold text indicates significant value................................. 32

Table 11. Three-way multivariate PERMANOVA for differences in assemblage structure among year, site and trip. Bold text indicates significant value. .............................................. 34

Table 12. SIMPER analysis for the comparison of assemblage structure between years, downstream of Lock 1. ................................................................................................ 35

Table 13. SIMPER analysis for the comparison of assemblage structure between years, downstream of Lock 6. ................................................................................................ 36

Table 14. SIMPER analysis for the comparison of assemblage structure between Lock1 and Lock 6, in 2005, 2006, 2007 and 2008.. ...................................................................... 37

Table 15. Pearson (r) and Kendall (τ) correlation coefficients between each NMS axis and the environmental variables and species. (Critical τ value for significance at 0.05 = 0.124)...................................................................................................................................... 39

Table 16. Environmental variables dissolved oxygen (ppm), electrical conductivity (µS/cm at 25 oC), pH and water temperature (oC) in the Lower Lakes sites. .................................... 40

Table 17. Total number of fish larvae collected at the Lower Lakes sites in 2008. .................... 40 Table 18. One-way multivariate PERMANOVA for differences in assemblage structure among

sites.. ........................................................................................................................... 41 Table 19. Pearson (r) and Kendall (τ) correlation coefficients between each NMS axis (figure

14) and the environmental variables and species. (Critical τ value for significance at 0.05 = 0.602). B. .......................................................................................................... 42

Bucater et al. 2009

3

LIST OF FIGURES

Figure 1. A map of Lower Murray River, South Australia. Regular sampling sites marked by the large red circles, prospective sites in the Lower Lakes marked by red dots.................. 9

Figure 2. Bongo nets used for plankton tows ............................................................................ 11

Figure 3. Environmental variables measured downstream of Wellington, Lock 1 and Lock 6, a) dissolved oxygen (ppm), b) electrical conductivity (µS/cm at 25 oC), c) water temperature (oC) and d) pH.. ....................................................................................... 15

Figure 4. Small-bodied freshwater native fish larvae sampled downstream of Wellington, Lock 1 and Lock 6, in 2008. Data presented as the mean of 6 replicates ± standard error. ... 17

Figure 5. Small-bodied estuarine native fish larvae sampled downstream of Wellington, Lock 1 and Lock 6, in 2008. Data presented as the mean of 6 replicates ± standard error. ... 18

Figure 6. Exotic freshwater fish larvae sampled downstream of Wellington, Lock 1 and Lock 6, in 2008......................................................................................................................... 19

Figure 7. Comparison of total abundance (fish per 1000 m3) and species richness of fish larvae collected during 2008 downstream of Wellington, Lock 1 and Lock 6. ........................ 20

Figure 8. Non-metric MDS ordination (2-dimensional plot) for assemblage structure (stress 0.18) comparing sites downstream of Wellington, Lock 1 and Lock 6. Superimposed vectors for species and the characterising environmental variables are presented……………23

Figure 9. Comparison of the environmental conditions between 2005, 2006, 2007 and 2008, downstream of Locks 1 and 6...................................................................................... 26

Figure 10. Small-bodied freshwater native fish larvae for 2005, 2006, 2007 and 2008 sampling events downstream of Locks 1 and 6. ......................................................................... 29

Figure 11. Large-bodied freshwater native fish larvae for the 2005, 2006, 2007 and 2008 sampling events downstream of Locks 1 and 6........................................................... 30

Figure 12. Exotic freshwater species fish larvae for the 2005, 2006, 2007 and 2008 sampling events downstream of Locks 1 and 6. ......................................................................... 31

Figure 13. Comparison of total abundance and species richness of fish larvae collected in a) 2005, b) 2006, c) 2007 and d) 2008 sampling events downstream of Locks 1 and 6........................................................................................................................................ 33

Figure 14. Non-metric MDS ordination (2-dimensional plot) for assemblage structure (stress 0.19) comparing 2005, 2006, 2007 and 2008, downstream of Locks 1 and 6. Superimposed vectors for the characterising environmental variables are presented ....................................................................................................................................... 38

Figure 15. Non-metric MDS ordination (2-dimensional plot) for assemblage structure (stress 0.03) comparing Clayton, Pomanda island and Point Sturt. Superimposed vectors for the characterising environmental variables are presented………………………………42

Bucater et al. 2009

4

ACKNOWLEDGEMENTS

Funding from the Murray-Darling Basin Authority’s (MDBA) The Living Murray Intervention

Monitoring Program was provided through the South Australia Murray-Darling Basin Natural

Resources Management (SA MDB NRM) Board.

Special thanks to Simon Westergaard, Lesley Alton and Phillipa Wilson who were integral in

assisting us with identification of fish larvae. Many thanks to Michael Guderian and Matt

Pellizzari who played major roles in the field and in sorting samples. We also thank Neil

Wellman, Josh Fredberg, Michelle Roberts, Natalie Bool, Catherine Lawless, David Short and

David Fleer for field and lab assistance. Additionally, thanks to Carlos Teixeira and David

Schmarr for computer assistance.

Thanks to Narrandera Fisheries Centre (NSW-DPI) and Mike Hammer, who provided us with

fish larvae vouchers and Anthony Miskiewicz for assisting us with identification of estuarine

species.

The Department of Water, Land and Biodiversity Conservation (DWLBC) Knowledge and

Information Division provided discharge, water level, temperature and conductivity data for the

sites throughout the Lower River Murray, thanks to Barry Porter and Peta Hansen for additional

information.

Thank you to David Honhberg, Stuart Little and Lex Cogle (MDBA) who provided project

management and conducted the MDBA review. Special thanks to Judy Goode, Adrienne Frears

and Glynn Ricketts (SA MDB NRM Board) for their continuous support for this project and for

conducting SA MDB NRM Board review.

Similarly, thanks to Jason Tanner for acting as editor and overseeing the review process, and to

Lachie McLeay and Sandra Leigh for conducting the SARDI internal reviews on the draft report

and providing constructive advice to improve the manuscript. Thank you to Suzanne Bennett

and Carmel Elmawey for organising the SARDI review process.

Bucater et al. 2009

5

EXECUTIVE SUMMARY

Fish spawning and recruitment studies are a good indicator of river and fish population health.

Larval fish sampling in the Lower River Murray was conducted fortnightly from 2005 -2008, at

Locks 1 and 6, from October to December, resulting in six trips per year. An additional site at

Wellington was added in 2008. Lower Lakes sites at Pomanda Island, Point Sturt, and Clayton

were sampled only once, in December 2008 as a pilot study. Environmental variables were

also monitored throughout the sampling period to determine whether linkages between

distribution of larval assemblage and any environmental variables could be identified.

Discharge, water level and conductivity differed between years, as a direct result of the drought

conditions. Discharge and water level were highest in 2005, and decreased downstream of

Locks 1 and 6 in subsequent years. The first year (2005) was an above regulation flow year,

with a significant period during which within-channel flow pulses occurred as a result of a

combination of increased inflows into the tributaries and an environmental water allocation

release in the Upper River Murray. The following three years (2006, 2007 and 2008) were

hydrologically similar, being drought years of below regulation flow. Conductivity was negatively

correlated to flow and water level, and was highest downstream of Lock 1 and Wellington.

Fifteen species of fish were collected as larvae, comprising nine native freshwater, four native

estuarine, and two exotic freshwater species. The freshwater fish assemblage was comprised of

highly abundant small-bodied species and some large-bodied iconic species. The estuarine

species were only collected during 2008, in the new sites, downstream of Wellington and in the

Lower Lakes.

Significant spatial variation was identified for total abundance, species richness and

assemblage structure between sites downstream of Lock 1, Lock 6 and Wellington in 2008.

These differences in assemblages are most likely a result of differences in habitats surrounding

the regions. Spatial differences between the Lower Lakes sites were also identified and are

most likely a function of differences in conductivity.

Inter-annual variation in the total abundance, species richness and assemblage structure was

identified downstream of Locks 1 and 6, over the four sampling years. These differences were

correlated to changes in discharge, water level, conductivity and temperature. Three distinct

larval responses were identified:

1) Increased flow response: larval abundances positively correlated to discharge and water

level (and negatively correlated to conductivity). Including: golden perch, silver perch and

freshwater catfish.

Bucater et al. 2009

6

2) Decreased flow response: larval abundances negatively correlated to discharge and water

level (and positively to conductivity). Including: Australian smelt, flathead gudgeons, carp

gudgeons and hardyheads (consistent with the Low Flow Recruitment Hypothesis (LFRH),

Humphries et al. 1999).

3) Temperature response: larval abundances strongly correlated to temperature. Applied to

most species, however, bony herring, carp gudgeons and redfin perch were more strongly

influenced by lower temperature than other variables.

Abundances of larvae of the large-bodied species have decreased in each consecutive year,

and were very low throughout the duration of the project, which should be of significant concern.

Murray cod larvae were only collected downstream of Lock 1 in the flow pulse year, and no

larvae were detected in either site in 2008. Notably, flow-cued spawners, golden perch and

silver perch, were only present during 2005 under the increased discharge conditions. Under

low flow conditions abundance and distribution of large-bodied native species is decreased. A

within-channel flow pulse may be sufficient to benefit spawning of many species, however,

further research is required to determine the impact on recruitment to the juvenile population.

Small-bodied native species appear to respond positively to the low flow conditions initially, with

higher abundances of larvae recorded in the low flow years. However, a decrease in the

abundances of these species was recorded in 2008, suggesting that longer term monitoring

may be needed.

This report details the results of a four year study on the inter-annual and spatial variation in

larval fish assemblages in the main channel of the Lower River Murray, South Australia.

Separate sections are included highlighting key findings, management implications and

recommendations for future research. Results indicated that water management strategies

should be of a high priority for native fish management in South Australia. Furthermore,

environmental water allocations upstream may indirectly benefit downstream sites, and during

prolonged periods of low flow, the importance of within-channel flow pulses should not be

under-estimated.

Bucater et al. 2009

7

1 INTRODUCTION

The severe drought conditions that began in 2002 are likely to have intensified pressure on

already stressed native fish communities. It is, therefore, important to understand the biological

impacts and responses of key fish species during the current drought conditions. This will

provide information for adaptive management to assist recovery of fish communities and

riverine health.

In recent years discharge in the Lower River Murray, South Australia (SA) has been the lowest

on record and the low flow patterns are predicted to continue (MDBC 2008). In the Lower River

Murray, the riverine characteristics and associated floodplains are substantially different from

those in the mid and upper River Murray (Walker 2006). Therefore, specific investigations in the

lower Murray region are needed to improve our understanding of the importance of flows,

flooding and floodplains on the life cycle of native fish, fish habitat and environmental

requirements of critical life stages of fish species. A combination of increased tributary inflows

and an environmental water allocation release in the Upper Murray, had flow-on effects,

resulting in an increase in within-channel flow in the Lower River Murray during 2005.

Larval fish sampling from 2005 to 2008, downstream of Locks 1 and 6 in the main channel of

the River Murray, had identified significant inter-annual variation in assemblage structure and

highlighted the importance of elevated flows. Higher flows in 2005 resulted in spawning and the

presence of larvae of golden perch and silver perch, whereas the results from 2006, 2007 and

2008 suggested that the low flow conditions as a result of extended drought had contributed to

recruitment failure of large-bodied native species. In 2006, 2007 and 2008, no golden perch or

silver perch were detected from any of the survey sites, furthermore, larval Murray cod and

freshwater catfish were not collected downstream of Lock 1 (Cheshire and Ye 2008a, Ye et al.

2008).

This project aimed to continue monitoring larval fish assemblages in 2008 downstream of Locks

1 and 6, with an additional site established near Wellington. More specifically, the aim was to

examine the impacts of prolonged low flow conditions and water quality deterioration on the

larval community, and provide recommendations on potential mitigation measures. In addition,

pilot sampling was conducted at three selected sites in the Lower Lakes, to identify the larval

fish assemblage during the peak spawning season and to inform future monitoring programs in

the region.

