South‐Western Minor Inlets Fish Habitat 2000

Curdies River, Gellibrand River, Aire River, Barham River, Painkalac Creek, Erskine River, Anglesea River and Barwon River.

Geoff Nicholson, Leanne Gunthorpe and Paul Hamer (Editors)

February 2009

Fisheries Victoria Assessment Report Series No. 31

South‐Western Minor Inlets 2000

If you would like to receive this Author Contact Details: Geoff Nicholson and Leanne Gunthorpe information/publication in an Fisheries Research Branch, Fisheries Victoria accessible format (such as large PO Box 114, Queenscliff Vic 3225 print or audio) please call the Authorised by the Victorian Government, Customer Service Centre on: 1 Spring Street, Melbourne 136 186, TTY: 1800 122 969, Printed by DPI Queenscliff, Victoria or email Published by the Department of Primary [email protected] Industries. © The State of Victoria, Department of Primary Copies are available from the website: Industries, 2009. www.dpi.vic.gov.au/fishing This publication is copyright. No part may be General disclaimer reproduced by any process except in accordance This publication may be of assistance to you but with the provisions of the Copyright Act 1968. the State of Victoria and its employees do not guarantee that the publication is without flaw of Preferred way to cite this publication: any kind or is wholly appropriate for your Nicholson, G. Gunthorpe, L. and Hamer, P. particular purposes and therefore disclaims all (Eds.) (2009) South ‐Western Minor Inlets Fish liability for any error, loss or other consequence Habitats 2000. Compiled by the Fish Habitat which may arise from you relying on any Assessment Group. Fisheries Victoria information in this publication. Assessment Report Series Report No. 31. ISSN 1329‐7287 ISBN 978‐1‐74217‐385‐6

South‐Western Minor Inlets 2000 ii Table of Contents

Executive Summary...... 1

Introduction...... 2

Goals, Objectives and Strategies for Maintenance of Fish Habitats ...... 3 Strategic Directions ...... 3 Strategic goals...... 3 Strategic objectives...... 3 Strategic activities ...... 3 Policy and Legislative Context ...... 3

South‐Western Minor Inlets...... 4 Background...... 4 Characteristics of South‐Western Inlets ...... 4 Curdies River...... 4 Gellibrand River...... 6 Aire River...... 6 Barham River...... 8 Erskine River ...... 8 Painkalac Creek...... 8 Anglesea River ...... 8 Barwon River...... 11 Fisheries of the South‐Western Minor Inlets ...... 11 Management Responsibilities for South‐Western Minor Inlets...... 12 Stakeholders ...... 12

The 2000 Assessment ...... 15 Aim, Objectives and Strategies of the assessment ...... 15 Aim ...... 15 Objectives...... 15 Strategies...... 15 Boundaries of the minor inlets...... 15 Definition of a Fish Habitat...... 15 Methods...... 15 Assessment Methods...... 15

South‐Western Minor Inlets 2000 iii Key Fish Species and Their Habitat Requirements ...... 16 Fish Species in South‐Western Inlets...... 16 Key Fishery Species and Habitat Links ...... 16 Black bream...... 16 Eel...... 17 Flathead ...... 18 Flounder (Greenback)...... 18 Sea mullet ...... 19 Yellow‐eye mullet ...... 19 Mulloway ...... 20 Estuary perch...... 20 Australian salmon...... 21 Important Fisheries Habitat ...... 21

2000 Assessment ...... 23 Status of Important Fish Habitat...... 23 Pelagic...... 23 Seagrass ...... 23 Unvegetated sediment...... 23 Snags ...... 23 Deep holes...... 23 Reeds, rushes and mangroves ...... 24 Threats...... 24 Alteration of environmental flows...... 24 Sedimentation and turbidity...... 24 Elevated nutrients and nuisance algal growth...... 25 Pollution /water quality...... 25 Impacts of fishing related activities ...... 25 Introduced species ...... 25 Status of Threats in Each River Inlet System...... 26 Curdies River...... 26 Gellibrand River ...... 26 Aire River ...... 27 Barham River ...... 27 Erskine River...... 28 Painkalac Creek ...... 28 Anglesea River...... 28 Barwon River ...... 29 Management Implications...... 29 Alteration of environmental flows...... 29 Sedimentation and turbidity...... 30 Elevated nutrients and nuisance algal growth...... 30

South‐Western Minor Inlets 2000 iv Pollution /water quality ...... 30 Increasing fishing pressure...... 30 Introduced species...... 30

2000 Assessment ‐ Summary ...... 31 Status...... 31 Research Priorities...... 31

Acknowledgements...... 33

References ...... 34

Appendix 1 ‐ Glossary ...... 39

South‐Western Minor Inlets 2000 v List of Tables Table 1 Management Agencies...... 13 Table 2. Stakeholders...... 14 Table 3. Fish species targeted by recreational fishers within the selected inlets...... 17 Table 4. Habitat requirements for each life stage of the more targeted fish species in the minor inlets...... 22 Table 5. A threat matrix for fish habitats in selected minor inlets of South‐western Victoria...... 32

List of Figures Figure 1. The location of the selected south‐western minor inlets...... 5 Figure 2. The Curdies Inlet...... 5 Figure 3. The Gellibrand River and estuary...... 7 Figure 4. The Aire River and surrounding Lake system ...... 7 Figure 5. The Barham River estuary...... 9 Figure 6. The Erskine River estuary...... 9 Figure 7. The inlet of the Painkalac Creek...... 10 Figure 8. The Anglesea River estuary...... 10 Figure 9. The Barwon River estuary...... 12

South‐Western Minor Inlets 2000 vi Executive Summary

The sustainable harvest of any fishery resource is • deep holes dependent on maintaining the integrity of the • fringing vegetation (reeds and rushes). habitats and the organisms that support production of target fish populations. Fisheries Likely major threats to these habitats were Victoria has established a Fish Habitat identified. In order of importance these threats Assessment process to provide scientific are: information on marine and estuarine fish habitats • alteration of environmental flows (including for facilitating habitat maintenance and thus artificial opening of inlet mouths) continued production of fisheries resources. • sedimentation and turbidity The minor inlets occurring in south‐western • elevated nutrients and nuisance algal growth Victoria (from Barwon Heads to Petersborough) • pollution/water quality contribute significantly to recreational fishing • impacts of increasing fishing‐related activities conducted in Victoria. activities The inaugural meeting of the South‐Western • introduced species. Minor Inlet Fish Habitat Assessment Group Based on limited scientific information and on (SWMI HAG) was held on 11 March 1999 at the observations of workshop participants, the Lorne . SWMI HAG members concluded that the fish The workshop identified the following inlets and habitats of the south‐western minor inlets are estuarine reaches of rivers that support generally still in fairly good condition, but that important recreational fisheries: this situation may not persist given increasing impacts from agricultural, urban and tourism • Curdies Inlet development in coastal catchments. • Gellibrand River • Aire River The greatest impediment to effective management action of fish habitats within the • Barham River south‐western minor inlets was identified as the • Erskine River lack of scientific information on the importance • Painkalac Creek of fish habitats, their current status, and threats • Anglesea River to their integrity. • Barwon River. The SWMI HAG identified research in four The main targeted fish species in each inlet were important areas, which it considered as a high identified and the known habitat requirements of priority to undertake to facilitate proper each life stage of these fish species and those of assessment and protection of fish habitats within the important prey species were then the south‐western Victorian inlets: determined. From this information the major • Within each inlet, obtain an ecological habitats supporting fishery species in the western ʹsnapshotʹ illustrating the ecological minor inlets were identified. processes maintaining inlet health and the biological processes that link fish to each An assessment of the status of each habitat was habitat made, the most likely main threats to each habitat were identified, and their implications for • Determine the environmental flow profile fisheries management were detailed. Finally the required to maintain good water quality future research and monitoring needs for each within each inlet; to maximise reproduction habitat were identified. and survival of key fish species and to restore more‐natural opening regimes at Six habitats within the above minor inlets were inlet/estuary mouths considered important to fish. These are: • Review the status of saline groundwater • pelagic (water) contamination of rivers and whether there • seagrass are almost permanently anoxic deep holes • unvegetated soft bottom that may be of importance to the spawning of • snags estuarine fish.

South‐Western Minor Inlets 2000 1 Introduction

The sustainable harvest of any fishery resource The coast of south‐western Victoria, from is dependent on maintaining the integrity of the Barwon Heads to Petersborough, is an habitats and the organisms that support increasingly popular tourist region and production of target fish populations. retirement destination. Located close to the state’s major population centres of Melbourne, Effective management of fisheries includes Geelong and Ballarat recreational fishing is an identification and implementation of important activity undertaken at the river management actions needed to protect and mouths and estuaries located in south‐western where possible enhance ecosystems that support Victoria by visitors and residents alike. An production of fish resources. To do this it is assessment of the condition of fish habitats essential to know: within a number of inlets was undertaken to • The type, significance to various fisheries assist in defining the research directions and resources, location and geographical extent management actions needed to ensure of each habitat within the specified waters sustainable utilisation of the fish resources. • The organisms (fish and others) which are dependent, directly or indirectly, on each This document is divided into discussion habitat sections in the following order: • Whether the location of a habitat within the • A summary of government policy and system affects its significance to fish management objectives applying to the minor inlets of south‐western Victoria. • The threats to each habitat • A brief description of management agencies • The management actions to be undertaken and user/interest groups that have to minimise or eliminate the identified influence, either directly or indirectly on the threats. fish habitats, fish stocks and/or fishing To provide this basic information on marine fish activities within the minor inlets. habitats for the purposes of advocating fish • Details of the aims and objectives of the habitat protection across Victoria, Fisheries south‐western minor inlet fish habitat Victoria has established a Fish Habitat assessment, and an explanation of the Assessment process. Under this process Fish methods and processes by which the Habitat Assessment Groups (HAGs) are assessment was conducted. established to review the status of marine and • Description of the physical and ecological estuarine fish habitats throughout Victoria. characteristics of the key minor inlets which Information and advice provided by HAGs support significant recreational fisheries. complements that produced by the stock and • Description of the key fishery target species fishery assessment groups to provide more in these inlets and their habitat comprehensive inputs into the development or requirements. review of Fishery Management Plans for specified waters. • The identification of important habitats for fish within the key minor inlets. The objectives of the Fish Habitat Assessment • Assessment of the likely main threats to the Process are to: well‐being of the recognised fish habitats. • Establish a standard framework for the • The possible fisheries management assessment of Victorian fish habitats implications of the identified threats to fish • Identify important fish habitats in Victoria habitat. • Assess the current status of fish habitats • A summary of the assessment of fish habitat • Determine processes threatening these in the key minor inlets in south‐western habitats Victoria and the prioritising of • Make recommendations on the habitat research/monitoring projects required to research and monitoring needed for more improve future assessments of fish habitats effective fish habitat assessment to underpin in these inlets. ESD‐based management of Victoria’s fisheries.

South‐Western Minor Inlets 2000 2 Goals, Objectives and Strategies for Maintenance of Fish Habitats

Strategic Directions There is increasing evidence worldwide that the Fisheries Victoria has reviewed its position in sustainable use of any fishery resource is relation to the ʹhabitat advocacyʹ debate and fish dependent not only on controlling the direct habitat management. impacts of fishing on fish stocks, but also on maintaining the integrity of the aquatic habitats, Policy and Legislative Context environmental conditions and ecological The Victorian Government and the Department processes that are crucial for the production of Primary Industries are committed to applying and/or survival of target fish species. This is the principles of Ecologically Sustainable particularly so in inshore marine, estuarine and Development (ESD) to fisheries management. inland waters that are facing increasing These principles are: pressures from human population growth and associated agricultural, industrial, urban and • To provide for equity within and between tourism development. generations in the use of natural resources • To enhance individual and community well‐ Strategic directions on fish habitat assessment being by following a path of economic provided in the “Fisheries Strategy Towards development that provides optimum 2000” (Fisheries Victoria, 1997) are relevant to current benefits while safeguarding the the deliberations of Habitat Assessment Groups resource use options of future generations as follows. • To protect biological diversity and maintain Strategic goals ecological processes and systems • To establish Fisheries Victoria as the lead • To adopt a precautionary principle, so that advocate for fish habitat management. where there are threats of serious or irreversible adverse effects on resources or Strategic objectives habitat, lack of full scientific certainty • Identify critical fish habitats and threatening should not be used as a reason for processes in conjunction with stakeholders. postponing measures to prevent resource • To lead and facilitate the development of depletion or environmental degradation. fish habitat management arrangements. The Fisheries Act 1995 recognises these principles Strategic activities by including the following stated objectives: • Commission focused habitat assessment, • To protect and conserve fisheries resources, monitoring and research programs. habitats and ecosystems including the • To establish partnership arrangements to maintenance of quality ecological processes influence the management of non‐fishery and genetic diversity threats. • To provide for the management, • To develop and implement fish habitat development, and use of Victoria’s fisheries, restoration programs in priority waters. aquaculture industries and associated • To establish a community based fish habitat biological resources in an efficient, effective protection focus across Victoria. and ecologically sustainable manner. • Identify funding opportunities for fish The Fisheries Act 1995 also specifies that a habitat improvement and cooperate with Fishery Management Plan declared for a given other agencies in accessing these funds. fishery must identify critical components of the • Review legislative and policy frameworks to ecosystem relevant to the fishery, current or potential threats to those components, and support fish habitat protection. existing or proposed measures to protect or maintain key fish habitats.

