Corangamite Estuaries Fish Habitats 2008

Julia Kent

December 2011

Fisheries Victoria Assessment Report Series Report No 32

Corangamite Estuaries Fish Habitats 2008

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ISSN 1329‐7287

ISBN 978‐1‐74326‐034‐0 (print)

Corangamite Estuaries Fish Habitats 2008 ii Table of Contents

Executive Summary...... 1

Introduction...... 2

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

2000 Assessment ...... 4

The 2008 Assessment ...... 5 Aims and Methods ...... 5 Aim, Objectives and Strategies of the Assessment...... 5 Boundaries of the Corangamite Estuaries ...... 5 Definition of a Fish Habitat ...... 5 Methods...... 5 Assessment Methods...... 5

Key Fish Species and Their Habitat Requirements ...... 6 Fish Species in the Corangamite Estuaries ...... 6 Key Fishery Species and Habitat Links...... 6 Black bream ...... 6 Mulloway...... 6 Estuary Perch...... 6 Important Fisheries Habitat...... 7

2008 Assessment ...... 8 Status of Important Fish Habitat ...... 8 Threats and status of threats in the Corangamite estuaries...... 8 Alteration of environmental flows ...... 8 Declining Water Quality...... 8 Sedimentation...... 9 Management Implications ...... 9

Corangamite Estuaries Fish Habitats 2008 iii 2008 Assessment ‐ Summary ...... 11 Status ...... 11 Research Priorities ...... 11

Acknowledgements ...... 12

References ...... 12

Glossary...... 14

Corangamite Estuaries Fish Habitats 2008 iv List of Tables Table 1. ‘Icon’ species for the Corangamite estuaries ...... 6 Table 2. Habitat assessment summary of estuaries in the Corangamite region...... 10

Corangamite Estuaries Fish Habitats 2008 v Corangamite Estuaries Fish Habitats 2008 vi Executive Summary

The sustainable harvest of fishery resources is • Changes in the timing and extent of dependent on maintaining the integrity of the spawning for fish species habitats, environmental conditions and • Changes in the distribution of fish species ecological processes that support production of target fish populations. Fisheries Victoria The 2008 assessment concluded that most of the established a formal Fish Habitat Assessment Corangamite estuaries were considered to be in process to provide scientific information on the adequate or good condition, although four were identity and status of marine fish habitats. This still considered to be in poor condition and information is essential for facilitating protection degrading. of important fish habitat and thus the sustainability of fisheries resources. The Corangamite catchment is vulnerable to human impacts which have altered fish habitats The Corangamite estuaries are important for in the inlets. Works to promote estuary health recreational fishing in Victoria, and are have been successfully implemented, and will comprised of the minor inlets in south‐western continue to help improve the condition of Victorian from Barwon Heads to Peterborough. waterways in the region. The second meeting of the Corangamite Fish Habitat Assessment Group (C HAG – previously The 2008 CHAG identified the following research called the South Western Minor Inlet Fish priorities: Habitat Assessment Group) occurred on 2 • Improve understanding of climate change December 2008 at Warrnambool. impacts on fisheries by monitoring changes to Participants in the workshop updated the ecosystems, including catch rates and changes previous assessment by reviewing new research in habitat structure on targeted fish species in the estuaries. The 2008 • Research on estuary perch habitat associations C HAG identified a select group of targeted fish in the Corangamite estuaries, including species, which best represented the recreational specific important spawning areas. fisheries in the Corangamite estuaries and which could be considered ‘icon’ species for this region. The ‘icon’ species identified were: • Black bream • Estuary perch • Mulloway

Alteration of environmental flows, declining water quality and sedimentation were identified as the major threats to habitats in the Corangamite estuaries and to fish production more broadly. Due to the lack of recent surveys of the fish habitats in the river inlet systems, it was not possible for the 2008 CHAG to assess the extent to which the threatening processes are affecting the production of key fish species. The threats may cause: • Reductions in habitat for fish species • Decreased availability of food • Reduced connectivity and migration between estuarine and freshwater habitats

