Movement and spawning of Murray cod (Maccullochella peelii) and golden perch (Macquaria ambigua ambigua) in response to a small-scale flow
manipulation in the Chowilla Anabranch system
S. J. Leigh and B. P. Zampatti
SARDI Publication No. F2010/000646-1 SARDI Research Report Series No. 536
SARDI Aquatic Sciences PO Box 120 Henley Beach SA 5022
June 2011
Movement and spawning of Murray cod (Maccullochella peelii) and golden perch (Macquaria ambigua ambigua) in response to a small-scale flow manipulation in the Chowilla Anabranch system
S. J. Leigh and B. P. Zampatti
SARDI Publication No. F2010/000646-1 SARDI Research Report Series No. 536
1 mm
June 2011 This Publication may be cited as: Leigh, S.J. and Zampatti, B.P (2011). Movement and spawning of Murray cod (Maccullochella peelii) and golden perch (Macquaria ambigua ambigua) in response to a small-scale flow manipulation in the Chowilla Anabranch system. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2010/000646-1. SARDI Research Report Series No. 536. 45pp.
South Australian Research and Development Institute SARDI Aquatic Sciences 2 Hamra Avenue West Beach SA 5024
Telephone: (08) 8207 5400 Facsimile: (08) 8207 5406 http://www.sardi.sa.gov.au
DISCLAIMER 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 Chief, Aquatic Sciences. Although all reasonable efforts have been made to ensure quality, SARDI Aquatic Sciences does not warrant that the information in this report is free from errors or omissions. SARDI Aquatic Sciences 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. The contents of this publication do not purport to represent the position of the copyright holders or MDBA as the funding agency in any way and are presented for the purpose of informing and stimulating discussion for improved management of Basin's natural resources.
© 2011 SARDI & MDBA This work is copyright. Graphical and textual information in the work (with the exception of photographs and logos) may be stored, retrieved and reproduced in whole or in part, provided the information is not sold or used for commercial benefit and its source is acknowledged. Reproduction for other purposes is prohibited without prior permission of the copyright holders. To the extent permitted by law, the copyright holders 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.
Printed in Adelaide: June 2011
SARDI Publication No. F2010/000646-1 SARDI Research Report Series No. 536
Author(s): S. J. Leigh and B. P. Zampatti
Reviewer(s): C. Bice (SARDI), M. Schutlz (DFW), D.Meyers and D.Hohnberg (MDBA)
Approved by: Dr. J. Nicol A/Principal Scientist – Inland Waters & Catchment Ecology
Signed:
Date: 1 June 2011
Distribution: MDBA, DFW, SAASC Library, University of Adelaide Library, Parliamentary Library, State Library and National Library
Circulation: Public Domain Movement and spawning of Murray cod and golden perch in response to flow manipulation
Table of Contents
List of Figures ...... ii
List of Tables ...... iv
Acknowledgements ...... 1
Executive Summary ...... 2
1 Introduction ...... 4
2 Methods ...... 7
2.1 Movement ...... 7 2.2 Spawning ...... 13
3 Results ...... 16
3.1 Movement ...... 16 3.2 Spawning ...... 33
4 Discussion ...... 36
4.1 Movement ...... 36 4.2 Spawning ...... 38
5 Conclusions ...... 41
6 References ...... 42
SARDI Aquatic Sciences i Movement and spawning of Murray cod and golden perch in response to flow manipulation
List0B of Figures Figure 1 Map showing the location of the impact and control site for the movement study...... 7 Figure 2 Location of the larval sampling sites in the Chowilla system...... 13 Figure 3 Discharge (ML d-1, solid line) and stage height (m, dotted line) measured in a) Little Slaney Creek above the Salt Creek / Slaney Creek junction and b) lower Slaney Creek from October 2007 – October 2009...... 17 Figure 4 Water velocity transects measured in a) Little Slaney Creek during the high flow period, b) Little Slaney Creek during the low flow period and c) the Murray River main channel under ‘entitlement flow’ conditions...... 18 Figure 5 Water velocity (m s-1, mean + standard error) measured at the impact and control sites during the high flow (hatched bars) and low flow (white bars) periods...... 19 Figure 6 Maximum water depth (m, mean + standard error) measured at the impact and control sites during the high flow (hatched bars) and low flow (white bars) periods...... 20 Figure 7 Radio-tagged Murray cod movements for the period November 2008 – August 2009 for those fish present in the impact site at the beginning of the high flow period (1st November 2008). 0 m represents the original tagging location...... 22 Figure 8 Radio-tagged Murray cod movements for the period November 2008 – August 2009 for those fish present in the control site at the beginning of the high flow period (1st November 2008). 0 m represents the original tagging location...... 23 Figure 9 Discharge in Little Slaney Creek from 1st November 2008 – 31st August 2009 and timing of Murray cod movement out of the impact site. Arrow indicates date when additional fish were tagged, number under arrow indicates the number of fish that were tagged...... 24 Figure 10 Discharge in lower Slaney Creek from 1st November 2008 – 31st August 2009 and timing of Murray cod movement out of the control site. Arrow indicates date when additional fish were tagged, number under arrow indicates the number of fish that were tagged...... 24 Figure 11 Cumulative distance (m, mean + standard error) moved by Murray cod at the impact and control sites during the high flow (hatched bar) and low flow (white bar) flow periods...... 25 Figure 12 Maximum distance (m, mean + standard error) moved by Murray cod at the impact and control sites during the high flow (hatched bar) and low flow (white bar) flow periods...... 25 Figure 13 Radio-tagged golden perch movements for the period November 2008 – August 2009 for those fish present in the impact site at the beginning of the high flow period (1st November 2008). 0 m represents the original tagging location...... 28
SARDI Aquatic Sciences ii Movement and spawning of Murray cod and golden perch in response to flow manipulation
Figure 14 Radio-tagged golden perch movements for the period November 2008 – August 2009 for those fish present in the control site at the beginning of the high flow period (1st November 2008). 0 m represents the original tagging location ...... 29 Figure 15 Discharge in Little Slaney Creek from 1st November 2008 – 31st August 2009 and timing of golden perch movement out of the impact site...... 30 Figure 16 Discharge in lower Slaney Creek from 1st November 2008 – 31st August 2009 and timing of golden perch movement out of the control site. Arrow indicates the date when additional fish were tagged, number under arrow indicates the number of fish tagged...... 30 Figure 17 Cumulative distance (m, mean + standard error) moved by golden perch at the impact and control sites during the high flow (hatched bar) and low flow (white bar) flow periods...... 31 Figure 18 Maximum distance (m, mean + standard error) moved by golden perch at the impact and control sites during the high flow (hatched bar) and low flow (white bar) flow periods...... 31 Figure 19 Discharge (ML d-1, solid line) and stage height (m, dotted line) in Little Slaney Creek from June 2007 – June 2009. Arrows indicate the larval sampling period in each year...... 33 Figure 20 Automated discharge (ML d-1) in Little Slaney Creek (dashed line) and lower Slaney Creek (solid line) and discharge calculated from manually read gauge heights in Little Slaney Creek (open circles) and lower Slaney Creek (black circles) from April 2007 – July 2008. ... 34 Figure 21 Surface water temperature (°C, solid line) measured in Chowilla Creek and stage height (m, dotted line) measured in Little Slaney Creek from June 2007 – June 2009. The timing of the presence of Murray cod larvae captured within the Chowilla Anabranch system during the spring/summer 2007/2008 and 2008/2009 season is represented by hatched bars...... 35
SARDI Aquatic Sciences iii Movement and spawning of Murray cod and golden perch in response to flow manipulation
List1B of Tables Table 1 Biological details, capture locations and transmitter specifications for golden perch and Murray cod implanted with radio transmitters...... 11 Table 2 Sites sampled for larval fish in the Chowilla system during spring/summer 2007/2008 and 2008/2009...... 14 Table 3 Results of global and pair-wise PERMANOVA comparing water velocity measured at impact and control site during each flow period (high and low). Significant values are highlighted in bold (P < 0.05)...... 19 Table 4 PERMANOVA results of pair-wise tests comparing maximum water depth measured at the impact and control sites during each flow period (high and low). Significant values are highlighted in bold (P < 0.05)...... 20 Table 5 Results of PERMANOVA comparing cumulative and maximum distances moved by Murray cod in the impact and control sites during high and low flow periods...... 26 Table 6 Results of PERMANOVA comparing both cumulative and maximum distances moved by golden perch in the impact and control sites during high and low flow periods...... 32 Table 7 Raw (absolute abundance) and CPUE (standardised abundance, number of fish per 1000 m3 (drift nets) + number of fish per 12 hour period (light traps)) of Murray cod larvae captured within the Chowilla Anabranch system during spring/summer 2007/2008 and 2008/2009. NS = not sampled...... 35
SARDI Aquatic Sciences iv Movement and spawning of Murray cod and golden perch in response to flow manipulation
Acknowledgements2B We would like to thank a number of SARDI staff for their help with the field components of this project, namely Ian Magraith, Paul Jennings, Neil Wellman, Phillipa Wilson and Chris Bice. We also thank Phillipa Wilson, Annelise Wiebkin and Neil Wellman for sorting larval drift net samples and Ian Magraith for entering and preparing fish movement data for analysis.
Thanks to Darryl Jones (SA Water) for facilitating a series of flow manipulations in Slaney Creek via the altered operation of Slaney Creek Weir and to Robbie Bonner, Warren Beer and Tony Wade (SA Water) for manipulating stop logs at the weirs.
Tim Branford and Paul Searle from the Department for Water (DFW), formerly the Department of Water, Land and Biodiversity Conservation (DWLBC) Knowledge and Information Division, undertook velocity measurements and provided the discharge and stage height data used in this report. Funding for this project was provided by The Living Murray (TLM) Initiative of the Murray Darling Basin Authority (MDBA) and the project was supported and managed by Mark Schultz and Tony Herbert (DFW), formerly the South Australian Murray Darling Basin Natural Resource Management Board (SAMDBNRMB).
SARDI Aquatic Sciences 1 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Executive3B Summary Anthropogenic alteration of flow may alter the abundance, diversity and structure of fish communities by changing the physical and hydraulic habitat available to fish and varying conditions that facilitate spawning and recruitment. Regulation of the lower Murray River has resulted in a loss of ecologically important components of the natural flow regime and homogenisation of aquatic habitats. The Chowilla Anabranch and Floodplain system is a significant ecological asset of the Murray-Darling Basin and contains hydraulically diverse aquatic habitats ranging from lotic (flowing) creeks to backwaters and large lake systems. Nevertheless, the Chowilla floodplain has become increasingly degraded and in order to maintain and restore the health of this region a number of interventions have been proposed, including alternative water delivery options and new regulating structures (MDBC 2006). These interventions have the potential to alter the existing connectivity and flow dynamics within the Chowilla system and hence the aquatic mesohabitat complexity and abundance and distribution of fish.
The broad aim of this study was to improve our understanding of the ecology of Murray cod and golden perch in the Chowilla system in order to inform the operation and management of existing and future regulating structures. More specifically, the aims were to investigate the movement and spawning response of Murray cod and golden perch to altered flow by manipulating discharge at the mesohabitat scale. Experimental sites were selected in the Slaney Creek region of Chowilla and flow was manipulated through Slaney Weir. Radio transmitters were used to investigate fish movement and a combination of larval fish capture techniques (drift nets and light traps) were used to capture larvae to investigate spawning.