South‐Western Minor Inlets 2000 3 South‐Western Minor Inlets

All of these minor inlets occur within the Background drainage basins of Otway and Barwon in the South‐western Victoria has a diverse geological Corangamite CMA region and are popular with history and a temperate Mediterranean climate recreational anglers, particularly for the taking of warm dry summers and cool wet winters. of black bream. Rainfall varies from less than 500 mm to a Victorian state maximum of 2000 mm (CCALP Four of the waterways were assessed for 1997). environmental values in the Corangamite Regional Nutrient Management Plan. These are Four drainage basins lie within this region; these the Curdies River, the Gellibrand River, the Aire are the Barwon, Corangamite, Otway and River and Painkalac Creek (CCMA 2000). Moorabool basins. Major rivers include the Barwon, Curdies, Aire and Gellibrand Rivers. Curdies River There are 14 proclaimed water catchments and The Curdies River (Figure 2) has a catchment coastal environments of high heritage, area of 1015 km2. The main stem of the river is recreation and environmental value. The region 117 km long, its headwaters are fed by Lake is renowned for aquatic habitats and wetlands Purrumbete near Camperdown and the Scotts of national and international importance Creek ‐ Coorimungle system is its one major (CCALP 1997). tributary. Private farms cover over 70% of the region and The Curdies River flows through forested and constitute the major land use. Major grazing land, with the catchment much manufacturing and service industries in the modified for agriculture, primarily dairy region generally operate from either Geelong, farming. The estuarine influence extends 16 ‐ 17 Ballarat or Colac. Other main land uses and km upstream, all through very flat country, industries include tourism and recreation, from the river mouth at Peterborough through extractive industries, forestry industries, fishing to Curdie Vale. Many parts of the stream are industries and national and state parks (CCALP choked with aquatic weeds and willows. 1997). The Curdies River ends at the Great Ocean Road Fisheries Victoria established the South‐Western Bridge. The inlet between the bridge and the Minor Inlet Habitat Assessment Group (SWMI entrance is considered as oceanic and fisheries HAG) to review the status of marine and regulations differ between the riverine and estuarine fish habitats in this area. estuarine sections of the Curdies River. The lower 4 km of the estuary has a depth of Characteristics of South‐Western about 1 m, while the riverine section is between Inlets 7 to 8 m deep. Following the end of the last ice age, about 20,000 years ago, sea level rose Eight inlets in south‐western Victoria were through the melting of the ice sheets and considered by the SWMI HAG to support reached the present level about 5000 ‐ 6000 years important recreational and/or commercial ago. Then the inlet was much deeper and fisheries (Figure 1). These are the inlet and supported a more diverse marine fauna than it estuarine regions of the following rivers and presently does. The inlet has gradually filled creeks: with sand and a sand dune has grown across the • Barwon River entrance from the eastern side leaving a narrow • Anglesea River entrance channel on the west. • Painkalac Creek The mouth gradually fills with sand over a • Erskine River period of 4 to 6 months. The length of closure • Barham River depends on the rainfall pattern of any particular • Aire River year. Periods of closure can extend up to 12 • Gellibrand River months in prolonged drought conditions • Curdies River. (Sherwood 1998).

South‐Western Minor Inlets 2000 4

N N

Victoria

0100200

kilometres Anglesea Curdies River Barwon River Erskine River River Painkalac Creek

Gellibrand Barham River Aire 0 25 50 River River kilometres

Figure 1. The location of the selected south‐western minor inlets.

Floodplain/Wetlands

Curdies River

N Curdies Inlet

Peterborough

0 1 2 kilometres

Figure 2. The Curdies Inlet.

South‐Western Minor Inlets 2000 5 The higher salinities of the Curdies River are in sulphide levels can increase in the deeper holes part a reflection of the high salinity of the of the estuary. surface water found in the north‐west of the Estuarine conditions can extend up to 10 km Otway Coast Basin (cited in Codd 1992). upstream of the river mouth, where the river is The Corangamite Regional Nutrient about 4 m wide, has depths of 3 ‐ 4 m and a sand Management Plan (CCMA 2000) assesses the substrate. In the lower 4 km section, the width Curdies River: is 50 m with a depth of 3 m, although the depth • to have a high category of environmental is uneven and holes of up to 9 m deep occur. value even though the river is recognised as The substrate in these lower regions is uneven having only local significance black and grey clay. The land surrounding the • having moderate biodiversity lower estuary has been mostly cleared (Tunbridge & Glenane 1988). Also of • the highest algal bloom risk rating importance are the wetlands on the floodplains • a medium on‐site risk of local biodiversity of the Gellibrand and Serpentine Creek, being detrimentally impacted by algal consisting of swamps of varying salinities. The blooms. wetlands have significant areas of woolly tea‐ Gellibrand River tree, reed beds and beaded glasswort. The upper reaches of the Gellibrand River and There was a fish death event in the estuary most of the major tributaries rise on the northern around April 2000. It was caused by a mouth slopes of the Otway Ranges. The Gellibrand opening, although it could not be determined catchment has an area of 1200 km2 and consists whether the inlet was manually opened or was of eucalypt forest and cleared grazing land. It is opened by a natural event. Anoxic water in the a high rainfall area with average annual falls lower estuary wetlands drained into the estuary varying from 800 mm in the northern section to channel, stopping freshwater from upstream 1800 mm in the south‐eastern corner of the entering and flushing out oxygenated surface catchment (Tunbridge & Glenane 1988). waters as well as deep anoxic water. The whole Distance of the river from source to mouth is lower estuary was anoxic and fresh for at least about 125 km. 48 hours. A large range of fish died, including flounder, mullet, juvenile bream, and large The Gellibrand River flows through extensive areas of Quaternary alluvial deposits of sand, numbers of galaxids which had congregated in silt, clay, gravels as well as Tertiary sediments the estuary to spawn (pers. comm. Prof. John Sherwood). and Cretaceous sandstone and mudstone. Slumping of surface soil material is common. The Corangamite Regional Nutrient The river is a shallow single‐channelled river of Management Plan (CCMA 2000) assesses the uniform depth with sand substrate and unstable Gellibrand River: steep banks. Logs and aquatic vegetation in the • as having a high category of environmental river are common (Tunbridge & Glenane 1988). value; The Gellibrand estuary (Figure 3) is classified as • as having state significance with respect to a salt wedge with entrance sand bars and at wildlife and/or lake reserves; times of low flow the river mouth can be closed • in the highest category of biodiversity; over. It is highly stratified with little mixing • having the lowest algal bloom risk rating; between fresh water and sea water. The inflow and, of fresh water controls the size and location of • having a high on‐site risk of local the salt wedge upstream. During the winter and biodiversity being detrimentally impacted spring high river flows, the estuary becomes by algal blooms. totally fresh, whereas the salt wedge extends upstream to its maximum limit during summer Aire River and autumn low river flows. This has a major The catchment of the Aire River (Figure 4) is influence on fish distribution and abundance. relatively small at about 260 km2 and lies to the Closure of the entrance during the periods of south of the main ridge of the Otway Ranges, low river flow can result in the stagnation and with the upper reaches near Beech Forest lowering of dissolved oxygen levels in the receiving an average rainfall of approximately underlaying salt water layer. Hydrogen 2000 mm.

South‐Western Minor Inlets 2000 6 Floodplain /Wetlands

N

Gellibrand estuary

01

kilometres

Figure 3. The Gellibrand River and estuary.

Aire River

N Lake Horden Lake Costin

Lake Craven Aire River West Camping Ground Aire River East Camping Ground 0 1 2

kilometres

Figure 4. The Aire River and surrounding Lake system

South‐Western Minor Inlets 2000 7 It flows from mountainous forested country to Painkalac Creek grazing land. A large percentage of the The mouth of the inlet of Painkalac Creek catchment occurs in state forest, with some pine (Figure 7) has been closed for most of 1998‐1999. plantations and smaller pockets in dairy The catchment incorporates regions where there country. The river runs through State forest (24 is agro‐forestry and grazing activity. The creek km), national park (2 km), softwood plantations flows past the outskirts of the townships of (2 km), a wildlife reserve (1 km) and through Fairhaven and Aireys Inlet. It suffers some public land water frontage (10 km). siltation problems but generally there is believed The Aire River is connected to three lakes (Lake to be not too much land disturbance, with most Horden, Lake Craven and Lake Costin) with the of the problems occurring further down the Ford River as a tributary. The Aire River is catchment. The Painkalac Reservoir is located 3 estuarine for 9 km upstream from the mouth. km to the north‐west of Aireys Inlet and draws River flows are lowest in summer and highest off water from the Painkalac Creek and stores it during the winter. for domestic purposes for Aireys Inlet and Fairhaven. The Corangamite Regional Nutrient Management Plan (CCMA, 2000) assesses the The Corangamite Regional Nutrient Aire River: Management Plan (CCMA 2000) assesses the Painkalac Creek: • as having the highest category of environmental value • as having a medium category of environmental value • as having significance under international treaty • as being recognised as having State significance; • to be in the highest category of biodiversity • as having a low to moderate category of • to be in the lowest algal bloom risk rating biodiversity • as having a high on‐site risk of local • to be in the lowest algal bloom risk rating biodiversity being detrimentally impacted by algal blooms. • as having a high on‐site risk of local biodiversity being detrimentally impacted Barham River by algal blooms. The Barham River is fast flowing from Painkalac Creek is considered to be an under‐ mountainous forested country to grazing land utilised bream fishery. and the outskirts of urban development at Apollo Bay. Some of the river has been Anglesea River channelled, while other areas have been The estuarine inlet of the Anglesea River modified for agriculture. The Barham River extends between 1.5 to 2.5 km upstream from (Figure 5) is estuarine for about 2 ‐ 3 km the mouth (Figure 8). upstream from the river mouth. As it approaches the coast it meanders through The majority of the catchment of the Anglesea wetlands and a region known as ʹThe River is situated within the boundaries of the Backwaterʹ. Alcoa World Alumina Australia lease. Within this area there are a number of mining leases, Water is drawn from the west branch of the predominantly for gravel extraction. As well, Barham River system for distribution to the there is an open cut mine for coal extraction urban centres of Apollo Bay and Skenes Creek. (1.09 x 106 tonnes for 1998/99) which is used to Erskine River fire a small power station which generates electricity (capacity 150 MW) for the Alcoa The Erskine River catchment consists of forested smelter at Point Henry. However, most of the lands, where little or no agricultural activities land within the Alcoa area boundary is are undertaken apart from two small areas of heathland. Some of the outer fringes of the freehold land around the region of Erskine Falls. catchment pass through Angahook ‐ Lorne State There appear to be few catchment pressures on Park and agricultural land. the river, apart from the township of Lorne (Figure 6), although there is a history of logging The bulk of the estuarine inlet area is within the upstream. The mouth of the estuary is Anglesea township. Anglesea has a resident intermittently open. population of ~ 2,500, which increases to ~ 10,000 during peak holiday periods. One of the smaller streams within the catchment passes

South‐Western Minor Inlets 2000 8 N

Apollo Bay

Barham River estuary

0 1

kilometre

Figure 5. The Barham River estuary.

Erskine River estuary N Lorne

0 1

kilometre

Figure 6. The Erskine River estuary.

South‐Western Minor Inlets 2000 9 Floodplain/ Wetland Aireys Inlet N

Painkalac Creek 0 1 estuary kilometre

Figure 7. The inlet of the Painkalac Creek.