Corangamite Estuaries Fish Habitats 2008 1 Introduction

A fishery resource is dependent on maintaining The objectives of the Fish Habitat Assessment the integrity of the habitats, environmental Process are to: conditions and ecological processes that support • Identify fish habitats in Victorian waters production of target fish populations. that are important in supporting production Management of fisheries includes identification of key fishery target species and advocacy of management actions needed to • Assess the current status of key fish habitats protect and where possible enhance ecosystems • Determine processes threatening these fish that support production of fishery resources. To habitats do this it is necessary to know: • Make recommendations on fish habitat • The type, location and extent of habitat and research and monitoring needed to assist in environmental conditions that are important the management of fish habitats. for production and/or survival of key target fish species within the system The coast of south‐western Victoria from • The links between particular Barwon Heads to Peterborough is an habitat/environment conditions and increasingly popular tourist region and production/survival of stocks of key target retirement destination. Recreational fishing is an species important activity undertaken at the river mouths and estuaries in this region by both • The current status and historical trends in residents and visitors. An assessment of the key the condition of key fish habitats fish habitats within the inlets was undertaken to • The main threats (whether from fishing or assist in defining research directions and other non‐fishing human activities) to the management actions needed to provide integrity of each key fish habitat. sustainable utilisation of fish resources.

In 1995 Fisheries Victoria established a formal Fish Habitat Assessment process to provide scientific information on the location and status of key marine and estuarine fish habitats, as an input to the development or review of fishery management arrangements. This process involves the participation of stakeholder representatives, scientists and fishery managers in fish habitat assessment workshops, and the publication of workshop findings in the Fisheries Victoria Assessment Report Series. Information and advice provided by these fish habitat assessment groups (HAGs) complement the matters and issues dealt with by formal stock assessment and fishery assessment processes, and informs the development or review of habitat protection objectives in Fishery Management Plans for specified waters.

Corangamite Estuaries Fish Habitats 2008 2 Goals, Objectives and Strategies for Maintenance of Fish Habitats

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

Corangamite Estuaries Fish Habitats 2008 3 2000 Assessment

The 1999 Fish Habitat Assessment for the There was insufficient information for the HAG Corangamite Estuaries region (previously participants to clearly identify or quantitatively referred to as ‘South Western Minor Inlets’) assess the status of fish habitats in the south‐ described its fisheries, management agencies and western minor inlets. key stakeholders (Nicholson et al. 2003). Despite the alterations that have already Sixteen species or families of fish were identified occurred to the inlets, it was thought that they as being encountered or observed by recreational generally supported productive recreational fishers in the selected inlets. Black bream was the fisheries, though most came under stress species most commonly targeted by recreational periodically as a result of the threats listed above. fishers in these estuaries, followed by estuary The HAG identified three important research perch and mulloway. areas which it considered as high priority: The habitat affinities of each life stage of key • Obtain an ecological ‘snapshot’ of each inlet, species were identified from a combination of illustrating the ecological processes which scientific knowledge and from the experience maintain inlet health and the biological and knowledge of HAG participants. processes that link fish to each habitat The 2000 SWMI HAG noted that: • Determine environmental flow profiles required to maintain good water quality • The pelagic (water), seagrass, and within each inlet unvegetated sediment habitats were used directly by most of the targeted species at • Review the status of saline groundwater various points in their life cycles contamination of rivers and whether there are almost permanently anoxic deep holes • Several species were also found to be that may be important to the spawning of associated with snags and riparian estuarine fish. vegetation at some point in their life cycle • Many species have salinity preferences and will move through the inlets to satisfy these specific requirements.

Likely major threats to the maintenance of these habitats were identified as: • Alteration of environmental river flows (including artificial opening of river mouths) • Erosion and deposition of sediment • Elevated nutrients and nuisance algal growth • Pollution/water quality • Potential overfishing • Introduced species.