This report has additional information complementing previous studies done by SARDI’s

researchers, for more comprehensive background information please see Cheshire and Ye

(2008a) and Cheshire and Ye (2008b).

Bucater et al. 2009

8

2 OBJECTIVES

The overall aim of this project was to determine the effect of drought induced weir pool lowering,

particularly in the reaches below Lock 1 and near Wellington, on fish spawning. The specific

objectives were:

To investigate the spatial variation of larval fish assemblage structure between sites

downstream of Wellington, Lock 1 and Lock 6, in 2008, in relation to environmental variables;

To describe the patterns and compare the inter-annual change in larval fish assemblage

structure in the main channel at sites downstream of Lock 1 and Lock 6, between 2005, 2006,

2007 and 2008, in the context of drought impact and

To describe the larval fish assemblage structure in the Lower Lakes under the current low water

level conditions.

3 METHODS

3.1 STUDY SITE

In South Australia, the River Murray encompasses four distinct geo-morphologic sections: “the

floodplain”, “gorge”, “swamplands” and “lakes” regions (Figure 1). The floodplain/valley region

extends from the Murray-Darling confluence to Overland Corner. The river meanders over a

wide, terraced floodplain with many anabranches, billabongs, deflation basins and Lake Victoria

(Walker 2006).

The lowland gorge runs from Overland Corner, where the river enters its limestone gorge, to

Mannum. The channel includes long, straight reaches aligned by geological faults, but retains

some inclination to meander. The diversity of wetlands is much less than in the floodplain

section (Walker 2006).

The swamplands section goes from Mannum to Wellington. The river flows through a section

flanked by reclaimed swamplands used for pasture and forage crops. There are no weirs, but

River Mouth barrages maintain a 450-600mm increase in the river level below Lock 1 (Walker

2006).

The lakes section starts from Wellington, where the river enters Lake Alexandrina and ends at

the sea. A small lake, Lake Albert, was historically fed from Lake Alexandrina, but due to

reduced water levels under current drought conditions, it has been disconnected from Lake

Alexandrina since April 2008. The River enters the sea through the Murray Mouth near Goolwa.

The Murray Mouth has been constantly dredged since 2002 (DWLBC 2007) to avoid closures

Bucater et al. 2009

9

caused by flow depletion and accumulated sediments and sand. The Coorong, a long and

narrow estuarine lagoon, adjoins the river mouth (Walker 2006).

Regular larval fish sampling was conducted at three sites in the main channel of the Lower

River Murray SA, in the floodplain (downstream of Lock 6), gorge (downstream of Lock 1) and

lakes section (downstream of Wellington) (Figure 1, Table 1). A pilot sampling trip was carried

out in the Lower Lakes, in the vicinity of Pomanda Island, Point Sturt and Clayton, in early

December 2008 (Figure 1, Table 1).

Figure 1. A map of Lower Murray River, South Australia. Regular sampling sites marked by the

large red circles, prospective sites in the Lower Lakes marked by red dots.

Bucater et al. 2009

10

Table 1. Sampling sites with corresponding geomorphic river section and coordinates.

Site Geo-morphologic section Coordinates Sampling regime

Downstream of Lock 6 Floodplain 33°59.725’ S, 140°53.152 E Regular sampling

Downstream of Lock 1 Gorge 34°21.138’ S, 139°37.061’ E Regular sampling

Downstream of Wellington Lakes 35°21.843’ S, 139°22.021’ E Regular sampling

Pomanda Island Lakes 35°24.686’ S, 139°19.170’ E Pilot sampling

Point Sturt Lakes 35°24.686’ S, 139°19.170’ E Pilot sampling

Clayton Lakes 35°30.545’ S, 138°57.447’ E Pilot sampling

3.2 HYDROLOGY

Flow in the Lower River Murray is extensively regulated, in recent years the flow within the

system has been little more than the irrigation allowance. However, 2005 was an above

regulation flow year, with a significant period during which within-channel flow pulses occurred.

This increase in flow was the result of a combination of increased tributary inflows, and the

release of the Barmah Millewa Forest Environmental Water Allocation (BM-EWA) (King et al.

2008). Although the BM-EWA was not specifically aimed at increasing flows in the Lower River

Murray, this release resulted in a within channel flow pulse in South Australia. In conjunction

with this flow pulse, the level of the weir pool at Weir 5 was raised by 50 cm, as a management

intervention. The following three years (2006, 2007 and 2008) were hydrologically similar, being

drought years of below regulation flow, and weir heights were maintained at the regulated pool

level.

3.3 SAMPLING REGIME

Regular sampling was conducted fortnightly at three sites (Table 1) during the spring/summer of

2008 from October through December, resulting in six trips. Sampling occurred during both day

and night, of the same day, resulting in six replicates at each site (three day and three night

replicates). All river sites were sampled within a four-day period. In 2005, 2006 and 2007

sampling was conducted downstream of Locks 1 and 6 using the same sampling regime

(Cheshire and Ye 2008a).

Pilot sampling was done once in the Lower Lakes sites at Pomanda Island, Point Sturt and

Clayto, during the day in December 2008, resulting in three replicates at each site. These sites

were sampled within a two-day period. The sampling period was selected based on the peak

spawning season and larval abundances within the river system as identified by Cheshire and

Ye (2008), Humphries et al (2002), Leigh et al. (2008) and Meredith et al. (2002).

Bucater et al. 2009

11

3.4 SAMPLING EQUIPMENT AND METHODOLOGY

Plankton tows were conducted using a pair of square-framed, 0.5 x 0.5 m, 3 m long bongo nets

of 500 µm mesh. Nets were equipped with a 60 cm pneumatic float in the centre of the frame,

so the frame sat five cm below the water surface. They were towed in circles using a 20 m

rope, in the main river channel and in the Lower Lakes sites, in areas with a depth greater than

1 m. The volume of water filtered through each net was determined using a flow meter (General

Oceanics), fitted in the centre of the mouth openings. Plankton tow data were standardised to

number of larvae per 1,000 m3 of water and then samples from left and right nets were grouped

for analysis. Day and night samples were taken to gain a representative picture of the whole

larval assemblage (Cheshire unpublished data).

Figure 2. Bongo nets used for plankton tows

3.5 SORTING AND IDENTIFICATION

Samples were preserved in 95% ethanol in situ and returned to the laboratory for sorting under

magnification lamps. Where possible, all larvae were identified to species level, using published

descriptions (Lake 1967; Neira et al. 1998; Puckridge and Walker 1990; Serafini and Humphries

2004), with the exception of carp gudgeons (Hypseleotris spp.), hardyheads (Craterocephalus

spp.) and some estuarine goby species. For carp gudgeons and hardyheads, each genus was

treated as a species complex due to close phylogenetic relationships and very similar

morphologies (Bertozzi et al. 2000; Serafini and Humphries 2004). Similarly, some of the

estuarine goby species were not identifiable due to the scarcity of fish larval species

descriptions and difficulties inherent to identification in the group; these were grouped into the

family Gobidae.

Bucater et al. 2009

12

3.6 MEASUREMENT OF ENVIRONMENTAL VARIABLES

In situ measurements of dissolved oxygen (mg/L), pH, water temperature (°C) and conductivity

(μS/cm @ 25 °C), using a TDS water quality meter, were taken at each site approximately 0.2 m

below the surface, during the day and at night. In addition, daily records of data for discharge

(ML per day), water level (mAHD = Level relative to Australian Height Datum), water

temperature (°C) and conductivity (μS/cm @ 25 °C) were obtained for sites downstream of

Locks 1 and 6, throughout the entire season from the Department of Water, Land and

Biodiversity Conservation, Knowledge and Information Division, Surface Water Archive (http://e-

nrims.dwlbc.sa.gov.au/swa/).

3.7 DATA ANALYSIS

3.7.1 Assemblage descriptors

The fish assemblage was characterised using three descriptors: total abundance, species

richness and assemblage structure. Total abundance of larvae was the total number of fish

calculated by summing standardised abundance of all species at each site for each replicate.

Species richness was the total number of species collected at a given site for each replicate.

Assemblage structure was characterised by species composition (presence/absence data) and

abundance of each species.

3.7.2 Statistical analyses

Prior to analysis, the environmental variables and assemblage descriptors were tested for

normality and homogeneity of variance. As few variables met the assumptions (normality and

homogeneity), data were analysed using permutational analysis of variance (PERMANOVA:

Anderson 2001) for univariate and multivariate data, which does not require the data to meet

these assumptions.

Spatial variation in assemblage descriptors (total abundance, species richness and assemblage

structure), between downstream of Wellington, Lock 1 and Lock 6 during 2008 was examined

using a two-way design, with site as fixed factor and trip as random factor. Inter-annual and

spatial variations in assemblage descriptors from 2005 to 2008, downstream of Lock 1 and Lock

6, were investigated using a three-way design, with year, site and trip as random factors.

Individual species have been documented to show diel variation, however, day/night was not

treated as a factor in the analyses as there is not a significant effect on the overall assemblage

structure (Cheshire unpublished data).

Bucater et al. 2009

13

In all analyses, total abundance and species richness were examined using univariate designs,

while assemblage structure was examined using a multivariate design. A fourth-root

transformation was performed on the larval assemblage data only, to prevent highly abundant

species from unduly influencing the similarity measure (Clarke 1993). All biological data were

examined using Bray-Curtis similarity measures (Bray and Curtis 1957). Unrestricted

permutations of data were performed for all analyses, with 999 permutations for the test, to

detect differences at α=0.05 (Anderson 2001). Where a low number of unique permutations

occurred, the Monte-Carlo p-values (p MC) were included and used to detect significant

differences (Anderson 2005). Where significant differences or interactions occurred pairwise

analyses, also using the PERMANOVA program, were performed to isolate where the

differences occurred.

In order to identify species contributing most to the differences between groups, a similarity

percentages (SIMPER) analysis was also performed for the comparison of assemblage

structure between sites and years. The abundance dataset was fourth root-transformed, a two

way crossed design and the Bray Curtis measure of similarity were used and a 95% cumulative

contribution cut-off was applied.

Mean daily values for discharge, water level, temperature and conductivity (from the DWLBC

surface water archive) were selected from the week of sampling to generate a set of six

replicates for each site and trip, to correspond to the six larval replicates. All environmental

variables were examined using a normalised Euclidean distance similarity measure. To detect

inter-annual and spatial variations, discharge, water level, temperature and conductivity were

analysed individually using a three-way univariate design. To determine spatial difference in

temperature, dissolved oxygen, pH and conductivity (from TDS field measurements) in 2008, a

two-way univariate design was applied.

The correlations between environmental variables and fish assemblage structure were analysed

using non-metric multidimensional scaling (NMS) ordination, using the Sorenson (Bray-Curtis)

measure in PC-ORD (McCune and Mefford 1999). Environmental variables and species were

added as vectors onto the NMS plots using a 0.1 R2 cut-off. Correlations between the NMS axis,

environmental variables and individual species were examined using Pearson (r) and Kendall

(τ) correlation coefficients (McCune and Mefford 1999). Where the Pearson (r) correlation

explained the amount of variance attributable, and Kendall (τ) correlation provided the

significance of the correlation.

Bucater et al. 2009

14

4 RESULTS

4.1 SPATIAL VARIATION IN 2008 DOWNSTREAM OF WELLINGTON, LOCK 1 AND LOCK 6

4.1.1 Environmental variables (from TDS field measurements)

All environmental variables showed a significant site-trip interaction, indicating that while spatial

variation occurred, it was not consistent through time (Table 2). The site at Wellington

represented a more dynamic system, showing considerable changes in dissolved oxygen and

conductivity over time. Dissolved oxygen ranged between 6 and 10ppm (Figure 3a). There was

a gradual increase in conductivity from upstream to downstream sites in the Lower River

Murray, as a result of geographical placement (Figure 3b). Temperature generally increased

from spring to late summer at all sites (Figure 3c) and the pH ranged between 7.5 and 8.5

(Figure 3d). All environmental variables represent spot measurements and should be

interpreted cautiously.