Power station

Tip N Marsh

Anglesea

Anglesea River 0 1 estuary kilometre

Figure 8. The Anglesea River estuary.

South‐Western Minor Inlets 2000 10 very close to the local tip site. Salt Creek, downstream at the south‐east end of Reedy Lake another catchment stream, passes through ~ 3.5 (Sherwood et al. 1988). km of tea‐tree swamp. Today, the estuarine influence of the Barwon During the 1970s a rock wall was built across the River sometimes extends upstream into and past mouth of the river with the intention of Lake Connewarre (Figure 9), depending on tide increasing the depth of the estuary and making and river flow. However, there are periods the inlet a pondage behind a weir. Tidal effects when the water in Lake Connewarre, in the and storms broke through the wall and while no lower reaches of the Barwon River, has been attempt has been made to repair it, remnants fresh enough to support fresh water fish species remain and anecdotal evidence indicates that such as redfin, tupong, brown trout, tench and sediment dynamics within the estuary differ to the common carp. pre‐wall periods. Lake Connewarre is a large estuarine lagoon of Swampy land has been reclaimed near the lower 950 ha area and with a mean depth of about 1 m. inlet and only remnant saltmarsh now remains Salinity within Lake Connewarre is greatly in this area. A new channel was cut in the peat influenced by inflows of fresh water from the beds around the Coogoohra Park region because Barwon River, as well as by atmospheric the original river channel through peat beds was conditions and evaporation. It is considered affected during the 2003 Ash Wednesday that river flows of 3000 ‐ 5000 ML d‐1 are bushfires. required to rapidly remove all saline water from the lake and flows of 1000 ML d‐1 are required to The bar undergoes frequent openings and maintain the freshwater conditions. Flows of closings, with closure occurring about 33% of less than 100 ML d‐1 result in salinities of about the time. During periods when the bar is open, 24 within the lake (Tunbridge 1988). The the cut is not very deep and water from the inlet wetlands of Lake Connewarre are renowned as is slowly passing out. Only in periods of high a habitat for migratory birds. river flows, spring tides and/or storm events, does the cut in the bar deepen to enable some Mangroves growing along the lower reaches of flushing into the inlet of sea water. the Barwon River near Barwon Heads are believed to be the most southerly in Australia. Stratification of the inlet has been observed, but The consistently estuarine extent of the river the de‐oxygenation was not complete. begins at the oceanic entrance and extends Barwon River upstream to Lake Connewarre, while the tidal The headwaters of the Barwon River drain from limit is 1.5 km upstream of the lake. The depth the Otway Ranges near Forrest. The river flows of the inlet around the mouth is limited by a bed northwards through Winchelsea and Inverleigh of rock (Nelson & Keats 1982). before heading in an easterly direction through At the time of the assessment two commercial Geelong and entering Bass Strait at Barwon eel fishermen have access to the Barwon River Heads. The Barwon system supplies about 70% and one fisher is licensed to collect bait from the of general urban and industrial water for the river. There is a large recreational fishery in the city of Geelong and its environs (pop. ~ 200,000). Barwon targeting a number of species, including The total catchment area above the Barwon inlet 2 bream, mulloway, mullet, salmon and trevally. is 4400 km (Nelson & Keats, 1982). Between 70 It is reputed to be one of the best mulloway ‐ 80% of the land in the Barwon catchment is nurseries in Victoria. There is substantial urban devoted to dryland farming, especially for and rural development along both sides of the broadacre cropping and sheep running. About Barwon River extending beyond the estuarine 10% of the river basin is covered by remnant influence past Geelong. forest and about 1% is under pine plantation. The two major urban centres in the river basin, Fisheries of the South‐Western Geelong and Ballarat, take up about 2% of the land (Loone 1996). Minor Inlets There are numerous perennial and Prior to European settlement, salt water intermittently flowing small creeks and rivers penetrated upstream in the Barwon River entering the ocean in this south‐western region beyond the site of the current City of Geelong. of Victoria, with many being popular with In 1844 a breakwater was built about 3 km recreational fishers mainly targeting black south‐east (downstream) of Geelong, and in bream. Commercial fisheries activities occur in 1898 a second breakwater was built further

South‐Western Minor Inlets 2000 11 Reedy Lake

Lake Connewarre

Hospital Swamp Ocean Grove N Wetlands

Barwon River Barwon Heads estuary 0 2 4

kilometres

Figure 9. The Barwon River estuary. the Curdies Inlet, the Curdies River, the Aire • recreation ‐ primary contact (eg bathing, River and the Gellibrand River. These are water‐skiing), secondary contact (eg classified as scheduled waters for the boating) and passive (eg aesthetic commercial taking of eels. enjoyment) • passage of fish Management Responsibilities for • production of edible fish and crustaceans – South‐Western Minor Inlets estuarine Responsibility for the management of activities • maintenance of aquatic ecosystems and in or adjacent to the south‐western minor inlets associated wildlife (moderate level of lies with 23 agencies (State Government protection) Departments, Local Government Agencies and • maintenance of foreshore and stream bank Statutory Authorities). The responsibility of vegetation. each agency or Authority is listed in Table 1. These inlets occur within the Corangamite The (former) Department of Natural Resources Catchment Management Authorityʹs and Environment, Parks Victoria and the jurisdiction. Environment Protection Authority (EPA) have the most direct influence on human activities in or near these minor inlets in south‐western Stakeholders Victoria. These three bodies administer the The users of the south‐west minor inlets are Fisheries Act 1995 (now administered by diverse and can be classified into three broad Fisheries Victoria, Department of Primary groups (Table 2) based on the types of activities Industries), the National Parks Act 1975, and the that are conducted in the minor inlets. These Environment Protection Act 1970. range from non‐profit recreational activities such as swimming, boating and fishing to The EPA currently uses the State Environment enterprises that are reliant on inlet(s) for Protection Policy (Waters of Victoria) to protect commercial activities. the beneficial uses of the south‐western minor inlets. The types of activities declared as One group of stakeholders includes the beneficial under this policy include: Government Agencies, Local Authorities and

South‐Western Minor Inlets 2000 12 Peak Bodies that represent or regulate the wide range of groups that use the inlets. The management agencies listed in Table 2 are also stakeholders in the minor inlets. Table 1 Management Agencies. Agency Responsibility Department of Infrastructure • Primarily as funding source for construction of public infrastructure. Department of Premier and Cabinet • The Department assists the Government to create sustainable growth and a vibrant, innovative society by leading policy advice and implementing key projects and activities. Department of Natural Resources and Environment (now • Management of the fisheries. Fisheries Victoria, Department of Primary Industries)

Department of Natural Resources and Environment (now • Management of catchments, coastal crown land Department of Sustainability and Environment) and national/coastal parks.

Corangamite Catchment Management Authority • Management of catchments and rivers. Southern Rural Water • Development of streamflow management plans, licence off‐stream diversions and undertake erosion and stream stabilisation works. Barwon Region Water Authority • Serves the greater Geelong area and manages the Barwon River, including public and water authority frontages through Geelong. Otway Region Water Authority • Serves Colac and coastal areas from Apollo Bay to Aireys Inlet. South West Region Water Authority • Management of water supplies, drainage and sewerage systems in urban communities. Corangamite Shire Council • Management of port of Port Campbell and the local coastal municipalities between and including Curdies and Gellibrand inlets. Colac‐Otway Shire Council • Management of port of Apollo Bay and local municipalities along the coast from east of the Gellibrand River inlet to Jamieson Creek. Surf Coast Shire • Management of the local coastal municipalities between and including Erskine and Anglesea inlets. City of Greater Geelong • Management of the local municipalities around the Barwon River. Environment Conservation Council • Provision of recommendations to the Victorian Government about public land (including marine, estuarine and coastal) to provide for its balanced use. Environment Protection Authority (Victoria) • Protection of the water quality of the minor inlets. Central Region Coastal Board • Provision of coordinated strategic planning and management including for the Barwon River. Western Coastal Board • Provision of coordinated strategic planning and management of all the minor inlets investigated in this study apart from the Barwon. Lorne Foreshore Committee of Management Inc. • Management of local port of Lorne. Barwon Coast Committee of Management Inc. • Management of local port of Barwon Heads. Marine Board • Issuing of licences for operation of various types of commercial vessels Parks Victoria • Manage national and coastal parks. Private Property Owners • Maintain fencing to prevent stock access to the minor inlets. State Boating Council • Provision of funding for infrastructure such as boat ramps and jetties. Water Police • Ensuring the compliance of the public with fisheries acts, maintaining water quality, responsible boating.

South‐Western Minor Inlets 2000 13 Table 2. Stakeholders. Stakeholder Community Coastcare. Conservation groups and organisations. Ecotourists. Landcare. Recreational boating. Recreational diving, snorkelling and other passive users. Recreational fishers. Recreational swimmers and beach goers. Industry Agriculture. The charter industry (tourism and recreational fishing). The commercial fishing industry (as harbour), retail outlets of local seafood and seafood restaurants. The diving and snorkelling industry. The recreational fishing and boating industry. The recreational fishing and boating media. The tourism industry. Waste dischargers. Non Management Government Agencies, Statutory Authorities and Peak Bodies Fisheries Co‐Management Council. Victorian Recreational Fishing Peak Body. (VRfish). Seafood Industries Victoria. Victorian National Parks Association. State Development (business development, tourism).

South‐Western Minor Inlets 2000 14 The 2000 Assessment

which support fish that are the target of fishing Aim, Objectives and Strategies of activities. the assessment Aim Methods To assess the status of minor inlet habitats upon A literature search was undertaken to provide which fisheries resources are dependent and to information on the minor inlets of south‐western recommend future directions for habitat research Victoria and the habitats contained therein. and management. Information was also obtained from the “grey Objectives literature” of unpublished data and reports held • Identify habitats and assess their importance by various state government research and to fish in the minor inlets. management agencies and statutory authorities. • Provide up‐to‐date summaries of research Unpublished information on the status of any of and monitoring programs. the minor inlet habitats was also sought from any • Assess the current state of fish habitats. studies currently being conducted by • Identify processes which pose major threats government agencies. to fish habitats. • Provide a qualitative risk assessment of the Assessment Methods main threats to fish habitats. The 1999 fish habitat assessment workshop in • Identify management issues for critical Lorne began by listing the minor inlets within habitats. south‐western Victoria that support important • Identify research and monitoring needs to recreational and/ or commercial fisheries. The address the management issues for each HAG then listed important fish species habitat. (including prey species) in each of the minor inlets. Available information on the habitat Strategies requirements in each life stage of these was then • Characterise the important habitats for each identified and from this information the likely of the fisheries resources of the minor inlets, major fish habitats in each of the minor inlets and for their dependent biological resources were identified. (food chains etc). A qualitative assessment of the status of each • Establish archival databases of all relevant habitat was undertaken based on available research and monitoring material for each scientific and anecdotal information. The main important fish habitat in the minor inlets. threats to each habitat were then identified and • Synthesise available data, identify the major their implications for fisheries management threats to each critical habitat and provide detailed. Finally, the future research and options to reduce these in the minor inlets. monitoring needs for each habitat were identified. Boundaries of the minor inlets The seaward boundaries of the south‐western minor inlets will be assumed to be a straight line across the mouth of the entrance between the seaward edge of each of the river banks. The upstream boundaries of the assessment area are the limits of tidal salt water intrusion. Definition of a Fish Habitat For the purposes of this assessment a habitat was defined as the broad physical structures, zones and biological communities that support fish. The emphasis of this report is on those habitats

