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Assessment of the Barwon River barrage vertical slot fishway J. O’Connor and A. Pickworth June 2015

Arthur Rylah Institute for Environmental Research, Department of Environment, Land, Water and Planning

Unpublished Client Report for Corangamite CMA

Assessment of the Barwon River barrage vertical slot fishway

J. O’Connor and A. Pickworth

Arthur Rylah Institute for Environmental Research 123 Brown Street, Heidelberg, Victoria 3084

Department of Environment, Land, Water and Planning 123 Brown Street, Heidelberg, Victoria 3084

June 2015

Arthur Rylah Institute for Environmental Research Department of Environment, Land, Water and Planning

Heidelberg, Victoria

Report produced by: Arthur Rylah Institute for Environmental Research Department of Environment, Land, Water and Planning PO Box 137 Heidelberg, Victoria 3084 Phone (03) 9450 8600 Website: www.delwp.vic.gov.au

Citation: O’Connor, J. and Pickworth, A. (2015). Assessment of the Barwon River barrage vertical slot fishway. Arthur Rylah Institute for Environmental Research Unpublished Client Report for Corangamite CMA, Department of Environment, Land, Water and Planning, Heidelberg, Victoria.

Front cover photo: photo of Barwon River barrage vertical slot fishway (D. Lovric).

© The State of Victoria Department of Environment, Land, Water and Planning 2015

This work is licensed under a Creative Commons Attribution 3.0 Australia licence. You are free to re-use the work under that licence, on the condition that you credit the State of Victoria as author. The licence does not apply to any images, photographs or branding, including the Victorian Coat of Arms, the Victorian Government logo, the Department of Environment, Land, Water and Planning logo and the Arthur Rylah Institute logo. To view a copy of this licence, visit http://creativecommons.org/licenses/by/3.0/au/deed.en

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Contents Summary ............................................................................................................... 7

INTRODUCTION .................................................................................................... 9

METHODS .............................................................................................................. 9

Study site ....................................................................................................................................... 9

Barwon River fish community ..................................................................................................... 11

Fishway trapping ......................................................................................................................... 12

Electrofishing surveys .................................................................................................................. 15

Fish processing ............................................................................................................................ 15 Analysis ....................................................................................................................................... 15

Results ................................................................................................................. 16

River discharge and water temperature ......................................................................................... 16

Entrance/exit sampling ................................................................................................................. 16

Analyses ...................................................................................................................................... 17

Abundance ......................................................................................................................... 17

Stream discharge and tide ................................................................................................... 17

Length ........................................................................................................................... 17 Timing of movements .................................................................................................................. 19

Overnight trapping ....................................................................................................................... 19

Electrofishing surveys .................................................................................................................. 20

DISCUSSION ....................................................................................................... 21

RECOMMENDATIONS ........................................................................................ 23

REFERENCES ..................................................................................................... 24


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List of tables and figures List of tables

Table 1 Summary of the species of fish recorded in the Barwon River (including estuary) (modified from Hindell et al. 2008). ................................................................................... 13

Table 2 Sampling dates ............................................................................................................... 14

Table 3 Fish collected sampling in the entrance/exit of the fishway.............................................. 17

Table 4 Fish collected in the overnight trapping ........................................................................... 20

Table 5 Fish collected upstream and downstream of the weir using electrofishing ........................ 20

List of figures

Figure 1 Location of Barwon River barrage fishway .................................................................... 10

Figure 2 Construction of the Barwon River barrage fishway ........................................................ 11

Figure 3 The completed Barwon River barrage fishway ............................................................... 11

Figure 4 The fishway was trapped at the entrance and exit baffles using a trap constructed of stainless steel mesh and perforated aluminium. ................................................................... 12

Figure 5 A conceptual model showing the seasonal timing of fish migration, response to river flows. The hydrograph is for conceptual purposes only, the fish migration data are from Koehn and O’Connor (1990). ............................................................................................. 14

Figure 6 Average discharge at Barwon River barrage between May 2013 and May 2014, all sample dates are also shown .............................................................................................. 16

Figure 7 Length frequency comparisons between the entrance and exit of the fishway for the six most abundant fish species ................................................................................................. 18

Figure 8 Percentage monthly abundance of each species collected from the entrance of the fishway .............................................................................................................................. 19


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Acknowledgements This project was funded by Corangamite Catchment Management Authority (CCMA) and Fisheries Victoria Recreational Fishing Licences. The authors would like to thank Denis Lovric from CCMA who managed this project. Graeme Hackett, Matthew Jones, Scott Raymond (from the Arthur Rylah Institute) and Wayne McLaren (CCMA) also participated in fieldwork for this project. Matthew Jones was involved in the initial design phase of this project. Ivor Stuart provided useful comments on an earlier version of this document.


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Summary Dams and weirs reduce river connectivity and water managers are increasingly required to provide fish passage around these structures. In the Barwon River, interrupted river connectivity is a major threat to the native fish populations. Widely regarded as the most detrimental of the Barwon River barriers is the Barwon River barrage, which is located about 30 km downstream of Geelong.