Corangamite Estuaries Fish Habitats 2008 4 The 2008 Assessment

Aims and Methods Definition of a Fish Habitat For the purposes of this assessment a habitat was Aim, Objectives and Strategies of the defined as the broad physical structures, zones Assessment and biological communities that support fish. Aim The emphasis of this report is on those habitats, To assess the status of the habitats in the which support fish targeted by recreational Corangamite estuaries upon which fisheries fishers and key prey species. resources are dependent; identify management actions and recommend future directions for Methods habitat research. Data A literature search was undertaken to provide Objectives information on the Corangamite estuaries and • Identify habitats and assess their importance the habitats therein published since the last to fish in the Inlets. workshop held in 2000. • Provide up‐to‐date summaries of research Information was also obtained from published and monitoring programs. papers and reports, and unpublished data and • Assess the current state of fish habitats. reports held by various state government • Identify processes which pose major threats research agencies and statutory authorities. to fish habitats. Assessment Methods • Provide a qualitative risk assessment of the The workshop began by updating the previous main threats to fish habitats. assessment, incorporating scientific data, • Identify management issues for critical anecdotal information and management which habitats. provided information on the current status of • Identify research and monitoring needs to fish habitats in the estuaries. assist in the management of each habitat. The main threats to fish habitats in the Strategies Corangamite estuaries were identified, and the • Characterise the important habitats for each status of fish habitat in each estuary was of the fisheries resources of the Corangamite evaluated based on available information. estuaries, and for their dependent biological Implications for fisheries management were resources (food chains etc). detailed, and future research and monitoring needs were identified. • Establish archival databases of all relevant research and monitoring material for each important fish habitat in the Corangamite estuaries. • Synthesise available data, identify the major threats to each critical habitat and provide options to reduce these threats in the Corangamite estuaries. Boundaries of the Corangamite Estuaries For the purpose of this assessment, the seaward boundaries of the south‐western minor inlets will be assumed to be s 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.

Corangamite Estuaries Fish Habitats 2008 5 Key Fish Species and Their Habitat Requirements

migratory cues (Elsdon and Gillanders 2005). Fish Species in the Corangamite They may also travel considerable distances in a Estuaries day (up to 30 km per day) (Hindell et al. 2008). The 2008 CHAG reviewed the list of previously Larger bream utilise a range of river and identified target species, based on recreational estuarine habitats, and make diurnal seasonal catches of boat and shore anglers and the movements (Hindell et al. 2008). commercial eel fishery. Mulloway The ‘icon’ species, which best represented the In estuaries in New South Wales, most small (2 – recreational fisheries in the Corangamite 40 cm TL) mulloway were captured in deeper estuaries, recognised by the 2008 CHAG were waters of the main river channel, particularly in black bream (Acanthopagrus butcheri), estuary areas where prawns were abundant (West and perch (Macquaria colonorum), and mulloway Walford 2000). (Argyrosomus hololepidotus) (Table 1). A recent tagging study showed most fish < 115 cm did not travel further than 3 km from the tag Key Fishery Species and Habitat site, so it is likely that there is a high degree of Links estuarine residency (Griffiths and Attwood 2005). New information on the critical habitats for each Individuals in the Swan River (WA) form life stage of fish species in the Corangamite spawning aggregations in turbid waters around estuaries was identified from the literature and high tide, during late afternoon and early recent research. evening, and produce varied pulsed vocalisations (Parsons et al. 2008). Black bream Hypoxia, low salinity and lowered temperatures Tracking of mulloway in New South Wales can severely affect survival and hatch rates of revealed important habitats were discrete holes black bream (Hassell et al. 2008). Larvae feed or basins up to 20 m deep (Taylor 2006). Smaller mostly on copepods and other zooplankton fish remained in these holes, whilst larger fish (Nicholson et al. 2008). left them at night. The larger mulloway were found to have a bigger home range, up to In the Gippsland Lakes, black bream spawn in 17710 m2 (Taylor 2006). the upper riverine regions of the estuaries, and forage throughout the lakes region during late Stable isotope analysis has shown evidence of summer and autumn (Hindell et al. 2008). diet shifts from crustaceans to teleost fish in mulloway > 50 cm TL (Taylor and Mazumder Bream have been found in rocky river beds, and 2010). amongst snags and other structures. They have been caught over seagrass, mud and sand Estuary Perch substrate (Cashmore et al. 2000). Seagrass beds Recent research on estuary perch has focused are an important habitat for larval and juvenile mainly on movement, diet and early life history. black bream (Cashmore et al. 2000). The larval development of estuary perch has been described by Trnski et al. (2005). Black bream move frequently between estuarine and coastal environments, and may act on Table 1. ‘Icon’ species for the Corangamite estuaries Common Name Species black bream Acanthopagrus butcheri estuary perch Macquaria colonorum mulloway Argyrosomus hololepidotus