South‐Western Minor Inlets 2000 15 Key Fish Species and Their Habitat Requirements

thought to occur in the upper reaches of estuaries Fish Species in South‐Western near the interface between fresh and brackish Inlets water (Cadwallader & Backhouse 1983; Ramm Sixteen species or families of fish were identified 1986), although the actual spawning areas may as being encountered by recreational fishers in vary from year to year. the selected inlets (Table 3). It is not known why some spawning years are Black bream is the species most commonly more successful than others, though targeted by recreational fishers in these estuaries environmental factors such as water temperature followed by estuary perch and mulloway. Eels and salinity appear to be of importance in are commercially fished in two of the inlets determining the timing and success of spawning associated with the Barwon and Curdies Rivers. (Winstanley 1985). Butcher (1945) suggested that The Barwon estuary also supports an important the optimal salinity range for spawning was 11 to recreational fishery for mulloway. Flathead, 18, while Ramm (1986) suggested the salinity flounder, yellow‐eye mullet, sea mullet and should be between 19 to 22 and the water Australian salmon are common bycatch for the temperature 21°C. Hobday and Moran (1983) recreational fishers. further suggested that spawning success and subsequent year class strength was higher when spring rainfall and river flows were lower than Key Fishery Species and Habitat average and when water temperatures were high Links in October. However, the water quality Black bream requirements for successful spawning and Black bream are common in estuaries from survival of eggs/larvae are still not well southern New South Wales to Shark Bay in West understood and this species is characterised by Australia (Gomon et al.. 1994). They have a wide variable recruitment (Coutin et al.. 1997; Morison salinity tolerance and may move into the et al.. 1998). freshwater reaches of estuaries (Kailola et al.. Sherwood and Backhouse (1982) suggest that an 1993). The life cycle of black bream is usually advancing salt wedge in an estuarine river, over completed within a specific estuary, although suitable habitat such as snags, is more likely to there may be some movement of black bream produce salinity and dissolved oxygen levels that between estuaries (Butcher & Ling 1958). are favourable to black bream spawning, rather Black bream are a relatively long‐lived species than a stable or retreating salt wedge. There is a with a life expectancy of at least 29 years variable seasonal and annual cycle in estuarine (Morison et al.. 1998) and are thought to reach salinity based on river discharge and this is most maturity at about four to five years of age. At likely instrumental in controlling the spawning maturity males are 20 ‐ 22 cm total length and of black bream. female fish are 22 ‐ 24 cm total length (Butcher Black bream eggs are planktonic and as a 1945; Goman, unpublished data cited in Ramm function of their buoyancy are mostly found in 1986; Coutin et al.. 1997). In Victoria, the waters where the salinity is greater than 15. Eggs spawning period for black bream extends from generally hatch two days after fertilisation August to December, though the timing and the although embryos fail to develop at salinities period of spawning is thought to vary between below 5 (Ramm 1986). The larvae remain in the estuaries (Kailola et al.. 1993). Black bream water column for approximately one month populations in eastern Victorian estuaries are before settling into shallow macrophyte beds thought to spawn earlier than other western when they are 10 to 15 mm in length (Ramm populations (Cadwallader & Backhouse 1983). 1986). Black bream will travel upstream until optimal water column conditions of salinity, temperature and dissolved oxygen are met. Spawning is

South‐Western Minor Inlets 2000 16 Table 3. Fish species targeted by recreational fishers within the selected inlets. Species Common Name Inlet (Fishery Type) Acanthopagrus butcheri Black bream All (Rec*) Anguilla australis Eel All bar Anglesea (Rec in all, Com** in Barwon, Aire, Gellibrand and Curdies) Platycephalus spp Flathead Barwon (Rec) Families PLEURONECTIDAE, Flounder or sole All bar Anglesea (Rec) BOTHIDAE; SOLEIDAE Girella tricuspidata Luderick Painkalac (Rec), Anglesea (Rec), Barwon (Rec) Hyporhamphus spp Garfish Curdies (Rec, mainly bycatch, trapped when entrance closed) Family MONACANTHIDAE Leatherjackets Curdies (Rec, mainly bycatch, trapped when entrance closed) Mugil cephalus Mullet, grey or poddy mullet or Aire (Rec), Barham (Rec), Painkalac (Rec), sea mullet Anglesea (Rec), Barwon (Rec) Aldrichetta forsteri Mullet, yellow eye All (Rec as table and baitfish) Argyrosomus hololepidotus Mulloway Curdies (Rec), Aire (Rec), Barwon (Rec) Macquaria colonorum Estuary perch All (Rec) Arripis georgianus Tommy ruff or Australian Gellibrand (Rec), Aire (Rec),Barham (Rec), herring Erskine (Rec) Arripis spp Australian salmon Gellibrand (Rec), Aire (Rec), Barham (Rec), Erskine (Rec), Painkalac (Rec), Anglesea (Rec), Barwon (Rec) Pseudocaranx dentex Silver trevally Curdies (Rec), Gellibrand (Rec), Barham (Rec), Anglesea (Rec), Barwon (Rec) Galaxias spp Whitebait or galaxid Curdies (Rec), Gellibrand (Rec), Barwon (Rec) Pseudolabrus spp Wrasse Curdies (Rec) Where * “rec” indicates recreational fishing activity, ** “com” indicates commercial fishing activity.

Shallow seagrass/algae beds appear to be Black bream are opportunistic feeders, important nursery areas for juvenile black bream consuming a wide range of animal species. as these areas support the highest abundance and While the diet of larval stages is not known, it is diversity of the food of juvenile black bream thought they feed on various types of (Poore 1982). The relative importance of each zooplankton (Ramm, 1986). The diet of juveniles macrophyte species as nursery habitat is not well and adults is composed primarily of organisms understood. Seagrass beds are predominant in associated with the sediments or with many estuaries and are suggested to be macrophytes, and may include bivalves and important nursery areas for black bream in the gastropod molluscs, crabs, amphipods and Gippsland Lakes (Rigby 1984). Ramm (1986) copepods, polychaete worms and small fish reported juvenile black bream in association with (Rigby 1984). Ruppia spiralis and Zostera muelleri seagrass beds in the Gippsland Lakes. The smallest black Eel bream juveniles recorded in Ramm’s study were Only the short‐finned eel, Anguilla australis, is located in Z. muelleri beds. found in the minor inlets of south‐western Victoria. Although larvae and small juveniles appear to be more abundant in salinities less than 28, Ramm Short‐finned eels are widespread from southern (1986) suggests that later life‐stages tolerate a Queensland to South Australia, and also in other wide range of salinity (from 0 to 32). Larger regions of the southwest Pacific such as New juveniles and adults may be found in association Zealand, Norfolk and Lord Howe Islands, the with a range of habitats within estuaries, Chatham Islands, Fiji and Tahiti (Cadwallader & including: unvegetated sand and mud, rocky Backhouse 1983). They are found in a range of sand, macrophytes and structures such as snags, habitats including upper reaches of rivers, rocks and pylons (Hobday & Moran 1983; S. estuaries, lakes and swamps. Walker unpublished data). Hobday and Moran Mature short‐finned eels migrate from (1983) suggest black bream juveniles and adults freshwater to estuaries in late spring and early move to deeper water in winter. summer, before migrating out of estuaries into ocean waters during late summer and early autumn (Koehn & O’Connor 1990). Spawning is

South‐Western Minor Inlets 2000 17 thought to occur in the Coral Sea north east of the Lancelin in Western Australia, including Queensland coast, and adults are thought to die Tasmania (Kailola et al. 1993). This species is after spawning. The leptocephali (larvae) and most common in Victorian and Tasmanian glass eels (small juveniles) drift south on the east waters and can be found in bays and inlets and in Australian current and may spend 1 to 3 years in coastal waters to depths of 100 m (Kailola et al. ocean waters before the glass eels move into 1993). estuaries at about 50‐70 mm in length. The Little is known concerning the spawning of sand annual migration of glass eels into estuaries in flathead in Victoria, although spawning is Victoria occurs from May in the east of the State thought to be triggered by increasing day length and continues until about October in the west and water temperature (Kailola et al. 1993). Sand (Koehn & O’Connor 1990). Eels in the brown flathead are also reported to spawn in shallow elver stage (larger juveniles) migrate from near‐shore coastal waters (Kailola et al. 1993). estuaries into freshwater from about late spring and during summer. Migrations of the brown Juveniles and adults use the same habitat and are elvers are triggered by reduced river flow and found over unvegetated sediments. In Port increasing water temperature, and high river Phillip Bay, sand flathead were found in flows during this period could inhibit upstream association with fine sediment (Hamer et al. migrations. Certain weirs and barriers can 1997). inhibit upstream migration or increase predation on the migrating elvers. Sand flathead are generally solitary and are active predators and foragers (Kailola et al. 1993). The Glass Eel may be found over seagrass in Their diet consists mainly of small fish, estuaries and may seek shelter in mud or crustaceans, worms and cephalopods (Kailola et vegetation. Short‐finned eels are generally a still al. 1993), though Brown (1977) reports the diets of water species preferring slow, silty stream sand flathead change seasonally. Crustaceans habitats. Whilst the annual migration of brown form the basis of the diet from October to May, elvers to freshwater occurs in spring/summer, while fish are principally consumed in the they may spend several years in estuaries before winter. undertaking this migration (Koehn & O’Connor 1990). As eels can absorb oxygen across their Flounder (Greenback) body surface, they can withstand drying of the Greenback flounder are commonly found in water body by burying in mud and can travel estuaries, bays and inshore coastal waters from considerable distances over land during night. southern New South Wales to the east coast of They are not overly strong swimmers and tend to West Australia, including Tasmania (Gomon et hug the bank when migrating upstream (Koehn al. 1994). Greenback flounder are demersal and & O’Connor 1990). are most common on unvegetated sediments (Hutchins & Swainston 1986; Kuiter 1993). Short‐finned eels can take many years to reach Greenback flounder can tolerate a wide range of maturity. Males may not leave freshwater for the salinities and water temperatures (Kailola et al. sea until 8‐12 years of age and females until 10 – 1993). 20 years of age (Koehn & O’Connor 1990). Maturing adults undergo a metamorphosis and Greenback flounder may live for three to four stop feeding, the gut degenerates and changes to years reaching a maximum size of 40 cm in eyes and body colouration occur. length and reach maturity at sizes of between 19 and 30 cm long (Kailola et al. 1993). Spawning is When inhabiting freshwater, eels are nocturnal. thought to occur in offshore waters from March They are bottom feeders that rely heavily on their through to October (Kurth 1957; Crawford 1984) strong sense of smell to find food. Feeding and the presence of eggs and recently hatched maybe more intense in spring and summer larvae in Port Phillip indicates that spawning (Cadwallader & Backhouse 1983). They are also occurs in coastal bays during winter (Jenkins predominantly carnivorous, feeding on a wide 1986a). In Corner Inlet, roed fish have been range of aquatic organisms, such as insects, caught in channels and in shallow areas, though crustaceans, worms, molluscs, fish and frogs. little is known about the spawning behaviour in They may also be cannibalistic. this inlet. The amount of roe increases Flathead significantly after May. Sand flathead are endemic to Australia and are Eggs are planktonic and hatch about four days found from Red Rock (New South Wales) to after fertilisation (Crawford 1984). In Port Phillip

South‐Western Minor Inlets 2000 18 larvae may spend a month or more drifting in the schools at the mouths of estuaries and along water column (Jenkins 1987) before beaches. After spawning they move back into metamorphosing and settling onto shallow estuaries, but not necessarily to the estuaries they inshore sand and mud flats during late winter originated from (Thompson 1963). Spawning has and early spring at a size of about 10 mm (May & been suggested to take place adjacent to the surf Jenkins 1992). zone of ocean beaches, although this is yet to be confirmed (Kailola et al. 1993). Some fish may fail Intertidal unvegetated areas are important to spawn if feeding is disrupted prior to the nursery areas for juvenile greenback flounder spawning migration (Thompson 1955). (Jenkins et al. 1997; Jenkins & Wheatley 1998). Areas with patchy macrophyte cover are also No field studies of the larval life of sea mullet likely to be important nursery areas. This is due have been conducted in Australia. Post‐larvae (20 to the increased food availability resulting from to 30 mm in length) move into estuaries after organic enrichment of the sediments by approximately two months in coastal waters macrophyte detritus (Shaw & Jenkins 1992). (Chubb et al. 1981). Small juvenile sea mullet Greenback flounder move into deeper probably enter inlets during winter and remain unvegetated habitats as they grow, but may still for possibly two to three years. Juveniles inhabit occur in shallow areas as older juveniles. shallow areas in the lower freshwater zones of Historically, thousands of juvenile fish were estuaries (Anon 1981). Migrations of two year reported from the mangrove habitats around old juveniles between estuaries often occurs in Corner Inlet. early summer (Anon 1981), although some fish Adult flounder can be found throughout Corner apparently remain resident within larger inlets Inlet, in both shallow and deep water usually on such as Mallacoota Inlet. Juvenile and adult sea bare substrates near seagrass beds (particularly mullet appear to utilise shallow bare sand and Posidonia). Adult flounder are generally not seagrass habitat (Anon 1981). found in macroalgal habitats. The diet of sea mullet varies depending on the Larval stages may feed on dinoflagellates and environment they inhabit. In estuarine waters sea zooplankton such as bivalve veligers, copepods mullet feed on detritus, algae, and small and nauplii (Jenkins 1986b). The diets of juveniles invertebrates that they filter from the sediment and adults are primarily composed of sediment‐ (Thompson 1963; Anon 1981). Sand is ingested to associated organisms such as diatoms, plant assist in grinding of food in the muscular material, polychaete worms, nematodes, small stomach. Small juveniles may consume larger bivalve molluscs, harpacticoid copepods and proportions of animal material than adults amphipods (Rigby 1984; Shaw & Jenkins 1992). (Anon, 1981). Sea mullet Sea mullet inhabit inshore coastal waters, bays Yellow‐eye mullet and estuaries in temperate and tropical waters all Yellow‐eye mullet inhabit bays, estuaries and around the world (Gomon et al. 1994). They have open coastal waters where they school and form a wide salinity tolerance and may be found in aggregations over sand and mud substrates fresh, estuarine and coastal waters in all states of (Kailola et al. 1993). Yellow‐eye mullet have Australia (Kailola et al. 1993). broad salinity and temperature tolerances and have been reported from both brackish and open Sea mullet may grow to 76 cm and possibly live ocean waters. to 16 years of age (Kailola et al. 1993). They Yellow‐eye mullet can reach up to 40 cm in mature at three years of age when the fish are length (Hall 1984) and mature at about two to approximately 30 to 35 cm in length (Thompson three years of age (Harris 1968). Mature fish form 1951). Outside the spawning season, adult sea large aggregations in coastal waters and marine mullet are typically found in the brackish reaches embayments prior to spawning (cited in of estuaries. Prior to spawning they migrate Gunthorpe & Hamer 2000). through the estuaries to inshore coastal waters (Thompson, 1955). In Victorian waters, spawning may occur from late spring until autumn (Ramm 1986; Rigby Spawning may occur as early as February, with 1984). The spawning locations and details of the peak spawning occurring from March to July larval life of yellow‐eye mullet in Victorian (Kesteven 1942). Migrating sea mullet form large waters are not well understood, but spawning is

