Environmental Water Requirements for The Rubicon River

Tom Krasnicki Aquatic Ecologist Water Assessment and Planning Branch Water Resources Division DPIWE.

Report Series WRA 02/01 May, 2002. Table of Contents

ACKNOWLEDGEMENTS i

GLOSSARY OF TERMS ii

EXECUTIVE SUMMARY 1

1. INTRODUCTION 3

2. THE RUBICON RIVER 3

2.1 General Description 4 2.1.1 Catchment and Drainage System 3 2.1.2 Geomorphology and Geology 6 2.1.3 Climate and Rainfall 7 2.1.4 Vegetation 8 2.1.5 Land Use and Degradation 9 2.1.6 Port Sorell Estuary 9 2.1.7 Hydrology 11

2.2. Site Selection 13 2.2.1 The Rubicon River at Smith and Others Rd. 13

3. VALUES 15

3.1 Community Values 15

3.2 State Technical Values 17

3.3 Endangered species 18

3.4 Values Assessed 19

4. METHODOLOGY 20

4.1 Physical Habitat Data 20

4.2 Biological Data 21 4.2.1 Invertebrates 21 4.2.2 Fish 21

4.3 Hydraulic Simulation 21

4.4 Risk Analysis 22

5. RESULTS 24

5.1 Physical Habitat Data 24

5.2 Biological Data 25 5.3 Risk Analysis 26

6. DISCUSSION 29

6.1 Vertebrate Fauna 30 6.1.1 Mordacia mordax and Geotria australis 30 6.1.2 Gadopsis marmoratus 30 6.1.3 Pseudaphritis urvillii 31 6.1.4 Galaxias truttaceus and Galaxias maculatus 31 6.1.5 Galaxias brevipinnis and Neochanna cleaveri 31 6.1.6 Prototroctes maraena 32 6.1.7 Lovettia sealii and Retropinna tasmanica 32 6.1.8 Anguilla australis 32 6.1.9 Salmo trutta 32 6.1.10 Nannoperca australis and Perca fluviatilis 33

6.2 Invertebrate Fauna 33 6.2.1 Astacopsis gouldi 33

6.3 Flow Recommendations 34 6.3.1 Rubicon River at Smith and Others Rd. 35

7. REFERENCES 36

APPENDIX 1. WUA GRAPHS FOR THE RUBICON RIVER 40

Front cover: Rubicon River Photo: Mic Clayton Acknowledgments

This study has been conducted under the Natural Heritage Trust as part of the project "Tasmanian Environmental Flows" (NRC13182) and has received funding from the Commonwealth Government and the Department of Primary Industries, Water and Environment.

The author would like to thank the following individuals from the DPIWE for their assistance in field data collection and for assistance in preparation of this report: Cameron Amos, John Gooderham, Adam Jagla, David Horner, Mark Nelson, Rebecca Pinto, Nick Probert, Martin Read, Bryce Graham and Ian Tye.

The author would also like to acknowledge the support received from landowners and stakeholders within the Rubicon River catchment and the assistance of Jo Bentley of the Greater Rubicon Catchment Management Group.

Copyright Notice:

Material contained in the report provided is subject to Australian copyright law. Other than in accordance with the Copyright Act 1968 of the Commonwealth Parliament, no part of this report may, in any form or by any means, be reproduced, transmitted or used. This report cannot be redistributed for any commercial purpose whatsoever, or distributed to a third party for such purpose, without prior written permission being sought from the Department of Primary Industries, Water and Environment, on behalf of the Crown in Right of the State of Tasmania.

Disclaimer:

Whilst DPIWE has made every attempt to ensure the accuracy and reliability of the information and data provided, it is the responsibility of the data user to make their own decisions about the accuracy, currency, reliability and correctness of information provided.

The Department of Primary Industries, Water and Environment, its employees and agents, and the Crown in the Right of the State of Tasmania do not accept any liability for any damage caused by, or economic loss arising from, reliance on this information.