The results from the study illustrate inter-species differences in behaviour and highlight the complex nature of the effects of flow on movement and spawning. Movement of Murray cod and golden perch was variable and no clear pattern of fish emigration during low or high flows was observed. Decreasing flow through Slaney Weir caused a significant decrease in velocities within Little Slaney Creek. Nevertheless, this region retained some hydraulic complexity and continued to provide suitable hydraulic and physical microhabitats for Murray cod. Further investigation is required, however, using larger sample sizes of fish, to determine the response of Murray cod to altered hydrodynamics, particularly the very low velocities and homogenisation of hydraulic habitats that may be caused by the pooling effects of regulating structures.
Murray cod spawned during both the low flow and high flow events and increased discharge did not appear to increase spawning activity. Increased discharge through Slaney Weir, however, entrained high abundances of Murray cod larvae from the Lock 6 weir pool immediately upstream of Slaney Weir. Importantly, irrespective of the origin of Murray cod larvae, the hydraulically diverse habitats of the Chowilla system may increase larval survival and hence recruitment into the adult population.
SARDI Aquatic Sciences 2 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Golden perch did not spawn as predicted in response to increased discharge and water levels. This is despite the hydrological conditions in Slaney Creek being similar to those in spring/summer 2005 when golden perch spawning and recruitment was observed throughout the mid - lower Murray River. Considering the current conceptual understanding of golden perch movement and recruitment we propose flow events that incorporate longitudinal physical and hydrological connectivity over scales of at least 100s of kilometres may be required to promote successful spawning and recruitment of golden perch in the highly regulated lower Murray River.
SARDI Aquatic Sciences 3 Movement and spawning of Murray cod and golden perch in response to flow manipulation
1 Introduction4B Components of the natural flow regime influence the life history of some fish species by stimulating spawning and/or increasing survival of early life stages (Mallen-Cooper and Stuart 2003; Brown et al. 2005; Dudley and Platania 2007; Górski et al. 2010; King et al. 2010). Furthermore, hydrological variability influences the structure (abundance, richness and diversity) of fish communities by shaping the physical habitat of river ecosystems (Gorman and Karr 1978; Poff and Allan 1995; Cattaneo 2005). As such, anthropogenic alteration of flows may alter the abundance, diversity and structure of fish communities by changing not only the physical habitat available to fish but conditions specific to spawning and recruitment.
The natural flow regime of the lower Murray River has been significantly altered by levies, five tidal barrages and 11 low level (< 3 m) weirs creating a series of impounded weir pools that have lost their lotic character and, under non-flood flows, have relatively stable water levels (Walker 2006). Regulation has also altered the timing, duration and magnitude of flow events (Maheshwari et al. 1995). Perhaps one of the most prominent effects is an increase in the return intervals of small and medium sized floods (i.e. 20,000 – 60,000 ML d-1) by approximately 50% leading to extended periods of floodplain isolation (Sharley and Huggan 1995) and the potential loss of ecologically important within-channel rises in flow (Mallen-Cooper and Stuart 2003).
The Chowilla Anabranch system bypasses Lock and Weir No. 6 on the Murray River, South Australia. Due to the head differential (~ 3 m) created by the weir, 20 – 90% of Murray River flows are now diverted through the Chowilla Anabranch system under low flow conditions (i.e. < 10,000 ML d-1) (Stace and Greenwood 2004) creating a series of hydraulically diverse lotic habitats, particularly in creeks that are strongly influenced by the Lock 6 weir pool. The Chowilla system is characterised by spatially heterogeneous hydraulic environments ranging from lotic (flowing) habitats to backwaters and large lake systems (Sheldon and Lloyd 1990).
Chowilla supports a diverse fish community including state and nationally listed threatened species such as Murray cod (Maccullochella peelii), silver perch (Bidyanus bidyanus) and freshwater catfish (Tandanus tandanus) (Zampatti et al. 2008). The mosaic of hydraulic habitats within the system has been shown to have a significant influence on the structure of the fish assemblage with specific species characterising certain aquatic mesohabitats (Zampatti et al. 2011). Specific regions within the Chowilla system (e.g. Slaney Creek), are characterised by high abundances of reproductively mature Murray cod (Zampatti et al. 2011). These regions have been classified as fast-flowing mesohabitats and contain physical habitat characteristics such as abundant large woody debris and average water velocities > 0.18 m s-1 (Zampatti et al. 2008) that are considered to be important habitat attributes for Murray cod (Koehn and Nicol 1998; Boys and Thoms 2006; Koehn 2009). As such, these regions
SARDI Aquatic Sciences 4 Movement and spawning of Murray cod and golden perch in response to flow manipulation may not only provide habitat for adult and juvenile Murray cod but may also provide important spawning habitat.
Recent research within the Chowilla system has shown that this region may also provide a recruitment refuge for Murray cod, particularly under low-flow conditions in the lower Murray River (Zampatti et al. 2008). Consequently, changes to the flow regime of fast-flowing mesohabitats in the Chowilla system may not only affect the habitat suitability, but may affect the recruitment success of Murray cod. Nevertheless, specific information on adult movement behaviour, key spawning locations and recruitment ecology in relation to flow remain unclear.
Higher abundances of golden perch (Macquaria ambigua ambigua) have also been found to be associated with fast-flowing mesohabitats within Chowilla (Zampatti et al. 2011). Spawning and recruitment of golden perch is generally considered to be flow dependent (Humphries et al. 1999; Mallen-Cooper and Stuart 2003) and larval fish and population age structure investigations in the Chowilla region have provided further evidence for this in the lower Murray River (Leigh et al. 2008; Zampatti et al. 2008). Despite this recent information, the specific hydrological aspects that stimulate spawning (e.g. timing, magnitude and duration) and the spatio-temporal scale over which spawning and recruitment take place remain poorly understood. In particular it is unknown whether an artificial increase in discharge at the mesohabitat scale (1 – 10 km) can trigger a spawning and recruitment event.
The Chowilla Anabranch and Floodplain system is a significant ecological asset of the Murray- Darling Basin and an Icon Site of The Living Murray program. The floodplain ecosystem has become increasingly degraded due to altered flow regimes, elevated saline groundwater, obstructions to fish passage, grazing, and pest plants and animals (DWLBC 2006). In order to maintain and restore the health of the Chowilla floodplain an environmental management plan has been developed outlining a number of interventions for the system (MDBC 2006). These interventions include a range of water delivery options, upgrading and constructing regulating structures and altered regulator operation. Each of these interventions has the potential to alter both connectivity and the flow dynamics within the Chowilla system and hence the aquatic mesohabitat complexity and abundance and distribution of fish species in the system. Perhaps the most significant of the proposed options is the construction of a regulating structure on the downstream end of Chowilla Creek that will be used to artificially inundate a large area of the Chowilla floodplain. One of the most likely impacts of the operation of this regulating structure is the alteration of the hydraulic characteristics of aquatic habitats within the system, particularly the loss of fast-flowing mesohabitats (Brookes et al., 2006; Mallen-Cooper et al., 2008).
SARDI Aquatic Sciences 5 Movement and spawning of Murray cod and golden perch in response to flow manipulation
To date there is little information on the behavioural and spawning responses of Murray cod and golden perch to altered flow at the mesohabitat scale within the Chowilla system or elsewhere in the MDB. The broad aim of this project was to improve our understanding of the behavioural ecology of Murray cod and golden perch in the Chowilla system in order to inform the operation and management of existing and future regulating structures. The proposed structural modification of Slaney Weir provided a unique opportunity to undertake a controlled manipulation of discharge within an existing fast-flowing mesohabitat (Slaney Creek region). In light of this, we specifically aimed to investigate the movement and spawning response of Murray cod and golden perch to altered flow within an existing fast-flowing mesohabitat. In order to investigate these aims, we tested four hypotheses that were based on our current conceptual understanding of the ecology of Murray cod and golden perch. The hypotheses were:
1. Decreasing flow in an existing fast-flowing mesohabitat will decrease habitat suitability and increase emigration of Murray cod. 2. Decreasing flow in an existing fast-flowing mesohabitat will decrease habitat suitability and increase emigration of golden perch. 3. Murray cod will spawn (as determined by the presence of larvae) during both high and low flows. 4. Golden perch will spawn (as determined by the presence of larvae) in association with increased flow but not during relatively stable low flows.
To test these hypotheses we used radio transmitters to investigate fish movement and a combination of larval fish capture techniques (drift nets and light traps) to investigate spawning under artificially manipulated high and low flows.
SARDI Aquatic Sciences 6 Movement and spawning of Murray cod and golden perch in response to flow manipulation
2 Methods5B
2.1 Movement10B
2.1.1 Site15B description
In order to investigate the movement of Murray cod and golden perch in response to changes in flow, study sites were selected within the Slaney Creek region of the Chowilla system (Figure 1). Under entitlement flow conditions Slaney Creek can be characterised as fast-flowing mesohabitat and the region has been shown to support high abundances of Murray cod and golden perch (Zampatti et al. 2011). The creek also contains abundant instream habitat in the form of large woody debris (snags), river red gum root masses and a diverse range of aquatic macrophytes (Zampatti et al. 2008; Zampatti et al. 2011). At the microhabitat scale, Murray cod and golden perch in the Chowilla system, and elsewhere in the MDB, have been shown to have a significant positive association with these habitat characteristics (Koehn and Nicol 1998; Koehn 2009; Zampatti et al. 2011).
Slaney Creek Control
Impact Flow Pipeclay Weir Slaney Weir Salt Creek Swifty’s Creek
Lock 6 Chowilla Creek Flow
Murray River
Figure 1 Map showing the location of the impact and control site for the movement study.
Flow to Slaney Creek is derived from the Murray River primarily via Swifty’s Creek, Salt Creek and Slaney Creek (Figure 1) and is partly regulated by Slaney Creek Weir, a stoplog weir that regulates flow from the Lock 6 weir pool down a short section of creek known as Little Slaney Creek. Two sites were selected in the Slaney Creek system, an impact site, immediately downstream of the Slaney Creek Weir (Little Slaney Creek) and a control site downstream of the junction of Salt Creek and Slaney Creek (Figure 1). Flow at the impact site could be manipulated by adding or removing stop
SARDI Aquatic Sciences 7 Movement and spawning of Murray cod and golden perch in response to flow manipulation logs in Slaney Creek Weir. Whilst this also influenced flow at the control site, the magnitude of change was less due to the constant unregulated flow from Salt Creek. Under regulated entitlement flows from 2005 - 2007 both sites were classified as fast-flowing mesohabitats (Zampatti et al. 2008).
Both sites were approximately 800 m long, hydraulically diverse and contained abundant instream habitat in the form of snags, river redgum root masses and a diverse range of aquatic macrophytes. The impact site extended from Slaney Creek Weir downstream to the junction of Slaney and Salt Creeks (Figure 1) and was approximately 15 – 20 m wide and 0.5 – 3 m deep. The control site commenced 200 m upstream of Slaney Billabong and extended in a downstream direction (Figure 1). The site was approximately 15 – 25 m wide and 0.5 – 5 m deep.
2.1.2 Flow16B manipulation
The proposed structural modification of Slaney and Pipeclay Weirs provided a unique opportunity to undertake a controlled manipulation of flow (discharge, velocity and water level) within the Slaney Creek region. Refurbishment of Slaney Weir was originally proposed for early 2008 during which time flow through the structure was to be decreased, however these works failed to occur. Furthermore, ongoing drought in the MDB and record low flows in the Murray River resulted in flows being reduced through Slaney Weir to ~ 200 ML d-1 from 2006 through to 2007. Consequently, during the early part of the proposed study period (June – December 2007) velocities at the impact site were analogous to a slow-flowing mesohabitat. In light of this, an alternative flow manipulation was undertaken in 2008/2009. Discharge through Slaney Weir was increased in November 2008 to simulate high flow conditions (returning the site to a fast-flowing mesohabitat) by removing 2.5 stop logs (1 log, 20 November and 1.5 logs, 27 November). Flows were then decreased at the end of March 2009 to create low flow conditions by replacing the stop logs (1 log, 16 March and 1.5 logs, 30 March).