South‐Western Minor Inlets 2000 19 suggested to occur predominantly in coastal 1993). Nothing is known of the larval lifestage waters outside bays and inlets (Chubb et al. 1981; though it is thought larvae remain in open Jenkins et al. 1996). coastal waters for several months (Kailola et al. 1993). Small juveniles enter estuaries/rivers Juvenile yellow‐eye mullet move into Victorian when they are 5 to 10 cm in length. Juveniles are bays and estuaries from late summer through to thought to have wide salinity tolerances. early spring when they attain a size of 30 to 40 mm in length (Robertson 1978; Ramm 1986; One to two year old juveniles are most common Jenkins et al. 1993; Jenkins et al. 1996). Juveniles in NSW estuaries from February to September are abundant in shallow water over seagrass and while young adults can be found in embayments unvegetated sand habitats, but are less common and estuaries from September to October (Kailola over shallow reefs (Jenkins et al. 1993; Jenkins et et al. 1993). al. 1996). Edgar et al. (1993) reported that yellow‐ Mulloway can live for 30 years and reach sexual eye mullet are abundant over both seagrass and maturity at 6 years when they are 75 cm long unvegetated habitats in Western Port. In (Kailola et al. 1993). This is a highly mobile Western Port, juveniles of 25 to 30 mm have also species and tagging studies conducted in NSW been reported from sheltered waters such as in indicate individual fish can travel hundreds of marinas and around mangroves, and in the kilometres between estuaries. mouth of the Bass River where they penetrate to the extent of the tidal influence (anecdotal Mulloway feed on a variety of fish including evidence). Juveniles from Gippsland Lakes yellow‐eye mullet, garfish and juvenile populations have been found in brackish water at mulloway, crabs, prawns and worms (Kailola et salinities of 20 (Gunthorpe et al. 1997). al. 1993).

The Barwon River mouth is kept constantly open. Estuary perch It is likely that yellow‐eye mullet feed just Estuary perch occur in tidal estuaries, rivers and outside of the river mouth and frequently move sometimes also in freshwater lakes (Allen 1989). in and out of the river. All of the other inlets They are found in association with riparian mentioned within this study have river mouths vegetation and snags, which provide habitats for that close over and consequently block in shoals shelter. of mullet. Adults migrate into estuarine areas of high salinity where spawning occurs in response to Yellow‐eye mullet are omnivores, with broad rising temperatures. This occurs in November or dietary requirements and are considered to be December in Victoria when water temperatures the seagulls of the oceans. Young juveniles feed reach 14 ‐ 16°C (Allen 1989). Spawning may also mainly on zooplankton. Older juveniles and be triggered by the freshwater flush that occurs adults feed on detritus, plankton, filamentous after the spring rains (September – November). algae, polychaetes and other small invertebrates Estuary perch spawn in areas with submerged and epiphytes (Thompson 1957; Rigby 1984), aquatic plant beds in brackish water adjacent to although algae may dominate the diet of some deep banks. Fishers contend that estuary perch larger fish (Edgar et al. 1993). take bait during the spawning period to such an Mulloway extent they are termed “suicide fish” at this time. Mulloway are found in waters from Bundaberg Eggs and larvae are pelagic and remain in the in Queensland to North West Shank in Western plankton for 2 to 3 days prior to hatching. Australia. They are a coastal fish and can be Juvenile perch remain in areas of high salinity found in a variety of habitats including the lower before moving into less saline areas as they grow reaches of rivers, estuaries, bays, inlets, along older (Koehn & O’Connor 1990) and may ocean beaches and in open waters to a depth of congregate in schools until they reach 7 cm in 150 m (Kailola et al. 1993). While mulloway are length. Larger fish do not appear to display common in western Victorian, this species is schooling behaviour. much less abundant between Melbourne and Adult estuary perch are found in a wide variety New South Wales (Kailola et al. 1993). This of habitats ranging from deep channels to species is highly prized by recreational anglers. shallow mud‐bottomed habitat and have a wide salinity tolerance. In Mallacoota Inlet, for Mulloway spawn in the surf zones close to ocean beaches from late spring to summer (Kailola et al.

South‐Western Minor Inlets 2000 20 example, estuary perch are found in association Jenkins et al. (1996) reported that juveniles of with snags. both species were most common over unvegetated sand/mud and seagrass as opposed Estuary perch are ambush feeders, preying on to reef. Juveniles can tolerate a wide range of small fish (such as anchovies), shrimp and salinities and temperatures (Ramm 1986; Kailola prawns. They may also consume worms and et al. 1993). Adults of both species are generally bivalve molluscs (Allen 1989). found in exposed coastal waters around rocky Australian salmon headlands, reefs and sandy beaches (Kailola et al. There are two species of Australian salmon 1993). found in Victorian waters, the West Australian The diet of larval stages of either the eastern or salmon, Arripis truttacea, and the East Australian western species of Australian salmon has not salmon, Arripis trutta. They are genetically been studied. West Australian salmon are distinguishable from each other, with A. truttacea opportunistic feeders. Juvenile West Australian possessing a more rapid growth rate and higher salmon feed mostly on bottom dwelling maximum size, lower number of gill rakers and crustaceans and fish (Robertson 1982). Adult temporally and spatially different spawning West Australian salmon feed on squid and a areas (Jones 1999). There is little information on range of fish species including pilchards, the relative proportions of each species in anchovies, southern sea garfish and Australian Victorian bays and inlets, probably because of the herring (Kailola et al. 1993). difficulty associated with identification. However, the proportion of East Australian Important Fisheries Habitat salmon in the total catch increases the further east the fishery is located. East Australian The habitat requirements of the fish species salmon are generally only found east of Cape found in the south‐western minor inlets are Otway in Victoria to Brisbane in Queensland, summarised in Table 4. The pelagic (water), including Tasmania. It is likely that the salmon seagrass, and other bottom flora and unvegetated taken in the minor inlets of this region are West sediment (soft sediments, either sand close to Australian salmon. river mouths or finer muds further upstream) habitats are used directly by these species at The spawning area for West Australian salmon various stages in their life cycles. Several species has not been exactly located, although the only also use snags, deep holes, fringing vegetation area where reproductively mature fish have been (reeds) and hard bottoms or rock outcrops as consistently found is in the coastal waters foraging grounds and/or spawning sites. Many adjacent to the south west corner of West species have salinity preferences and will move Australia. Advection of eggs, larvae and post‐ throughout the inlets to satisfy these specific larvae from the spawning area occurs over a requirements. wide area of southern Australia, with juveniles settling in sheltered gulfs, embayments and inlets Hard structures such as any jetties, public from south‐west Western Australia to Tasmania. wharves and highway bridges over the inlets are With increasing size, the schooling behaviour also used as habitats by some fish species. becomes more apparent and the fish move to All of the habitats important to fish species are higher‐energy coastal waters. The fastest present in varying degrees within the south‐ growing fish migrate back to the spawning areas western minor inlets. at about 3 years of age. There is no evidence that any adult fish found in Western Australia migrates back to South Australian waters (Jones 1999).

South‐Western Minor Inlets 2000 21

22 South

‐ Western Table 4. Habitat requirements for each life stage of the more targeted fish species in the minor inlets. Species Spawning Gametes Larvae Juvenile Adult

Minor black bream pelagic in lower salinity pelagic pelagic, settle out to seagrass, macroalgae, seagrass, macroalgae, water. (over muddy seagrass/macroalgae beds unvegetated sediments, snags, unvegetated sediments, snags, sediments?) holes holes

Inlets eels ‐ ‐ ‐ over seagrass in estuaries, may silty freshwater habitats, pass seek shelter in mud or through estuaries on migration vegetation, transitory stage to sea

prior to upstream migration to 2000 freshwater flathead ? near shore coastal waters ?pelagic ?pelagic unvegetated sediments unvegetated sediments flounder ‐ ‐ pelagic settle onto shallow unvegetated sediments, shallow and deep unvegetated unvegetated sediments sediments with patchy algal habitat cover sea mullet coastal waters adjacent to ?pelagic outside estuary ?pelagic outside estuary lower freshwater zones of lower freshwater zones of estuary mouths estuaries, unvegetated estuaries, unvegetated sediments, seagrass sediments, seagrass yellow‐eye mullet in inlets and proximate pelagic pelagic, over all bottom types pelagic, over all bottom types pelagic, over all bottom types marine unvegetated sediments mulloway ‐ ‐ ‐ pelagic, in deep holes, around pelagic, in deep holes, around hard structures hard structures estuary perch riparian vegetation, after pelagic pelagic high salinity areas before snags, unvegetated habitats spring rains moving to fresher regions, cosmopolitan Australian salmon ‐ ‐ ‐ unvegetated sand/mud and unvegetated sand/mud and seagrass, through out Inlet seagrass, through out Inlet

where “?” indicates data is not known for the minor inlets; “‐” does not occur in the minor inlets.