Table 2. Two-way univariate PERMANOVA for differences among sites and trips for dissolved oxygen, conductivity, temperature and pH. Bold text indicates significant value.

Dissolved oxygen Conductivity Temperature pH

Source of variation df MS p MS p MS p MS p

Site 2 0.57 0.727 39.80 0.001 7.45 0.002 10.34 0.018

Trip 4 15.28 0.001 0.48 0.001 16.04 0.001 10.05 0.001

Site x Trip 8 1.95 0.001 0.63 0.001 0.45 0.001 1.57 0.001

Residual 75 0.15 0.03 0.08 0.21

Bucater et al. 2009

15

D/S WellingtonD

isso

ved

oxyg

en (p

pm)

5

6

7

8

9

10

11 Day measurementsNight measurements

Con

duct

ivity

(µS/

cm)

0200400600800

1000120014001600

Tem

pera

ture

(Co )

14

16

18

20

22

24

26

Sampling date

06-1

1/Oct/

0820

-24/O

ct/08

3-7/N

ov/08

17-2

1/Nov

/081-

5/Dec

/0815

-19/D

ec/08

pH

7.0

7.5

8.0

8.5

9.0

06-1

1/Oct/

0820

-24/O

ct/08

3-7/N

ov/08

17-2

1/Nov

/081-

5/Dec

/0815

-19/D

ec/08

06-1

1/Oct/

0820

-24/O

ct/08

3-7/N

ov/08

17-2

1/Nov

/081-

5/Dec

/0815

-19/D

ec/08

(a)

(b)

(c)

(d)

D/S Lock 1 D/S Lock 6

Figure 3. Environmental variables measured downstream of Wellington, Lock 1 and Lock 6, a) dissolved oxygen (ppm), b) electrical conductivity (µS/cm at 25 oC), c) water temperature (oC) and d) pH. Late October trip measurements were disregarded, due to problems with water quality meter.

Bucater et al. 2009

16

4.1.2 Larval assemblage in 2008

4.1.2.1 Catch summary

A total of 22,334 larvae were collected during 2008 from the three regularly sampled sites. The

numbers of larvae caught downstream of Lock 1 and Wellington were substantially higher than

downstream of Lock 6 (Table 3). Eleven species were collected throughout the study,

comprising six native freshwater, two exotic freshwater and three native estuarine species.

Common galaxias, considered a diadromous species, was grouped with other estuarine species

in this study.

The small-bodied freshwater species, Australian smelt, carp gudgeons, flathead gudgeon, and

bony herring*, were most abundant (Table 3, Figure 4). Freshwater catfish larvae were only

collected on one occasion downstream of Lock 6 during early December (Table 3). The exotic

species, common carp and redfin perch, were collected in relatively low numbers (Table 3,

Figure 6). Common galaxias, lagoon goby and Gobidae, were present only downstream of

Wellington (Table 3, Figure 5).

Table 3. Total number of fish larvae collected downstream of Wellington and Lock 1 and Lock 6,

in 2008.

Species

Species group Common name Scientific name D/S Wellington D/S Lock 1 D/S Lock 6 Total

Native freshwater Australian smelt Retropinna semoni 4,801 630 3,421 8,852

Bony herring Nematalosa erebi 124 348 357 829

Carp gudgeon Hypseleotris spp. 329 1,991 350 2,670

Flathead gudgeon Philypnodon grandiceps 2,016 6,931 489 9,436

Hardyhead Craterocephalus spp. 0 34 1 35

Freshwater catfish Tandanus tandanus 0 0 4 4

Exotic freshwater Common carp Cyprinus carpio 9 109 3 121

Redfin Perca fluviatilis 218 0 0 218

Native estuarine Common galaxias Galaxias maculatus 59 0 0 59

Lagoon goby Tasmanogobius lasti 87 0 0 87

Unidentified goby Gobidae 23 0 0 23

Total 7,666 10,043 4,625 22,334

Percentage of total catch 34.3 45.0 20.7

_________________________

* Bony herring is usually qualified as a medium sized fish, however the larvae are very similar to those of the small-

bodied species so for the context of this report they have been included as a small-bodied species.

Bucater et al. 2009

17

Aus

tralia

n sm

elt

0

200

400

600

800

1000

1200B

ony

Her

ring

0

20

40

60

80

100

120

140

D/S WellingtonD/S Lock 1D/S Lock 6

Rel

ativ

e ab

unda

nce

(fish

per

100

0m3)

Car

p gu

dgeo

m

0

200

400

600

800

Sampling date

11/Oct 25/Oct 08/Nov 22/Nov 6/Dec 20/Dec

Flat

head

gud

geon

0

200

400

600

800

1000

1200

1400

Figure 4. Small-bodied freshwater native fish larvae sampled downstream of Wellington, Lock

1 and Lock 6, in 2008. Data presented as the mean of 6 replicates ± standard error.

Bucater et al. 2009

18

Com

mon

gal

axia

s

0

20

40

60

80

100

120

Rel

ativ

e ab

unda

nce

(fish

per

100

0m3)

Lago

on g

oby

0

50

100

150

200

250

300

Sampling date


Gob

idae

0

20

40

60

80

D/S WellingtonD/S Lock 1D/S Lock 6

Figure 5. Small-bodied estuarine native fish larvae sampled downstream of Wellington, Lock 1

and Lock 6, in 2008. Data presented as the mean of 6 replicates ± standard error.

Bucater et al. 2009

19

Car

p

0

20

40

60

80D/S WellingtonD/S Lock 1D/S Lock 6

Rel

ativ

e ab

unda

nce

(fish

per

100

0m3)

Sampling date


Red

fin

0

200

400

600

800

1000

1200

Figure 6. Exotic freshwater fish larvae sampled downstream of Wellington, Lock 1 and Lock 6,

in 2008. Data presented as the mean of 6 replicates ± standard error.

4.1.2.2 Spatial variation in total larval abundance and species richness

There were significant spatial and seasonal differences in total larval abundance, although

these were not consistent throughout the season as indicated by a site-trip interaction (Table 4).

Pairwise analysis indicated significant differences in total abundance between Wellington, Lock

1 and Lock 6. This was mainly driven by differences in the number of fish larvae collected

downstream of Locks 1 and 6 in all trips, with the exception of late December (Figure 7). In

general, differences in total abundance between Wellington and Lock 6 were not significant

throughout the season, with the exception of mid-season trips.

Spatial variation in species richness occurred, but was not consistent through time (Table 4).

Pairwise analysis indicated significant differences in the early season, which were driven by the

low number of species collected downstream of Lock 6 in October (Figure 7).

Bucater et al. 2009

20

Table 4. Two-way univariate PERMANOVA for total larval abundance and species richness in 2008, amongst site and trip. Bold text indicates significant value.

Total abundance Species richness

Source of variation df MS p MS p

Site 2 6471.0 0.185 5017.7 0.019

Trip 5 3692.6 0.001 781.6 0.006

Site x Trip 10 3340.5 0.001 1054.4 0.001

Residual 90 698.9 203.4

0

500

1000

1500

2000

2500 D/S Wellington D/S Lock 1D/S Lock 6

Mea

n to

tal a

bund

ance

(lar

vae

per 1

000m

3 )

Sampling date


Spec

ies

richn

ess

0

1

2

3

4

5

6

Figure 7. Comparison of total abundance (fish per 1000 m3) and species richness of fish larvae

collected during 2008 downstream of Wellington, Lock 1 and Lock 6. Data presented as the

mean of 6 replicates ± standard error.

Bucater et al. 2009

21

4.1.2.3 Spatial variation in larval assemblage structure with reference to environmental variables

There were significant spatial and seasonal differences in the larval assemblage structure in

2008, however, as indicated by the significant site-trip interaction, the patterns of differences

were not consistent (Table 5). Pairwise analysis failed to detect any patterns in the differences.

Fish assemblage structure was different between all sites throughout the season.

Table 5. Two-way multivariate PERMANOVA for assemblage structure in 2008, among site and trip. Bold text indicates significant value.

Assemblage structure

Source of variation df MS p

Site 2 19996 0.07

Trip 5 5221.4 0.001

Site x Trip 10 9109.6 0.001

Residual 90 1088.8

Spatial differences between Wellington, Lock 1 and Lock 6 were generally driven by

abundances of Australian smelt, flathead gudgeon, carp gudgeon and bony herring (Table 6).

When comparing Wellington with Locks 1 and 6, the presence of the estuarine common

galaxias and lagoon goby and the exotic freshwater redfin perch, also contributed to the

differences between the sites. Wellington and Lock 6 had more similar mean abundances of

flathead gudgeon, carp gudgeon and Australian smelt, accounting for the similarities between

these sites (Table 6).

Bucater et al. 2009

22

Table 6. SIMPER analysis for the comparison of assemblage structure between Wellington, Lock 1 and Lock 6, collected in 2008. Results are based on fourth root-transformed of abundance dataset. CR (consistency ratio) indicates species distributions between site, with larger values indicating greater consistency. The contribution (%) indicates the proportion of difference between sites (shown by PERMANOVA) attributable to individual species, a 95% cumulative contribution cut-off was also applied. Mean dissimilarity is expressed as a percentage ranging from 0% (identical) and 100% (totally dissimilar).

Species names Mean abundance CR Contribution (%) Cumulative contribution

Lock 1 Lock 6 Mean dissimilarity = 47.05

Flathead gudgeon 4.35 2.41 2.06 31.93 31.93

Carp gudgeon 2.96 1.57 1.49 23.82 55.76

Australian smelt 2.99 3.22 1.07 19.61 75.37

Bony herring 1.51 1.91 1.06 12.8 88.16

Common carp 0.89 0.05 0.81 7.78 95.94

Lock 1 Wellington Mean dissimilarity = 45.26



Carp Gudgeon 2.96 1.69 1.36 16.18 57.69

Bony herring 1.51 0.81 1.21 14.41 72.1

Common carp 0.89 0.23 0.77 6.43 78.54

Common galaxias 0 0.65 0.66 5.46 84

Redfin perch 0 0.64 0.5 5.44 89.44

Lagoon goby 0 0.66 0.68 5.43 94.87

Lock 6 Wellington Mean dissimilarity =42.11

Carp gudgeon 1.57 1.69 1.44 19.92 19.92



Bony herring 1.91 0.81 1.06 14.95 70.9

Redfin perch 0 0.64 0.5 7.79 78.69

Common galaxias 0 0.65 0.68 6.94 85.63

Lagoon goby 0 0.66 0.67 6.44 92.07

The NMS ordinations of assemblage structure displayed a discrete separation of Lock 1

samples, whereas Lock 6 and Wellington samples were more interspersed (Figure 8). Axis 1

had a strong negative correlation with temperature (Table 7). Species that showed strong

negative correlations with axis 1 were bony herring, carp gudgeon and flathead gudgeon,

indicating that these species are positively correlated to temperature. A weaker correlation

existed for hardyhead and common carp (Table 7), Australian smelt was the only species that

shows a strong positive correlation with axis 1, indicating that it is negatively correlated to

temperature.

Bucater et al. 2009

23

Axis 2 was significantly positively correlated to conductivity, dissolved oxygen and pH and

negatively correlated to temperature; the strongest correlation was with conductivity (Table 7).

Australian smelt, carp gudgeon, flathead gudgeon, common carp, redfin perch, lagoon goby and

Gobidae had significant positive correlations to axis 2, indicating higher abundances occurred in

conjunction with higher conductivity, dissolved oxygen and pH and lower temperature.

Figure 8. Non-metric MDS ordination (2-dimensional plot) for assemblage structure (stress

0.18) comparing sites downstream of Wellington, Lock 1 and Lock 6. Superimposed vectors for

species and the characterising environmental variables are presented, an R2 cut- off of 0.1 was

applied. Refer to table 7 for species codes.