2.1.3 Radio17B transmitter implantation
Murray cod (impact site, n = 5; control site n = 6) and golden perch (impact site, n = 10; control site n = 7) were initially tagged in October 2007 and April 2008 in anticipation that flow through Slaney Weir would increase (as flow typically increases into SA during spring/summer) but would then be reduced during weir refurbishment. During delays in refurbishment commencing, and hence flow manipulation occurring, a number of both Murray cod and golden perch emigrated from the experimental sites. Consequently, three additional tagging events (July 2008, November 2008 and January 2009) were necessary to attempt to maintain a sufficient sample size of radio-tagged fish in the impact and control sites at the commencement of the alternative flow manipulation period.
SARDI Aquatic Sciences 8 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Transmitters used were cylindrical 150 MHz, internal radio transmitters with 30 cm (0.7 mm diameter) trailing antenna (Advanced Telemetry Systems (ATS), Insanti, MN, USA). Four sizes of transmitter were used; models F1835B (1/2AA), F1850 (AA), F1855 (C) and F1860 (D) weighing 18, 25, 80 and 150 g respectively in air and having a warranted battery life of 258, 560, 1657 and 3937 days respectively (Table 1). The functional life of the transmitter batteries was maximised by incorporating a duty cycle of 5 periods on and 7 periods off. Transmitters were also fitted with a mortality circuit, which is activated if the fish (transmitter) has not moved for a period of 8 hours.
Murray cod and golden perch were captured from the experimental sites by boat electrofishing. Fish were anesthetised using 0.75 ml of Alfaxan (Jurox, Rutherford, NSW, Australia) per 10 L of river water or 1.5 ml AQUI-S® (AQUI-S New Zealand Ltd., Lower Hutt, New Zealand) in 50 L of river water. Fish were measured for length (LT, mm) and weight (g) and inverted onto a v-shaped cradle. The gills of the fish were irrigated throughout the surgery with a 50% dilute solution of Alfaxan or AQUI-S®. A 2 – 3 cm incision was made through the ventral wall slightly dorsally of the midventral line beginning adjacent to the pelvic fin and extending towards the anus. The sex of the fish was determined and the transmitter inserted into the abdominal cavity. To ensure fish buoyancy was not compromised transmitter weight was ≤ 2% of fish body weight.
A shielded needle technique (Adams et al. 1998) was used to guide the trailing antenna through the lateral body wall posterior to the incision. The incision was closed with two internal and three external sutures. The fish was then injected in the dorsal musculature with a long-term (2 weeks) antibiotic Baytril® (Bayer Australia, Pymble, NSW, Australia) at a dose of 0.1 ml/kg. A PIT tag was inserted in the dorsal musculature forward of the dorsal fin and a dart tag (PDL or PDXL, Hallprint, Victor Harbor, SA, Australia) was positioned between the dorsal pterygiophores to enable external visual identification of fish and reporting of captures by anglers. Following recovery fish were released at their capture location.
Over the course of the study seven Murray cod were implanted with radio transmitters in the impact site. Six of these fish were male whilst the sex of the remaining fish could not be determined. Tagged Murray cod ranged in length from 486 – 1230 mm (mean ± SE, 795 + 95 mm) and weighed 1.5 – 30 kg (11.7 + 4.0 kg) (Table 1). Seventeen golden perch were also implanted with radio transmitters at the impact site. Twelve fish were female and five male. Fish ranged in length from 378 – 500 mm (419 + 7 mm) and weighed 0.87 – 2.02 kg (1.1 + 0.07 kg) (Table 1).
Eight Murray cod were implanted with radio transmitters in the control site. Four of these fish were female whilst the sex of the remaining four fish could not be determined. Tagged Murray cod ranged in length from 435 – 1125 mm (722 + 77 mm) and weighed 0.9 – 27 kg (8.0 + 3.0 kg) (Table 1).
SARDI Aquatic Sciences 9 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Eleven golden perch were implanted with radio transmitters at the control site (Table 1). Nine fish were female and two males. Fish ranged in length from 370 - 455 mm (, 418 + 9 mm) and weighed 0.77 – 1.38 kg (1.2 + 0.09 kg) (Table 1).
2.1.4 Tracking18B
Radio-tagged Murray cod and golden perch were manually tracked by boat every 2 – 3 weeks using an ATS radio receiver/logger (model No. RC4500C). Signals could be detected from approximately 800 m and the position of each fish, as determined by the point of greatest signal strength, was recorded by GPS. Trials with hidden transmitters indicated that using this technique, transmitters could be located consistently to within an area of 3 m2.
The movement patterns and approximate locations of all fish were also investigated using data downloaded from six logging stations (ATS radio receiver/loggers model No. RC4500C). These logging stations were located throughout the Chowilla Anabranch system on major tributaries of Chowilla Creek and at the junction of Chowilla Creek and the River Murray. The presence of fish in the vicinity of a logger was detected by three Yagi antennae positioned on each logging station; one directed upstream, one downstream and one in the direction of the tributary. The presence of a radio-tagged fish was recorded automatically as a frequency, antenna number, time and signal strength, thus enabling the direction of the fish movement to be determined.
SARDI Aquatic Sciences 10 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Table 1 Biological details, capture locations and transmitter specifications for golden perch and Murray cod implanted with radio transmitters.
Release Transmitter Fish Length Weight Surgery Transmitter Warr battery site no. number Species (mm) (g) Sex date size life (days) Impact 150.203 (20) GP 1 Golden perch 391 884 F 23/10/2007 1/2AA 258 Impact 150.243 (21) GP 2 Golden perch 390 940 F 23/10/2007 1/2AA 258 Impact 150.224 (20) GP 3 Golden perch 445 1244 F 23/10/2007 1/2AA 258 Impact 150.203 (24) GP 4 Golden perch 415 1041 F 24/10/2007 1/2AA 258 Impact 150.224 (21) GP 5 Golden perch 435 1300 F 24/10/2007 1/2AA 258 Impact 150.243 (22) GP 6 Golden perch 422 1222 F 24/10/2007 1/2AA 258 Impact 150.203 (22) GP 7 Golden perch 428 1265 F 24/10/2007 1/2AA 258 Impact 150.224 (23) GP 8 Golden perch 412 941 M 24/10/2007 1/2AA 258 Impact 150.243 (23) GP 9 Golden perch 500 2022 M 24/10/2007 1/2AA 258 Impact 150.203 (23) GP 10 Golden perch 398 974 M 24/10/2007 1/2AA 258 Impact 150.113 (20) GP 18 Golden perch 442 1401 F 22/07/2008 1/2AA 258 Impact 150.203 (16) GP 19 Golden perch 394 1020 F 22/07/2008 1/2AA 258 Impact 150.243 (19) GP 20 Golden perch 407 910 M 22/07/2008 1/2AA 258 Impact 150.224 (19) GP 21 Golden perch 378 877 F 23/07/2008 1/2AA 258 Impact 150.203 (19) GP 25 Golden perch 405 1029 F 23/07/2008 1/2AA 258 Impact 150.224 (17) GP 26 Golden perch 425 1254 F 23/07/2008 1/2AA 258 Impact 150.243(18) GP 27 Golden perch 435 1120 M 23/07/2008 1/2AA 258 Impact 150.302 (24) MC 1 Murray cod 810 9000 unsure 23/10/2007 C 1657 Impact 150.263 (22) MC 2 Murray cod 640 5500 M 23/10/2007 AA 560 Impact 150.284 (22) MC 3 Murray cod 1010 23000 M 23/10/2007 D 3937 Impact 150.302 (23) MC 4 Murray cod 750 8500 M 24/10/2007 C 1657 Impact 150.263 (18) MC 14 Murray cod 486 1500 M 02/04/2008 AA 560 Impact 150.483 (25) MC 43 Murray cod 1230 30000 M 20/01/2009 D 3937 Impact 150.342 (25) MC 44 Murray cod 640 4500 M 20/01/2009 C 1657 Control 150.243 (20) GP 11 Golden perch 370 765 F 25/10/2007 1/2AA 258 Control 150.224 (22) GP 12 Golden perch 405 933 F 25/10/2007 1/2AA 258 Control 150.224 (24) GP 13 Golden perch 424 1085 F 25/10/2007 1/2AA 258 Control 150.113 (25) GP 14 Golden perch 374 815 M 25/10/2007 1/2AA 258 Control 150.243 (24) GP 15 Golden perch 380 846 F 25/10/2007 1/2AA 258 Control 150.203 (21) GP 16 Golden perch 435 1176 F 25/10/2007 1/2AA 258 Control 150.133 (21) GP 17 Golden perch 450 1359 F 25/10/2007 1/2AA 258 Control 150.224 (18) GP 24 Golden perch 442 1455 F 25/11/2008 1/2AA 258 Control 150.203 (17) GP 23 Golden perch 455 1759 M 25/11/2008 1/2AA 258 Control 150.133 (20) GP 22 Golden perch 425 1208 F 25/11/2008 1/2AA 258 Control 150.243 (17) GP 28 Golden perch 441 1376 F 25/11/2008 1/2AA 258 Control 150.263 (23) MC 5 Murray cod 630 3500 F 25/10/2007 AA 560 Control 150.263 (24) MC 6 Murray cod 640 3800 F 25/10/2007 AA 560 Control 150.263 (20) MC 11 Murray cod 545 2000 F 01/04/2008 AA 560 Control 150.302 (19) MC 12 Murray cod 910 12700 Not sighted 01/04/2008 C 1657 Control 150.342 (23) MC 15 Murray cod 782 7500 F 02/04/2008 C 1657 Control 150.203 (18) MC 16 Murray cod 435 904 Not sighted 02/04/2008 1/2AA 258 Control 150.503 (20) MC 38 Murray cod 1125 27000 Not sighted 27/11/2008 D 3937 Control 150.342 (20) MC 39 Murray cod 710 6500 Not sighted 27/11/2008 C 1657
SARDI Aquatic Sciences 11 Movement and spawning of Murray cod and golden perch in response to flow manipulation
2.1.5 Analysis19B
To investigate if decreasing flow resulted in increased emigration of Murray cod and golden perch, the movement of each individual fish was described during two flow periods. These flow periods were defined as high flow (1st November 2008 – 31st March 2009) and low flow (1st April 2009 – 31st August 2009).
The cumulative and maximum distance moved by each fish in each flow period was calculated. The cumulative distance was defined as the sum of the distances moved between each detection (manual and remote) and the maximum distance was defined as the maximum river distance moved from the original capture location. In order to investigate if there were differences in the distances travelled (cumulative and maximum distance) by Murray cod and golden perch between sites and between flow periods, permutational multivariate analysis of variance (PERMANOVA) (Anderson 2001) were performed on unpooled data.
Discharge and stage height at the impact site were measured at the Little Slaney Creek gauging station, immediately upstream of the Little Slaney Creek and Salt Creek junction. Data for the control site were measured at the gauging station located on lower Slaney Creek. Velocity profiles were measured at both the impact and control site on two occasions, in November 2008 during the increased flow period and in April 2009 after stop logs were replaced and flows were reduced to simulate a low flow period. At each site, an acoustic Doppler current profiler (ADCP) was used to measure velocity at 10 cm cell widths across six transects. The mean velocity and maximum depth calculated for each transect was then used to determine the mean velocity and mean maximum depth (+ SE) for each site during each flow period. PERMANOVA were performed on unpooled data in order to test if mean velocity and maximum depth were significantly different between sites and flow periods.