In February 2013, in order to improve fish passage at the Barwon River barrage, Corangamite Catchment Management Authority (CCMA) installed a vertical-slot fishway to replace an old rock fishway. The ecological objective of the new fishway was to pass fish from 20 to 400 mm long. The present study reports on monitoring of the fishway for upstream fish passage to ensure it was operating to specification so that, if required, appropriate design or operational adjustments could be made.

To assess whether the fishway was working to its ecological objective it was trapped at the entrance and exit to gather data on the diversity, length and abundance of fish at the entrance and exit of the fishway. The fishway was trapped between April 2013 and May 2014 during spring and autumn on nine occasions. On each sampling occasion, three entrance/exit replicates were completed. Following completion of the fishway trapping a section of the river upstream and downstream of the fishway was boat electrofished to assess what species of fish inhabited these areas.

Greater than 14,000 fish comprising 16 native and two introduced species were collected from within the fishway and fish migrated over a wide range of seasons. Up to 3,500 fish migrated through the fishway per hour. The current study indicated that fish are able to locate and enter the fishway entrance and that the fishway entrance with extra auxiliary water was efficiently attracting fish from the estuary.

Within the fishway, there were no significant differences in the abundance of Tupong, Common galaxias, Australian smelt, Australian grayling and Yellow eye mullet collected from the exit and entrance of the fishway. There were, however, significantly fewer Flat headed gudgeon collected at the exit compared to the entrance of the fishway. Although Australian smelt and Yellow eye mullet were significantly smaller at the entrance compared to the exit the original ecological objective of passing fish from 20-400 mm was met.

Eighteen native and two introduced species were collected by boat electrofishing the area immediately below the Barwon River barrage while eight native and four introduced species were collected electrofishing the area immediately upstream of the Barwon River barrage. Twelve species of fish which were found below the weir were also collected within the fishway. Of the remaining eight species of fish located downstream of the weir and not collected in the fishway all are considered to be estuarine dependant with the exception of the non-native common carp, which often inhabit the fresher areas of estuaries.

No Estuary perch were collected from within the fishway or in the river upstream despite this species being known to enter freshwater reaches of rivers and streams. Yellow eye mullet were trapped in large numbers at the exit of the fishway and a single fish was also collected while electrofishing upstream indicating that this angling species may colonise upstream. We suggest that, to document the restoration of fish communities upstream of the barrage further sampling is required.

Vertical slot fishways appear to be a very suitable design for Victorian coastal systems particularly if further improvements for the passage of some of the smaller species and size class of fish such as Yellow eye mullet, Australian smelt and Flat headed gudgeon can be made. In conclusion, the Barwon River barrage vertical-slot fishway appears to be an excellent ecological investment and will strongly contribute to future restoration of native fish communities in the lower Barwon River system.


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Recommendations:

Undertake fish surveys in the area upstream of the Barwon River barrage to assess colonisation of species including Estuary perch and Yellow eye mullet.

Ensure an environmental water allocation for year-round operation of the Barwon River barrage vertical-slot fishway.

Consider targeted experiments to improve passage of the smallest size classes of fish. Consider investigating whether downstream migrating fish can efficiently negotiate structures

to return to estuarine waters.


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INTRODUCTION Large numbers of dams and weirs have been constructed around the world to provide for hydropower, irrigation, navigation, storage and flood control with important benefits to the communities they support (Bowman 2002). But along with the social benefits that these structures provide there are also many detrimental impacts, particularly to the natural environment. Dams and weirs modify flow regimes, disrupt sediment transport, alter water quality, and reduce river connectivity (Poff and Hart 2002). Given that many aquatic animals need to migrate up and down river systems and that many important life history traits such as spawning and dispersal are driven by river flow and temperature, there are detrimental impacts that such structures can have on the natural environment.

Unimpeded passage for fish throughout streams is crucial for spawning migrations, recolonisation, general movement and habitat selection (Koehn and O’Connor 1990). Furthermore, connectivity of river habitats is recognised as important for maintaining and restoring native fish populations. In Victoria fish movement is protected by legislation through a number of Acts (Water Act 1999, Fisheries Act 1995, Flora and Fauna Guarantee Act 1988, Conservation, Forests and Lands 1987) and “…the prevention of passage of aquatic biota as a result of instream structures…” is identified as a potentially threatening process (Flora and Fauna Guarantee Act 1988). In coastal drainages of Victoria up to seventy percent of native fish may need to migrate between freshwater and marine/estuarine habitats to complete their life history (Koehn and O’Connor 1990). Considering the importance of movement by fish in maintaining biodiversity, the provision of fish passage has become an important aspect of stream rehabilitation.