Bucater et al. 2009

24

Table 7. Pearson (r) and Kendall (τ) correlation coefficients between each NMS axis and the environmental variables and species. (Critical τ value for significance at 0.05 = 0.205). Bold text indicates significant correlations.

Axis 1 Axis 2 Species code r τ r τ

EC 0.047 0.017 0.614 0.421

Temp -0.348 -0.268 -0.418 -0.262

DO -0.002 0.033 0.462 0.301

pH -0.092 -0.017 0.324 0.231

Australian smelt Ret sem 0.703 0.543 0.386 0.275

Bony herring Nem ere -0.763 -0.550 -0.267 -0.169

Carp gudgeon Hyp spp -0.762 -0.602 0.448 0.285

Flathead gudgeon Phi gra -0.847 -0.643 0.395 0.300

Hardyhead Cra spp -0.387 -0.302 0.159 0.155

Freshwater catfish Tan tan -0.047 -0.037 -0.030 -0.032

Common carp Cyp car -0.327 -0.239 0.276 0.252

Redfin perch Per flu 0.153 0.178 0.463 0.336

Common galaxias Gal mac 0.204 0.203 0.202 0.163

Lagoon goby Tas las 0.041 0.074 0.517 0.363

Gobidae Gobidae -0.089 -0.066 0.307 0.255

Bucater et al. 2009

25

4.2 INTER-ANNUAL AND SPATIAL VARIATION DOWNSTREAM OF LOCK 1 AND LOCK 6 FROM 2005 TO 2008

4.2.1 Environmental variables 2005-2008 (from DWLBC data)

All environmental variables showed a significant year-site-trip interaction, indicating that while

inter-annual and spatial variation occurred, it was not consistent through time (Table 8). Flow

variability downstream of Locks 1 and 6 was greatest in 2005, reduced in 2006 and 2007, and

became stable in 2008 (Figure 9a). Discharge was similar within years, but different between

both Locks, likely being a result of geographical placement.

Water level differed between years and sites. It was higher downstream of Lock 6, due to

management of the weir pools. Over the four years, there was a steady decrease in water level

downstream of Locks 6 and 1 (Figure 9b).

Temperature showed no consistent patterns between sites; within sites the seasonal pattern

was relatively consistent, with temperature increasing steadily from spring to late summer.

Temperatures in 2007 and 2008 were slightly lower when compared to 2005 and 2006 (Figure

9c).

Conductivity within each site showed an increase from 2005, peaking in 2007, followed by a

slight decrease in 2008 (Figure 9d). The values recorded downstream of both Locks almost

doubled from 2005 to 2007. Spatially, conductivity was always significantly higher downstream

of Lock 1.

Table 8. Three-way univariate PERMANOVA for differences among years, sites and trips for discharge, water level, temperature and salinity. Bold text indicates significant value.

Discharge Water level Temperature Conductivity

Source of variation df MS p MS p MS p MS p

Year 3 84.09 0.001 0.19 0.009 1.13 0.583 19.16 0.217

Site 1 0.68 0.773 286.26 0.001 0.21 0.742 164.52 0.003

Trip 5 1.32 0.285 0.00 0.126 15.95 0.001 1.33 0.594

Year x Site 3 1.41 0.001 0.04 0.001 2.06 0.347 10.95 0.001

Year x Trip 15 0.94 0.001 0.00 0.59 1.20 0.771 0.74 0.003

Site x Trip 5 0.19 0.304 0.00 0.103 1.51 0.537 0.96 0.002

Year x Site x Trip 15 0.14 0.001 0.00 0.001 1.73 0.001 0.17 0.001

Residual 240 0.02 0.00 0.61 0.03

Bucater et al. 2009

26

Dis

char

ge (M

L pe

r day

)

02000400060008000

10000120001400016000 2006 2007

01/O

ct/07

15/O

ct/07

29/O

ct/07

12/Nov

/07

26/Nov

/07

10/Dec

/07

24/Dec

/07

2005W

ater

leve

l (m

AHD

)

-1.0

-0.5

0.0

0.5

1.0

1.5

Tem

pera

ture

(o C)

10

15

20

25

30

(a)

(b)

(c)

(d)

D/S

Loc

k 1

wat

er le

vel (

mAH

D)

2008

Lock 1 Lock 6

06/O

ct/08

20/O

ct/08

03/Nov

/08

17/Nov

/08

01/Dec

/08

15/Dec

/08

29/Dec

/08

D/S

Lock 6 water level (m

AH

D)16.0

16.2

16.4

16.6

16.8

17.0

17.2

17.4

03/O

ct/05

17/O

ct/05

31/O

ct/05

14/Nov

/05

28/Nov

/05

12/Dec

/05

26/Dec

/05

Con

duct

ivity

(µS/

cm)

0

200

400

600

800

Date02

/Oct/

06

16/O

ct/06

30/O

ct/06

13/Nov

/06

27/Nov

/06

11/Dec

/06

25/Dec

/06

Figure 9. Comparison of the environmental conditions between 2005, 2006, 2007 and 2008, downstream of Locks 1 and 6, a) discharge (MLd-1), b) water level (mAHD), c) mean daily water temperature (°C) and d) mean daily electrical conductivity (µS/cm at 25 oC).

Bucater et al. 2009

27

4.2.2 Larval assemblage 2005-2008

4.2.2.1 Catch summary

The total number of fish larvae caught increased from 2005 to 2007, but then decreased in 2008

to a similar level as recorded in 2006. Catch rates downstream of Lock 1 were consistently

greater than those downstream of Lock 6, in all years of the survey (Table 9). Eleven species

were collected throughout the study, comprising of nine native and two exotic freshwater

species.

The small-bodied native species, Australian smelt, bony herring, carp gudgeons and flathead

gudgeon, were the most abundant of the larval catch (Table 9, Figure 10). Additional species

sampled included freshwater catfish, Murray cod, golden perch, silver perch and hardyheads

(Figure 11). The exotic species were common carp and redfin perch (Table 9, Figure 12).

Freshwater catfish were collected in low numbers in 2007 (Cheshire and Ye 2008a), however, it

is not shown in these results due to the reduction of replicates from eight in previous years to

six in 2008, as random selection of samples from 2007 did not include those with catfish larvae

present.

Bucater et al. 2009

28

Table 9. Total number of freshwater fish larvae collected downstream of Locks 1 and 6 in 2005, 2006, 2007 and 2008.

Species D/S Lock 1 D/S Lock 6 Total

Common name Scientific name 2005 2006 2007 2008 2005 2006 2007 2008 2005 2006 2007 2008 Australian smelt Retropinna semoni 1,100 4,964 8,951 630 193 3,143 7,797 3,421 1,293 8,107 16,748 4,051 Bony herring Nematalosa erebi 633 1,435 117 348 83 618 3,530 357 717 2,053 3,647 705 Carp gudgeon Hypseleotris spp. 694 998 4,885 1,991 359 565 2,486 350 1,053 1,563 7,371 2,341 Flathead gudgeon Philypnodon grandiceps 186 2,475 6,674 6,931 282 821 2,336 489 468 3,296 9,010 7,420 Hardyhead Craterocephalus spp. 3 5 14 34 1 51 10 1 4 56 24 35 Murray cod Maccullochella peelii peelii 2 0 0 0 2 3 2 0 4 3 2 0 Freshwater catfish Tandanus tandanus 1 0 0 0 7 3 0 4 7 3 0 4 Golden perch Macquaria ambigua 0 0 0 0 26 0 0 0 26 0 0 0 Silver perch Bidyanus bidyanus 0 0 0 0 9 0 0 0 9 0 0 0 Carp Cyprinus carpio 2 0 9 109 10 1 4 3 12 1 13 112

Redfin Perca fluviatilis 0 0 5 0 1 12 0 0 1 12 5 0

Total 2,621 9,877 20,655 10,043 972 5,217 16,165 4,625 3,593 15,094 36,820 14,668

Yearly % catch 72.9 65.4 56.1 62.7 27.1 34.6 43.9 37.3

Bucater et al. 2009

29

2007

Bon

y he

rrin

gFl

athe

ad g

udge

onC

arp

gudg

eon

Rel

ativ

e ab

unda

nce

(fish

per

100

0m3)

0300600900

120015001800

Aust

ralia

n sm

elt

0

500

1000

1500

2000

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

0300600900

120015001800

Date

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

20062005

0

1000

2000

3000

4000 D/S Lock 1D/S Lock 6

2008 Discharge (M

L per day)0200040006000800010000120001400016000

Discharge Lock 1 Discharge Lock 6

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

Figure 10. Small-bodied freshwater native fish larvae for 2005, 2006, 2007 and 2008 sampling events downstream of Locks 1 and 6. Data presented as the mean of the 6 replicates ± standard error. Water discharge downstream of Locks 1 and 6 is also presented for this period.

Bucater et al. 2009

30

Fres

hwat

er c

atfis

hS

ilver

per

chG

olde

n pe

rch

Rel

ativ

e ab

unda

nce

(fish

per

100

0m3)

0123456

Mur

ray

cod

0

5

10

15

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

0

1

2

3

4

5

Date

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

Discharge (M

L per day)0200040006000800010000120001400016000 Discharge Lock 1

Discharge Lock 6

200820072005

0

1

2

3

4

5

2006

D/S Lock 1D/S Lock 6

Figure 11. Large-bodied freshwater native fish larvae for the 2005, 2006, 2007 and 2008 sampling events downstream of Locks 1 and 6. Data presented as the mean of 6 replicates ± standard error. Water discharge downstream of Locks 1 and 6 is also presented for this period.

Bucater et al. 2009

31

Com

mon

car

p

20072005

0

4

8

12

16

20

2006

Red

fin p

erch

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

0

2

4

6

8

10

Date

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

Rel

ativ

e ab

unda

nce

(fish

per

100

0m3)

Discharge (M

L per day)0200040006000800010000120001400016000

2008

11/Oct25/Oct

08/Nov22/Nov

6/Dec20/Dec

50.57 Discharge Lock 1 Discharge Lock 6

D/S Lock 1D/S Lock 6

Figure 12. Exotic freshwater species fish larvae for the 2005, 2006, 2007 and 2008 sampling events downstream of Locks 1 and 6. Data presented as the mean of 6 replicates ± standard error. Water discharge downstream of Locks 1 and 6 is also presented for this period.

.

Bucater et al. 2009

32

4.2.2.2 Inter-annual and spatial variation in total larval abundance and species richness

Overall there were significant inter-annual and spatial differences in the total larval abundance,

however, as indicated by the significant year-site-trip interaction, the patterns of differences

were not consistent (Table 10). Pairwise analysis demonstrated a significant variation in total

abundance between all years downstream of Lock 1, while significant differences occurred

between 2005 and 2007 downstream of Lock 6. Where differences were identified between

years, total larval abundance was highest at all sites in 2007 (Figure 13c & d). In general,

significant spatial differences occurred in all years, however, the patterns of differences were

not consistent. Furthermore, where site differences were identified, the total abundance

downstream of Lock 1 was always significantly higher, except for November and December

2007 (Figure 13c).

There were significant inter-annual and spatial differences detected for species richness,

however, these patterns were not consistent as indicated by the significant year-site-trip

interaction (Table 10). Pairwise analysis detected significant differences between all years, but

only during October and early November, downstream of both Locks. In general, there was no

spatial variation in species richness throughout the time, except for the early season of 2008

(Figure 13). Total species richness ranged from one to five at any one point in time (Figure 13),

however, the greatest species richness occurred in 2005 downstream of Lock 6, where eleven

species were collected (Table 9).

Table 10. Three-way univariate PERMANOVA for total larval abundance and species richness among years, site and trip. Bold text indicates significant value.