SARDI Aquatic Sciences 12 Movement and spawning of Murray cod and golden perch in response to flow manipulation
2.2 Spawning1B
2.2.1 Site20B descriptions
In order to investigate the spawning response of Murray cod and golden perch to flow alteration, larval fish sampling was conducted in spring/summer 2007/2008 and 2008/2009 (Table 2). In 2007/2008 sites were located in Hypurna Creek downstream of Swifty’s Creek, Salt Creek upstream of Slaney junction, Little Slaney Creek immediately downstream of Slaney Weir, Lower Little Slaney Creek and Lower Slaney Creek (Figure 2). Due to difficulty in distinguishing the origin of Murray cod larvae captured below the Slaney Creek Weir in 2007/2008 (i.e. if larvae were spawned directly below the Slaney Creek Weir or were drifting over the weir from the Murray River) site locations were modified for the 2008/2009 season. In the 2008/2009, six sites were sampled for larval fish (Table 2). To attempt to separate the origin of larvae from the Murray River main channel and immediately below the Slaney Creek Weir, two sites were selected, namely, the Murray River immediately upstream Slaney Weir and Little Slaney Creek immediately downstream Slaney Weir. Lower Little Slaney Creek was sampled to capture larvae spawned within Little Slaney Creek (or coming over the weir), Salt Creek immediately upstream Slaney junction to capture larvae that may have originated from the Murray River, Hypurna, Salt or Swifty’s creeks, and Lower Slaney Creek to potentially capture larvae spawned in the lower reaches of Slaney Creek. An additional site was placed in Chowilla Creek to detect spawning in the lower reaches of the Chowilla system (Figure 2).
6
3 4 2 5 1
7
Figure 2 Location of the larval sampling sites in the Chowilla system.
SARDI Aquatic Sciences 13 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Table 2 Sites sampled for larval fish in the Chowilla system during spring/summer 2007/2008 and 2008/2009.
Site number Location 2007/2008 2008/2009 1 Hypurna Creek d/s Swifty’s yes no 2 Salt Creek u/s Slaney junction yes yes 3 Lower Little Slaney Creek yes yes 4 Little Slaney Creek immediately d/s Slaney Weir no yes 5 Murray River immediately u/s Slaney Weir yes yes 6 Lower Slaney Creek yes yes 7 Chowilla Creek d/s Lock 6 Bridge no yes
2.2.2 Sampling21B
Larval surveys were conducted during a low flow period in spring/summer 2007/2008 and during an artificially manipulated high flow period (in Slaney Creek) in spring/summer 2008/2009. In late November 2008, 2 stop logs were removed from the Slaney Creek Weir thus increasing discharge, velocity and water level at sites downstream of the weir.
Larval samples were collected fortnightly from 9th September 2007 – 10th January 2008 (low flow) and 30th September 2008 – 9th December 2008 (high flow). A combination of collection methods were used to capture larvae. Three drift nets were set per site (500 µm mesh, 0.5 m diameter opening, 1.5 m length) and a flow meter (General Oceanics Inc. Florida, USA) was attached to the mouth of each drift net to determine the volume of water filtered through each net. Upon retrieval the contents of each drift net were washed to the cod end, rinsed into a sample jar and preserved in 95% ethanol. Five light traps were also set at each site among littoral habitat (e.g. submerged and emergent aquatic macrophytes, and woody debris). To prevent entry by larger fish and predation of larvae, 5 mm stretched mesh was used to cover the entrances to the trap (Meredith et al. 2002). The sampling effort was increased during the high flow period in order to investigate if increased flow (discharge and velocity) stimulated golden perch to spawn. Site 3 (lower Little Slaney Creek) was sampled twice (using drift nets only) during the November and December sampling trips.
Larvae were separated from vegetation in drift net samples under a magnification lamp (x 2). Samples from light traps did not require sorting prior to identification. All larvae were identified under a dissecting microscope using descriptions from Serfafini and Humphries (2004). Only larvae of the target species (Murray cod and golden perch) were counted.
SARDI Aquatic Sciences 14 Movement and spawning of Murray cod and golden perch in response to flow manipulation
2.2.3 Analysis2B
The total number of larvae captured at each site was determined for each year. The number of fish captured was also standardised to reflect catch per unit effort (CPUE) for drift nets and light traps combined. CPUE was determined as the number of fish per 1000 m3 (drift nets) + number of fish per 12 hour period (light traps). A uni-variate single factor PERMANOVA was performed to determine if CPUE varied significantly between the two sampling seasons. Discharge and stage height for the spawning study were measured at the gauging station in Little Slaney Creek immediately upstream of the Salt Creek junction.
SARDI Aquatic Sciences 15 Movement and spawning of Murray cod and golden perch in response to flow manipulation
3 Results6B 3.1 Movement
3.1.1 Site23B characteristics
Discharge in Little Slaney Creek increased in November 2008 from approximately 100 – 600 ML d-1 in response to the removal of 1 stop log from the Slaney Creek Weir on the 20th November 2008 (Figure 3a). On the 27th November 2008 a second stop log was removed and discharge increased to approximately 1,200 ML d-1. Discharge ranged from 1,100 – 1,300 ML d-1 from mid December 2008 to mid March 2009. Stop logs were replaced on the 16th (1 stop log) and 30th March 2009 (1.5 stop logs) and flows subsequently decreased to approximately 100 ML d-1. From the 1st April 2009 – 31st August 2009 discharge remained low at approximately 100 ML d-1.
Stage heights recorded in Little Slaney Creek mirrored the discharge observed from 1st November 2008 – 31st August 2009 (Figure 3a). At the beginning of the high flow period (1st November 2008) water level increased from 17.6 – 17.9 m after the removal of 1 stop log. Levels increased again to 18.2 m after the removal of second stop log. Water levels remained at approximately 18.2 m until 16th March 2009 when 1 stop log was replaced. The water level decreased to 17.9 m and following the replacement of a further 1 and ½ stop logs on the 30th March 2009 levels decreased further to 17.5 m. At the beginning of April 2009 the water level was approximately 17.5 m and remained at this level until the end of the low flow period. The patterns for discharge and stage height observed in Little Slaney Creek were also observed for lower Slaney Creek (Figure 3b) however the magnitude of change was generally not as large.
Water velocity transects measured in Little Slaney Creek during the high and low flow period indicate that the velocity profile varied between the two flow periods (Figure 4). During the high flow period the velocity profile was hydraulically diverse (Figure 4a). Velocities ranged from approximately 0.05 – 0.60 m s-1 and a high proportion of measurements were > 0.45 m s-1. The velocity profile during the low flow period also shows a diverse range of velocities. Nevertheless, the proportion of velocity measurements > 0.45 m s-1 decreased and a large proportion of measurements were between 0.30 – 0.50 m s-1 (Figure 4b). In comparison, a cross-section for the main channel of the Murray River shows a homogenous distribution of velocities ranging from 0.00 – 0.12 m s-1 (Figure 4c).
SARDI Aquatic Sciences 16 Movement and spawning of Murray cod and golden perch in response to flow manipulation
1800 18.5 Little Slaney Stop log replaced a) 1600
1400 18.0 Stop log removed )
-1 1200 17.5 1000
800 17.0
600 Stage height (m) Discharge (ML d
400 High flow 16.5 Low flow 200
0 16.0 Oct - 07 Feb - 08 Jun - 08 Oct - 08 Feb - 09 Jun - 09 Oct - 09
1800 18.5 Lower Slaney b) 1600
1400 18.0 )
-1 1200 17.5 1000
800 17.0
600 Stage height(m) Discharge (ML d
400 16.5 200
0 16.0 Oct - 07 Feb - 08 Jun - 08 Oct - 08 Feb - 09 Jun - 09 Oct - 09
Date
Figure 3 Discharge (ML d-1, solid line) and stage height (m, dotted line) measured in a) Little Slaney Creek above the Salt Creek / Slaney Creek junction and b) lower Slaney Creek from October 2007 – October 2009.
SARDI Aquatic Sciences 17 Movement and spawning of Murray cod and golden perch in response to flow manipulation
a)
b)
c)
Figure 4 Water velocity transects measured in a) Little Slaney Creek during the high flow period, b) Little Slaney Creek during the low flow period and c) the Murray River main channel under ‘entitlement flow’ conditions.
SARDI Aquatic Sciences 18 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Mean water velocity varied significantly between the high and low flow periods (PERMANOVA (sites pooled), Psuedo-F = 134.090, df = 1,21, P = 0.001), between sites (flow periods pooled) (Psuedo-F = 87.203, df = 1,21, P = 0.001) and there was a significant interaction between flow period and site (Psuedo-F = 31.123, df = 1,21, P = 0.001). Pair-wise comparisons show that mean water velocity during the high flow period was significantly greater at the control site (Table 3). Nevertheless, based on velocity categories used to classify mesohabitats within the Chowilla system (Zampatti et al. 2008) both sites would be classified as fast-flowing mesohabitats (average velocities > 0.18 m s-1) (Figure 5). During the low flow period mean water velocities decreased significantly at both the impact and control sites (Table 3 and Figure 5) but the control site remained a fast-flowing mesohabitat (> 0.18 m s-1) whilst the impact site was reclassified as a slow-flowing mesohabitat (i.e. 0.05 – 0.18 m s-1).
Table 3 Results of global and pair-wise PERMANOVA comparing water velocity measured at impact and control site during each flow period (high and low). Significant values are highlighted in bold (P < 0.05).
Pair-wise test t P High-impact v Low-impact 13.336 0.005 High-impact v High-control 2.401 0.050 High-impact v Low-control 1.865 0.095 Low-impact v High-control 12.628 0.008 Low-impact v Low-control 13.787 0.005 High-control v Low-control 4.101 0.011
0.5
0.4 ) -1 0.3
0.2 Water velocity (ms velocity Water
0.1
0.0 Impact Control Site
Figure 5 Water velocity (m s-1, mean + standard error) measured at the impact and control sites during the high flow (hatched bars) and low flow (white bars) periods.
SARDI Aquatic Sciences 19 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Mean maximum water depths varied significantly between the high and low flow periods (PERMANOVA (sites pooled), Psuedo-F = 31.063, df = 1,21 P = 0.001) but not between sites (Psuedo-F = 0.006, df = 1,21 P = 0.942) and there was no significant interaction between flow period and site (Psuedo-F = 2.202, df = 1,21 P = 0.149). Pair-wise comparisons between flow and site indicate that mean maximum water depths were not significantly different between the impact and control site during the high or low flow periods (Table 4 and Figure 6). Mean maximum water depth did, however, decrease significantly at both sites between the high and low flow periods (Table 4 and Figure 6). At the impact site, mean maximum water depth decreased by 0.82 m from 2.45 m (+ 0.09) in the high flow period to 1.63 m (+ 0.17) in the low flow period. At the control site, mean maximum water depth decreased by 0.48 m from 2.29 m (+ 0.10) in the high flow period to 1.81 m (+ 0.11) in the low flow period.
Table 4 PERMANOVA results of pair-wise tests comparing maximum water depth measured at the impact and control sites during each flow period (high and low). Significant values are highlighted in bold (P < 0.05).
Pair-wise comparison t P High-impact v Low-impact 4.607 0.006 High-impact v High-control 1.193 0.246 High-impact v Low-control 4.455 0.010 Low-impact v High-control 3.490 0.004 Low-impact v Low-control 0.928 0.400 High-control v Low-control 3.138 0.008
3.0
2.5
2.0
1.5 Depth (m)
1.0
0.5
0.0 Impact Control Site Figure 6 Maximum water depth (m, mean + standard error) measured at the impact and control sites during the high flow (hatched bars) and low flow (white bars) periods.