Corangamite Estuaries Fish Habitats 2008 6 Salt wedges may contribute to the successful spawning of estuary perch, (Newton 1996; Important Fisheries Habitat McGucken 2006). Estuary perch generally spawn Based on the information considered by the C in brackish waters; however, there have been HAG, and in the previous South‐Western Minor indications that spawning may also occur in the Inlets HAG, participants noted that: ocean (Trnski et al. 2005). Although estuary perch • Pelagic (water), seagrass, snags, deep holes have been found to be associated with structural and unvegetated sediment habitats are used habitat, such as mangroves, fallen trees and over‐ directly by key species at various stages in hanging branches (Conron et al. 2010; Douglas their life cycles 2010), adult fish were only present on unvegetated mudflats and not in mangrove • Several species feed on prey found in habitats in Western Port and Corner Inlet seagrass beds, or are dependent on seagrass (Hindell and Jenkins 2004). derived food webs Acoustic tagging showed the species to be highly • Many species had salinity preferences or mobile, moving throughout the Snowy River required specific conditions for successful estuary across a range of different habitats, spawning, and will move throughout the particularly at night time (Douglas 2010). They inlets to satisfy these requirements were generally found in the lower reaches of the • All of the habitats important to fish species Snowy River. Estuary perch may move away are present in varying degrees within the from the river mouth in autumn (Douglas 2010). Corangamite estuaries. Small estuary perch were found almost exclusively in the middle to upper regions of the Tarwin River estuary. There was evidence of spatial structuring of sexes during spring and summer, when females were found in the lower river, and males were found close to mangrove habitat (Conron et al. 2010). Estuary perch have been found to feed mainly on crustaceans (Howell et al. 2004; Conron et al. 2010). The specific prey items varied between freshwater and brackish environments (Howell et al. 2004), and with size of the fish (Conron et al. 2010). In the Hopkins River, prey items indicated feeding occurred mainly in the mid‐water to surface during the summer months (Howell et al. 2004). From stable isotope analysis, it was determined that the nutrition of estuary perch in Anderson Inlet is mostly derived from seagrass (up to 80%), but Spartina also made a significant contribution to the food chain (Conron et al. 2010).

Corangamite Estuaries Fish Habitats 2008 7 2008 Assessment

Low flows often coincide with the closure of Status of Important Fish Habitat estuary mouths, which can influence Since the previous South‐Western Minor Inlets temperature, salinity, and other water quality HAG, a substantial amount of work has been parameters. The water column within a closed carried out to improve estuary health in the estuary can become stratified, with saline water Corangamite region. These works include on the bottom becoming toxic and depleted in stormwater and waterway management dissolved oxygen. Fish deaths often occur as a activities, river rehabilitation works including result of manual opening, as they are forced into weed management, and riparian control. Funds the anoxic water when the top oxygenated layer through state programs have also allowed the flows out. Prolonged closure of the estuary construction of structures to allow fish passage mouth during drought can also affect the through weirs and gauging stations on the successful recruitment of some species, and the Barwon River, Gellibrand River, Thompson replenishment of stocks of marine fish which Creek and Barham River. inhabit the inlet periodically. A number of estuaries in the Corangamite region Threats and status of threats in undergo artificial openings of the estuary mouth the Corangamite estuaries during periods of low flow (DPI 2008). CCMA is Substantial agricultural, industrial, urban and currently implementing the Estuary Entrance tourism development has occurred along the Management Support System (EEMSS) to Victorian coast, impacting on a number of manage artificial estuary mouth openings. estuaries in the Corangamite region. Many areas Extraction and diversion of water for irrigation also experience a huge population growth during and urban water supply needs also results in summer, making the estuaries increasingly changed water flows. Construction works have susceptible to urban and recreational impacts. impeded water flow through Thompson Creek, The main threats to fish habitats in the which will be addressed by raising the height of Corangamite estuaries are thought to arise from: the road and installing box culverts to help improve flow and connectivity (CCMA 2010). • Alteration of environmental flows Declining Water Quality • Declining water quality Water quality is determined by the concentration • Sedimentation. of contaminants and nutrients in the water. Poor water quality, including increased sediment and Alteration of environmental flows nutrient loads and turbidity, can result from Changes to flows in the Corangamite estuaries catchment‐related processes such as land have occurred as a result of both diversion of clearing. Sources of nutrients to the Corangamite water for urban use and a changing climate. estuaries include runoff from farms, dairy Victoria is predicted to receive reduced rainfall, a effluent, stock access to waterways, erosion and continuing warming temperature, and more sewage systems. Drainage patterns in the region frequent extreme weather events (DAFF 2008, are generally conducive to increased nutrients Hobday et al. 2008). Reduced river flows affect and pollutant entering lakes and wetlands connectivity and available fish habitat, and may (CCMA 2006). alter spawning cues for fish. The recruitment of black bream is affected by freshwater flow, and is Many rivers in the region have high levels of found to be significantly higher during periods of nitrogen and phosphorous, which can result in intermediate flow, when the water column is significant algal blooms, particularly during the strongly stratified (Jenkins et al. 2010). summer (CCMA 2006). These blooms have recently been an issue in the Barwon River, Heavy rainfall after extended dry periods can where they can smother vegetation and cause flush nutrients and chemicals from the catchment changes in species composition. downstream. This occurs periodically in the Anglesea River, causing the water in the estuary The release of water from the Alcoa power plant, to become very acidic, and resulting in fish kills. runoff from surrounding areas and riverbank