2000 Assessment

these are affected by the frequency with which Status of Important Fish Habitat the lagoon entrance is broached by the sea. There was some literature available for reviewing Seagrass coverage within coastal lagoons and habitats and fish behaviour within the minor estuaries that perennially close is greater during inlets. State government departments, marine conditions when the bar is open than particularly the (former) Department of Natural during less saline conditions (Kirkman 1997). Resources and Environment, and statutory authorities produced the majority of reports. Seagrass has been identified in the Curdies Inlet, There are also a number of leaflets originating the Barham River estuary, the Anglesea River from government departments, local government estuary and the Barwon River estuary complex. and statutory authorities, which can be accessed It is likely that seagrass (most likely Z. muelleri) is on the web. Most of the cited literature referring present in most if not all of the minor inlets in to habitat‐related issues dealt predominantly south west Victoria. with investigations in the Barwon River. Unvegetated sediment The habitat assessment process is designed to be Soft sediments are typically found in estuaries, one of the instruments through which Fisheries with generally clear sand around the river mouth Victoria manages the sustainable harvest of fish and gradually altering to finer muds further resources. Under the principals of Ecologically upstream. Near estuary mouths, sand is carried Sustainable Development (ESD), a precautionary in by flood tides and accumulates to form flood approach must be applied to the management of tide deltas while finer mud brought downstream biological resources. This approach requires that by rivers settles out due to either lessening water a “lack of full scientific certainty” not be used as velocity or aggregation as the salinity of the a reason for postponing measures to prevent water increases or both. environmental degradation. Snags The experiences of members of the assessment Snags are collections of tree limbs entrapped group provided guidance with observations of together to form both small and large solid threats impacting the minor inlets, fish species structures on the river bottom and throughout and habitat types encountered in the minor the water column of the river. While there is no inlets. detailed information on the distribution or importance of snag habitats to fish within these Pelagic minor inlets, citations in Gunthorpe et al. (1997) The pelagic habitat is the water column and suggest that larger juveniles of black bream and encompasses waters of various depths, salinities, adult black bream may be found in association temperatures, flow rate, nutrients and other with a range of habitats within estuaries, contaminants. It is likely that all of the inlets including structures such as snags and rocks. exhibit a common behaviour with maximum water flow during winter and, apart from the Most of the rivers within the Otway Basin pass Barwon River, have mouth closures during the through forested land and it is likely that snags lower flow regimes that occur during summer. are not only established but are also replenished. The Barwon River estuary is listed as a local port, Seagrass has been highly modified and bounded by The high energy coastline of south‐eastern agricultural and urban land and most snags have Australia restricts seagrass to estuaries and been historically cleared. protected bays. Distribution of seagrasses can vary between types of estuary and is also Deep holes affected by the age, catchment area and stability It is likely that all of the minor inlets have a of each estuary. Generally, seagrass cover number of deep holes in their estuarine sections. extends about 3 km back from the estuary These holes provide area of refuge during low entrance, although Z. muelleri may be found in water flow events and periods of extreme feeder creeks and cut‐off bays further upstream. temperature. Coastal lagoons also harbour seagrasses though

South‐Western Minor Inlets 2000 23

Reeds, rushes and mangroves Artificial opening of closed river mouths usually Semi‐aquatic emergent plants such as cumbungi happens when properties or roads become or bullrush (Typha spp), rush (Juncus spp), club inundated by rising levels of river water and is rush (Scirpus spp) and the common reed usually done by either local councils or (Phragmites australis) are present in all of the individuals to relieve flooding. south‐western minor inlets. These can provide When the mouths of the Curdies River, the cover for fish and for various fish food species Gellibrand River and the Aire River have been such as invertebrates and amphibians. closed for some time, there is local officially‐ Cumbungi is considered in some areas to be a sanctioned action taken to manually break local pest species. through and open the river mouth. The other A lot of the Painkalac River inlet area is rivers in the Otway drainage basin are allowed to surrounded by saltmarsh. The Barwon River break their closed bars naturally. There have estuary has extensive salt marsh on the 1 km been infrequent manual openings of other rivers. wide flood plain situated in the lower reaches of The Barham River mouth, for example, has been the estuary and has belts of white mangrove opened occasionally by shovel, but since at least (Avicennia marina) extending up to 4 km 1997, has been allowed to open naturally. upstream from the river mouth (Yugovic 1985). Stream salinities throughout much of the Otway drainage basin, apart from the Curdies River, are Threats low. The Barwon River, within the Barwon Environment Australia (1995) considers that the drainage basin, has salinity problems (Codd most serious habitat issues within estuaries stem 1992). Salt affected soils, streams and from poor catchment use and, therefore, groundwater were a cyclic feature of the declining water quality where increased levels of Victorian environment prior to European nutrients and sediment are the major problems. settlement, although land use changes following While the threats that arise from soil erosion and settlement have caused the spread of the increased nutrient input and their resultant salinisation of land and streams (Codd 1992). habitat impacts are recognised in inland waters, Groundwater and steam salinity may be minor it also needs to be acknowledged that these issues within estuaries, but it can be a problem in threats have both direct and indirect flow‐on the more fresh upstream regions. Stream impacts on fish habitats in estuaries. morphology, hydrology and flow regulation patterns ultimately determine the extent and The greatest threats to fish habitats in the minor duration of saline pools in river systems. inlets in south‐western Victoria are thought to arise from: Sedimentation and turbidity • alteration of environmental river flows One of the greatest determining factors of erosion (including artificial opening of river mouths) and excessive sediment deposition in inlets and • erosion and deposition of sediment rivers is land use practises in the catchment and, in particular, degradation and loss of riparian • elevated nutrients and nuisance algal growth areas. Logging and associated activities also have • pollution /water quality an impact. Unsealed roads, river crossings and • potential overfishing poor logging road design encouraging land • introduced species. slippage are all sources of sediment entering water courses (SKM 2000). Alteration of environmental flows Water abstraction and diversion for domestic and Urban developments in the catchment and rural purposes occurs in some of the rivers in directly adjacent to some inlets can also increase south‐western Victoria. It has been noted that no sedimentation, especially during the more than 25 ‐ 30% of the historical river flow to development phases of these towns/villages. an estuary can be diverted without ʹdisastrousʹ The ecological benefits of native vegetation with ecological consequences (Clark & Benson 1981). respect to minor inlets and their upstream Overall, water quality in the minor inlets is components are: affected by rainfall in the catchments and • protecting water resources whether the river mouth is open. Generally, the • protecting soil worst water quality for a number of streams • maintaining cycling of nutrients occurs during summer when rainfall and water • maintaining biodiversity flows are low and the river mouth is closed.

South‐Western Minor Inlets 2000 24

• contributing to the maintenance of regional introduced species, agricultural activities and rainfall patterns (DNRE, 2000). increasing human populations. Under conditions of enhanced levels of nutrients, warm Removal of native vegetation alters many temperatures and abundant light, phytoplankton ecological processes including: growth rates can explode and continue until the • unbalancing water and nutrient cycles nutrients are depleted. Rapid growth of • increasing soil erosion phytoplankton, or algal blooms, can adversely • increasing upstream salinity through the affect the biota in a waterbody and cause loss of clearing of riparian vegetation from the habitat for a variety of fauna, including fish and catchment their prey species. • raising the water table Epiphytic algal growth on seagrass has • flooding of low lying land downstream. demonstrable, negative effects on seagrass Dryland agriculture is the major land use production by blocking light access to leaves. throughout the south‐western Victorian region Excess nutrients are therefore likely to have an and occupies 70% of the total area incorporating indirect effect on seagrass production by grazing practices and broad‐acre cropping promoting epiphyte growth and/or water industries. A relatively small area of pasture turbidity (Cappo et al. 1998). within the region is irrigated, mostly by spray Pollution /water quality irrigation (CCMA 2000). It is unlikely that more Pesticides, herbicides, heavy metals and land will be made available for clearing for petroleum hydrocarbons entering waterbodies agricultural purposes. are sourced from human activities and Logging will most likely be a regionally cyclic depending on their concentration within the activity. At present logging is generally remote waterbody at the time, can detrimentally affect from inlets, occurring in the upper catchment the success of fish spawning and larval survival. area of the Otway basin within this south‐ These pollutants can also alter the community western region. However, it is possible that composition of benthic invertebrates which are suspended sediment sourced from logging food for many species of estuarine fish and in activities could be transported to, and impact extreme cases can cause fish kills. upon, inlets. Impacts of fishing related activities Turbidity levels in streams and rivers throughout Increasing numbers of people frequenting south‐ the Corangamite region are generally classified western Victoria can directly pressure fish stocks. as excellent, although trend analysis indicated Most of the inlets are accessible and a significant that turbidity levels are increasing in just over proportion of those who visit the area come to half of the waterbodies. During winter, levels are fish for bream in the inlets. often elevated in certain areas (DNRE 2000). Increasing fishing effort in the inlets also poses Seagrass growth parameters have strong positive indirect pressures on fish habitat, in the form of relationships to irradiance and therefore negative localised physical disturbance to riparian relationships to light attenuation. Increases in vegetation, benthic vegetation and deposition of the turbidity of waters may decrease seagrass litter. Indirect threats arising from the increasing cover within an inlet. Most seagrass losses are popularity of the inlets include actions such as attributed to reduced light intensity through the illegal camping causing water pollution via water column due to enhanced levels of seepage from pit toilets. Increased catchment suspended sediment (Kirkman 1997). pressures due to expanding urban settlement around the inlet and urban runoff from general It is likely that the amount of soft sediment population expansion, can be considered as a habitat within minor inlets will gradually general threat for all of the inlets investigated in increase as catchment erosion continues. this report. Elevated nutrients and nuisance algal Introduced species growth Introduced species can include aquatic weeds, While nutrients enter waterbodies naturally via willows and carp. Weeds and willows spread weathering of high nutrient soils and rocks, in down watercourses altering natural water flows many cases elevated nutrient levels in water and when established can severely alter the courses are a result of the clearing of native natural ecology. Carp is an introduced forest, replacement of native grasses with

South‐Western Minor Inlets 2000 25

freshwater fish which has adapted well to River and it is likely that some domestic septic Australian conditions and competes with native waste as well as farm waste from milking sheds fish species for food, space and shelter. at times may enter the Curdies River. Peterborough is not sewered and some septics Status of Threats in Each River may leak into the lower reaches of the inlet. Levels of phosphorus measured in the estuarine Inlet System reaches of the river are 12 ‐ 14 mg L‐1 (pers. Based on the observations of its members, SWMI comm. Prof. John Sherwood). This value is HAG listed the threats to each of the inlets and extremely high when it is considered that their estuarine river areas. These observations concentrations 30 μgL‐1 Total phosphorus in were augmented by material gleaned from the estuarine water are the trigger values for scientific literature and the ‘grey’ literature. assessing the risk of adverse effects on estuarine systems under the Australian and New Zealand Curdies River Environment Conservation Council “Water Much of the catchment has been cleared for Quality Guidelines” (ANZECC 2000). agricultural purposes, with dairy farming as the predominant activity. Cattle access to the river is Elevated levels of nutrients have encouraged pressuring riverbanks and causing bank erosion. excessive levels of filamentous algae to grow in Erosion from the clearing of riparian vegetation, the estuarine ʹlakeʹ just behind Peterborough, and where there is only a remnant remaining, has blue‐green algal blooms occur within the river. enhanced the amount of particulate matter The estuary has twice been closed to fishing entering the Curdies. Areas within the because of blue‐green algal blooms; once in 1991 catchment that are very steep and have been and once in 1998. In fact, the Curdies Inlet is the mostly cleared contribute substantial loads of only south‐west Victorian estuary to be closed sediment via overland runoff to the Curdies because of blue‐green algal blooms. River. During the building of the new Great Ocean Some of the water within the reaches of the Road Bridge over the inlet, waste concrete and Curdies River upstream of the inlet is withdrawn rubble was dumped into the big channel that was for irrigation and the filling of large dams. This termed the ʹBlue Holeʹ. The channel filled up and has so lessened the river flow that it affects the altered the flow regime within the inlet. duration of the opening of the entrance and No information is available on the pollutant encourages massive sand buildup within the levels (herbicides, pesticides and disinfecting downstream regions of the inlet. The consequent products used during agricultural operations) in movement of sand from the buildup overflows water, biota or sediment taken from the Curdies onto tea‐tree and marram grass (Ammophila River. arenaria) growing at the river bank. At the eastern side of the inlet around the bridge, what The higher salinity within the Curdies is due to a used to be the main swimming area has filled in. combination of the high levels of dissolved solids About 2 km upstream from the river mouth, the originating from the soils of volcanic nature in reduced flow has allowed the river to become the catchment and the clearing of riparian clogged with silt entrapped by weeds. vegetation within the catchment which has permitted the water table to rise. Saline The river mouth is mechanically opened when groundwater entering the freshwater region of the water depth reaches 1.3 AHD on the gauge the river pools in the deeper holes along the river board located on the first pylon at the western bottom, making them uninhabitable to fish. side on the Peterborough bridge crossing the inlet. The period of opening lasts about 10 days There is a significant growth of ragwort, in before the entrance shuts again. Historically the particular, around the Curdies River. All weeds river mouth stayed open for about 6 months and are managed by a program of herbicide spraying. the estuarine area within the influence of oceanic tidal movements was well flushed. Gellibrand River Apart from the headwaters that flow in fern Elevated levels of nutrients from various origins gullies with intact closed canopies, most of the enter the river at point and diffuse sources. Gellibrand and its tributaries suffer some degree Agricultural practises, such as aerial fertilisation of disturbance. One or both sides of the bank of land with superphosphate, are a widespread have been cleared for agriculture or the bank diffuse source of phosphorus (P) into the river. vegetation has been modified by cattle access and Sewerage overflows in Cobden enter the Curdies