Given the potential impacts upon fish assemblages as a result of restricted movement around weirs and dams, water managers are increasingly required to provide upstream fish passage around these structures. Frequently, this constitutes construction of a fishway. In the Barwon River, Victoria decreased connectivity has long been recognised as a major threat to the fish populations where a number of weirs exist to regulate water diversions (Hindell et al. 2008; Raadik and Koster 2000, O’Brien 1997). The Barwon River supports a diverse community of fish, including 16 species of native freshwater fish some of which are considered threatened at state and national level. Nine of these species are considered to be diadromous and require free access to estuarine or marine waters to successfully complete their life cycles. Among these are the Australian mudfish (Neochanna cleaveri), Broad-finned galaxias (Galaxias brevipinnis), Common galaxias (Galaxias maculatus), Pouched lamprey (Geotria australis), Short-finned eels (Anguilla australis), Short-headed lamprey (Mordacia mordax), Spotted galaxias (Galaxias truttaceus), Tupong (Pseudaphritis urvillii) and the nationally endangered, EPBC listed species Australian grayling (Prototroctes maraena). Widely regarded as the most detrimental of the Barwon River barriers is the Barwon River barrage, which is located about 30 km downstream of Geelong.

In 2012, in order to improve fish passage at the Barwon River barrage Corangamite Catchment Management Authority (CCMA) commissioned the installation of a new vertical slot fishway designed to improve longitudinal connectivity for fish and other aquatic fauna in the Barwon River. This report documents a study commissioned by the CCMA to assess the functioning of this structure. We monitored the fishway for upstream fish passage to ensure the fishway was operating to specification so that appropriate design or operational adjustments could be made if required. This monitoring program was undertaken to gather data on the diversity, length and abundance of fish at the entrance and exit of the fishway.

METHODS

Study site The study site was located approximately 15 km downstream of Geelong, at a tidal barrage on the lower Barwon River (Figure 1). This barrage was constructed in the late 1930s and is located


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approximately 1.5 km upstream of Lake Connewarre, and consists of a sheet-pile structure and two floating gates to control upstream water levels to a crest height of 0.85 m AHD. The weir was installed to prevent upstream incursion of salt water, and to maintain upstream levels of freshwater for irrigation and recreation. The barrage forms a barrier between fresh and estuarine water and the fish species associated with these habitats. The tidal range below the barrage is 0 to 0.5 m AHD.

The Barwon River barrage vertical-slot fishway was installed in February 2013 and replaced an ineffective rock ramp fishway built in 1995. The fishway is a 29 metre long, precast concrete, vertical-slot design, comprising 12 baffles with a 75 mm head loss (maximum water velocity at vena contracta was 1.21 m/s) between each baffle resulting in a total head differential along the entire length of the fishway of 0.85 m (this will vary depending on head and tailwater levels (Figure 2).

The slope of the fishway is 1v:30h. Cell dimensions of 1200 mm wide x 2400 mm long and the drop between pools, slot widths (0.18 m tapering to 0.14 m wide slots) and pool volume was designed to minimise turbulence levels (average 18 W/m3) for the passage of small fish (Water Technology 2010). A continuous layer of small rocks (0.1-0.15 m diameter) were installed in the floor of the fishway to enhance roughness and thus passage of small demersal fish and crustaceans. The freshwater discharge into the estuary from the fishway is 6.6 ML/d. The fishway operates with a pool depth of 0.4 to 0.6 m which was limited by the upstream invert being set at 0.45 m due to stakeholder concerns relating to the unlikely event of the fishway significantly reducing the weir pool level. The downstream fishway invert was set at -0.40 m AHD which provided a minimum depth of 0.4 m even when the tide was low (0.0 m AHD). To increase fish attraction, an auxiliary flow is introduced at the fishway entrance by a small box culvert (Figure 3).

Figure 1 Location of Barwon River barrage fishway


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Figure 2 Construction of the Barwon River barrage fishway

Figure 3 The completed Barwon River barrage fishway

Barwon River fish community Twenty estuarine/marine fish species and 21 freshwater fish species (including seven alien species) occur in the Barwon River (Hindell et al. 2008; O’Brien 1997) (Table 1). Many of the freshwater species found in the Barwon River are small bodied species of less than 300 mm in length. The size of the species has important implications for the passage of fish across barriers and hence the internal hydraulics of the fishway were conservative to enable the passage of these fish. At least eight of the


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species listed in Table 1 are diadromous, and must move between freshwater and estuaries to complete their lifecycle.

The size range of fish targeted for passage at the Barwon River barrage fishway was 20-400 mm long (Water Technology 2010). The target size range of small fish was based on the data from the previous monitoring of the rock fishway at the Barwon River barrage (O’Brien 1997). Some larger fish may also be present at the Barwon River barrage, such as Bream (Acanthopagrus butcheri), Estuary Perch (Macquaria colonorum) and Mulloway (Agyrosomus japinicus) and they may migrate as juveniles through the fishway or when the structure is drowned out during a high flow event (Hindell et al. 2008).

Fishway trapping To assess whether the fishway was functioning to the target ecological specification (to pass fish from 20-400 mm long) it was trapped at the entrance and exit baffles. This method was used to gather data on the diversity, length and abundance of fish at the entrance and exit of the fishway.

A trap was constructed and used to monitor fish movements at the entrance and exit of the fishway. Previous studies (Hindell et al. 2008; O’Brien 1997) indicated that many of the species utilising the fishway would be juvenile diadromous species moving into freshwater habitats following their marine larval phase. The fishway traps were constructed using 3.2 mm sized stainless steel mesh and perforated aluminium to ensure that both small and large fish were captured (Figure 4).

Figure 4 The fishway was trapped at the entrance and exit baffles using a trap constructed of stainless steel mesh and perforated aluminium.