Corangamite Estuaries Fish Habitats 2008 8 condition influence water quality in the Anglesea Revegetation and stock exclusion works have River. In general, water quality within the helped reduce the problem in recent years, Anglesea estuary is relatively good, and meets although riverbank erosion continues to be a objective for water quality described by the State threat for the area. Government (Surf Coast Shire 2005). Modelling indicates a high risk of sedimentation From 1998–2002 depth profiles of water quality in some parts of the Barwon River, with bank were measured at 6 sites along the Anglesea erosion being the most important source of River estuary each month (Surf Coast Shire 2005). sediment input (Lett et al. 2007). Salinity was typically less than 10 in surface As erosion has been a problem in Painkalac waters and increased with depth to levels typical Creek, a rock chute has been used to dissipate the of marine waters (36–38). Phosphorus levels were energy during high water flows, and reduce the low, although Nitrogen levels were slightly amount of sediment reaching the estuary. Rocks higher than SEPP water quality objectives at have also been used to stabilise riverbanks and some times. Turbidity levels met national prevent further erosion. guidelines and dissolved oxygen levels were variable. Management Implications The condition of Lake Connewarre has The 2008 C HAG participants assessed the deteriorated, becoming a shallow bog due to the condition of the estuaries in the Corangamite build‐up of silt caused by flooding followed by a region (Table 2). They concluded that four lack of tidal flow. Most recently, heavy rains estuaries were in poor condition and degrading, have lead to a ‘blackwater event’ in the area. This while the remainder were still classed as being occurs when plant and other material is washed adequate with the capacity to improve. into a waterway and starts to break down, leaching oxygen from the water and resulting in The 2008 C HAG posed the following questions: the death of fish and other aquatic life. • How do the threatening processes impact on Dissolved oxygen levels in the Curdies River are the factors that link fish to habitat? indicative of degraded water quality (Water • Which, if any, of these processes are Technology 2008). High levels of nitrogen and significantly decreasing fisheries production phosphorus are also known to occur in the river, in the Corangamite estuaries? with concentrations upstream of the estuary previously exceeding State objectives (EPA 2001). Climate Change and Alteration of Stock access, dairy effluent and other agricultural Environmental Flows runoff further contribute to high nutrient levels. Climate change predictions for Victoria include Nutrient budgeting will help improve nutrient increasing water temperatures, variations to: management on dairy farms in the Curdies River catchment, and minimise the amount of nutrients • Ocean currents entering waterways. • Changes in salinity There is a risk of pollution (sediment, • Changes in primary productivity hydrocarbons, litter etc.) in Thompson Creek from stormwater run‐off from the Great Ocean • Reduced rainfall and water availability. Road during periods of high rainfall. Elevated These factors influence the distribution and levels of E. coli have also been reported in the productivity of fish stocks. Erskine River mouth after high rainfall events. Key fish species in the Corangamite estuaries Sedimentation such as estuary perch and black bream have Estuary sedimentation and erosion caused by specific water quality requirements for spawning channel modification, human activity and stock and larval survival. Reduced freshwater flows access is an issue in the Corangamite estuaries. are likely to result in a reduction of suitable Increased sediment loads can reduce the amount spawning areas, and therefore lower recruitment. of light able to penetrate the water, thus smothering benthic vegetation and other Some climate change impacts will be gradual and structural fish habitat, and filling deeper holes difficult to detect, or may become apparent which are used by key species. suddenly when a threshold is reached (Hobday et al. 2008). Changes in the distribution and abundance of fish species may occur, which