SARDI Aquatic Sciences 20 Movement and spawning of Murray cod and golden perch in response to flow manipulation
3.1.2 Murray24B cod
Two radio-tagged Murray cod left the impact site prior to the high flow period (1st November 2008). At the beginning of the high flow period five radio-tagged Murray cod were present. Three fish (MC 4, 44 and 14) made small movements (< 500 m) within the impact site for the duration of the flow manipulation period (1st November 2008 - 31st August 2009) (Figure 7). Two Murray cod moved out of the impact site during the high flow period (Figure 7 and Figure 9). MC 2 moved downstream and was tracked in lower Slaney Creek below the control site on the 25th March 2009. On the 22nd April 2009, however, the tag was found to be emitting a mortality signal suggesting the fish had shed the tag. The other Murray cod (MC 43) moved to lower Slaney Creek in mid January 2009. In late April 2009 it had moved to the control site and in July 2009 was located in Salt Creek upstream of the Little Slaney / Slaney Creek junction. Two additional Murray cod were tagged in the impact site on 20th January 2009.
At the control site, eight Murray cod were present at the beginning of the high flow period. Six fish made small-scale movements (< 500 m) within the control site over the duration of the flow manipulation period (Figure 8). Two Murray cod (MC 12 and MC 38) moved out of the control site during the low flow period (Figure 8 and Figure 10). MC 12 moved out of the control site in April 2009 and was recorded at the Swifty’s logger (junction of Swifty’s Creek and the Murray River main channel upstream of Lock 6) in late April and early May 2009, however by 28th May 2009 it had returned to the control site. The other fish (MC 38) moved out of the control site in May 2009 to Slaney Creek approximately 300 m upstream of the control site and remained there for the rest of the flow manipulation period.
SARDI Aquatic Sciences 21 Movement and spawning of Murray cod and golden perch in response to flow manipulation
600 3000 MC 14 MC 43 400 2000 u/s Little Slaney / Slaney Ck junc 200 1000
0 0
-200 -1000 control site -400 -2000 Salt logger lower Slaney Ck -600 -3000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
600 3000 MC 4 MC 2 400 2000
200 1000
0 0
Distance (m) -200 -1000
-400 -2000
lower Slaney Ck -600 -3000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
Date 600 MC 44 400
200
0
-200
-400
-600 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Date Figure 7 Radio-tagged Murray cod movements for the period November 2008 – August 2009 for those fish present in the impact site at the beginning of the high flow period (1st November 2008). 0 m represents the original tagging location.
SARDI Aquatic Sciences 22 Movement and spawning of Murray cod and golden perch in response to flow manipulation
200 500 MC 39 MC 11
100 250
0 0
-100 -250
-200 -500 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
200 500 MC 16 Slaney Ck u/s control site MC 38
100 250
0 0 battery expired
-100 -250
-200 -500 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
200 500 Distance (m)Distance MC 15 MC 6
100 250
0 0
-100 -250
-200 -500 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
200 5000 MC 5 MC 12
Swify's logger 100 2500
0 0 Slaney Ck Salt logger u/s control site
-100 -2500
-200 -5000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Date Date Figure 8 Radio-tagged Murray cod movements for the period November 2008 – August 2009 for those fish present in the control site at the beginning of the high flow period (1st November 2008). 0 m represents the original tagging location.
SARDI Aquatic Sciences 23 Movement and spawning of Murray cod and golden perch in response to flow manipulation
1800 5
1600
4 1400
) 1200 -1 3 1000
800 2 Number of fish
Discharge (ML d (ML Discharge 600
400 1
200
0 0 ^ 2 Jul-09 Apr-09 Apr-09 Jun-09 Jun-09 Jan-09 Jan-09 Mar-09 Mar-09 Feb-09 Feb-09 Nov-08 Nov-08 Aug-09 Aug-09 Sep-09 Dec-08 Dec-08 May-09 May-09 Date
Figure 9 Discharge in Little Slaney Creek from 1st November 2008 – 31st August 2009 and timing of Murray cod movement out of the impact site. Arrow indicates date when additional fish were tagged, number under arrow indicates the number of fish that were tagged.
1800 5
1600
4 1400
) 1200 -1 3 1000
800 2 Number of fish
Discharge (ML d 600
400 1
200
0 0 ^ 2 Jul-09 Jul-09 Apr-09 Apr-09 Jan-09 Jan-09 Jun-09 Jun-09 Feb-09 Feb-09 Mar-09 Mar-09 Nov-08 Aug-09 Sep-09 Dec-08 Dec-08 May-09 Date
Figure 10 Discharge in lower Slaney Creek from 1st November 2008 – 31st August 2009 and timing of Murray cod movement out of the control site. Arrow indicates date when additional fish were tagged, number under arrow indicates the number of fish that were tagged.
SARDI Aquatic Sciences 24 Movement and spawning of Murray cod and golden perch in response to flow manipulation
The mean cumulative and maximum movement distances calculated for Murray cod over the two flow periods in both the impact and control site were similar (Figure 11 and Figure 12). In the impact site mean cumulative and maximum distances travelled were greater in the high flow period. In the control site mean distances were slightly greater in the low flow period. Distances travelled were greater in the impact site than the control site. Nevertheless there was no significant difference in either the cumulative distance or maximum distance travelled by Murray cod in either the impact or control site in either flow period (Table 5).
2500
n = 5 2000
1500
1000 Cumulative distance (m) n = 3 n = 7 500 n = 8
0 Impact Control Site Figure 11 Cumulative distance (m, mean + standard error) moved by Murray cod at the impact and control sites during the high flow (hatched bar) and low flow (white bar) flow periods.
1600 n = 5
1400
1200
1000
800
600 n = 7
Maximum distance (m) n = 3 400
200 n = 8
0 Impact Control Site Figure 12 Maximum distance (m, mean + standard error) moved by Murray cod at the impact and control sites during the high flow (hatched bar) and low flow (white bar) flow periods.
SARDI Aquatic Sciences 25 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Table 5 Results of PERMANOVA comparing cumulative and maximum distances moved by Murray cod in the impact and control sites during high and low flow periods.
Factor df F P Cumulative distance Site 1,22 2.164 0.117 Flow 1,22 1.226 0.296 Site x Flow 1,22 1.713 0.256 Max distance Site 1,22 2.269 0.117 Flow 1,22 1.164 0.315 Site x Flow 1,22 2.033 0.176
SARDI Aquatic Sciences 26 Movement and spawning of Murray cod and golden perch in response to flow manipulation
3.1.3 Golden25B perch
At the impact site, eleven golden perch left the site prior to the flow manipulation period. At the beginning of the high flow period (1st November 2008) six radio-tagged golden perch were present. Two fish (GP 20 and 10) made small-scale movements (< 1 km) within the impact site for the duration of the flow manipulation period (1st November 2008 – 31st August 2009) (Figure 13). The remaining four golden perch moved out of the impact site, three in the high flow period and one in the low flow period (Figure 13 and Figure 15). GP 1 moved out of the impact site in late November 2008 and relocated to Salt Creek upstream of the Little Slaney/Slaney Creek junction. It remained here until April 2009 when it was manually tracked but this was the last recording of this fish in the system (manual and remote) (Figure 13). GP 18 moved out of the impact site in late November 2008 and moved upstream. This fish was last recorded on the Swifty’s logger (junction of Swifty’s and the Murray River main channel upstream of Lock 6) (Figure 13). GP 21 moved downstream to lower Slaney Creek in late March 2009 and remained there for the remainder of the flow manipulation period (Figure 13). GP 8 moved downstream out of the impact site and was recorded at the junction of Boat Creek and Chowilla Creek (Boat Creek logger) in early February 2009 before returning to the impact site in March 2009. In late April the tag emitted a signal indicative of a low battery and was not located after this date. At the commencement of the low flow period (mid March 2009) only 3 golden perch remained in the impact site (GP 20, 10 and 8).
Four fish left the control site prior to the flow manipulation period. Seven radio-tagged golden perch were present at the beginning of the high flow period (Figure 14). Two fish (GP 11 and 23) made small-scale movements (< 1 km) within the control site over the duration of the flow manipulation period (Figure 14). The remaining five fish moved out of the control site but during the course of the flow manipulation four of these fish temporarily undertook return movements to the control site. Movement of golden perch out of the control site occurred predominantly during March and April 2009 (Figure 16). GP 13 made small-scale movements (< 0.5 km) within the control site before being recorded twice at the Salt Creek logger (junction of Little Slaney/Slaney Creek) between early February and late April 2009 (Figure 14). GP 16 and 28 remained in the control site until April 2009 when they moved upstream and were last recorded on the Swifty’s logger (Figure 14). GP 15 remained in the control site until May 2009 when it was recorded downstream at the Boat Creek logger (Boat Creek/Chowilla Creek junction). This fish then moved back upstream to Salt Creek ~ 2 km upstream of the control site where it remained through June and July 2009 (Figure 14). GP 22 remained in the control site until April 2009 before moving upstream through Salt Creek in April 2009 and into the Murray River main channel upstream of Lock 6 where it was last recorded in June 2009 (Figure 14).
SARDI Aquatic Sciences 27 Movement and spawning of Murray cod and golden perch in response to flow manipulation
2000 4000 GP 20 Swifty's logger GP 18
1000 2000
0 0
-1000 -2000 Salt logger
-2000 -4000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
2000 4000 GP 1 GP 21
1000 2000
0 0 Distance (m) Distance -1000 Salt logger -2000 lower Slaney Ck Salt Ck u/s little Slaney / Slaney junc -2000 -4000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
2000 15000 GP 10 GP 8 10000 1000 5000
0 0
-5000 Battery fading -1000 Salt logger -10000 Boat logger -2000 -15000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Date Date Figure 13 Radio-tagged golden perch movements for the period November 2008 – August 2009 for those fish present in the impact site at the beginning of the high flow period (1st November 2008). 0 m represents the original tagging location.
SARDI Aquatic Sciences 28 Movement and spawning of Murray cod and golden perch in response to flow manipulation
400 10000 GP 11 GP 28 Swifty's logger 200 5000 Salt logger
0 0
-200 -5000
-400 -10000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
400 10000 GP 23 MR u/s swifty's GP 22
200 5000 Salt logger
0 0
-200 -5000
-400 -10000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
Distance (m) 1000 15000 Salt logger GP 13 GP 15 10000 500 Salt logger 5000
0 0
-5000 -500 -10000 Boat logger -1000 -15000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09
Date 8000 GP 16 6000 Swifty's logger 4000 Salt logger 2000 0 -2000 -4000 -6000 -8000 Nov - 08 Jan - 09 Mar - 09 May - 09 Jul - 09 Sep - 09 Date Figure 14 Radio-tagged golden perch movements for the period November 2008 – August 2009 for those fish present in the control site at the beginning of the high flow period (1st November 2008). 0 m represents the original tagging location
SARDI Aquatic Sciences 29 Movement and spawning of Murray cod and golden perch in response to flow manipulation
1800 5
1600
4 1400
) 1200 -1 3 1000
800 2 Number of fish
Discharge (ML d 600
400 1
200
0 0 Jul-09 Jul-09 Apr-09 Jun-09 Jun-09 Jan-09 Jan-09 Feb-09 Feb-09 Mar-09 Aug-09 Sep-09 Nov-08 Nov-08 Dec-08 Dec-08 May-09 May-09 Date
Figure 15 Discharge in Little Slaney Creek from 1st November 2008 – 31st August 2009 and timing of golden perch movement out of the impact site.