Total abundance Species richness

Source of variation df MS p MS p

Year 3 48943.0 0.002 772.8 0.906

Site 1 12447.0 0.504 1062.5 0.774

Trip 5 3605.7 0.322 1788..0 0.004

Year x Site 3 12376.0 0.008 2229.8 0.010

Year x Trip 15 1968.2 0.892 343.1 0.875

Site x Trip 5 3732.9 0.326 390.1 0.693

Year x Site x Trip 15 3115.6 0.001 564.4 0.002

Residual 240 1147.9 230.8

Bucater et al. 2009

33

(a)

0

1000

2000

3000

4000

5000

(b)

Mea

n to

tal a

bund

ance

(lar

vae

per 1

000m

3 )

0

1000

2000

3000

4000

5000

(c)

0

1000

2000

3000

4000

5000

0

1

2

3

4

5

6 D/S Lock 1 D/S Lock 6

Spec

ies

Ric

hnes

s0

1

2

3

4

5

6

Sampling Date

11-Oct 25-Oct 08-Nov 22-Nov 06-Dec 20-Dec0

1

2

3

4

5

6

0

1

2

3

4

5

6

(d)

11-Oct 25-Oct 08-Nov 22-Nov 06-Dec 20-Dec0

1000

2000

3000

4000

5000

(a)

(b)

(c)

(d)

Figure 13. Comparison of total abundance and species richness of fish larvae collected in a) 2005, b) 2006, c) 2007 and d) 2008 sampling events downstream of Locks 1 and 6. Data presented as the mean of 6 replicates ± standard error.

Bucater et al. 2009

34

4.2.2.3 Inter-annual and spatial variation in larval assemblage structure with reference to environmental variables

There were significant inter-annual, spatial and seasonal differences in assemblage structure

downstream of Locks 1 and 6, however, the patterns of differences were not consistent, as

indicated by the significant year-site-trip interaction (Table 11). Pairwise results indicated that

inter-annual variation occurred between all years, downstream of Lock 1 and between 2005,

2006 and 2008 downstream of Lock 6. Significant spatial differences occurred in all years,

however, in 2006 it was only identified in late December.

Table 11. Three-way multivariate PERMANOVA for differences in assemblage structure among year, site and trip. Bold text indicates significant value.

Assemblage structure


Year 3 38516 0.076

Site 1 27906 0.343

Trip 5 19259 0.001

Year x Site 3 24651 0.001

Year x Trip 15 4992 0.243

Site x Trip 5 4108 0.537

Year x Site x Trip 15 4247 0.001

Residual 240 1664

Inter-annual variation between samples collected downstream of Locks 1 and 6 was mainly

driven by abundances of Australian smelt, bony herring, flathead gudgeon, and carp gudgeon

(Table 12, Table 13). At both sites, Australian smelt, bony herring and flathead gudgeon

showed an increase in abundance from 2005 to 2007 followed by a decrease in 2008. Carp

gudgeon, however, was captured in higher abundance in 2007 and 2008, downstream of Lock

1, while downstream of Lock 6 it peaked in 2007 followed by a substantial decrease in 2008,

reaching lower abundance when compared to numbers recorded in 2005 and 2006. (Table 12,

Table 13).

In all years, spatial variation between samples collected downstream of Locks 1 and 6 was

driven by differences in abundance of Australian smelt, bony herring, flathead gudgeon and

carp gudgeon, which in most cases occurred in higher abundances downstream of Lock 1

(Table 14). Additionally in 2005, common carp, golden perch and silver perch also contributed

to spatial variation, occurring in higher abundances downstream of Lock 6 (Table 14).

Bucater et al. 2009

35

Table 12. SIMPER analysis for the comparison of assemblage structure between years, downstream of Lock 1. Results are based on fourth root-transformed of abundance dataset. CR (consistency ratio) indicates species distributions between sites, with larger values indicating greater consistency. The contribution (%) indicates the proportion of difference between sites (shown by PERMANOVA) attributable to individual species, a 95% cumulative contribution cut-off was also applied. Mean dissimilarity is expressed as a percentage ranging from 0% (identical) and 100% (totally dissimilar).


2005 2006 Mean dissimilarity = 42.70


Bony herring 1.33 1.82 1.2 20.68 45.56


Carp gudgeon 2.12 1.99 1.15 15.65 80.88

Hardyhead 0.08 0.37 0.69 5.33 86.2

Common carp 0.27 0.03 0.51 4.00 90.2




Bony herring 1.33 2.09 1.12 20.34 68.97

Carp gudgeon 2.12 3.19 1.33 18.52 87.49

Common carp 0.27 0.17 0.6 3.73 91.22




Carp gudgeon 2.12 2.27 1.25 17.35 67.96

Bony herring 1.33 1.71 1.06 15.56 83.52

Common carp 0.27 0.47 0.76 7.03 90.55



Bony herring 1.82 2.09 1.33 23.02 48.02

Carp gudgeon 1.99 3.19 1.29 20.73 68.74


Hardyhead 0.37 0.26 0.76 5.17 94.58




Bony herring 1.82 1.71 1.21 20.01 65.89

Carp gudgeon 1.99 2.27 1.31 19.69 85.58

Hardyhead 0.37 0.24 0.76 6.14 91.71



Carp gudgeon 3.19 2.27 1.3 23.40 47.20

Bony herring 2.09 1.71 1.12 21.40 68.59


Common carp 0.17 0.47 0.61 5.16 94.44

Bucater et al. 2009

36

Table 13. SIMPER analysis for the comparison of assemblage structure between years, downstream of Lock 6. Results are based on fourth root-transformed of abundance dataset. CR (consistency ratio) indicates species distributions between sites, with larger values indicating greater consistency. The contribution (%) indicates the proportion of difference between sites (shown by PERMANOVA) attributable to individual species, a 95% cumulative contribution cut-off was also applied. Mean dissimilarity is expressed as a percentage ranging from 0% (identical) and 100% (totally dissimilar).




Bony herring 0.58 1.42 1.04 17.68 41.31


Carp gudgeon 1.91 1.93 1.05 13.4 70.87

Hardyhead 0.05 0.62 0.91 7.3 78.17

Common carp 0.43 0.07 0.71 5.98 84.15

Golden perch 0.34 0.00 0.49 4.13 88.28

Redfin perch 0.03 0.30 0.51 3.77 92.05



Bony herring 0.58 2.97 1.27 23.96 50.24

Flathead gudgeon 1.65 3.29 1.4 18.76 69

Carp gudgeon 1.91 3.08 1.32 15.86 84.86

Common carp 0.43 0.16 0.75 4.63 89.49

Golden perch 0.34 0.00 0.5 3.02 92.51



Carp gudgeon 1.91 1.22 1.34 17.68 49.45


Bony herring 0.58 1.47 1.09 16.19 82.49

Common carp 0.43 0.09 0.7 5.79 88.29

Golden perch 0.34 0.00 0.49 3.92 92.21


Bony herring 1.42 2.97 1.35 26.02 26.02


Carp gudgeon 1.93 3.08 1.29 18.33 67.59


Hardyhead 0.62 0.23 0.94 6.79 92.22



Bony herring 1.42 1.47 1.17 20.19 46.01


Carp gudgeon 1.93 1.22 1.31 18.89 84.18

Hardyhead 0.62 0.04 0.89 7.35 91.53

Bucater et al. 2009

37

Table 13. cont.


2007 2008 Mean dissimilarity =41.09

Bony herring 2.97 1.47 1.28 27.4 27.4

Carp gudgeon 3.08 1.22 1.45 25.37 52.77


Australian smelt 4.26 3.95 1 17.21 93.42

Table 14. SIMPER analysis for the comparison of assemblage structure between Lock1 and Lock 6, in 2005, 2006, 2007 and 2008. Results are based on fourth root-transformed of abundance dataset. CR (consistency ratio) indicates species distributions between sites, with larger values indicating greater consistency. The contribution (%) indicates the proportion of difference between sites (shown by PERMANOVA) attributable to individual species, a 90% cumulative contribution cut-off was also applied. Mean dissimilarity is expressed as a percentage ranging from 0% (identical) and 100% (totally dissimilar).


2005 Lock 1 Lock 6 Mean dissimilarity = 41.85

Bony herring 2.11 0.58 1.46 27.33 27.33


Carp gudgeon 2.35 1.91 1.13 15.82 62.46


Common Carp 0.11 0.43 0.73 7.18 84.09

Golden perch 0 0.34 0.5 4.87 88.96

Silver perch 0 0.27 0.5 3.96 92.92

2006 Lock 1 Lock 6 Mean dissimilarity = 40.86


Bony herring 2.22 1.42 1.26 23.74 51.6


Carp gudgeon 2.05 1.93 1.25 16.57 86.23

Hardyhead 0.13 0.62 0.96 7.18 93.41

2007 Lock 1 Lock 6 Mean dissimilarity =38.81

Bony herring 1.2 2.97 1.4 24.41 24.41



Carp gudgeon 3.31 3.08 1.29 21.86 91.14

2008 Lock 1 Lock 6 Mean dissimilarity =48.62


Carp gudgeon 3.31 1.22 1.49 22.94 53.64


Bony herring 1.95 1.47 1.25 15.13 88.67

Common Carp 0.85 0.09 0.79 7.12 95.79

Bucater et al. 2009

38

The NMS ordination of assemblage composition displayed a distinct separation of 2005

samples, whereas 2006, 2007, and 2008 were more interspersed (Figure 14). Axis 1 indicated a

strong negative correlation with discharge and water level and a positive correlation with

conductivity (Table 15). Significant positive correlations with axis 1 were identified for Australian

smelt, carp gudgeon and flathead gudgeon; hardyheads were also positively correlated,

although this correlation is relatively low (Table 15). These results indicate that these species

are negatively correlated to discharge and water levels, but positively correlated to conductivity.

Species with significant negative correlations to axis 1 were freshwater catfish, golden perch

and silver perch, however, the correlation coefficients are relatively low therefore, should be

interpreted cautiously.

Axis 2 was significantly positively correlated to temperature (Table 15). Australian smelt and

redfin perch had significant negative correlations to axis 2, indicating higher abundances during

lower temperatures. Bony herring, carp gudgeon, flathead gudgeon and hardyheads had

positive correlations with axis 2, indicating higher abundances occurred in conjunction with

warmer temperatures.

Figure 14. Non-metric MDS ordination (2-dimensional plot) for assemblage structure (stress 0.19) comparing 2005, 2006, 2007 and 2008, downstream of Locks 1 and 6. Superimposed vectors for the characterising environmental variables are presented and an R2 cut- off of 0.2 was applied. Refer to table 15 for species codes.

Bucater et al. 2009

39

Table 15. Pearson (r) and Kendall (τ) correlation coefficients between each NMS axis and the environmental variables and species. (Critical τ value for significance at 0.05 = 0.124). Bold text indicates significant correlations.

Axis 1 Axis 2

Species code r τ r τ

Discharge -0.531 -0.390 0.000 -0.016

Conductivity 0.446 0.332 0.128 0.074

Temperature -0.179 -0.128 0.303 0.358

Water level -0.252 -0.327 -0.232 -0.153

Australian smelt Ret sem 0.562 0.429 -0.573 -0.429

Bony herring Nem ere 0.167 0.089 0.670 0.551

Carp gudgeon Hyp spp 0.443 0.307 0.652 0.502

Flathead gudgeon Phi gra 0.716 0.584 0.452 0.292

Hardyhead Cra spp 0.253 0.179 0.242 0.200

Murray cod Mac pee -0.056 -0.057 0.067 0.042

Freshwater catfish Tan tan -0.164 -0.127 0.108 0.098

Golden perch Mac amb -0.288 -0.189 0.029 0.040

Silver perch Bid bid -0.276 -0.170 0.012 0.009

Common carp Cyp car 0.175 0.122 0.029 -0.035

Redfin perch Per flu 0.109 0.060 -0.136 -0.135

Bucater et al. 2009

40

4.3 LOWER LAKES LARVAL ASSEMBLAGE

4.3.1 Environmental variables (from TDS field measurements)

Temperature ranged between 18.5 and 21.0 oC during larval fish sampling at three sites.