Corangamite Estuaries Fish Habitats 2008 9 could alter the species targeted by recreational at different water levels, and considers the fishers. Management strategies will need to be impact on vegetation and fish. The system also adaptive, and adjust in response to any observed stores information from past events to inform or expected changes. future decisions. Declining Water Quality Due to the lack of recent surveys of the fish Degraded water quality may restrict or prevent habitats in the river inlet systems, it was not fish movement and migration through estuarine possible for the 2008 CHAG to assess the extent systems. This may impact negatively on species to which the threatening processes are affecting which migrate to certain sections of the estuary, the production of key fish species. or move extensively throughout it. The threats may cause: Sedimentation • Reductions in habitat for fish species Sediment can smother aquatic plants including seagrasses. A reduction in seagrass may reduce • Decreased availability of food the abundance of prey available to key species. • Build up of sediment will also gradually restrict Reduced connectivity and migration between estuarine and freshwater habitats movement to important habitats within the water body, and may cause estuary entrances to close. • Changes in the timing and extent of To address the threats of artificial opening of spawning for fish species estuary mouths, the CCMA has implemented the • Changes in the distribution of fish species Estuary Entrance Management Support System (EEMSS) at Gellibrand, Curdies, Anglesea and These threats have the potential to decrease the Barwon River and Painkalac Creek (CCMA productivity and quality of the Corangamite 2010). The system uses a risk‐based approach to estuaries consider the risks of opening the estuary mouths

Table 2. Habitat assessment summary of estuaries in the Corangamite region.

Estuary Status Trend Reason

Lake Connewarre Poor Degrading Problems with low river flows, water extraction, Anglesea River Poor Degrading sedimentation and high nutrient levels, fish kills, acid runoff, hypoxia, use of fertilisers, stock access, degraded Curdies River Poor Degrading riparian vegetation, algal blooms, urban expansion and impaired wetland and ocean connectivity. Spring Creek Poor Degrading

Barwon River Adequate Unchanged Intermittent or permanent entrances, rivers in good condition Painkalac Creek/Aireys Inlet Adequate Improving

Barham River Adequate Improving

Gellibrand River Adequate Improving

Thompson Creek Adequate Improving

Erskine River Good Improving Generally high river flows, woody debris, reed beds and absence of algal blooms and hypoxia. Aire River Good Improving

Skenes Creek Good Improving

.

Corangamite Estuaries Fish Habitats 2008 10 2008 Assessment ‐ Summary

Status The threats may cause: The observations of the 2008 C HAG were in part • Reductions in habitat for fish species based on research findings since the previous assessment, and assumptions on impacts of • Decreased availability of food known catchment activities made by the • Reduced connectivity and migration between participating members of the HAG. estuarine and freshwater habitats Building upon the 2000 assessment, the 2008 • Changes in the timing and extent of CHAG focused on updating information on life spawning for fish species cycle requirements for key species, and the ecological threats to critical habitats. • Changes in the distribution of fish species It was considered by HAG participants that the These threats have the potential to decrease the status of the habitats within the estuaries in the productivity and quality of the Corangamite Corangamite region was varied. Most of the estuaries. estuaries were considered to be in adequate or good condition, and had showed signs of The Corangamite catchment is vulnerable to improvement since the last assessment, although human impacts, including cattle grazing, land four were still considered to be in poor condition clearing and water extraction, which have altered and degrading. fish habitats in the inlets. As a result of these The major threats to Corangamite estuaries fish impacts, extensive work has been carried out in habitats and to fish production more broadly the Corangamite region to promote estuary identified by the 2008 CHAG were: health, including weed management, erosion control works, revegetation and stock exclusion. • Alteration of environmental flows These works, along with the implementation of • Declining water quality estuary management plans and catchment strategies, will continue to help improve the • Sedimentation condition of waterways in the region. All of these threats are amplified by human impacts. Research Priorities Due to the lack of recent surveys of the fish The 2008 CHAG identified the following research habitats in the river inlet systems, it was not priorities: possible for the 2008 CHAG to assess the extent • Improve understanding of climate change to which the threatening processes are affecting impacts on fisheries by monitoring changes to the production of key fish species. ecosystems, including catch rates and changes in habitat structure • Research on estuary perch habitat associations in the Corangamite estuaries, including specific important spawning areas.