Preferred Citation

Krasnicki, T. J. (2002). Environmental Water Requirements for the Rubicon River . Department of Primary Industries, Water and Environment, Hobart Technical Report No. WRA 02/01

ISSN: 1448-1626

The Department of Primary Industries, Water and Environment

The Department of Primary Industries, Water and Environment provides leadership in the sustainable management and development of Tasmania’s resources. The Mission of the Department is to advance Tasmania’s prosperity through the sustainable development of our natural resources and the conservation of our natural and cultural heritage for the future.

The Water Resources Division provides a focus for water management and water development in Tasmania through a diverse range of functions including the design of policy and regulatory frameworks to ensure sustainable use of the surface water and groundwater resources; monitoring, assessment and reporting on the condition of the State’s freshwater resources; facilitation of infrastructure development projects to ensure the efficient and sustainable supply of water; and implementation of the Water Management Act 1999 , related legislation and the State Water Development Plan.

i Glossary of Terms

ARMCANZ Agriculture and Resource Management Council of Australia and New Zealand ANZECC Australian and New Zealand Environment and Conservation Council cumec a measure of flow discharge. 1 cubic meter per second; equivalent to 86.4 ML/day

Commissional Water Under the Water Act 1957, the right to take water from a water resource Right (C.W.R.) (watercourse, lake, river, stream or any surface water or groundwater) for commercial (irrigation) use. discharge a volume of water passing a given point in unit time

Water Provisions for Are that part of the Environmental Water Requirements that can be met. That is, the the Environment water regime for the environment through agreement or negotiation. (WPEs) Environmental Water Are descriptions of the water regimes needed to sustain ecological values of aquatic Requirements ecosystems at a low level of risk. These descriptions are developed through the (EWRs) application of scientific methods and techniques or through the application of local knowledge based on many years of observations. IFIM Instream Flow Incremental Methodology macrophytes large aquatic plant macroinvertebrates invertebrate (without a backbone) animals which can be seen with the naked eye. megalitre a measure of water equivalent to 1000 000 litres (or about the size of an Olympic swimming pool) pools deep, still water , usually within the main river channel riffles areas of fast moving, broken water

Riparian Right Under the Water Management Act 1999 a person who owns land or occupies a property may take water from a watercourse or lake on, or adjoining, that land for the purposes of domestic use, or irrigation of a household garden, or stock watering, or firefighting, or drilling. riparian vegetation vegetation on the banks of streams and rivers run unbroken, moving water sinuosity degree of “bendiness” of a river (ratio of valley length: river length) snags instream woody debris substrate the structural elements of the river bed; boulder, cobble etc. taxon (plural: taxa) the member of any particular taxonomic group eg. a particular species, family etc. transect in this study, a line across the river bed perpendicular to flow, used for a standardised collection of depth, velocity and substrate information

WL Water licence – Under the Water Management Act 1999 water licences are issued for the purpose of taking water from a water resource (watercourse, lake, river, stream or any surface water or groundwater). The amount of water taken depends upon the water allocation under the issued licence. The Department of Primary Industry, Water and the Environment allocates water for irrigation, stock and domestic, aesthetic, commercial and industrial purposes. WUA Weighted Useable Area, or the amount of useable habitat available in the river for a species

ii Executive Summary

This report details the ecological assessment of minimum flow requirements for the Rubicon River. Both community values and State technical values were identified as part of the assessment process and the ecological values identified from this process were used to focus the assessment of Environmental Water Requirements.

Ecological values specifically targeted included:

• Maintain habitat for common jollytail ( Galaxias maculatus ), blackfish ( Gadopsis marmoratus ) and short finned eel ( Anguilla australis ) populations; • Maintain in-stream habitat for macroinvertebrate populations.

Recreational values targeted were:

• Maintain fish stocks of brown trout ( Salmo trutta ). • Maintain rearing and/or spawning habitat for brown trout.

A risk analysis was performed to provide (1) a series of options for negotiation of Water Provisions for the Environment and (2) the ecological risk of failure in not achieving these flows for each of these values. This was achieved by determining the flows at which certain percentages of habitat loss occurred for individual species, relative to the habitat available at a pre-determined reference condition. The percentage changes in habitat that determined risk categories were taken from Davies and Humphries (1996). This analysis was done for each of the key biota (including both fish and invertebrate species).