Conductivity showed a gradual increase in sites further downstream, and was highest at

Clayton. Dissolved oxygen and pH were relatively consistent between all sites. All

environmental variables represent spot measurements and should be interpreted cautiously.

Table 16. Environmental variables dissolved oxygen (ppm), electrical conductivity (µS/cm at 25 oC), pH

and water temperature (oC) in the Lower Lakes sites.

DO (ppm) Cond (uS) pH Temp (oC)

Pomanda island 10.74 3,220 8.69 21.00

Point Sturt 10.25 5,670 8.81 18.50

Clayton 9.50 10,050 8.61 19.40

4.3.2 Catch summary

In the pilot sampling of the Lower Lakes sites a total of 5,502 larvae were captured, eight

species were collected, which include four freshwater and four estuarine (Table 17). The small-

bodied estuarine species were present in greater numbers at Point Sturt and Clayton, however,

at Pomanda Island the freshwater species were dominant (Table 17). Catch of larvae at Clayton

was highest accounting for 77.1% of the total catch, followed by Point Sturt and Pomanda

Island, with 19.7% and 3.2%, respectively (Table 17).

Table 17. Total number of fish larvae collected at the Lower Lakes sites in 2008.

Species Species group Common name Scientific name Pomanda

IslandPoint Sturt

Clayton Total

Freshwater Australian smelt Retropinna semoni 53 10 13 76

Bony herring Nematalosa erebi 2 0 0 2

Carp gudgeon Hypseleotris spp. 9 0 0 9

Flathead gudgeon Philypnodon grandiceps 94 1 3 98

Estuarine Common galaxias Galaxias maculatus 0 0 6 6

Lagoon goby Tasmanogobius lasti 17 771 1,488 2,276

Bridled goby Arenigobius bifrenatus 0 43 1,161 1,204

Unidentified goby Gobidae 0 261 1,570 1,831

Total 175 1,086 4,241 5,502

Percentage of total catch 3.2 19.7 77.1

Bucater et al. 2009

41

4.3.3 Spatial variation

There was significant spatial variation in assemblage structure between all sites in the Lower

Lakes (Table 18). These differences were reflected in the NMS ordination, which displayed a

distinct separation of Clayton, Pomanda Island and Point Sturt (Figure 15). Axis 1 had a strong

positive correlation with conductivity and a negative correlation with dissolved oxygen (Table

19). A significant negative correlation was identified with axis 1 and carp gudgeon. Significant

positive correlations with axis 1 were identified for common galaxias, lagoon goby, bridled goby

and gobidae (Table 19). The results indicate that these species are positively correlated to

conductivity. No significant correlation were identified for axis 2, suggesting additional factors

may be influencing this separation of samples (Table 19).

Table 18. One-way multivariate PERMANOVA for differences in assemblage structure among sites. Bold text indicates significant value.


Site 2 9666.3 0.004

Residual 6 1128.2

Bucater et al. 2009

42

Figure 15. Non-metric MDS ordination (2-dimensional plot) for assemblage structure (stress 0.03) comparing Clayton, Pomanda island and Point Sturt. Superimposed vectors for the characterising environmental variables are presented and an R2 cut- off of 0.2 was applied. Refer to table 19 for species codes. Table 19. Pearson (r) and Kendall (τ) correlation coefficients between each NMS axis (figure 14) and the environmental variables and species. (Critical τ value for significance at 0.05 = 0.602). Bold text indicates significant correlations.

Axis 1 Axis 2 Species code r τ r τ

Conductivity 0.863 0.886 -0.018 0.086

Dissolved oxygen -0.825 -0.886 -0.104 -0.086

pH 0.047 -0.340 -0.727 -0.526

Temperature -0.821 -0.340 0.734 0.588

Australian smelt Ret sem -0.756 -0.479 0.547 0.423

Bony herring Nem ere -0.633 -0.473 0.370 0.301

Carp gudgeon Hyp spp -0.718 -0.618 0.484 0.400

Flathead gudgeon Phi gra -0.883 -0.319 0.418 0.261

Common galaxias Gal mac 0.491 0.645 0.117 0.043

Lagoon goby Tas las 0.761 0.667 -0.341 -0.333

Bridled goby Are bit 0.608 0.899 0.249 0.087

Gobidae Gobidae 0.533 0.783 0.091 -0.145

Bucater et al. 2009

43

5 DISCUSSION

5.1 SPATIAL VARIATION

Significant spatial variation was identified in total abundance, species richness and assemblage

structure between sites downstream of Locks 1 and 6, in 2005, 2006, 2007 and 2008; and

Wellington, Lock 1 and Lock 6 in 2008. Differences in larval assemblage were also observed in

the pilot study between the Lower Lakes sites: Pomanda Island, Clayton and Point Sturt. These

variations were mainly driven by the presence of highly abundant species (i.e. small-bodied

freshwater species at all sites except Point Sturt and Clayton, where estuarine species were

most abundant). Downstream of Locks 1 and 6 the larval assemblage was comprised

exclusively of freshwater species. In contrast, downstream of Wellington and in other Lower

Lakes sites, estuarine species were present, and showed a gradual increase in numbers

downstream toward the Murray estuary. This is likely due to the increased conductivity and

their geographical location closer to the Murray barrages. The Lower Lakes sites were

characterised by early-summer spawners or species with protracted spawning season, as

sampling was conducted only once in early December, 2008.

Although differences in micro-habitats and water quality within each region are likely to

contribute to the differences in species abundances (i.e. condition being more or less suited to

specific species), spatial differences between Locks 1 and 6 identified in this study, are more

likely to be due to differences in the habitats of the regions surrounding these sites. The

floodplain region, surrounding Lock 6, is a wide floodplain (5-10 km), the main channel is

characterised by large woody debris (LWD) and macrophytes; it has a high diversity of off-

channel habitats including anabranch channels, billabongs and wetlands (Walker and Thoms

1993; Young 2001). The lowland gorge, surrounding Lock 1, is an incised section characterised

by limestone cliffs with a constrained floodplain (2-3 km); off-channel habitats are less diverse,

being restricted to wetlands, but there is a higher number in comparison to the floodplain region

(Walker and Thoms 1993; Young 2001). These habitat differences, particularly the higher

number of wetlands, may contribute to the higher abundances of the small-bodied species in

the gorge region, as these species are able to exploit both the wetlands and main channel

environments (CRCFE 2003; Humphries et al. 1999; King et al. 2003). This may also account

for the lower abundances, and indeed absence from 2006-2008, of large-bodied fish species

downstream of Lock 1, although further research is needed on habitat associations of larvae

and juveniles.

Observed spatial differences in the assemblage structure between the Lower Lakes sites, and

between Wellington and both Locks are likely to be driven by differences in conductivity.

Significant correlations were identified with conductivity, dissolved oxygen and pH for Australian

smelt, carp gudgeon, flathead gudgeon, common carp, redfin perch, common galaxias, lagoon

Bucater et al. 2009

44

goby, bridled goby and gobidae. Some species were more strongly correlated with increasing

temperature, however, is likely to be a result of the seasonal nature of fish spawning.

Freshwater fish in the Lower River Murray have been identified to have three spawning periods

within the season: spring, spring/summer and summer (Cheshire unpublished data). There is a

paucity of information on the dissolved oxygen and pH requirements on the early life stages of

many MDB fish species (Alton et al. In preparation), however, conductivity is most likely to be a

key driver for the observed spatial differences in this study.

While salinity tolerances of the early life stages for Australian native fish are still in need of

further investigation, recent research suggests most species have relatively high tolerances

(McNeil et al. in preparation), at least under relatively short term exposure. Adults have been

documented to have relatively high tolerance for freshwater species, which is likely due to

relatively recent divergences from marine ancestors (Williams and Williams 1991). Australian

smelt, carp gudgeon, flathead gudgeon, common carp and redfin perch all have relatively high

salinity tolerances and broad habitat associations. Given these tolerances they can be found

throughout the Lower River Murray in SA, in both main channel and off-channel habitats

including large floodplain lakes, billabongs, small terminal lakes and small and large

anabranches (Cadwallader and Backhouse 1983; Lloyd and Walker 1986; Mallen-Cooper

2001).

Estuarine species were only collected downstream of Wellington and in the Lower Lakes.

Common galaxias, a diadromous species, usually migrate downstream to spawn in autumn,

assuming a catadromous migration with a marine larval phase (Becker et al. 2005). Common

galaxias larvae collected downstream of Wellington are likely to have developed from a

landlocked population; given the lack of connectivity between the Lower Lakes and the

Coorong. Adult galaxias may make a short migration upstream to spawn in spring. These

results support findings by Pollard (1971) and Becker et al. (2005) in Victoria. The lagoon goby,

an estuarine species which is also able to complete its lifecycle in freshwater streams and lakes

(Lintermans 2007), was collected downstream of Wellington, among other unidentified gobidae

species. The Gobioidei is one of the most diverse groups of teleost, compromising

approximately 2,000 species and 270 genera (Gill et al. 1996), with very similar morphologies,

hence the difficulties associated with identification of individual species (Miskiewicz Pers.

Comm.).

Bucater et al. 2009

45

5.2 INTERANNUAL VARIATION DOWNSTREAM OF LOCKS 1 AND 6, FROM 2005-2008

Environmental variables: discharge, water level and conductivity differed between all years and

sites, as a direct result of the drought conditions. Discharge and water level were highest in

2005 and both variables are continuing to decrease downstream of Locks 1 and 6. Conductivity

almost doubled from 2005 to 2008, and is highest further downstream at Lock 1 and Wellington.

Despite these changes, the field measurements of temperature, conductivity, dissolved oxygen

and pH, were generally within the acceptable range for fish reproduction and survival during this

study (Boyd 1990).

The most distinct difference occurred in hydrology where discharge was different between 2005,

and 2006, 2007 and 2008. The increased discharge in 2005 was still well below that required to

flood over the river banks (~50,000 ML/d), thus, the flow event was categorised as a within

channel flow pulse (Puckridge et al. 1998). This increase occurred as a result of increased

inflows into the tributaries being enhanced by the release of 513GL as a part of the Barmah-

Millewa Environmental Water Allocation (BM-EWA) (King et al. 2008).

Inter-annual variation was identified in the total abundance and assemblage structure

downstream of Locks 1 and 6, over the four sampling years. The most abundant species were

Australian smelt, bony herring, carp gudgeon and flathead gudgeon, which is consistent with

results within the Chowilla Anabranch system, South Australia, and a study in the Barmah-

Millewa region, mid Murray (King et al. 2007; Leigh et al. 2008).

A decreased abundance of small-bodied species was also documented in 2008, after a peak in

2007, suggesting that while initially these species may benefit from the low flow conditions,

there may be a negative effect of long term low flow conditions. Inter-annually, species richness

was highest in 2005, due to the presence of golden perch and silver perch, which were absent

in all other years. Species richness was lowest in 2008, specifically due to the absence of

Murray cod larvae. The abundance of large-bodied larval fish (Murray cod, silver perch and

golden perch) decreased each year. Freshwater catfish was the only large-bodied species

present in 2008.

Changes in the larval assemblages between years were variously correlated to discharge, water

level and conductivity. The negative correlation between discharge and conductivity should also

be highlighted. At present, none of the values for conductivity measured across the years are

outside the suitable range for growth and survival of larvae (McNeil et al. in preparation).

Therefore, conductivity is unlikely to be shaping the changes in the assemblage and the

response of individual species in each year. It is much more likely to be the relationship

between life history strategies of native fish and the varying hydrology (Humphries et al. 1999).

Bucater et al. 2009

46

Using correlations between changes in larval abundance and environmental variables three

distinct responses were identified:

1) Increased flow response: larval abundances positively correlated to discharge and water

level (and negatively correlated to conductivity). Including: golden perch, silver perch and

freshwater catfish.