Corangamite Estuaries Fish Habitats 2008 11 Acknowledgements

This report was compiled by the Fish Habitat Assessment Group from discussions and a compilation of contributions by members of the group attending the Corangamite estuaries fish habitat assessment workshop held on 2 December 2008 at Warrnambool.

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Corangamite Estuaries Fish Habitats 2008 12 Howell, T., Laurenson, L.J., Myers, J.H. and climate change implications for Jones, P.L. (2004). Spatial, temporal and recruitment in intermittently open size‐class variation in the diet of estuary estuaries. Marine and Freshwater Research perch (Macquaria colonorum) in the 59, 735–749. Hopkins River, Victoria, Australia. Parsons, M.J., McCauley, R.D., Mackie, M.C., Hydrobiologia 515, 29–37. Siwabessy, P. and Duncan, A.J. (2008) Jenkins, G.P., Conron, S.D. and Morison, A.K. Localisation of individual mulloway (2010). Highly variable recruitment in an (Argyrosomus japonicus) within a estuarine fish is determined by salinity spawning aggregation and their stratification and freshwater flow: behaviour throughout a diel spawning implications of a changing climate. period. Journal of Marine Science 66, 1007‐ Marine Ecology‐Progress Series 417, 249‐ 1014. 261. Surf Coast Shire (2005) Anglesea Estuary Lett, R., Abernethy, B. and Chaplin, H. (2007). Management Plan. Surf Coast Shire. Are all river reaches created equal? Taylor, M. (2006) Key habitat and home range of Identifying erosion hotspots for mulloway Argtrosomus japonicas in a catchment management. Proceedings of south‐eastern Australian estuary: the 5th Australian Stream Management finding the estuarine niche to optomise Conference: Australian rivers: making a stocking. Marine Ecology‐Progress Series difference, Albury, New South Wales. 328, 237–247. McGucken, J. (2006) Aquatic fauna survey after Taylor, M. and Mazumder, D. (2010) Stable the re‐snagging of a 250 metre reach of isotopes reveal post‐release the Barham River estuary. Report trophodynamic and ontogenetic prepared for the Corangamite changes in a released finfish, mulloway Catchment Management Authority, (Argyrosomus japonicas). Marine and Colac, Victoria. Freshwater Research 63, 302‐308. Newton, G.M. (1996) Estuarine ichthyoplankton Trnski, T., Hay, A.C. and Fielder, D.S. (2005). ecology in relation to hydrology and Larval development of estuary perch zooplankton dynamics in a salt‐wedge (Macquaria colonorum) and Australian estuary. Marine and Freshwater Research bass (M. novemaculeata) (Perciformes: 47, 99–111. Percichthyidae), and comments on their Nicholson, G., Gunthorpe, L. and Hamer, P. life history. Fishery Bulletin 103, 183–194. (Eds) 2003. South‐Western Minor Inlets Water Technology (2008) Curdies Estuary Fish Habitats 2000. Compiled by the Management Plan. Notting Hill, Fish Habitat Assessment Group. Victoria. Fisheries Victoria Assessment Report No. 31. (Fisheries Victoria: East West, R.J. and Walford, T.R. (2000) Estuarine Melbourne). fishes in two large eastern Australian coastal rivers – does prawn trawling Nicholson, G., Jenkins, G.P., Sherwood, J. and influence fish community structure? Longmore, A. (2008). Physical Fisheries Management Ecology 7, 523‐536 environmental conditions, spawning and early‐life stages of an estuarine fish:

Corangamite Estuaries Fish Habitats 2008 13 Glossary

Algae: A large group of non vascular plants, compromising the ability of future many are microscopic, and live in water. generations to meet their own needs. Anoxic: Devoid of oxygen. Ecosystem: The physical, chemical and biological environment of a community of Anthropogenic: Changes resulting from human organisms, and all the interactions among activities. those organisms and between organisms Aquaculture: Farming of plants or animals in and their environment. water. Effluent: An outflow usually wastewater (eg Benthic: Belonging to the sea floor. sewage). Benthos: Organisms living on or in association Epiphyte: A plant growing on top of another with the sea floor. surface (eg crab shell, pier pylon, seagrass). Bioaccumulation: The concentration of Estuary: That area within the mouth of a river substances (especially toxicants) in the which is influenced by the sea. . tissues of plants and animals. Eutrophication: An increase in the nutrient Biota: All living organisms in a region. status of a water body, and consequently the rapid growth of plants, both natural Bivalve: a type of mollusc possessing a two shell and as a result of human activity. Excessive valves joined by a hinge (eg scallops and plant production may deplete oxygen and mussels). suffocate animals. Bloom: Microalgae occurring in dense numbers Exotic species: Any species that is not of natural in a water body. origin to a location. Catchment: The area of land from which run‐off Fauna: All kinds of animals. from rain enters a waterway. Filter feeder: An animal that obtains food by Chronic: Over a long period of time. Opposite filtering particles from water. of acute. Fish: (a) live, fresh, imported or processed Community: In the biological sense, a aquatic invertebrates with gills including community is a group of plants and crustaceans, molluscs and all other forms of animals that live together in a particular aquatic life other than reptiles, amphibians habitat. Often they are critically dependent and mammals. on each other, with a loss of one species (b) Fish products or any part of the fish. leading to an impact on others. Fishery: The taking of fish described by Contaminant: A substance out of place (also reference to the species taken, the gear used pollutants). and the purpose of the Fishery. Crustacean: Animals living in water which have Fishery resources: The stock or stocks which a hard outer surface and jointed limbs and support the fishery. belong to the class crusteacea. Flora: All kinds of plants. Demersal: Used for fish that live on or near the sea floor. Food chain: The sequence of consumption of plants by animals and those animals by Detritus: Non‐living organic matter (eg dead other animals. seagrass). Food web: A complex of food chains. Ecology: The study of living of organisms and their relationships to one another and the Groundwater: The part of rainfall which seeps environment. into the ground and moves slowly in a horizontal direction. Ecologically sustainable development: The management of resources to meet the needs Habitat: The place where a plant or animal lives. of the present generation without

Corangamite Estuaries Fish Habitats 2008 14 Heavy metals: A general term for cadmium, Sediment: The solid material that sinks to the copper, iron, mercury, nickel, manganese, substrate. lead, zinc, arsenic and selenium. Sewage: Loosely applied to any waste sent to a Hydrocarbons: Compounds of hydrogen and treatment plant. carbon such as petroleum. Stakeholder: An individual or organisation Ichthyoplankton: Fish eggs and larvae which interested in and able to influence the float in water. management of (in this instance) the Corangamite estuaries and their fisheries. Infauna: Animals living within the sediment on the sea bed. Stormwater: Run‐off during storms. Inputs: Substances entering a water body. Substrate: A surface on which organisms live or into which they burrow. Invertebrate: Animals without a backbone. Sustainability: A characteristic of a process or a Larvae/Larval Fish: Early stage(s) of the life‐ state that can be maintained indefinitely. cycle of fish. Often fish drift in the upper layers of the water column with varying Sustainable development: Improving the degrees of swimming ability. capacity to convert a constant level of physical resource use to the increased Macrophyte: A seaweed. satisfaction of human needs. Microalgae: Single celled plants. Sustainable growth: A term applied only to Mollusc: An invertebrate animal with a shell (eg renewable resources. It means using them mussel) and belonging to the phylum at rates within their capacity for renewal. Mollusca. Suspended matter: Particles suspended in Nutrients: Substances required for plant growth water. (eg fertilisers). Toxic: Poisonous. Organism: A living entity. Toxicant: A poison. Organochlorines: Complex organic molecules Trophic: Related to food chains and food webs. with chlorine atoms attached (eg pesticides). Turbidity: Cloudiness caused by sediments suspended in water. Pelagic: The water column. Wastewater: Water that has been used and Phytoplankton: Microalgae that live in the discarded. water column. Zooplankton: Small animals which live in the Plankton: Aquatic, free‐drifting suspended water column. organisms, generally but not always microscopic. Pollutant: A substance in excess or not Glossary compiled from definitions belonging. contained in Producer: An organism that can create living Port Phillip Bay Environmental Study : Final matter out of inorganic or inanimate matter. Report (Harris et al, 1996). Productivity: The magnitude of a producer’s Port Phillip Bay Fisheries Management Plan: activity. Background Paper (Fisheries Victoria, 1996). Recreational use: The harvesting of fish or any other aquatic resource for personnel 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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