Other values identified, and discussed elsewhere in the report include: . • Protect whitebait and native fish populations. • Maintain suitable flows for the protection of the Australian grayling ( Prototroctes maraena ) and the giant freshwater crayfish ( Astacopsis gouldi) , • Maintain fish stocks, including Australian grayling ( Prototroctes maraena ), freshwater flathead ( Pseudaphritis urvillii ), spotted galaxias ( Galaxias truttaceus ), climbing galaxias (Galaxias brevipinnis ), common jollytail ( Galaxias maculatus ), Tasmanian mudfish (Neochanna cleaveri ) Tasmanian whitebait ( Lovettia sealii ), Smelt ( Retropinna tasmanica ), river blackfish ( Gadopsis marmoratus ), brown trout ( Salmo trutta ) and shortfinned eel ( Anguilla australis ). • Maintain rearing and/or spawning habitat for, freshwater, spotted galaxias, climbing galaxias, common jollytail, Tasmanian mudfish Tasmanian whitebait, smelt, brown trout and river blackfish • Maintain in-stream woody debris as habitat for giant freshwater crayfish, brown trout and river blackfish.

Recommendations

The Environmental Water Requirements for brown trout ( Salmo trutta ) and macroinvertebrate taxa present in the Rubicon River considerably influence the flow recommendations (ie "Low Risk" flows) resulting from the risk analysis. The macroinvertebrate taxa that have determined the EWRs for these months include: Hydrobiidae spp., Austrolimnius spp ., Tilyardophlebia spp ., Pisidium casertanum, Ecnomus.spp, Ceratopogonidae spp, and Oligochaeta . While it is important to consider the implication of different flow regimes on individual taxa (macroinvertebrate and fish), it is important to adequately protect the endangered giant freshwater crayfish, Astacopsis gouldi and Prototroctes maraena. It is

1 strongly recommended that flows remain in the ‘low risk’ category to ensure these values are maintained.

The Environmental Water Requirements relate to the Rubicon River reach extending upstream from Smith and Others Road to where the Rubicon River intersects the Bass Highway.

Risk Category Low risk (EWR) Moderate risk High risk Month Cumecs ML/Day Cumecs ML/Day Cumecs ML/Day January > 0.04 > 3.5 0.04 – 0.02 3.5 - 1.7 < 0.02 < 1.7 February > 0.02 > 1.7 0.02 – 0.01 1.7 - 0.9 < 0.01 < 0.9 March > 0.08 > 6.9 0.08 – 0.06 6.9 - 5.2 < 0.06 < 5.2 April > 0.15 > 13.0 0.15 – 0.09 13.0 - 7.8 < 0.09 < 7.8 May > 0.38 > 32.8 0.38 – 0.35 32.8 - 30.2 < 0.35 < 30.2 June > 0.84 > 72.6 0.84 – 0.68 72.6 - 58.8 < 0.68 < 58.8 July > 0.90 > 77.8 0.90 – 0.43 77.8 - 37.2 < 0.43 < 37.2 August > 0.96 > 82.9 0.96 – 0.42 82.9 - 36.3 < 0.42 < 36.3 September > 0.87 > 75.2 0.87 – 0.50 75.2 - 43.2 < 0.50 < 43.2 October > 0.87 > 75.2 0.87 – 0.70 75.2 - 60.5 < 0.70 < 60.5 November > 0.32 > 27.6 0.32 – 0.26 27.6 - 22.5 < 0.26 < 22.5 December > 0.15 > 13.0 0.15 – 0.09 13.0 - 7.8 < 0.09 < 7.8

An important caveat to this report is that the EWRs recommended for each month are the minimum flows for a low risk of failure to meet ecological values. If peak flow rates are impacted or threatened in any month, including the irrigation season, additional work will be required. Additional work will also be required if significant water developments (eg. dams) are proposed in this catchment.