1800 5
1600
4 1400
) 1200 -1 3 1000
800 2 Number of fish of Number
Discharge (ML d 600
400 1
200
0 0 ^ 4 Jul-09 Jul-09 Apr-09 Jan-09 Jan-09 Jun-09 Jun-09 Feb-09 Feb-09 Mar-09 Mar-09 Nov-08 Nov-08 Aug-09 Sep-09 Dec-08 Dec-08 May-09 May-09 Date
Figure 16 Discharge in lower Slaney Creek from 1st November 2008 – 31st August 2009 and timing of golden perch movement out of the control site. Arrow indicates the date when additional fish were tagged, number under arrow indicates the number of fish tagged.
SARDI Aquatic Sciences 30 Movement and spawning of Murray cod and golden perch in response to flow manipulation
The mean cumulative and maximum distances calculated for golden perch show a similar pattern (Figure 17 and Figure 18). In the impact site, mean cumulative and maximum distances were greatest during the high flow period whereas in the control site distances were greatest in low flow period (Figure 17 and Figure 18). Nevertheless, there were no significant differences between sites or between periods (Table 6).
14000
n = 5 12000
10000 n = 6
8000
6000
Cumulative distance(m) 4000
n = 7 2000 n = 3 0 Impact Control Site Figure 17 Cumulative distance (m, mean + standard error) moved by golden perch at the impact and control sites during the high flow (hatched bar) and low flow (white bar) flow periods.
7000
n = 6 6000 n = 5
5000
4000
3000
Maximum distanceMaximum (m) 2000
1000 n = 7 n = 3 0 Impact Control Site Figure 18 Maximum distance (m, mean + standard error) moved by golden perch at the impact and control sites during the high flow (hatched bar) and low flow (white bar) flow periods.
SARDI Aquatic Sciences 31 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Table 6 Results of PERMANOVA comparing both cumulative and maximum distances moved by golden perch in the impact and control sites during high and low flow periods.
Factor df F P Cumulative distance Site 1,20 0.255 0.593 Flow 1,20 0.002 0.960 Site x Flow 1,20 2.71 0.119 Max distance Site 1,20 0.150 0.704 Flow 1,20 0.007 0.951 Site x Flow 1,20 3.345 0.085
SARDI Aquatic Sciences 32 Movement and spawning of Murray cod and golden perch in response to flow manipulation
3.2 Spawning12B
3.2.1 Site26B characteristics
Discharge in Little Slaney Creek during the low flow (2007/2008) sampling period appears to fluctuate (Figure 19). Nevertheless, manual readings of the gauging boards indicated that discharge in Little Slaney Creek and Lower Slaney Creek remained relatively constant during this sampling period at approximately 200 ML d-1 and 800 ML d-1 respectively (Figure 20). The variation between automated and manual discharge measurements was likely due to fouling of the automated gauging stations.
At the beginning of the high flow sampling period (early October 2008) discharge was approximately 200 ML d-1 until mid November when stop logs were removed. A stepped increase in discharge occurred over approximately 1 week and at the end of the sampling period discharge was approximately 1,200 ML d-1.
Stage height also varied between the two sampling periods (Figure 19). In 2007/2008 water level was relatively stable ranging between 17.6 – 17.8 m. At the beginning of the 2008/2009 sampling period the water level was similar to that observed for 2007/2008 (approximately 17.6 m) however in mid November, after stop logs were removed, water level had increased by approximately 0.6 m – 18.2 m.
1800 19.0
1600 18.5 1400 )
-1 1200 18.0
1000 17.5 800
600 17.0 Stage height (m) Discharged (ML low flow high flow 400 16.5 200
0 16.0 Jun - 07 Oct - 07 Feb - 08 Jun - 08 Oct - 08 Feb - 09 Jun - 09 Date
Figure 19 Discharge (ML d-1, solid line) and stage height (m, dotted line) in Little Slaney Creek from June 2007 – June 2009. Arrows indicate the larval sampling period in each year.
SARDI Aquatic Sciences 33 Movement and spawning of Murray cod and golden perch in response to flow manipulation
1600
Little Slaney 1400 Lower Slaney Little Slaney gauge Lower Slaney gauge 1200 )
-1 1000
800
Discharge (MLd 600
400
200
0 Apr - 07 Jun - 07 Aug - 07 Oct - 07 Dec - 07 Feb - 08 Apr - 08 Jun - 08 Aug - 08 Month
Figure 20 Automated discharge (ML d-1) in Little Slaney Creek (dashed line) and lower Slaney Creek (solid line) and discharge calculated from manually read gauge heights in Little Slaney Creek (open circles) and lower Slaney Creek (black circles) from April 2007 – July 2008.
3.2.2 Murray27B cod
In 2007/2008, Murray cod larvae were collected at all sites and were present in the catch from 22/10/2007 to 2/12/2007 as surface water temperature exceeded 20 °C (Table 7 and Figure 21). A total of 46 (absolute abundance) larvae were captured and the greatest standardised abundances (catch per unit effort) of Murray cod larvae were captured from Little Slaney Creek immediately downstream of Slaney Weir (Table 7).
In 2008/2009, Murray cod larvae were present in the catch from 28/10/2008 to 10/12/2008 when a total of 202 (absolute abundance) larvae were captured (Table 7 and Figure 21). Murray cod larvae were collected at all sites, however, the greatest standardised abundances (catch per unit effort) were collected from upstream of Slaney Weir and downstream of Slaney Weir (Table 7). The timing of the presence of larvae coincided with water temperatures > 20 °C.
Mean standardised abundances, for the four sites that were sampled in consecutive years, were not significantly different between the two sampling periods (uni-variate single factor PERMANOVA, t = 0.03, df = 6, P = 0.97).
SARDI Aquatic Sciences 34 Movement and spawning of Murray cod and golden perch in response to flow manipulation
3.2.3 Golden28B perch
No golden perch larvae were captured at any site during the 2007/2008 or 2008/2009 sampling.
Table 7 Raw (absolute abundance) and CPUE (standardised abundance, number of fish per 1000 m3 (drift nets) + number of fish per 12 hour period (light traps)) of Murray cod larvae captured within the Chowilla Anabranch system during spring/summer 2007/2008 and 2008/2009. NS = not sampled.
2007/2008 2008/2009 Site No. Location Raw CPUE Raw CPUE 1 Hypurna Creek d/s Swifty’s 5 13.6 NS NS 2 Salt Creek u/s Slaney junction 7 19.5 6 10.0 3 Lower Little Slaney Creek 6 3.0 21 21.7 4 Little Slaney Creek immediately d/s Slaney Weir 20 26.5 96 29.5 5 Murray River immediately u/s Slaney Weir NS NS 75 55.0 6 Lower Slaney Creek 8 13.5 1 0.3 7 Chowilla Creek d/s Lock 6 Bridge NS NS 3 11.5 Total 46 76.1 202 128.0
30 19.0
25 18.5 C) o
20 18.0
15 17.5
10 17.0 (m) height Stage
Surface water temperature ( Surface water 5 16.5
0 16.0 Jun - 07 Oct - 07 Feb - 08 Jun - 08 Oct - 08 Feb - 09 Jun - 09
Date Figure 21 Surface water temperature (°C, solid line) measured in Chowilla Creek and stage height (m, dotted line) measured in Little Slaney Creek from June 2007 – June 2009. The timing of the presence of Murray cod larvae captured within the Chowilla Anabranch system during the spring/summer 2007/2008 and 2008/2009 season is represented by hatched bars.
SARDI Aquatic Sciences 35 Movement and spawning of Murray cod and golden perch in response to flow manipulation
4 Discussion7B
4.1 Movement13B Between June 2007 and June 2009, 15 Murray cod and 28 golden perch were radio-tagged at a control and impact site in the Slaney Creek region of the Chowilla system to investigate behavioural responses to altered flow conditions. Low flows in the Murray-Darling Basin and delays to the refurbishment of Slaney Weir, however, caused extensive delays in conducting a flow manipulation in Slaney Creek. Many radio-tagged fish emigrated from the study sites prior to a flow manipulation commencing and when the study eventually commenced in November 2008 sample sizes were low (n = 5 – 8 fish/species/site).
High discharges (high flow period) at the impact and control sites (~ 1,100 and 1,400 ML d-1 respectively) created hydraulically complex habitats with mean average cross-sectional water velocities > 0.3 m s-1 and water depths > 2.0 m. Accordingly, both sites were classified as fast- flowing aquatic mesohabitats using the flow categories of Zampatti et al. (2008). Decreasing discharge at the impact site to ~ 100 ML d-1 caused a significant decrease in maximum depth and water velocities altering the hydrodynamics of this site so that it represented a slow-flowing mesohabitat. Nevertheless, the impact site still retained some hydraulic complexity and flowing water hydrodynamics, particularly in comparison to the hydraulically homogenous lentic habitats of the main channel of the Murray River. At the same time, the control site remained a hydraulically complex fast-flowing mesohabitat, albeit with some decrease in water depth.
Murray cod and golden perch movement in both the impact and control sites were variable and there was no distinct pattern of fish emigration during low or high flows. Over the flow manipulation period (1 November 2008 – 31 August 2009), Murray cod in both the impact and control site generally had high site fidelity and made small-scale movements around their original capture location, suggesting that Murray cod in this region are highly site specific. Strong site fidelity has also been observed for Murray cod in other anabranch systems, and the main channel and tributaries of the mid reaches of the Murray River (Jones and Stuart 2007; Saddlier et al. 2008; Koehn 2009). A small number of individuals moved away from the original tagging site and exhibited a shift in home range to alternative locations but generally remained within the Slaney Creek system. Whilst the results of this investigation indicate that our original hypotheses regarding Murray cod emigration during low flows could be rejected, the data should be interpreted with caution due to the low sample size (n = 3) of fish present at the impact sites when flow was reduced. Importantly, over the short time frame of the study, despite decreased flow, suitable aquatic habitats for Murray cod (including physical and hydraulic microhabitats) remained in Little Slaney Creek.
SARDI Aquatic Sciences 36 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Under low flow conditions freshwater fish may increase their range of movement, and select suboptimal habitats as preferred habitats along stream margins are lost (Riley et al. 2009). Cumulative and maximum movement distances for radio-tagged Murray cod were generally low (< 2 km) and there was no significant difference between sites or high and low flow periods. Murray cod are likely to select stream habitats with particular characteristics (e.g. water depth, velocity and large wood) (Koehn, 2009). Given the large physical size of Murray cod (maximum > 1.4 m long) deep pools (> 1.5 m) and scour holes (e.g. under snags) are likely to be important habitat attributes. Such habitats appeared to remain available at the impact site, even under significantly reduced flow. Nevertheless, small (e.g. young-of-year and 1+, < 200 mm) Murray cod may require alternative habitats such as complex physical regions in the littoral zone (Koehn 2009). It is likely that these habitats would have been considerably affected by the flow reduction and juvenile fish may have been displaced to less favourable habitats. The movement of Murray cod < 400 mm, however, was not investigated in our study, nor was the microhabitat use by juvenile and adult Murray cod. Consequently, these form important questions for further investigation.
Movement of Murray cod in response to hydrological alteration and the temporal and spatial availability of suitable habitat remains relatively unexplored in the MDB, with most studies investigating microhabitat (e.g. structural habitat and water depth) and macrohabitat (e.g. floodplain or main channel) use and temporal variation in movement (Reynolds 1983; Jones and Stuart 2007; Saddlier et al. 2008; Koehn 2009). Further investigation is required, using larger sample sizes of fish, to determine the response of Murray cod to altered hydrodynamics, particularly the very low velocities (< 0.1 m s-1) and homogenisation of hydraulic habitats that may be caused by the pooling effects of weirs.