2) Decreased flow response: larval abundances negatively correlated to discharge and water

level (and positively to conductivity). Including: Australian smelt, flathead gudgeons, carp

gudgeons and hardyheads (consistent with the LFRH, Humphries et al. 1999).

3) Temperature response: larval abundances strongly correlated to temperature. Including most

species, however, bony herring, carp gudgeons and redfin perch were more strongly influenced

by lower temperature than other variables.

There was some overlap between groups two and three for most species, however, bony

herring and redfin perch were the only species exclusively correlated to low temperature. Carp

gudgeon was most strongly correlated to changes in temperature, however, discharge, water

level and conductivity also had significant influence. Temperature is frequently identified as a

strong driver within fish spawning patterns simply as a result of the seasonal nature of fish

spawning; freshwater fish in the Lower Murray have been identified to have three spawning

periods within the season, spring, spring/summer and summer (Cheshire unpublished data).

In previous studies, small-bodied species have been identified to respond positively to low flow

conditions (Cheshire and Ye 2008a), as described by the low flow recruitment hypothesis

(Humphries et al. 1999). Despite the suggestion that the abundance of small-bodied species are

positively associated with low flows and high conductivities, the decrease in abundance during

2008 may suggest that as the initial response of these species to low flows may not be

sustainable under continued drought conditions.

There are also potential disadvantages for species spawning and recruiting under low flow

conditions such as decreased water quality, increased predation, increased competition, and

potentially decreased growth rates and body conditions (Copp 1992; Heagney 2008; Humphries

et al. 1999). This may be reflected in subsequent recruitment into the juvenile/adult populations

as small-bodied species are generally short lived, the prolonged low flow conditions may have

contributed, in part, to the decreased abundance of some species in 2008.

Large-bodied iconic species were collected in low numbers throughout the study, therefore it is

difficult to determine patterns in abundance in association with environmental conditions.

Notably, flow-cued spawners, golden perch and silver perch were only present in 2005, when

an increase in discharge into South Australia was observed. The abundances of golden perch,

Bucater et al. 2009

47

silver perch and freshwater catfish were positively correlated with discharge and water level,

although this must be interpreted cautiously, it should not be discounted.

These results correspond with other studies that suggested spawning of golden perch and silver

perch only occur under within channel flow pulses and over bank floods, and spawning may be

withheld if these conditions are not met (Cheshire and Ye 2008a; Harris and Gehrke 1994; Lake

1967; Leigh et al. 2008; Mackay 1973; Mallen-Cooper and Stuart 2003; Reynolds 1983;

Rowland 1983). Murray cod spawn at the same time of the year regardless of variations in flow

discharge (Cheshire and Ye 2008a; Humphries 2005; Koehn and Harrington 2005; Koehn and

Harrington 2006; Leigh et al. 2008). The presence of Murray cod larvae in this study was

variable; in 2005 they were present downstream of Lock 1 and downstream of Lock 6 from 2005

through to 2007, but were not recorded in 2008. This may be due to low abundances and the

patchy distribution of larvae, it is possible that the abundance decreased further in 2008 and our

sampling was not sufficient to collect any specimens. For example, Murray cod larvae were

collected in the Chowilla Anabranch system during 2008 (Leigh unpublished data), indicating

Murray cod spawned in the main channel upstream of Lock 6 and within the Chowilla

Anabranch system.

Despite, not being specifically aimed at increasing flows in the Lower River Murray, the BM-

EWA also provided benefit for large-bodied species throughout the Lower Murray. The

response of the large bodied species (particularly, golden perch and silver perch) in this study

are similar, although to a lesser degree, to those from the Barmah-Millewa Forest, where the

EWA was targeted (King et al. 2008). The increase in abundances and/or presence of the large-

bodied species in conjunction with the flow pulse year, and the decrease and/or absence of

these species in subsequent drought years, further reinforces the need to consider

environmental water allocations for South Australia in an effort to maintain/enhance key native

fish populations.

Bucater et al. 2009

48

6 KEY FINDINGS

• Discharge, water level and conductivity differed between years, as a direct result of the

drought conditions.

• Conductivity was negatively correlated to flow and water level, and was highest

downstream of Lock 1 and Wellington.

• Fifteen species of fish were collected as larvae, comprising nine native freshwater, four

native estuarine and two exotic freshwater species.

• The freshwater fish assemblage was comprised of highly abundant small-bodied species

and some large-bodied iconic species. The estuarine species were only collected during

2008, in the new sites, downstream of Wellington and in the Lower Lakes sites.

• Significant spatial variation was identified for total abundance, species richness and

assemblage structure between sites downstream of Lock 1, Lock 6 and Wellington in

2008. Spatial variation was correlated to temperature, pH and conductivity.

• The greatest differences were between the assemblage downstream of Lock 1 and

those from sites downstream of Lock 6 and Wellington, due to differences in the

abundance of the small-bodied freshwater species.

• Spatial differences in the structure of assemblages between the Lower Lakes sites are

likely driven by differences in conductivity.

• Inter-annual and spatial variation in the total abundance, species richness and

assemblage structure was identified downstream of Locks 1 and 6, over the four

sampling years.

• Inter-annual variation between years was most strongly correlated to differences in

hydrology (discharge and water level).

• Spatial variation was likely due to differences in habitat regions surrounding the study

sites.

• There were three distinct larval responses identified:

o Increased flow response: Larval abundances positively correlated to

discharge and water level (and negatively correlated to conductivity). Species

include Golden perch, Silver perch and Freshwater catfish.

Bucater et al. 2009

49

o Decreased flow response: Larval abundances negatively correlated to

discharge and water level (and positively correlated to conductivity). Species

include Australian smelt, Flathead gudgeons, Carp gudgeons and Hardyheads.

This response follows the Low Flow Recruitment Hypothesis of Humphries et al.

(1999).

o Temperature response: Larval abundances strongly correlated to

temperature. This applied to most species, however strong correlations were

found for Bony herring, Carp gudgeons and Redfin perch. Only Bony herring and

Redfin perch showed responses exclusively to temperature. Carp gudgeons

were most strongly correlated to temperature; however discharge, water level

and conductivity also had significant influences.

• Abundance of larvae of the large-bodied fish species has declined each year since

2005. However, due to the very low abundances throughout the study, this needs further

research with targeted sampling.

• The large-bodied species, golden perch and silver perch, being flow-cued spawners,

were only present during the higher discharge year of 2005. This finding reinforces the

need to consider environmental water allocations for the Lower Murray.

• Murray cod larvae were found below Lock 1 in 2005 only and below Lock 6 in 2005,

2006 and 2007. No larvae were detected in 2008.

• Decreased abundance of small-bodied species downstream of Locks 1 and 6 in 2008

compared to the peak 2007 suggests that whilst low flow conditions may benefit these

species initially, there may be a negative effect as low flow conditions continue.

• Under low flow conditions, abundance and distribution of larvae of large-bodied native

species is decreased. A within channel pulse, as occurred in 2005, may be sufficient to

provide suitable conditions for spawning of key large-bodied native species.

• Upstream environmental water allocations may provide indirect benefits for native fish

downstream in the Lower River Murray.

Bucater et al. 2009

50

7 MANAGEMENT IMPLICATIONS

The natural flow regime of the Lower River Murray in SA has been greatly impacted by river

regulation (Maheshwari et al. 1995). Consequently, this has resulted in significant

environmental degradation (Arthington and Pusey 2003; Walker 1985; Walker and Thoms

1993), and detrimental effects upon aquatic organisms (Gehrke et al. 1995; Humphries et al.

2002). Modification of the hydrology within a system can have cascading effects, potentially

influencing water quality, energy sources, physical habitat and biotic interactions, resulting in an

overall reduced ecological integrity (Poff et al. 1997). In addition, the drought, which began in

2002, may increase the impact of a changed flow regime on the native fish and overall

ecological health of the Lower River Murray.

This study suggests that protracted low flow conditions may affect spawning success and/or

larval survivorship of freshwater catfish, Murray cod, golden perch and silver perch. Given their

significant conservation value throughout the MDB, these species should be of greatest

concern. Under current low flow conditions, species richness, abundance and distribution of the

larvae of large-bodied native species appears to be decreasing. Furthermore, a within channel

flow pulse, as occurred in 2005, may be sufficient to provide suitable conditions for spawning

and enhanced larval survivorship of the large-bodied native species. Further support for

environmental flows can be seen in this study where the within channel flow pulse that occurred

in South Australia during 2005 was in part due to the release of the Barmah-Millewa

environmental water allocation (King et al. 2008). The small-bodied species are all relatively

short-lived (1-3 yrs), while species with short generation times are likely to be most seriously

effected by changes to the environment, these species have demonstrated the ability to

respond positively to low flow conditions initially. Following the decline in abundance of all

species in 2008, however, it is imperative to continue monitoring these species, to ensure that

continued prolonged periods of low flow do not have a detrimental effect on the recruitment of

these species, as time progresses. Regardless of the ability for these species to tolerate low

flows, restoring the River Murray to a more natural flow regime is important for all native

species, and the overall ecological health of the river. Additionally, as discharge continues to

decrease, conductivity is increasing, while this is not yet of significant concern for larval

assemblages, if conductivity continues to increase, it has the potential to restructure the

communities of the River Murray, particularly downstream of Lock 1.

Providing a more “natural” flow regime in regulated rivers, through environmental water

allocations (EWA’s), is one of the potential management options for the restoration of native fish

(Marchetti and Moyle 2001; Arthington et al. 2006). There are few applied examples and there

have been varied levels of success attributed to manipulations of flows (e.g. Nesler et al. 1988;

Travinchek et al. 1995; King et al. 1998; Freeman et al. 2001). However, in a recent study,

Bucater et al. 2009

51

golden perch, silver perch and Murray cod have all been shown to have increased spawning

and recruitment success during a managed flood (in 2005), using an environmental water

allocation (King et al. 2008). These studies highlight the need to consider attributes of the flow

regime, including timing and duration, within individual river systems in order to manage flows

for improved fish populations. King et al. (2003) suggested that for successful spawning and

recruitment of fish during flood conditions a range of environmental conditions would need to

occur. These included the coupling of high flows and temperatures, a predictable flood pulse,

slow rate of rise and fall, a duration which spans months, and that the magnitude is sufficient to

inundate the floodplain. However, all of these factors require further research before optimal

management strategies can be outlined.

Bucater et al. 2009

52

8 RECOMMENDATIONS FOR FUTURE RESEARCH

The significant decrease in the abundance of larvae of some small-bodied species, and

particularly Australian smelt, downstream of Lock 1 requires further monitoring to determine if

this is natural inter-annual variation or a continuing problem as a result of changing conditions

due to prolonged low flows.

Recruitment studies for the small-bodied native species, assessing age structures and

identifying years with strong recruitment would yield significant benefit in determining the effect

of prolonged low flows on recruitment of these species.

Continued monitoring is required to determine if the variation in presence of Murray cod and

freshwater catfish larvae downstream of Lock 1 in 2006, 2007 and 2008, and absence of Murray

cod in 2008 downstream of Lock 6, is an ongoing problem, or an artefact of sampling species

with low abundances of larvae.

Further investigations into the age structures of the large-bodied native species will help identify

years with strong recruitment. Comparing strong year classes to environmental variables should

also be considered in an effort to increase our understanding of factors affecting the larval

survivorship and to identify key factors that drive recruitment success.

More comprehensive understanding of the influence of pH and dissolved oxygen on early life

history stages of MDB fish species is required to better understand the potential implications of

decreased water quality in low discharge years.

Fish spawning and recruitment processes in the Lower Lakes are relatively unknown. Further

research is suggested to investigate these key processes and monitor the changes in

assemblage structure under the drought conditions, especially in regard to the impacts of the

continued low flows, low water levels and increasing conductivity.