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Table 1 Summary of the species of fish recorded in the Barwon River (including estuary) (modified from Hindell et al. 2008). Common name Scientific name

Estu

arin

e/m

arin

e Australian herring Arripis georgianus Luderick Girella tricuspidata Greenback flounder Rhombosolea tapirina Silver trevally Pseudocaranx dentex Sandy sprat Hyperlophus vittatus Spotted pipefish Stigmatopora argus Longsnout flounder Ammotretis rostratus Smooth toadfish Tetractenos glaber King george whiting Sillaginodes punctatus Australian salmon Arripis trutta esper Yelloweye mullet Aldrichetta fosteri Sea mullet Mugil cephalus Tailor Pomatomus saltatrix Small mouthed hardyhead Atherinosoma microstoma Bridled goby Arenigobius bifrenatus Tamar goby Afurcagobius tamarensis Scary’s Tasman goby Tasmanogobius lasti Mulloway Sciaena Antarctica Black bream Acanthopagrus butcheri Estuary perch Macquaria colonorum

Fres

hwat

er

Australian grayling* Prototroctes maraena Pouched lamprey* Geotria australis Short-headed Lamprey* Mordacia mordax Tupong* Pseudaphritis urvillii Short-finned eel* Anguilla australis Broad-finned galaxias* Galaxias brevipinnis Spotted galaxias* Galaxias truttaceus Common galaxias* Galaxias maculatus River blackfish Gadopsis marmoratus Yarra pygmy perch Edelia obscura Australian smelt Retropinna semoni Flat-headed gudgeon Philypnodon grandiceps Southern pygmy perch Nannoperca australis Brown trout Salmo trutta

Exot

ic

Rainbow trout Oncorhynchus mykiss Carp Cyprinus carpio Goldfish Carassius auratus Gambusia Gambusia holbrooki Redfin Perca fluviatilis Roach Rutilus rutilus Tench Tinca tinca

*diadromous


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The fishway was trapped at the exit and entrance baffles on nine occasions between April 2013 and May 2014 during spring, summer and autumn (Table 2). Sampling was undertaken during these periods to coincide with peak migration periods of the target fish species moving upstream into freshwater following their marine larval phase (Figure 5).

Table 2 Sampling dates Sampling occasion Date 1 3-4/4/2013 2 7-8/5/2013 3 5-6/9/2013 4 17-18/10/2013 5 19-20/11/2013 6 12-13/2/2014 7 19-20/3/2014 8 14-15/4/2014 9 14-15/5/2014

Each sampling event was undertaken over two days and three entrance/exit paired replicates were completed. The trap was set in the morning of Day 1in the exit cell of the fishway (usually between 11am -12 pm) and checked approximately every 1.5 hours. Three replicates were completed on Day 1of sampling; two exit cell samples followed by an entrance cell sample. At the completion of daytime sampling the trap was left in overnight in the exit cell of the fishway (usually set between 4-6 pm) and checked the following morning (usually checked between 7-9 am). When the overnight set had been processed the trap was set at the exit cell of the fishway followed by two fishway entrance cell samples. The exit cell was never sampled immediately after sampling the entrance cell (with the exception of the overnight set) to avoid the entrance trap impacting on the number of fish collected in the exit cell. All fish captured were returned to the river upstream of the fishway.

Figure 5 A conceptual model showing the seasonal timing of fish migration, response to river flows. The hydrograph is for conceptual purposes only, the fish migration data are from Koehn and O’Connor (1990).


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Electrofishing surveys Following completion of the fishway trapping, a section of the river approximately 500 m immediately upstream and downstream of the fishway was electrofished to assess what species of fish inhabited these areas. This sampling was undertaken to coarsely determine if the fishway was passing all the species of fish found below the fishway and assess any changes in the upstream fish community. We acknowledge that more upstream sites would be required and a longer sampling timeframe to determine any changes but this was beyond the scope of the present project. Extra effort would be required because many of the diadromous fish that pass through the fishway may swim well upstream into the Barwon River catchment beyond the study area.

We used a modified Sustainable Rivers Audit (SRA) methodology (Davies et al. 2008) to conduct the fish surveys. Electrofishing was conducted using a boat mounted prototype Grassl electrofishing unit capable of operating in elevated conductivities (Warry et al. 2013). At each site, 12, 90-second electrofishing shots were undertaken. All habitat types within a site were sampled to increase the likelihood of collecting all fish species. All electrofishing was undertaken during daylight hours.

Fish processing At the conclusion of each trapping or electrofishing sampling event, fish collected were placed into aerated containers until they were processed. Fish captured were identified to species and most measured for fork or total length (mm), however if large numbers of an individual species were captured, a sub sample of 50 fish were measured for length, and the remaining fish counted. Fish that were collected in the fishway were released upstream while fish collected electrofishing were released in the area where they were captured.

Analysis A statistical assessment of the abundance and length frequency between the entrance and exit of the fishway was undertaken on fish species that were collected in sufficient numbers. These species included Tupong, Common galaxias, Australian smelt, Flat headed gudgeon, Australian grayling and Yellow eye mullet. To assess for differences in abundance the number of fish collected at the entrance and exit of the fishway were compared using a Wilcoxon’s rank sum test using raw abundance data from each sampling occasion. The length frequency of the fish at the exit and entrance were also compared using Kolmogorov-Smirnov two-tailed test for the paired samples.