Movement of golden perch from the impact site was greater in the high flow period (n = 3) than the low flow period (n = 1). Emigration of three golden perch at the commencement of the high flow period may have been due to an upstream migratory response stimulated by a substantial increase in discharge and water level (Mallen-Cooper and Brand 2007). These fish were constrained from moving upstream by Slaney Weir and moved back downstream, out of the experimental reach, potentially looking for an alternative route upstream. Such behaviour has previously been observed for radio-tagged golden perch encountering barriers to movement in the Chowilla system (B. Zampatti unpublished data).
Movement of golden perch out of the control site was concentrated between March and May 2009 and occurred during both high and low flows and the transition between. Seven radio-tagged golden perch (three fish from the impact site and four from the control site) moved out of the Chowilla Anabranch system and into the Murray River. Three of these fish were re-captured by anglers between the Rufus River and Lock 11 and four were recorded on the Passive Integrated
SARDI Aquatic Sciences 37 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Transponder (PIT) tag receivers located on the Lock 7 – 10 fishways. Similar large scale uni- directional movements have been observed for fish tagged in the lower reaches of Chowilla Creek (Zampatti et al. 2011). In fact these large scale movements have been widely observed for golden perch and whilst an upstream pre-spawning migration has been proposed (Reynolds 1983; O’Connor et al. 2005) the purpose of such movements remains unresolved (Zampatti et al. 2011).
Overall, movement of golden perch was highly spatio-temporally variable with fish exhibiting the three discrete types of movement (i.e. foraging, ranging and migratory) previously described for adult golden perch in the Chowilla system (Zampatti et al. 2011). Golden perch movement was more variable than Murray cod, and cumulative and maximum movement distances were greater, with maximum movement distances during the study period of up to 12 km. Like Murray cod, however, there was no significant difference in these parameters between sites or between flow events. Detecting flow related variation in golden perch movement with low sample sizes of radio-tagged fish may be difficult. Consequently, we suggest that future investigations of golden perch movement in relation to hydrological variability, particularly investigation of movement out of the Chowilla system, could be undertaken by using PIT tags and PIT tag readers on the proposed Slaney and Pipeclay Weir fishways. The low cost of PIT tags (< $5/tag) would enable a large sample (e.g. 100 – 1000s fish) to be tagged and monitored.
4.2 Spawning14B Murray cod larvae were collected in association with stable low flows in 2007/2008 and during a substantial increase in discharge through the Slaney Creek system in 2008/2009. In both years larvae were collected over a discrete period from late October to early December during which time water temperatures ranged from 20 – 25 °C. These observations are consistent with other studies in the MDB and support the general view that Murray cod spawn annually during a discrete season, independent of hydrological conditions and in association with increasing water temperatures (variously reported as > 15 – 20 °C) (Rowland 1983; Rowland 1998; Humphries 2005; Koehn and Harrington 2006).
Murray cod larvae were collected at all sites sampled in the Slaney Creek system and in fast-flowing mesohabitats in Hypurna Creek (immediately downstream of Swifty’s Creek), Salt Creek and Chowilla Creek. Nevertheless, the highest standardised abundances of Murray cod larvae were collected in 2008 in Little Slaney Creek immediately downstream of Slaney Weir and in the Murray River immediately upstream of Slaney Weir. These data indicate that high abundances of Murray cod larvae may be entrained in flow from the Lock 6 weir pool into the creeks of the Chowilla system. In 2008, the large increase in discharge (> 1,000 ML d-1) through Slaney Weir would have created a localised increase in discharge in the main channel potentially increasing the number of larvae entrained in the drift. Standardised abundances of larvae collected from sites consistently
SARDI Aquatic Sciences 38 Movement and spawning of Murray cod and golden perch in response to flow manipulation sampled across years, however, did not differ significantly. Given that Murray cod are a circa-annual spawner that shows strong site fidelity and may undertake annual return visits to a spawning site (Humphries 2005; Koehn et al. 2009) it would not be expected that spawning activity would increase in response to flow.
Despite the growing evidence that Murray cod spawn annually regardless of flow conditions (Humphries et al. 2002; Koehn and Harrington 2005; Koehn and Harrington 2006; Leigh et al. 2008) the current size distribution of adult Murray cod in the lower Murray River indicates there has been little recruitment over the last 16 years (Ye and Zampatti 2007). In comparison, the size distribution of fish captured from the Chowilla system shows that low levels of recruitment have occurred during this period (Zampatti et al. 2008). The natural flow characteristics of the lower Murray River have been substantially altered since the construction of locks and weirs (Walker 2006). Importantly, lotic habitats in the main channel of the Murray River are rare at flows less than ~ 20,000 ML d-1 and the river only regains its true lotic nature when weirs are removed at ~ 50,000 ML d-1. Flows of this magnitude have not occurred in the lower Murray River since 2000. In contrast, the Chowilla Anabranch system retains aspects of the flow characteristics of the pre-regulation Murray River, particularly flowing water habitats. It may be these characteristics that promote Murray cod larval survival and growth. Consequently, during low flows, Murray cod larvae that originate from the Chowilla system, or are transported into the system from the Lock 6 weir pool, may have a higher chance of survival than those that remain in lentic main channel habitats.
Early studies of golden perch spawning and recruitment indicated that spawning was initiated by a rise in water level and floodplain inundation (Lake 1967; Harris and Gehrke 1994). More recently, however, golden perch spawning and recruitment has been described during periods of within channel flows (Humphries et al. 1999; Mallen-Cooper and Stuart 2003; Cheshire and Ye 2008; King et al. 2008; Leigh et al. 2008). Over a 5 year period (2004 – 2008) golden perch larvae were collected only once in the Chowilla Anabranch system (Leigh et al. 2008). These larvae were spawned in spring/summer 2005 coinciding with a small (~ 15,000 ML d-1) but prolonged (~ 3 months) increase in discharge into South Australia. Importantly, over the same period, golden perch spawning was detected in the lower and mid - lower reaches of the Murray River over a spatial scale of 1000s km (Cheshire and Ye 2008; King et al. 2008; Zampatti et al. 2011).
Spawning in 2005 contributed to a significant recruitment event for golden perch in the lower Murray River, despite the relatively small increase in discharge and rise in water level (~ 0.5 m) (Ye et al. 2008; Zampatti et al. 2008; Leigh et al. 2009). Further investigation of the age structure of golden perch populations in the lower Murray River has demonstrated the existence of discrete age groups that indicate episodic recruitment of golden perch occur only in years of increased discharge, either within-channel or overbank (Ye et al. 2008, Zampatti et al. 2008). Consequently, overbank flows are
SARDI Aquatic Sciences 39 Movement and spawning of Murray cod and golden perch in response to flow manipulation not imperative for spawning and recruitment of golden perch and within channel rises in flow may promote more consistent recruitment in highly variable river systems (Mallen-Cooper and Stuart 2003). However, age structure analysis of golden perch collected from different regions of the Lower Lakes (Ye 2005; Mayrhofer 2007; Bice 2010) show consistent annual recruitment with dominant age groups evident in years where recruitment was either low or absent from the population upstream of Lock 3 (Ye et al. 2008; Zampatti et al. 2008; Leigh et al. 2009), suggesting differences in recruitment between these two regions.
In the present study golden perch larvae were not collected in the Chowilla system during low stable flows in spring/summer 2007/08, nor during a substantial rise in flow (200 – 1,200 ML d-1) and water levels (~ 0.6 m) in spring/summer 2008/2009. This is despite the rise in discharge and water level in the Slaney Creek region being similar to that observed in 2005. In 2005, the flow event in the Murray River occurred across a spatial scale of thousands of kilometres, compared to the 2009 event in Slaney Creek that occurred at a scale of tens of kilometres. The factors which initiate spawning and promote recruitment of golden perch, and the spatial scale at which these occur, are complex and remain unresolved. Lake (1967) observed golden perch spawning in response to static water level rise in earthen ponds; nevertheless, most contemporary records of golden perch spawning and recruitment in the MDB have been associated with increasing discharge and water level in riverine habitats (Zampatti et al. 2011; King et al. 2010).
Golden perch larvae collected in the Chowilla region in 2005 were 22 – 38 days old and their origin was unknown (Zampatti et al. 2011). Furthermore, despite this spawning event contributing significantly to the age structure of golden perch collected above Lock 3 (Ye et al. 2008; Zampatti et al. 2008; Leigh et al. 2009) this age group is absent from the golden perch age structure below Lock 3 (Ye et al. 2008). Considering the drifting nature of golden perch eggs and larvae, and the travel time of water in the Murray River, the golden perch cohort spawned in 2005 may have originated from the Rufus River/Lock 7 region, approximately 80 km upstream of the Chowilla system.
Considering the available data on the movement (including the downstream displacement of eggs and larvae) and recruitment ecology of riverine populations of golden perch in the lower Murray River, we suggest that golden perch may require longitudinal physical and hydrological connectivity over scales of at least hundreds of kilometres to promote successful spawning and recruitment. Consequently, flow manipulation at the mesohabitat scale (1 – 10 km), in physical and hydrological isolation to larger spatial-scale flows, may not aid in the maintenance of golden perch populations in the lower Murray River.
SARDI Aquatic Sciences 40 Movement and spawning of Murray cod and golden perch in response to flow manipulation
5 Conclusions8B The results from the study illustrate the highly variable nature of golden perch and Murray cod movement in the regulated lower Murray River. Low samples sizes of radio-tagged fish throughout the flow manipulation period made it difficult to test our original hypotheses. Nevertheless, despite significant reductions in discharge, water depth and average cross-sectional water velocities at the site immediately downstream of Slaney Weir, low numbers of Murray cod and golden perch remained within this reach. Importantly, even though discharge was decreased markedly, the impact site still retained some hydraulic complexity and flowing water hydrodynamics, and provided suitable hydraulic and physical microhabitats for Murray cod. Further investigation is required, however, using larger sample sizes of fish, to determine the response of Murray cod to altered hydrodynamics particularly the very low velocities (< 0.1 m s-1) and homogenisation of hydraulic habitats that may be caused by the pooling effects of regulating structures.
Murray cod spawned during both the low flow and high flow events, supporting our original hypothesis. Murray cod is a circa-annual spawner and increased discharge did not appear to increase spawning activity. Nevertheless, our investigation showed that high abundances of larvae in the Slaney Creek system may originate from the Lock 6 weir pool in the vicinity of Slaney Weir, particularly when high discharge is passed through Slaney Weir. Importantly, irrespective of the origin of Murray cod larvae, the hydraulically diverse habitats of the Chowilla system may increase larval survival and hence recruitment into the adult population.
Golden perch did not spawn as predicted in response to increased discharge and water level. This is despite the hydrological conditions in Slaney Creek being similar to those in spring/summer 2005 when golden perch spawning and recruitment was observed throughout the mid – lower Murray River. Flow manipulation at the mesohabitat scale (1 – 10 km), in physical and hydrological isolation to larger spatial scale flows, may not facilitate spawning. Considering the current conceptual understanding of golden perch movement and recruitment, we propose flow events that incorporate longitudinal connectivity (physical and hydrological) over scales of at least hundreds of kilometres may be required to promote successful spawning and recruitment of golden perch in the highly regulated lower Murray River.
The present study investigated the movement and spawning of Murray cod and golden perch in response to varying discharge through Slaney Weir, one of several proposed hydrological interventions for the Chowilla system (DWLBC 2006). The study contributes to our current understanding of Murray cod and golden perch ecology and can be used to inform ecosystem restoration at Chowilla and more broadly in the MDB. Nevertheless, due to the range of physical and hydrological interventions proposed at Chowilla, further specific investigations will be required to assess risks and benefits to native fish and to facilitate an adaptive management approach.