Bucater et al. 2009

53

9 REFERENCES

Alton LA, Cheshire KJ, Westergaard S and Ye Q (In preparation) Influences of Salinity and Water Quality on the Recruitment Dynamics of Fishes in the Lower River Murray – Larval Distribution in Relation to Habitats: A Literature Review. In 'Influence of Salinity, Water Quality and Hydrology on Early Life History of Fishes in the Lower River Murray. A report in preparation for the Centre for Natural Research Management.' (Eds Q Ye, K Cheshire and D McNeil). (South Australian Research and Development Institute, Aquatic Sciences Adelaide, SA). Anderson MJ (2001) A new method for non-parametric multivariate analysis of variance. Austral Ecology 26, 32-46. Anderson MJ (2005) 'PERMANOVA: a FORTRAN computer program for permutational multivariate analysis of variance.' (Department of Statistics: University of Auckland: New Zealand) Arthington AH, Pusey BJ (2003) Flow restoration and protection in Australian rivers. River Research and Applications 19, 377-395. Arthington AH, Bunn SE, Poff LN, Naiman RJ (2006) The challenge of providing environmental flow rules to sustain river ecosystems. Ecological Applications 16, 1311-1318. Becker A, Laurenson LJB, Jones PL, Newman DM (2005) Competitive Interactions between the Australian Native Fish Galaxias maculatus and the Exotic Mosquitofish Gambusia holbrooki in a Series of Laboratory Experiments. Hydrobiologia 549, 187-196. Bertozzi T, Adams M, Walker KF (2000) Species boundaries in carp gudgeons (Eleotrididae: Hypseleotris) from the River Murray, South Australian: evidence for multiple species and extensive hybridization. Marine and Freshwater Research 51, 805-815. Boyd CE (1990) 'Water quality in ponds for aquaculture.' (Brimingham Publishing Co.: Birmingham, Alabama) Bray J, Curtis J (1957) An ordination of the upland forest communities of Southern Wisconsin. Ecological Monographs 27, 325-349. Cadwallader PL, Backhouse GN (1983) 'A Guide to the freshwater fish of Victoria.' (Victorian Government Printing Office: Melbourne, VIC) Clarke K (1993) Non-parametric multivariate analysis of changes in community structure. Australian Journal of Ecology 18, 117-143. Copp G (1992) Comparative microhabitat use of cyprinid larvae and juveniles in a lotic floodplain channel. Environmental Biology of Fishes 33, 181-193.

Bucater et al. 2009

54

CRCFE (2003) 'Ecological assessment of environmental flow reference points for the River Murray system: Interim Report.' Cooperative Research Centre for Freshwater Ecology Prepared by the Scientific Reference Panel for the Murray-Darling Basin Commission, Living Murray Initiative. DWLBC (2007) 'Dredging and boating access continue through summer.' Government of South Australia. Freeman MC, Bowen ZH, Bovee KD, Irwin ER (2001) Flow and habitat effects on juvenile fish abundance in natural and altered flow regimes. Ecological Applications 11, 179-190. Gehrke PC, Brown P, Schiller C, Moffatt DB, Bruce AM (1995) River regulation and fish communities in the Murray- Darling River System, Australia. Regulated Rivers: Research & Management 11, 363-375. Gill HS, Wise BS, Potter IC, Chaplin JA (1996) Biannual spawning periods and resultant divergent patterns of growth in the estuarine goby Pseudogobius olorum: Temperature induced? Marine Biology 125, 453-466. Harris JH, Gehrke PC (1994) Development of predictive models linking fish population recruitment with stream flow. In 'Australian Society for Fish Biology Workshop'. Perth. (Ed. DA Hancock) pp. 195-97. (Australian Society for Fish Biology, Sydney) Heagney E (2008) 'Growth and condition of Australian smelt and bony bream in the Gwidyer wetlands: an otolith based analysis ', Final report to the Rivers & Wetlands Unit, NSW Department of Environment and Climate Change. Humphries P (2005) Spawning time and early life history of the Murray cod, Maccullochella peelii peelii (Mitchell) in an Australian river. Environmental Biology of Fishes 72, 393-407. Humphries P, King AJ, Koehn JD (1999) Fish flows and flood plains: links between freshwater fishes and their environment in the Murray-Darling River system, Australia. Environmental Biology of Fishes 56, 129-151. Humphries P, Serafini LG, King AJ (2002) River regulation and fish larvae: variation through space and time. Freshwater Biology 47, 1307-1331. King AJ, Humphries P, Lake PS (2003) Fish recruitment on floodplains: the roles of patterns of flooding and life history characteristics. Canadian Journal of Fisheries and Aquatic Sciences 60, 773-786. King AJ, Tonkin Z, Mahoney J (2007) 'Assessing the effectiveness of environmental flows on fish recruitment in Barmah-Millewa Forest.' Arthur Rylah Institute for Environmental Research, DSE, MDBC Project No. BMF 2004.09, Heidleberg, Vic.

Bucater et al. 2009

55

King AJ, Tonkin Z, Mahoney J (2008) Environmental flow enhances native fish spawning and recruitment in the Murray River, Australia. River Research and Applications. Published online in Wiley InterScience (DOI:10.1002/rra.1209) King J, Cambray JA, Impson ND (1998) Linked effects of dam-released floods and water temperature on spawning of the Clanwilliam yellowfish (Barbus capensis). Hydrobiologia 384, 245-265. Koehn JD, Harrington DJ (2005) Collection and distribution of the early life stages of the Murray cod (Maccullochella peelii peelii) in a regulated river. Australian Journal of Zoology 53, 137-144. Koehn JD, Harrington DJ (2006) Environmental conditions and timing for the spawning of Murray cod (Maccullochella peelii peelii) and the endangered trout cod (M. macquariensis) in Southeastern Australian Rivers. River Research and Applications 33, 327-342. Lake JS (1967) Rearing experiments with five species of Australian freshwater fishes: II. Morphogenesis and ontogeny. Australian Journal of Marine and Freshwater Research 18, 155-173. Leigh SJ, Zampatti BP, Nicol JM (2008) 'Spatial and temporal variation in larval fish assemblage structure in the Chowilla Anabranch system: with reference to water physico-chemistry and stream hydrology.' South Australian Research and Development Institute (SARDI) Aquatic Sciences, SARDI Aquatic Sciences Publication No: F2008/000051-1, Adelaide, SA. Lintermans M (2007) 'Fishes of the Murray-Darling Basin: an introductory guide.' (Murray-Darling Basin Commission) Lloyd LN, Walker KF (1986) Distribution and conservation status of small freshwater fish in the River Murray, South Australia. Transactions of the Royal Society of South Australia 110, 49-57. Mackay NJ (1973) Histological changes in the ovaries of the golden perch, Plectroplites ambiguus, associated with the reproductive cycle. Australian Journal of Marine and Freshwater Research 24, 95-101. Maheshwari BL, Walker KF, McMahon TA (1995) Effects of regulation on the flow regime of the River Murray, Australia. Regulated Rivers: Research & Management 10, 15-38. Mallen-Cooper M (2001) 'Fish passage in off-channel habitats of the lower River Murray.' Fishway Consulting Services, NSW. Mallen-Cooper M, Stuart IG (2003) Age, growth and non-flood recruitment of two potamodromous fishes in a large semi-arid/temperate river system. River Research and Applications 19, 697-719. Marchetti MP, Moyle PB (2001) Effects of flow regime on fish assemblages in a regulated California stream. Ecological Applications 11, 530-539.

Bucater et al. 2009

56

McCune B, Mefford MJ (1999) PC-ORD. Multivariate Analysis of Ecological Data. In. (Ed. M Software). (Gleneden, Oregon, USA) McNeil DG, Westergaard S, Alton LA (in preparation) Salinity tolerances of eggs, larvae and juveniles, for native fish in the Lower River Murray, South Australia. In 'The influence of environmental variables on larval and juvenile stages of native fish in the Lower River Murray. A report in preparation for the Centre for Natural Research Management. '. (Eds Q Ye). (South Australian Research and Development Institute, Aquatic Sciences: Adelaide) MDBC (2008) 'River Murray system drought update number 13.' Murray-Darling Basin Commission, Canberra, ACT. Meredith SN, Gawne B, Sharpe C, Whiterod N, Conallin A, Zukowski S (2002) 'Dryland Floodplain Ecosystems: influence of flow patterns on fish production.' Murray Darling Freshwater Research Centre, report no. 1/2002, Mildura. Neira FJ, Miskieweicz AG, Trnski T (1998) 'Larvae of temperate Australian fishes: laboratory guide for larval fish identification.' (University of Western Australia Press: Nedlands, WA) Nesler TP, Muth RT, Wasowicz AF (1988) Evidence for baseline flow spikes as spawning cues for Colorado squawfish in the Yamba River, Colorado. American Fisheries Society Symposium 5, 68-79. Poff NL, Allan JD, Bain MB, Karr JR, Prestegaard KL, Richter BD, Sparks RE, Stromberg JC (1997) The natural flow regime: A paradigm for river conservation and restoration. Bioscience 47, 769-784. Pollard DA (1971) The biology of a landlocked form of the normally catadromous salmoniform fish Galaxia maculatus (Jenyns). Australian Journal of Marine and Freshwater Research 22, 91-123. Puckridge JT, Walker KF (1990) Reproductive biology and larval development of a gizzard shad Nematalosa erebi (Dorosomatinae: Teleostei), in the River Murray, South Australia. Australian Journal of Marine and Freshwater Research 41, 695-712. Puckridge JT, Sheldon F, Walker KF, Boulton AJ (1998) Flow variability and the ecology of large rivers. Marine and Freshwater Research 49, 55-72. Reynolds LF (1983) Migration patterns of five fish species in the Murray-Darling River System. Australian Journal of Marine and Freshwater Research 34, 857-71. Rowland SJ (1983) The hormone-induced ovulation and spawning of the Australian freshwater fish golden perch, Macquaria ambigua (Richardson) (Percicithyidae). Aquaculture 35, 221-238. Serafini LG, Humphries P (2004) 'Preliminary guide to the identification of larvae of fish, with a bibliography of their studies, from the Murray-Darling Basin.' Cooperative Research Centre for

Bucater et al. 2009

57

Freshwater ecology, Murray-Darling Freshwater Research Centre, Albury and Monash University, Clayton, Identification and Ecology Guide No. 48. Travinchek VH, Bain MB, Maceina MJ (1995) Recovery of a warm water fish assemblage after initiation of a minimum-flow release downstream from a hydroelectric dam. Transactions of the American Fisheries Society 124, 836-844. Walker KF (1985) A review of the ecological effects of river regulation in Australia. Hydrobiologia 125, 111-129. Walker KF (2006) Serial weirs cumulative effects: the Lower River Murray, Australia. In 'Ecology of desert rivers'. (Ed. RT Kingsford) pp. 248-279. (Cambridge University Press: Cambridge) Walker KF, Thoms MC (1993) Environmental effects of flow regulation on the Lower River Murray, Australia. Regulated Rivers: Research & Management 8, 103-119. Williams MD, Williams WD (1991) Salinity tolerances of four species of fish from the Murray-Darling River system. Hydrobiologia 210, 145-160. Ye Q, Cheshire KJ, Fleer D (2008) 'Recruitment of golden perch and selected large-bodied fish species following the weir pool manipulation in the River Murray, South Australia.' South Australian Research and Development Institute (SARDI), Aquatic Sciences, SARDI research report series number: 303, SARDI Aquatic Sciences Publication Number F2008/000606-1, Adelaide, SA. Young WJ (Ed.) (2001) 'Rivers as ecological systems: The Murray-Darling Basin.' (Murray Darling Basin Commission: Canberra, ACT)

10 PERSONAL COMMUNICATION

Anthony Miskiewicz (2009) - Environment and Recreation Planning Manager. Wollongong City Council

fish spawning in the lower river murray icon sites, south australia: with reference … ·...

Documents