An analysis of variance was also conducted on the abundance of these species and sample location with stream discharge and tide as co-variants. Stream discharge data was collected from the Water Measuring Information System: http://data.water.vic.gov.au/wini/webintro.htm?news=webnews.htm&2015032513022 at the Barwon River upstream of the lower barrage (Site No. 233269). Tide was measured at the Barwon Heads bridge (http://tides.willyweather.com.au/vic/barwon/barwon-heads-bridge.html) and categorised into four states; 1st half of incoming tide, 2nd half of incoming tide, 1st half of outgoing tide, 2nd half of outgoing tide. The time that each replicate began was allotted to one of the above states of tide.


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Results

River discharge and water temperature River discharge in the Barwon River ranged from 0 - 3600 ML/day during the study period (Figure 6). Stream discharge was variable, however peak discharges occurred during June – October 2013.

Figure 6 Average discharge at Barwon River barrage between May 2013 and May 2014, all sample dates are also shown ( )

Entrance/exit sampling A total of over 14,000 fish comprising 16 native and two introduced species were collected from within the fishway (Table 3). The most abundant species was the Common galaxias comprising 92% of the catch. Tupong, Australian smelt and Yellow eye mullet were also common. Juvenile Australian grayling, a nationally endangered species, were present while a single Australian salmon, Broad finned galaxias, Short headed lamprey and Smooth toadfish were also collected from the entrance of the fishway.


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Table 3 Fish collected sampling in the entrance/exit of the fishway

Species Abundance Length

Entrance Exit Minimum Maximum Australian grayling 12 12 45 54 Australian salmon 1 0 136 n/a Australian smelt 125 90 20 68 Broad finned galaxias 1 0 44 n/a Common galaxias 9657 3533 31 135 Flat headed gudgeon 196 23 21 112 Sea mullet 4 2 28 30 Short finned eel 2 0 60 950 Small mouthed hardyhead 24 1 29 96 Southern pygmy perch 2 4 44 55 Spotted galaxias 23 2 44 55 Toad fish 1 0 142 n/a Tupong 245 130 22 194 Yellow eye mullet 102 9 26 348 *Gambusia 16 9 18 41 *Redfin 1 8 85 236

*Introduced

Analyses

Abundance Statistical analysis using a Wilcoxon’s rank sum test showed there were no significant differences in the abundance of Tupong (p>0.05), Common galaxias (p>0.05), Australian smelt (p>0.05), Australian grayling (p>0.05) and Yellow eye mullet (p>0.05) collected from the exit and entrance of the fishway. There were, however, significantly fewer Flat headed gudgeon (p<0.05) collected at the exit compared to the entrance of the fishway.

Stream discharge and tide An ANOVA conducted on the abundance of these species and sample location with stream discharge and tide as co-variants indicated that abundance did vary with stream discharge for Common galaxias, Tupong and Australian grayling (p< 0.05) with abundance increasing with increasing river discharge. There was no significant influence of tide on fish abundance.

Length Length frequency graphs of the six most abundant species were produced to compare the lengths of fish located between the entrance and exit of the fishway. This assessment indicated that the length of Australian smelt and Yellow eye mullet were smaller at the entrance compared to the exit of the fishway (Figure 7). A statistical analysis using Kolmogorov-Smirnov test showed there were no significant differences in the length frequency of Tupong (p>0.05), Flat headed gudgeon (p>0.05), Common galaxias (p>0.05) or Australian grayling (p>0.05). However, this analysis did confirm that Australian smelt and Yellow eye mullet were significantly smaller (p<0.05) at the entrance compared to the exit of the fishway. Specifically, Australian smelt and Yellow eye mullet less than 35 mm long appeared unable to efficiently ascend the fishway.


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Figure 7 Length frequency comparisons between the entrance and exit of the fishway for the six most abundant fish species


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Timing of movements An assessment of the timing of movements of the five most common species was undertaken by assessing the percentage monthly abundance of each species collected from the entrance of the fishway (Figure 8). The majority of fish movements were undertaken during spring with peak migration of Common galaxias (78%) and Australian smelt (40%) occurring in November. However, peak migration of Flat headed gudgeon (36%), Yellow eye mullet (70%) and Tupong (40%) was in February. While the total number of Australian grayling collected was relatively low compared to other species, the majority of these juvenile fish were collected in November (n=22).

Figure 8 Percentage monthly abundance of each species collected from the entrance of the fishway

Overnight trapping Over 3,500 fish comprising seven native and one introduced species were collected from within the fishway during the overnight exit trap sets (Table 4). Once again the most common species was the Common galaxias while two Australian grayling were also collected. No fish species were detected that exclusively migrated at night.