2 1. Introduction

In accordance with the water reform agenda set out by the Council of Australian Governments, or COAG (ARMCANZ and ANZECC, 1996), Tasmania is currently assessing Environmental Water Requirements for many of its rivers. Intrinsic to this process is the requirement that a supply of water will be provided to the environment as well as to human users to maintain or improve ecosystem quality and health of river systems. For full details about the process refer to Fuller and Read (1997). Briefly, the process involves:

• the identification of water values by the community and the State Technical Committee for Environmental Flows (a panel representing the State government’s technical and scientific expertise); • the assessment of the flow necessary to maintain these values, which includes an environmental flow assessment; • negotiation and tradeoff of these values if required when determining a new flow management regime; and • monitoring of both compliance and environmental benefit of the new flow regime once this is in place.

This report details the assessment of the environmental water requirements of key aquatic fauna that show distinct preferences to changes in discharge. The values identified by the community and the State Technical Panel play a key role in focussing this assessment. Therefore both sets of values for the Rubicon River have been provided in the report, and addressed where appropriate.

The Rubicon River has been subject to water abstraction for many years in order to provide irrigation for agricultural purposes. The water is diverted throughout the year for off-stream storage, for irrigation and for stock and domestic use. This assessment will address the flow regime required for each month including the irrigation periods during the summer months as well as flow requirements for the winter period.

2. Rubicon River

2.1 General Description

2.1.1 Catchment and Drainage System

The Rubicon River originates 6 kilometres south of Elizabeth Town at an elevation of approximately 320 metres. From the headwaters, the river meanders in a northerly direction through a gentle gradient for several kilometres. After intersecting Smith and Others Road, the river descends rapidly before reaching its point of discharge at Port Sorell (Figure 1).

The Greater Rubicon catchment covers an area of approximately 610 km 2 (Bentley, 2001) and incorporates a number of waterways which drain into Port Sorell eg Franklin Rivulet, Panatana Rivulet, Browns Creek, Branchs Creek as well as a number of small coastal catchments (See Figure 5). However only the Rubicon River catchment will be considered in this report.

3 The Rubicon River has a catchment area of approximately 263 km 2 and a total length of 40 kilometres. The Mersey and Franklin Rivulet bound the Rubicon River catchment to the west and east respectively while to the south the Rubicon River is bounded by the Meander Catchment. Major tributaries of the river include Bradys Creek, Parrot Creek, Staggs Creek and Gum Scrub Creek. Other smaller tributaries enter the Rubicon River throughout the catchment.

350 325 300 275 250 225 Elizabeth Town Elizabeth 200 175 Bradys Creek Bradys Parrot Creek Parrot Staggs Creek Staggs 150 Site Study Altitude (m) Altitude 125 100 75

50 Creek Scrub Gum

25 Weir 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 Distance from source (km)

Figure 1 . Longitudinal profile of the Rubicon River

The Rubicon River has numerous in-stream structures (weirs, dams, culverts) which are a barrier to the natural migration of fish. These structures can present a physical barrier to fish by physically blocking fish or by creating excessive turbulence or water velocities greater than those which the fish can swim against. Behavioural barriers to fish migration can be caused by changes to the habitat structure of streams including; the creation of large still water storages behind weirs and dams; the reduction of suitable habitat by flooding and/or erosion and by altering the natural streamflow regime which can disrupt the environmental cues for triggering fish migration.

The location of a barrier within a catchment can influence its impact on fish populations (Thorncraft and Harris, 2000). Where the catchment area upstream of a barrier is small, barriers to fish passage may isolate and impact only a relatively small portion of the total habitat available in a catchment. In contrast, barriers to fish migration in the lower reaches of a system have the potential to cause the greatest effect on fish recruitment and distribution upstream.