South‐Western Minor Inlets 2000 26

the introduction of exotic plants such as Aire River blackberries (Tunbridge & Glenane 1988). Most of the catchment occurs in state forest, The Gellibrand River is a major source of urban although some of the catchment is used for pine water supply for Warrnambool, Colac and a plantations and dairy farming activities. number of smaller Western District townships, The digging of drainage ditches alongside with a total of 15,500 ML per year being pastures to facilitate drainage has brought about withdrawn. It also provides water resources for the elevated siltation seen in Lake Horden. The agricultural uses such as irrigation (McKay 2000). constant drainage of peat‐impacted land has Local landowners report that during a normal caused land levels to drop and consequently the rainfall year, the Gellibrand River mouth needs land floods more frequently. The lakes are to be opened only once to reduce flooding, as starting to become brackish through the high discharge rates maintain the open river introduction of salt water. mouth. During a dry year (1982) the river mouth There is no urban water demand from the Aire was artificially opened 9 times (McKay 2000). River and its tributary system, although for the The trigger point for artificial opening of the year 1999 ‐ 2000, private users diverted 108 ML river mouth is a white marker on the Great out of a whole basin yield of 145,549 ML (SKM Ocean Road side of the lower Gellibrand bridge. 2000). Although some land alongside the river has been The mouth of the Aire River experiences modified for agriculture, nutrients are not as big occasional ʹuncontrolledʹ openings by local a problem in the Gellibrand River as in the farmers who use a bulldozer or tractor with a Curdies River. However, nutrients from diffuse scraper attached to open the bar. The bar has sources enter the river along its length and been opened in this fashion since about 1940. It originate from soil erosion, dispersed agricultural was opened manually several times during 1999. runoff and forestry activities. Phosphorus and Otherwise, the Aire River Drainage Committee nitrogen concentrations occasionally exceed of clears the mouth. The trigger‐mark is the 1.9 m levels suggested to cause extensive aquatic plant depth marked on the gauge board at the lower growth (Tunbridge & Glenane 1988). Aire River bridge. The water in the upper reaches of the Gellibrand Over‐fertilising and the method and timing of the River is well aerated and has low salinity. Iron application, and the amount and timing of water concentrations in the water are high. The waters applied for irrigation, can have a negative impact are usually highly coloured due to dissolved with respect to nutrient levels in the Aire River. humic and fulvic acids (Tunbridge & Glenane 1988). There are camping grounds on the east and west side of the Aire River just below Lake Craven Turbidity becomes moderate, with respect to and nutrients may enter the river from pit toilets. other water courses, during high flow events (Tunbridge & Glenane 1988). Stock Vehicular access to the shore is possible at encroachment around the lower reaches of the several places and may contribute to erosion of Gellibrand and the wetlands pressures river banks and particulate matter entering the riverbanks and enhances suspended sediment Aire River. Cattle also have access to the river in levels within the water. certain regions and are pressuring riverbanks causing bank erosion. The extensive flood plains along the lower Gellibrand River have been mostly cleared and Barham River the remaining riparian vegetation is frequently The Barham River in the upper catchment has an dominated by willows, blackberries and African east and a west branch. Up to 1 ML of water is Boxthorn (Lycium ferocissimum) (Koehn 1984). withdrawn daily from the west branch of the Control of weeds is undertaken by spraying. Barham River for domestic use in Apollo Bay, Skenes Creek and Marengo. The urban water Goldfish have been observed in the Gellibrand demand for the year 1999 ‐ 2000 was 307 ML out River. It is not known what sort of impact of a whole basin yield of 8,793 ML. Private, or goldfish have on fish habitat in the Gellibrand essentially rural diverters withdraw from the east River, but it is possible that they may also be able branch of the Barham River and had a demand of to utilise estuarine habitats to the detriment of 6.6 ML for 1999 ‐ 2000 (SKM 2000). native fish.

South‐Western Minor Inlets 2000 27

Land clearing for farmland and for urban during periods of low rainfall. The inlet itself requirements around the lower reaches of the loses a lot of water by evaporation. Barham River increases the level of nutrients in the river and enhances the turbidity. Anglesea River Some stormwater and overland runoff from the Historically there has been a large erosion township enter the inlet adding nutrients, metal problem upstream due to land clearing and tree and hydrocarbon contaminants to the water. felling practices. Logging roads put through the One of the smaller streams within the catchment forest have sometimes been laid on steep and passes very close to the local tip site. cleared slopes. Landslides occurred in the west Barham sub‐catchments following an extreme A number of unsealed roads are present within rainfall event in March 1983. The rainfall event the catchment and are popular with trail bike was estimated to have an average recurrence riders and off‐road recreational vehicles. Some interval of between 10 and 17 years (SKM 2000). of the tracks provide direct access to the banks of During 1996 there was a landslip where a surface a number of catchment streams. There are area of land of about 4 ha slid into the east working gravel pits and the local tip site within branch of the Barham River and caused a high the catchment. Illegal roadside rubbish dumping degree of turbidity in the water. occurs along the unsealed roads. There is an infestation of ragwort in parts of the Cooling water from various sources within the catchment of the Barham River. Alcoa power station site is pumped into the Anglesea River. Erskine River The open cut mine extends about 70 m below sea The upper reaches of the Erskine River appear to level and dewatering actions are necessary. Some be in good condition. Some pressure on the river of the freshwater is diverted to the power station begins at Erskine Falls, where a camping ground for cooling purposes before it enters the Anglesea is situated, and when the river passes through River and the remainder is pumped directly to the developed regions of Lorne. the Anglesea River. Nutrients from stormwater flows and Epiphytic algae has been observed growing on encroaching development of Lorne enter the seagrass within the estuary and is likely to have lower Erskine River. A constant level of been caused by the presence of excess nutrients. opportunistic/ epiphytic type algae exists around the river mouth, maintained by nutrients sourced Acid sulphate soils are common near marine and from the township of Lorne. estuarine environments and are a product of anoxic breakdown of organic matter, forming A diesel spill from a local garage during 1997 iron pyrite or iron sulphide which concentrates was the acknowledged last hydrocarbon spill in the top metre of the sediment. While this into the river which killed some of the pyritic layer is submerged and protected from opportunistic algae. the atmosphere it is innocuous. However, when There was a past history of logging upstream, sufficient oxygen reaches the pyrite layer, but currently there does not appear to be much of through land clearing activities, drainage and/or a siltation problem and this probably reflects the high energy water flow events, the pyrite is good vegetative cover of the catchment. oxidised to sulphuric acid. The low pH in the water mobilises otherwise soil‐bound metal ions Painkalac Creek such as aluminium, which when mobilised in Some of the catchment has agro‐forestry and sufficient concentration in the water, can clog the grazing activities. Grazing land comes down to gills of fishes and cause mortalities (Klaveren the waters edge around the estuarine reaches and 1999). Sudden high influxes of water elevated in causes bank destabilisation, increased suspended aluminium and iron entering estuaries can cause sediments within the water and organic wastes fish mortalities, one of which occurred in the from faecal matter. Parts of the catchment may be Anglesea estuary during September 2000 (pers. affected by neighbouring logging practises. comm. EPA Geelong). The extent of fish killed Aireyʹs Inlet obtains domestic water from the during these events could possibly be moderated Painkalac Creek. The demand for the year 1999 ‐ if there was a bigger seawater flush into the 2000 was 177 ML out of a total basin yield of estuary, as seawater would have buffered the 5,374 ML. There are no private diverters (SKM effects of acidity to some extent. Some of the 2000). Water abstraction can become a problem Anglesea catchment passes through tea‐tree

South‐Western Minor Inlets 2000 28

swamps and peaty soils, which can enhance low Colac/Lough Calvert drainage scheme and the pH effects in the Anglesea estuary. Lake Corangamite Reclamation scheme. Swampy land has been reclaimed near the lower Widespread clearing in the catchment, for urban, inlet and only remnant saltmarsh now remains in semi‐rural and rural purposes also encourages this area. The alteration of land use and the catchment and riverbank erosion and enhanced reduction of foliage cover may contribute to turbidity in the Barwon. alteration of sediment dynamics by changing the Carp have been observed in the middle reaches flow behaviour of the river and increased of the Barwon River. overland sedimentary runoff. Barwon River Management Implications There is substantial urban and semi‐rural In the absence of information on changes to the development along both sides of the Barwon aquatic habitats and environment in the estuaries River as well, extending beyond the estuarine and minor inlets of south‐western Victoria it was influence past Geelong. Overland and not possible for the SWMI HAG to assess the stormwater runoff from these origins contributes extent to which the threatening processes have not only nutrients but also metal and already affected the fish habitats. hydrocarbon contaminants to the Barwon. The Barwon River is used as a receiving water for Neither was it possible for the HAG to directly some of the stormwater runoff from the City of determine the implications of these impacts on Greater Geelong. reliant fish populations, beyond basic concepts. Dryland farming is the biggest contributor of Alteration of environmental flows nutrients such as nitrogen (N) and phosphorus It has been noted that no more than 25 ‐ 30% of (P) to the Barwon (29 ‐ 47% of total N and 15 ‐ the historical river flow to an estuary can be 225% of total P) and sewerage works contribute diverted without ʹdisastrousʹ ecological 10 ‐ 18% total N and 23 ‐ 40% total P to the river consequences (Clark & Benson 1981). system. Under comparison to guidelines from Flooding is an important component of the the Office for the Commissioner of the hydrological and ecological processes operating Environment, the Barwon River basin was within estuaries. Regular early river mouth classed as degraded/poor with respect to total N openings prior to water levels reaching their and total P (Loone 1996). Blue‐green algal peak and forcing a natural break through the blooms have occurred in 1992, 1993 and 1995 in closed mouth may degrade wetlands and the Barwon River near Geelong. riparian vegetation, reduce fisheries production Stream salinity as measured at Connʹs Lane (cited over the long term and contribute to a decline in in Codd 1992) was found to increase by about regional biological diversity (Harty 2000). The 12% over a 30 year period between 1950s to river mouth is likely to close over more rapidly 1980s. Activities that contribute to the salinity in as the scouring of the mouth by the escaping the Barwon River include the Lough Calvert waters is diminished and the variation and drainage scheme (Kefford & Robley 1996), the upstream reach of water quality within inlets Ballarat sewerage authority, groundwater from tidal flushing is lessened. pumping of Australian Portland Cement Limited During periods of low flow within a closed (McGuckin et al. 1991) and widespread clearing estuary, the water column can become stratified in the catchment (cited in Codd 1992). The and the saline bottom water can become depleted Lough Calvert scheme diverts water from several in dissolved oxygen and have high saline lakes to control the water height in these concentrations of toxic solutes such as lakes. The water from these lakes, situated ammonium and hydrogen sulphide. If the river outside the Barwon River catchment, is diverted mouth is mechanically opened at times like these, into the middle reaches of the Barwon River the top oxygenated layer may flow out, forcing (Kefford & Robley 1996). Widespread land fish into the remaining anoxic layer and clearing causes the groundwater level to rise and consequently causing massive fish kills (pers. streamflow to increase, which in turn increases comm. Prof. John Sherwood). the leaching and flushing of salts in the soil into the river (cited in Codd 1992). McGuckin et al. Wrongly timed openings can cause large fish (1991) estimated that 41% of the salt load to the mortalities and also be detrimental to the overall Barwon River originated from the Lake health of the estuary. When estuaries break