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

Flat headed gudgeon

common galaxiid

Australian smelt

Yellow eye mullet

Tupong


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Table 4 Fish collected in the overnight trapping

Species Abundance Australian grayling 2 Australian smelt 83 Common galaxias 2321 Flat headed gudgeon 279 Tamar river goby 4 Tupong 840 Yellow eye mullet 145 Gambusia* 60

*introduced

Electrofishing surveys Eighteen native and two introduced fish species were collected by electrofishing the area below the Barwon River barrage while eight native and four introduced species were collected by electrofishing the area upstream of the Barwon River barrage (Table 5). Eight of the species located downstream of the weir were considered to be estuarine dependant species.

Twelve species of fish which were found below the weir were also collected within the fishway. Of the remaining eight species downstream of the weir and not collected in the fishway all are considered to be estuarine dependant with the exception of carp. However some of these species are known to periodically inhabit freshwater including Estuary perch and Black bream. Table 5 Fish collected upstream and downstream of the weir using electrofishing

Species Downstream of barrage

Upstream of barrage

Australian grayling 0 1 Australian smelt 267 378 Bream# 92 0 Common galaxias 1271 378 Estuary perch# 96 0 Flat headed gudgeon 292 404 Lamprey (unidentified species) 1 0 Luderick# 82 0 Sandy sprat# 1032 0 Sea mullet# 33 0 Short finned eel 1295 7 Silver trevally# 2 0 Small mouthed hardyhead 8 2 Smooth toadfish# 35 0 Southern pygmy perch 1 0 Tamar river goby 1 0 Tupong 118 149 West Australian salmon# 1270 0 Yellow eye mullet 1273 1 Carp* 39 404 Gambusia* 0 26 Goldfish* 0 30 Redfin* 13 366

*introduced; # estuarine dependant


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DISCUSSION Entrance attraction efficiency The current study indicated that fish were able to locate and enter the fishway entrance. All of the species found downstream of the weir that would be expected to enter the fishway were collected in the fishway. This indicates that the position of the fishway entrance and that the addition of auxiliary water provides optimal attraction conditions. Given that the weir dramatically separates freshwater and estuarine water it is not surprising the estuarine dependant species did not enter the fishway where only freshwater was present. Indeed on one occasion immediately downstream of the fishway entrance large numbers (10,000’s) of sandy sprat were observed but none of these entered the fishway. Passage through the Fishway The results of this project indicate that the Barwon River vertical slot fishway successfully passed most of the initial design’s target size range of fish (20-400 mm long; Hindell et al. 2008; Water Technology 2010). The new vertical-slot fishway passed 18 fish species and very large numbers (up to 3500 per hour) of small fish including galaxiids, Australian smelt, Flat headed gudgeon and Yellow eye mullet. One important finding was that young-of-the-year Australian grayling, a nationally threatened species, also migrated through the fishway. The new fishway operates for a greater range of fish sizes and river flows compared to the old rock fishway and represents a major step forward for restoration of migratory fish communities in the Barwon River system. The Barwon River barrage vertical-slot fishway was designed with very conservative water velocities and turbulence to meet the challenging objective of passing fish from 20+ mm long. However, it appears that small (<35 mm long) Australian smelt and Yellow eye mullet are unable to pass upstream efficiently. The minimum size of the target species of fish reflects fish with the weakest swimming ability and determines the maximum water velocity and turbulence levels required within a fishway. Swimming ability is directly related to body size and smaller fish are generally weaker swimmers. Maximum attainable swimming speed increases with body length (Rodgers et al. 2014), with larger fish producing more power and attaining higher velocities (Baker and Boubee 2006). There was no significant difference in the size of Flat headed gudgeon between the entrance and exit of the fishway, however these were significantly more abundant at the entrance suggesting that this species regardless of its size was not efficiently moving up the fishway. Previous studies have documented the poor swimming ability of gudgeon (Kilsby and Walker 2010). A closely related gudgeon species was completely unable to ascend low gradient vertical slot fishways which had higher pool headloss (100 mm each) and turbulence (35-45W/m3) than at the Barwon River barrage (Stuart and Mallen-Cooper 1999; Stuart et al. 2008). Despite some small gudgeon not fully ascending at the Barwon River barrage fishway it appears that the lower headloss between pools (75 mm each) and turbulence (18 W/m3) did facilitate some gudgeon passage which is a major advancement in providing effective passage for weak swimming fishes. Exiting the Fishway Sampling in the upstream weirpool indicated that the fishway was successfully exiting fish out of the fishway. In particular large numbers of juvenile Common galaxias (0+) were found upstream of the fishway. Given that during the monitoring period the barrier was not drowned out it follows that all of these fish successfully negotiated their way upstream through the fishway. The presence of juveniles (0+) of other species including Australian grayling, Australian smelt, Yellow eye mullet and Tupong also suggest that the fishway is performing all three facets of function (attraction, passage and exit) successfully. Luderick, Sandy sprat and Black bream were consistently collected by electrofishing downstream of the Barwon River barrage (Mulloway were also reported by anglers), however these species were never collected in the fishway or upstream of the barrage. Importantly, the Barwon River barrage not