Despite the presence of a fishway or fish ladder (Figure 2a), the stream gauging weir (Figure 2b) at the tidal limit of the Rubicon River (Grid Reference 5433600N 463500E – Tasmap 1:25000) is of most concern in terms of fish passage. The weir has the potential to isolate 259km 2 or over 98% of the catchment. The concrete weir was completed on 22/6/1967 and the fishway was installed on 21/1/1982. In 2001, in consultation with the Inland Fisheries Service, the angles were removed, effectively lowering the height of the weir by 52mm. On a number of occasions, juvenile galaxias and/or whitebait species have been observed successfully negotiating the weir. However, several electrofishing surveys above the weir have failed to record a number of species which are present in Port Sorell estuary including the Spotted galaxias ( Galaxias truttaceus ), Jollytail, ( G. maculatus ), Tasmanian mudfish ( N. cleaveri ), Climbing galaxias ( G. brevipinnis ), Tasmanian smelt ( Retropina tasmanica ), Tasmanian whitebait ( Lovettia seali ) and freshwater flathead ( Pseudaphritis urvillii ) (Figure 3).

4 Figure 2a . The fishway at the Rubicon weir

Figure 2b . The Rubicon weir

5 Further surveys of fish populations above and below the weir as well as investigations into flow conditions and fish movements need to be undertaken before an assessment of the performance of the fishway and other conclusions can be made. Nevertheless it is unlikely that the current structure meets the criteria for an effective fishway (95% of individuals of 95% of taxa negotiate the barrier under 95% of flow conditions experienced at that site) (Thorncraft and Harris, 2000).

In addition, the Greater Rubicon Catchment Management Group (GRCMG) have installed 4 v-notch weirs (See Figure 4) to monitor flows in the upper Rubicon over the summer period.

The Rubicon catchment is experiencing a steady increase in instream water storages in order to provide irrigation for agricultural purposes. In 1995 there were 78 dams on record in the Rubicon Catchment. Currently there are 90 in-stream storages on the WIMS (Water Information Management System) database including 66 irrigation, 21 stock and 3 aesthetic dams, the largest of which is an 1860 megalitre dam on a tributary of Staggs Creek. The total storage capacity of all dams is 4077 megalitres.

From Figure 4 it is evident that tributaries, particularly in the upper catchment are most subject to in-stream development. Several of these individual tributary systems have the potential to become hydrologically disconnected from the remainder of the catchment and hence change the fish community structure in that part of the catchment.

2.1.2 Geomorphology and Geology

The geological history of the Rubicon catchment has a major influence on the present day topography and landforms as rock type strongly influences erosion, drainage and soil type which, in turn influence land use activities.

The Rubicon River originates from the Elliott Land System, which is a Tertiary basalt system that occurs in the area around Deloraine (Richley, 1978) and flows through this system for the first kilometre before intersecting the Rubicon River Land System to the north of Coxs Road. The Rubicon River Land System is an area of undulating plains formed on Quaternary clays, sands and gravels which are the most recent geological deposits in the catchment. The major occurrence of this system is in the Elizabeth Town area and includes many extremely wet areas (eg. Avenue Plains) and areas which are frequently flooded.

From the confluence with Parrot Creek, the Rubicon River passes through the Dalgarth Hill Land System, which is composed of Jurassic dolerite, before discharging into Port Sorell.

6 7 2.1.3 Climate and Rainfall

The Rubicon River catchment falls within the Central North region of the State. The area generally experiences a temperate marine climate, with an average summer maximum temperature range of 20 – 21°C and average summer minimum temperature range of 11-12°C recorded at East Devonport (Richley, 1978). Rainfall is slightly higher in the upper reaches where the influence of topography generates around 1000 – 1050 mm of rain per year. Rainfall decreases to around 950 mm per annum within the middle of the catchment. Throughout the lower reaches of the river and surrounding country, the rainfall totals around 800 – 850mm per annum. The highest monthly rainfall occurs in winter, with July and August generally being the wettest months and January and February the driest through the summer period.

2.1.4 Vegetation

Throughout the catchment, vegetation varies according to topography, rainfall, soil type and land usage. Large areas of the catchment have undergone considerable modification to vegetation characteristics since European settlement . Extensive clearing for residential and agricultural development has occurred throughout the catchment to such an extent that all remaining native riparian vegetation is considered to be of high conservation value (Bentley, 2001).