SARDI Aquatic Sciences 41 Movement and spawning of Murray cod and golden perch in response to flow manipulation
6 References9B Adams, N. S., Rondorf, D. W., Evans, S. D., Kelly, J. E. and Perry, R. W. (1998). Effects of surgically and gastrically implanted radio transmitters on swimming performance and predator avoidance of juvenile Chinook salmon. Canadian Journal of Fisheries and Aquatic Sciences 55, 781-787. Anderson, M. J. (2001). A new method for non-parametric analysis of variance. Austral Ecology 26, 32-46. Bice, C. (2010). Biological information and age structure analysis of large-bodied fish species captured during the Lake Albert trial fish-down, October 2009. Report to Primary Industries and Resources South Australia – Biosecurity. South Australian Research and Development Institute (Aquatic Sciences), Adelaide, 27pp. SARDI Publication No. F2010/000159-1. SARDI Research Report Series No. 430. Boys, C. A. and Thoms, M. C. (2006). A large-scale, hierarchical approach for assessing habitat associations of fish assemblages in large dryland rivers. Hydrobiologica 572, 11-31. Brookes, J. D., Baldwin, D., Ganf, G., Walker, K. and Zampatti, B. (2006). Comments on the ecological case for a flow regulator on Chowilla Creek, SA. Report to DWLBC, September 2006. Brown, P., Sivakumaran, K. P., Stoessel, D. and Giles, A. (2005). Population biology of carp (Cyprinus carpio L.) in the mid-Murray River and Barmah Forest Wetlands, Australia. Marine and Freshwater Research 56, 1151-1164. Cattaneo, F. (2005). Does hydrology constrain the structure of fish assemblages in a french stream? Regional scale analysis. Archiv für Hydrobiologie 164, 367-385. Cheshire, K. and Ye, Q. (2008). Larval fish assemblages below Locks 5 and 6, in the River Murray, South Australian from 2005 – 2007: with reference to water manipulation trials. SARDI Aquatics Sciences, Adelaide, pp 42. SARDI Aquatic Sciences Publication Number: F2007/000705-1. SARDI research report series number: 175. Dudley, R. K. and Platania, S. P. (2007). Flow regulation and fragmentation imperil pelagic-spawning riverine fishes. Ecological Applications 17, 2074-2086. DWLBC (2006). Asset Environmental Management Plan: Chowilla Floodplain (excluding Lindsay – Wallpolla) Significant Environmental Asset. DWLBC. Gorman, O. T. and Karr, J. R. (1978). Habitat structure and stream fish communities. Ecology 59, 507-515. Górski, K., Winter, H. V., De Leeuw, J. J., Minin, A. E. and Nagelkerke, A. J. (2010). Fish spawning in a large temperate floodplain: the role of flooding and floodplains. Freshwater Biology 55, 1509-1519. Harris J. H. and Gehrke P. C. (1994). Development of predictive models linking fish population recruitment with streamflow. In: Population Dynamics for Fisheries Management (Hancock, D.A. ed.). Australian Society for Fish Biology Workshop Proceedings, Perth, 24–25 August 1993.
SARDI Aquatic Sciences 42 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Humphries, P., King, A. J. and Koehn, J. D. (1999). Fish, flows and floodplains: links between freshwater fishes and their environment in the Murray-Darling River system, Australia. Environmental Biology of Fishes 56, 129-151. Humphries, P., Serafini, L. G. and King, A. J. (2002). River regulation and fish larvae: variation through space and time. Freshwater Biology 47, 1307-1331. Humphries, P. (2005). Spawning time and early life history of Murray cod, Maccullochella peelii peelii (Mitchell) in an Australian River. Environmental Biology of Fishes 72, 393-407. Jones, M. J. and Stuart, I. G. (2007). Movement and habitat use of common carp (Cyprinus carpio) and Murray cod (Maccullochella peelii peelii) juveniles in a large lowland Australian river. Ecology of Freshwater Fish 16, 210-220. King, A. J., Tonkin, Z. and Mahoney, J. (2008). Environmental flow enhances native fish spawning and recriutment in the Murray River, Australia. River Research and Applications 25, 1205-1218. King, A. J., Ward, K. A., O'Connor, P., Green, D., Tonkin, Z. and Mahoney, J. (2010). Adaptive management of an environmental watering event to enhance native fish spawning and recruitment. Freshwater Biology 55(1), 17-31. Koehn, J. and Nicol, S. (1998). Habitat movement requirements of fish. In Proc. 1996 Riverine Environment Forum (Eds. R.J. Banens and R. Lehane) pp. 1 – 6. October 1996, Brisbane, QLD. Publ. Murray Darling Basin Commission. Koehn, J. D. & Harrington, D. J. (2005). Collection and distrubution of the early life stages of the Murray cod (Maccullochella peelii peelii) in a regulated river. Australian Journal of Zoology 53, 137- 144. Koehn, J. D. & Harrington, D. J. (2006). Environmental conditions and the timing for the spawing of Murray cod (Maccullochella peelii peelii) and the endangered trout cod (M. macquariensis) in southeastern Australian rivers. River Research and Applications 22, 327-342. Koehn, J. D. (2009). Multi-scale habitat selection by Murray cod Maccullochella peelii peelii in two lowland rivers. Journal of Fish Biology 75, 113-129. Koehn, J. D., McKenzie, J. A., O'Mahony, D. J., Nicol, S. J., O'Connor, J. P. & O'Connor, W. G. (2009). Movements of Murray cod (Maccullochella peelii peelii) in a large Australian lowland River. Ecology of Freshwater Fish 18, 594-602. Lake, J. S. (1967). Rearing experiments with five species of Australian freshwater fishes 1. Inducement to spawning. Australian Journal of Freshwater Research 18, 137-153. Leigh, S. J., Zampatti, B. P. and Nicol, J. M. (2008). Spatial and temporal variation in larval fish assemblage structure in the Chowilla Anabranch system: with reference to water physico-chemistry and stream hydrology. SARDI (Aquatic Sciences), Adelaide pp 47. SARDI Aquatic Sciences Publication Number F2008/000051-1. SARDI Report Series Number 286. Leigh, S. J., Beyer, K. and Zampatti, B. P. (2009). Fish condition monitoring for the Katarapko Anabranch system 2009. SARDI (Aquatic Sciences), Adelaide pp 23. SARDI Aquatic Sciences Publication Number F2009/000469-1. SARDI Report Series Number 392.
SARDI Aquatic Sciences 43 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Maheshwari, B. L., Walker, K. F. and McMahon, T. A. (1995). Effects of river regulation on the flow regime of the River Murray, Australia. Regulated Rivers: Research and Management 10, 15-38. Mallen-Cooper, M. and Stuart, I. (2003). Age, growth and non-flood recruitment of two potamodromous fishes in a larage semi-arid/temperate river system. River Research and Applications 19, 697-719. Mallen-Cooper, M. and Brand, D. A. (2007). Non-salmonids in a salmonid fishway: what do 50 years of data tell us about past and future fish passage? Fisheries Management and Ecology 14, 319- 332. Mayrhofer, M. (2007). Comparison of the life history and population biology of golden perch, Maquaria ambigua (Richardson 1845) (Perciformes: Perchichthyidae) from the lower Murray River and lake Alexandrina, South Australia. Hons Thesis. School of Earth and Environmental Sciences, Adelaide University. MDBC (2006). The Chowilla Floodplain and Lindsay-Wallpolla Islands Icon Site Environmental Management Plan 2006-2007. MDBC Publication No. 33/06. Meredith, S., Gawne, B., Sharpe, C., Whiterod, N., Conallin, A. and Zukowski, S. (2002). Dryland floodplain ecosystems: influence of flow pattern on fish production. p. 44. Mildura, Victoria: Murray- Darling Freshwater Research Centre. O’Connor, J., O’Mahony, D. and O’Mahony, J. (2005). Movement of Macquaria ambigua, in the Murray River, south-eastern Australia. Journal of Fish Biology 66, 392-402. Poff, N. L. and Allan, J. D. (1995). Functional organization of stream fish assemblages in relation to hydrological variability. Ecology 76, 606-627. Reynolds, L. F. (1983). Migration patterns of five fish species in the Murray-Darling river system. Australian Journal of Marine and Freshwater Research 34, 857-871. Riley, W. D., Maxwell, D. L., Pawson, M. G. and Ives, M. J. (2009). The effects of low summer flow on wild salmon (Salmo salar), trout (Salmo trutta) and grayling (Thymallus thymallus) in a small stream. Freshwater Biology 54, 2581-2599. Rowland, S. J. (1983) Spawning of the Australian freshwater fish Murray cod, Maccullochella peeli (Mitchell), in earthen ponds. Journal of Fish Biology 23, 525-534. Rowland, S. J. (1998). Aspects of the reproductive biology of Murray cod, Maccullochella peelii peelii. Proceedings of the Linnean Society of New South Wales 120, 147-162. Saddlier, S., O’Mahony, J. and Ramsey, D. (2008). Protection and enhancement of Murray cod populations. Arthur Rylah Institute for Environmental Research Technical Report Series No. 172. Department of Sustainability and Environment, Heidelberg, Victoria. Serfafini, L. G. and Humphries, P. (2004). Preliminary guide to the identification of larvae of fish, with a bibliograpgy of thier studies, from the Murray Darling Basin. NSW: Cooperative Research Centre for Freswater Ecology. Sharley, T. and Huggan, C. (1995). Chowilla Resources Management Plan: Final Report. Murray Darling Basin Commission, Canberra.
SARDI Aquatic Sciences 44 Movement and spawning of Murray cod and golden perch in response to flow manipulation
Sheldon, F. and Lloyd, L. (1990). Physical limnology and aquatic habitats. In Chowilla Floodplain Biological Study (O’Malley, C. and Sheldon, F., eds.) pp 121-135. Nature Conservation Society of South Australia, Adelaide. Stace, P. and Greenwood, A. (2004). Chowilla Anabranch System Surface Water Information Summary. p. 88. Department of Water, Land and Biodiversity Conservation. Walker, K. F. (2006). Serial weirs, cumulative effects: the lower River Murray, Australia. In Ecology of Desert Rivers (Kingsford, R.., ed.), pp 248-279. Cambridge: Cambridge University Press. Ye, Q. (2005). Golden perch (Macquaria ambigua). Fishery assessment report to PIRSA Fisheries 2004. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Aquatic Sciences Publication Number RD04/0167, No. 71. Ye, Q. and Zampatti, B. (2007). Murray cod stock status: the Lower River Murray, South Australia. Stock status report to PIRSA Fisheries. South Australian Research and Development Institute (Aquatic Sciences), Adelaide, 32 pp. SARDI Publication No. F20007-000211-1. Ye, Q., Cheshire, K. and Fleer, D. (2008). Recruitment of golden perch and selected large-bodied fish species following the weir pool manipulation in the River Murray, South Australia. SARDI Aquatic Sciences, Adelaide, 33 pp. SARDI Aquatic Sciences Publication Number: F2008/000606-1. Zampatti, B. P., Leigh, S. J. and Nicol, J. M. (2008). Chowilla Icon Site – Fish Assemblage Condition Monitoring 2005 - 2008. South Australian Research and Development Institute (Aquatic Sciences), Adelaide, 38 pp. SARDI Publication Number F2008/000907-1. SARDI Research Report Series Number 319. Zampatti, B.P., Leigh, S.J. and Nicol, J.M. (2011). Fish and Aquatic macrophyte communities in the Chowilla Anabranch system, South Australia: A report on investigations from 2004 – 2007. South Australian Research and Development Institute (Aquatic Sciences), Adelaide.
SARDI Aquatic Sciences 45