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only acts as a physical barrier to upstream fish movement but it has also altered upstream habitat potentially making large areas less suitable for obligatory estuarine species, which were all once found as far upstream as Geelong. This type of altered river ecology has been documented in other coastal rivers (Zampatti et al 2011). No Estuary perch were collected from the fishway or areas upstream despite this species being known to enter freshwater reaches of rivers and streams (O’Connor et al. 2012; Austral Ecology 2014). The estuarine/freshwater interface at the Barwon River barrage is abrupt whereby salinity levels increase from freshwater immediately above the barrage to approaching sea water immediately downstream of the barrage. Under natural conditions this estuarine/freshwater interface occurs over a much gentler gradient which may allow fish to acclimatise as they move upstream over many kilometres. The dramatic decrease in salinity at the estuarine-freshwater interface at the barrage may discourage estuarine residents known to enter freshwater (such as Estuary perch) from continuing further upstream. Another possible reason for the lack of Estuary perch upstream may be the loss of tidal influence. In many Victorian streams Estuary perch can be found within the freshwater reaches of rivers but usually still within the tidal influence (O’Connor et al. 2012). However, in contrast to this, a population of Estuary perch in the Glenelg River are found many 10’s of kilometres upstream in the freshwater reaches well beyond the tidal influence (Austral Ecology 2014). Yellow eye mullet, a popular angling species, was found in large numbers at the exit of the fishway and a single fish was also collected in the river upstream of the fishway. While a more rigorous assessment of the fish community upstream of the barrage is required these early results indicate that this angling species may colonise upstream. We specifically suggest that further upstream sampling at sites where these species many accumulate would be useful in documenting the recovery of diadromous fish in the freshwater reaches of the Barwon River system. Notable sites where future sampling could be conducted are at the old breakwater in Geelong and in the Bunyip pool below Buckley Falls. A large proportion of juvenile Tupong were collected below the weir in February. This is in contrast to Hortle (1979), where in a study undertaken in Tasmania it was found that juvenile Tupong began their return to freshwater habitats at the beginning of spring. This finding does not exclude the importance of spring for return movements into freshwater as some fish were collected during this period. However, it does indicate that in Victoria the autumn months up until April are also important for movement of juvenile Tupong.

Previous studies have indicated that it was unclear if individuals within coastal populations of Australian smelt exhibit diadromous migrations (McDowall 2006). However, the collection of juvenile fish found in the Barwon River barrage fishway in the current study suggests that these fish may be undertaking an upstream diadromous migration following a facultative marine larval phase. This is consistent with a recent study (Crook et al. 2008) which found that there was a diadromous population of Australian smelt present in some coastal Victorian streams. For the Barwon River barrage fishway this extends the importance of providing passage for Australian smelt.

There are only three vertical-slot fishways operating on coastal rivers in Victoria, one built at Cowwarr Weir (Thompson River) in 2011, the second built at Dights Falls (Yarra River) in 2012 and the third at the Barwon River barrage in 2013. All of these vertical-slot fishways replaced inefficient rock ramp fishways. Velocity and turbulence levels in these fishways were optimised for small to medium bodied fish (e.g. 20-400 mm long). In addition, Dights Falls and the Barwon River barrage fishways have a continuous layer of 150 mm diameter rocks placed on the floor of the fishway to enhance passage of macroinvertebrates and demersal fish (i.e. Tupong). To date these vertical-slot fishways appear to be providing good fish passage outcomes as their design has been based on similar fishways in coastal Queensland and inland rivers of the Murray-Darling Basin (Stuart and Mallen-Cooper 1999; Baumgartner et al. 2014).


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Vertical slot fishways appear to be a suitable design for Victorian coastal systems, particularly if improvements for the passage of some of the smaller species and size class of fish such as Yellow eye mullet, Australian smelt and Flat headed gudgeon can be made. Passage of fish in the Barwon River barrage fishway was improved by the low drops between pools and the low turbulence levels. There is some scope for further improvement in the current fishway design by further reducing turbulence (Mallen-Cooper et al. 2008). This can be achieved through retrospectively fitting metal strips to decrease slot area. However, there is a trade-off between potentially reducing turbulence and passing some smaller gudgeon and reducing fishway discharge and thus fish attraction below the barrage. Decreasing the slot width can also limit the passage of medium and large fish. The ecological necessity of passing the smallest fish (e.g. <20 mm long) therefore needs to be carefully balanced against other ecological criteria. An experiment to test the ecological value of temporary fishway modifications, such as narrowing slot width, is worth considering during future work. There are also other options for potentially extending the range of the fishway to small fish and this includes using sills to maximise water depth and low turbulence as the tide recedes and some of these may warrant further investigation. The installation of the vertical slot fishway is an major improvement on the previous rock ramp fishway and is a crucial step in restoration of migratory fish in the Barwon River system. Although the smallest size classes of some small-bodied fish species were restricted the majority of fish expected to utilise the fishway were able to successfully. Hence, the fishway met its original design objectives. Future improvements to the fishway function may be possible with targeted experiments to maximise passage of even smaller fish. In conclusion, the Barwon River barrage vertical-slot fishway appears to be an excellent ecological investment and will strongly contribute to future restoration of native fish communities in the lower Barwon River system.

RECOMMENDATIONS

Undertake fish surveys in the area upstream of the Barwon River barrage to assess colonisation of species including Estuary perch and Yellow eye mullet.