South‐Western Minor Inlets 2000 29

through the bars naturally, there is usually a microalgal species, presence of water‐borne much higher head of water than when broken toxins) through manually. The scouring away of the bar • the extent of eutrophication is bigger, the mouth stays open longer and • the geographical extent of habitats. greater upstream expanses of the estuaries are The effects of filamentous algae on fish are able to be flushed by the tidal cycling of ocean unknown. water. The timing of the opening and its duration is also Pollution /water quality important to allow many fish species to enter the Chemical pollution from heavy metals, inlet, replenishing the stocks of essentially petroleum hydrocarbons and other synthesised marine fish that inhabit the inlets periodically eg hydrocarbons such as PCBs, pesticides and mulloway. herbicides can exert a number of effects on fish and fish habitats: Sedimentation and turbidity • Effects on fish can range from death when The major effect of land clearing that is noticed in contaminant concentrations are high, to rivers is the enhanced sediment transport from impaired reproduction as a result of chronic land erosion. or intermittent exposures Turbidity of water may act generally to reduce • Food availability for the targeted fish species benthic vegetative habitat in the system. The loss is affected due to the reduction in abundance of stabilising vegetation can lead to: of prey species such as invertebrates, fishes • reductions in habitat for fish species, and flora • decreased availability of food. • Fish become unsuitable for human consumption if the levels of toxicants in the The burial of snags and smothering by flesh taken for consumption are above sedimentation of seagrass and other structural complement levels of the Australian and features for fish (eg deep holes) has adverse New Zealand Food Authority (ANZFA) impacts for fish with respect to loss of habitat for standard. spawning and protection. Saline groundwater enters the freshwater region Changes to the depth and the particulate size of of rivers and pools in the deeper holes along the the sediments, such as the covering of sand or river bottom, making them uninhabitable to fish gravel with fine alluvial sediment transported and consequently causing fish to become more from further upstream, may also alter the vulnerable to predation and subjecting them to composition of infaunal and benthic species. temperature stress during summer. Food availability for fish and habitat for important prey species may also be reduced as a Estuarine fish such as bream go upstream to consequence of the deposition of this sediment. spawn in waters of lower salinity. Other fish species that have low tolerance of saline water Generally, management will have to contend can also be impacted. The availability of with reductions in habitat for fish species by locations desired by these fish species could be sediment smothering of bottom profiles and compromised by enhanced groundwater sourced decreased availability of food. salinity within rivers. Elevated nutrients and nuisance algal Increasing fishing pressure growth Bait collection, propeller disturbance, dragging of Increased nutrients may lead to the growth of boats over seagrass and anchoring can all have epiphytic algae and smothering of benthic detrimental impacts on vegetated and vegetation, the simplification of diverse algal unvegetated habitats, while waves induced by communities, and/or the reduction of extent of boating activities can possibly cause bank shallow unvegetated habitats as epiphyte areas erosion. expand. Introduced species Changes to the species composition and Introduced plants such as weeds and willows can abundance of primary producers (plants) within alter the structure of the local ecosystem, by the system can alter: changing the riparian vegetation. Introduced • the availability of food for fish species such as goldfish may compete with local • the quality of habitats used by fish (eg species for space or food. heavily fouled seagrass, blooms of problem

South‐Western Minor Inlets 2000 30

2000 Assessment ‐ Summary

recreational fisheries, though most periodically Status show signs of stress which are related to There was insufficient information for the SWMI alterations of natural water flows, elevated HAG to clearly identify or quantitatively assess nutrients and high sediment loads. the status of fish habitats in the south‐western minor inlets. There is some literature relating to Research Priorities habitat degradation of the Barwon River. There The SWMI HAG developed a threat matrix for is also literature with respect to the quality of the the habitats within the south‐western minor habitat within the fresh and estuarine reaches of inlets (Table 5). From this table it is evident that the Gellibrand River. However, there is a effective management of sustainable fish habitat paucity of information on other inlets within the in the inlets is hampered by the overall lack of Otway basin. knowledge concerning the current status of fish The observations of the SWMI HAG were in part habitat. based on known catchment activities and To avoid causing massive fish mortalities, a assumptions made generically about the type of much better understanding of the alterations of impacts these activities are known to have in natural water flows to the inlets is needed, other locations, supported by the observations of including the timing of manual opening of closed habitat condition made by the participating river mouths is required. The most common members of the HAG. motivation for the manual opening of estuaries is The most serious issues in Australiaʹs marine to relieve flooding of low‐lying land or buildings. (and estuarine) environments stem from As mentioned in Harty (2000), strategies should catchment use and development, and consequent be directed to the restoration of as natural an poor water quality. Soil erosion and water opening regime as possible. These strategies will turbidity, saline groundwater and elevated levels have to incorporate better land use practices of nutrients entering some streams from within the relevant catchments to keep water anthropogenic land‐based activities all exert quality within the estuary at a good level while pressure on fish stocks and fish habitats. the bar is closed. Undoubtably fish habitat within the inlets has The SWMI HAG identified the following as likely been altered by activities that have occurred in threats to fish habitats: the catchment since the times of European • Water quality compromised from nutrient settlement. However, most of the threats to the inputs and recycling within the sediments habitats identified by the SWMI HAG, are now and water of the inlets, particularly for those being mitigated by the implementation of inlets that close over during low inflows catchment management plans and strategies, from tributary rivers and creeks which aim to reduce the impact of these threats. • Inopportune openings of estuary mouths It is acknowledged that the mitigation and resulting in large fish mortality events and elimination of catchment derived threats occurs superficial flushing of the inlets over the long term and feedback of the efficacy of • Saline groundwater intrusions reducing the threat minimisation strategies is required to available spawning habitat for certain ensure the management actions undertaken in estuarine fish species, including black bream the catchment are effective. and estuary perch It is clear from the deliberations of the SWMI • Acidic freshwater pulses in the Anglesea HAG that insufficient scientific baseline data on River can either kill fish and other aquatic the condition of the estuarine reaches of these organisms or have sub‐lethal effects such as inlets exists or is being planned, for such epizootic ulcerative or ʹred spotʹ disease on feedback to be given. fish (Klaveren 1999) Despite the alterations that have already • Chemical contamination (heavy metals, occurred to the south‐western minor inlets, these herbicides, pesticides etc) of the estuary (the inlets still generally support productive extent of which is not well known)

South‐Western Minor Inlets 2000 31

• Changes to the dynamics of the food chains • Determine environmental flow profiles within the inlets required to maintain good water quality • The loss of snags as habitats for fish species within each inlet; to maximise reproduction within these inlets, while acknowledged in and survival of key fish species and to the literature is not known. restore more‐natural opening regimes at inlet/estuary mouths The SWMI HAG identified three important • Review the status of saline groundwater research areas which it considered as a high contamination of rivers and whether there priority to undertake to ensure the fish habitats are almost permanently anoxic deep holes within the south‐western Victorian inlets are that may be of importance to the spawning of sustainably managed: estuarine fish. • Within each inlet, obtain an ecological

ʹsnapshotʹ illustrating the ecological processes maintaining inlet health and the biological processes that link fish to each habitat

Table 5. A threat matrix for fish habitats in selected minor inlets of South‐western Victoria. THREAT HABITAT TYPE 1 2 3 4 5 6 Seagrass Pelagic Unvegetated Snags Deep Reeds sediments holes and rushes Alteration of natural • •••? • ‐ •• • flows Sedimentation and ••? ••? •• •• ••• ••• turbidity Increased nutrients and ••? •••? •• •• ‐ ‐ nuisance algal growth Pollution/ water quality •? ••? •• •• •• •? Increased fishing • ‐ ‐ • ‐ • pressure Introduced species ? ? ? ? ? • Chronic lack of •• ••• •• ••• ••• •• knowledge

Both threats and habitats types are listed in order of their importance in the selected minor inlets in the Corangamite CMA. Dots indicate priorities as follows; ‘•••‘ High; ‘••‘ Medium, ‘•‘ Low and ‘?’ unknown or uncertainty. “*” indicates localised areas of threat, ‘‐’indicates the threat is not applicable to the habitat.

South‐Western Minor Inlets 2000 32

Acknowledgements

This report was prepared by the Fish Habitat • Geoffrey Holbery‐Morgan (Anglesea, Aireys Assessment Group from discussions and a Inlet Society for the Protection of Flora and compilation of contributions by members of the Fauna) group. Participants at the South‐western Minor • Sarojini Krishnapillai (Victorian National Inlet fish habitat assessment workshop, held on Parks Association) 09 March 1999, at Lorne, are listed as follows: • Henry Love (Commercial fisherman) • Tim Allen (Marine Conservation Community • Murray MacDonald (Fisheries Victoria, Network) Department of Natural Resources and • Leanne Gunthorpe (HAG Chair, Marine and Environment) Freshwater Resources Institute) • Paul Millar (Department of Natural • Ian Hastings (Manager PFF, Department of Resources and Environment) Natural Resources and Environment) • Geoff Nicholson (HAG Secretary, Marine • Katie Young (Coast Action Co‐ordinator) and Freshwater Resources Institute) • Neville Stewart (Commercial fisherman)

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Appendix 1 ‐ Glossary

Algae A large group of non vascular plants, many are microscopic, and live in water. Anoxic Devoid of oxygen. Anthropogenic Changes resulting from human activities. Aquaculture Farming of plants or animals in water. Benthic Belonging to the sea floor. Benthos Organisms living on or in association with the sea floor. Bioaccumulation The concentration of substances (especially toxicants) in the tissues of plants and animals. Biota All living organisms in a region. Bivalve a type of mollusc possessing two shell valves joined by a hinge (eg scallops and mussels). Bloom Microalgae occurring in dense numbers in a water body. Catchment The area of land from which run‐off from rain enters a waterway. Chronic Over a long period of time. Opposite of acute. Community In the biological sense, a community is a group of plants and animals that live together in a particular habitat. Often they are critically dependent on each other, with a loss of one species leading to an impact on others. Contaminant A substance out of place (also pollutants). Crustacean Animals living in water which have a hard outer surface and jointed limbs and belong to the class crustacea. Demersal Used for fish that live on or near the sea floor. Detritus Non‐living organic matter (eg dead seagrass). Ecology The study of living of organisms and their relationships to one another and the environment. Ecologically sustainable The management of resources to meet the needs of the development present generation without compromising the ability of future generations to meet their own needs. Ecosystem The physical, chemical and biological environment of a community of organisms, and all the interactions among those organisms and between organisms and their environment. Effluent An outflow usually wastewater (eg sewage). Epiphyte A plant growing on top of another surface (eg crab shell, pier pylon, seagrass). Estuary That area within the mouth of a river which is influenced by the sea. Eutrophication An increase in the nutrient status of a water body, and consequently the rapid growth of plants, both natural and as a result of human activity. Excessive plant production may deplete oxygen and suffocate animals. Exotic species Any species that is not of natural origin to a location. Fauna All kinds of animals.

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Filter feeder An animal that obtains food by filtering particles from water. Fish (a) live, fresh, imported or processed aquatic invertebrates with gills including crustaceans, molluscs and all other forms of aquatic life other than reptiles, amphibians and mammals. (b) fish products or any part of the fish Fishery The taking of fish described by reference to the species taken, the gear used and the purpose of the Fishery. Fishery resources The stock or stocks which support the fishery. Flora All kinds of plants. Food chain The sequence of consumption of plants by animals and those animals by other animals. Food web A complex of food chains. Groundwater The part of rainfall which seeps into the ground and moves slowly in a horizontal direction. Habitat The place where a plant or animal lives. Heavy metals A general term for cadmium, copper, iron, mercury, nickel, manganese, lead, zinc, arsenic and selenium. Hydrocarbons Compounds of hydrogen and carbon such as petroleum. Ichthyoplankton Fish eggs and larvae which float in water. Infauna Animals living within the sediment on the sea bed. Inputs Substances entering a water body. Invertebrate Animals without a backbone. Larvae/Larval Fish Early stage(s) of the life‐cycle of fish. Often fish drift in the upper layers of the water column with varying degrees of swimming ability. Macrophyte A seaweed. Microalgae Single celled plants. Mollusc An invertebrate animal with a shell (eg mussel) and belonging to the phylum Mollusca. Nutrients Substances required for plant growth (eg fertilisers). Organism A living entity. Organochlorines Complex organic molecules with chlorine atoms attached (eg pesticides). Pelagic The water column. Phytoplankton Microalgae that live in the water column. Plankton Aquatic, free‐drifting suspended organisms, generally but not always microscopic. Pollutant A substance in excess or not belonging. Producer An organism that can create living matter out of inorganic or inanimate matter. Productivity The magnitude of a producer’s activity. Recreational use The harvesting of fish or any other aquatic resource for personnal use. Salinity The salt content of the seawater. Seafood The edible marine organisms. Seagrass A group of flowering vascular plants which live in seawater. They take root in the sea floor.

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Sediment The solid material that sinks to the substrate. Sewage Loosely applied to any waste sent to a treatment plant. Stakeholder An individual or organisation interested in and able to influence the management of (in this instance) western minor inlets and their fisheries. Stormwater Run‐off during storms. Substrate A surface on which organisms live or into which they burrow. Sustainability A characteristic of a process or a state that can be maintained indefinitely. Sustainable development Improving the capacity to convert a constant level of physical resource use to the increased satisfaction of human needs. Sustainable growth A term applied only to renewable resources. It means using them at rates within their capacity for renewal. Suspended matter Particles suspended in water. Toxic Poisonous. Toxicant A poison. Trophic Related to food chains and food webs. Turbidity Cloudiness caused by sediments suspended in water. Wastewater Water that has been used and discarded. Zooplankton Small animals which live in the water column.

Glossary compiled from definitions contained in Port Phillip Bay Environmental Study : Final Report (Harris et al. 1996). Port Phillip Bay Fisheries Management Plan: Background Paper (Fisheries Victoria, 1996).

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