Ensure an environmental water allocation for year-round operation of the Barwon River barrage vertical-slot fishway.

Consider targeted experiments to improve passage of the smallest size classes of fish. Consider investigating whether downstream migrating fish can efficiently negotiate structures

to return to estuarine waters.


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REFERENCES Austral Ecology (2014). VEFMAP Adult Fish Monitoring of the Glenelg River 2014. Client Report for Glenelg Hopkins CMA. Baker, C. and Boubée, J. (2006). Upstream passage of inanga Galaxias maculatus and redfin bullies Gobiomorphus huttoni over artificial ramps. Journal of Fish Biology, 69(3):668 - 681. Baumgartner, L., Zampatti, B., Jones, M., Stuart, I. and Mallen-Cooper, M. (2014). Fish passage in Australia: not just an uphill battle. Ecological Management & Restoration 15, 28-39. Bowman M. B. (2002). Legal perspectives on dam removal. BioScience 52: 739–747. Crook, D., Macdonald, J. and Raadik, T. (2008). Evidence of diadromous movements in a coastal population of southern smelts (Retropinninae: Retropinna) from Victoria, Australia. Marine and Freshwater Research, 59, 638–646.

Davies P., Harris P., Hillman T. and Walker K. (2008). SRA Report 1: A Report on the Ecological Health of Rivers in the Murray-Darling Basin, 2004-2007. Prepared by the Independent Sustainable Rivers Audit Group for the Murray-Darling Basin Ministerial Council. Hindell, J.S., Stuart I. and Jones M. (2008). Assessment and recommendations on restoring fish passage across the Lower Barrage Tidal Barrage of the Barwon River. Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/98. Department of Sustainability and Environment, Heidelberg, Victoria. Hortle, M. E. (1979). The ecology of the Sandy, Pseudaphritis urvillii in south-east Tasmania. B.Sc. (Hons.) thesis, Zoology Department, University of Tasmania, Hobart. Kilsby, N. and Walker, K. (2010). Linking the swimming ability of small freshwater fish to body form and ecological habit. Transactions of the Royal Society of South Australia. Vol. 134, No. 1, pp.89-96. Koehn, J.D. and O’Connor, W.G. (1990). Biological information for management of freshwater fish in Victoria. ARI report. 165 pp. Kroes, M.J., Gough P., Schollema P. P. & Wanningen H. (eds) (2006). From sea to source: Practical guidance for restoration of fish migration in European rivers. Groningen: Interreg IIIC project ‘‘Community Rivers’’, 119 pp.Mallen-Cooper, M. and co-authors (2008). Innovative Fishways – Manipulating turbulence in the vertical slot design to improve performance and reduce cost. Fishway Consulting Services report to MDBA. McDowall, R. M. (2006). Crying wolf, crying foul, or crying shame: alien salmonids and a biodiversity crisis in the southern cool-temperate galaxioid fishes? Reviews in Fish Biology and Fisheries 16, 233–422. O’Brien, T. (1997). Rock fishways in Victoria. Proceedings of the 2nd National Fishway Technical Workshop, Rockhampton, June 1997. Ed.s A. Berghuis, P. Long and I. Stuart. O'Connor, J., Raymond, S. and Dodd, L. (2012). Offsets for Conservation of the EPBC Act-listed Australian Grayling, Prototroctes maraena. Arthur Rylah Institute for Environmental Research Technical Report Series No. 233. Department of Sustainability and Environment, Heidelberg, Victoria. Poff L, Hart D. (2002). How Dams Vary and Why It Matters for the Emerging Science of Dam Removal. BioScience 52 (8): 659-668.


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Raadik, T. and Koster, W. (2000). Pre and post fishway construction assessments – Barwon and Moorabool Rivers and Otway streams. Client Report for CCMA by Arthur Rylah Institute for Environmental Research. Department of Natural Resources and Environment, Heidelberg, Victoria. Rodgers, E., Cramp, R., Gordos, M., Weier, A., Fairfall, S., Riches, M. and Franklin, C. (2014). Facilitating upstream passage of small-bodied fishes: linking the thermal dependence of swimming ability to culvert design. Marine and Freshwater Research, 65, 710–719 Stuart, I.G. and Mallen-Cooper, M. (1999). An assessment of the effectiveness of a vertical-slot fishway for non-salmonid fish at a tidal barrier on a large tropical/sub-tropical river. Regulated Rivers: Research and Management 15, 575-590. Stuart, I., Zampatti, B. and Baumgartner, L. (2008). Can a low-gradient vertical-slot fishway provide passage for a lowland river fish community? Marine and Freshwater Research, 59, 332–346. Water Technology (2010). Barwon River fishway design. Client drawings for Corangamite Catchment Management Authority. Warry F, Reich P, Hindell J, McKenzie J, Pickworth A. (2013). Using new electrofishing technology to amp-up fish sampling in estuarine habitats. J Fish Biol. 82(4):1119-37.

Zampatti, B., Bice, C and Jennings, P. (2011). Movement of female congolli in the Coorong and lower lakes in the River Murray. SARDI Research Report Series No. 577. SARDI Publication No. F2011/000333-1.


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