Vegetation on the upper and lower terraces of the Rubicon River Land System is dominated by white gum ( Eucalyptus viminalis ), stringybark ( E. obliqua ) and black peppermint ( E. amygdalina ), while on the floodplains the main species are swamp gum ( E.ovata ) and paperbark ( Melaleuca sp .). In the Dalgarth Hill Land System, stringybark, black peppermint and white gum dominate the open forest vegetation. The main understorey plants are silver wattle ( Acacia dealbata ) and prickly mimosa ( A. verticillata ).

Under the Regional Forest Agreement, a number of forest types have been classified as high priority for conservation in the Rubicon catchment. These include:

• Shrubby or sedgy black-gum dry forest and woodland; • Black peppermint on sandstone; • Damp sclerophyll forest on river flats; • All forest remnants on basalt soils.

Significant works have occurred in the catchment of the Rubicon over the past century, which have altered the natural drainage patterns. Many flats have been drained for development of pasture and natural streambeds have been straightened and de-snagged aiming to facilitate drainage capacity and to reduce flooding. The river works have created many problems, for example, in many cases, native vegetation was not re-established along the channels and erosion of channel banks and beds has developed. Additionally, the river works created enhanced flooding in some areas and siltation in others which reduced channel capacity and promoted in-stream vegetation growth (Armstrong, 2000).

A number of in-stream and riverbank weeds affect riparian areas within the catchment. Some of the more prominent weed species include willows, cumbungi, blackberries and gorse. The upper Rubicon River (from Elizabeth Town to the Avenue Plains) has been identified as having one of the most significant infestations of willows in the catchment. The Greater Rubicon Catchment Management Group has recently developed a Rivercare Plan (Armstrong, 2000) which addresses willow and erosion issues in the upper Rubicon. Implementation of the Plan aims to achieve a substantial improvement in the state of the Rubicon River, through a program of rivercare planning, protection and re-establishment of native vegetation, arresting stream-bank erosion as well as wetland rehabilitation.

8 2.1.5 Land Use and Degradation

The geological history of the Rubicon catchment has a major influence on the soil types and where they occur as well as the present day topography and landforms as rock type strongly influences erosion, drainage and consequently land use activities.

The soils in the upper catchment have been formed largely on Tertiary basalt. Tertiary basaltic materials have extensively intruded throughout this area and it is from these materials that the productive soils of the catchment have been derived. These soils are characteristically deep red or reddish brown in colour, are well structured and free draining. Almost the entire area on which these soils occur has been cleared for cropping and grazing.

The deep soils in the middle part of the catchment are generally less than 10 metres above local stream level. Mottled duplex soils on the upper and lower terraces give way to a clay soil on the flood plains. Ironstone or quartz gravel is often scattered throughout the soil profiles on the lower terraces. Land use is limited by the flat and often wet topography.

Present land and soil degradation in the catchment includes sheet, streambank and gully erosion, nutrient and structural decline of soils from overworking through continuous cropping, mass movement, waterlogging and flooding.

2.1.6 Port Sorell Estuary

Estuaries are typically defined as the interface of marine and freshwater systems. They are semi-enclosed or periodically closed bodies of water that receive sediment sourced from both river and marine environments and contain habitats influenced by tide, wave and river processes (Edgar, et al , 1999, Heap et al , 2001). Anthropogenic activities within a catchment can have significant impacts on the integrity of the estuarine ecosystem and environment (Edgar et al ., 1999). Land usage (eg; agriculture, forestry and urban development) within a catchment have been shown to alter water quality (eg; increased turbidity and nutrient loads, and decreased oxygen levels) and water quantity (eg; abstraction for irrigation and domestic water supply ).

The main river systems draining into Port Sorell are the Rubicon River and the Franklin Rivulet. A number of smaller catchments are found along the western and eastern side of the Estuary but can have intermittent flows (eg. Little Branches Creek, Marshalls Creek, Little Browns Creek, Panatana Rivulet and Greens River). The estuary is tidal to the bridge on Frankford Road. The tide range is 3 metres and the water depth is typically very shallow across much of the estuary. The estuary contains many sandbanks/mudbanks and rock outcrops and these are exposed at low tide. Deeper water (up to 8 metres) is found at the mouth of the estuary and channels have formed through sandbanks, carrying much of the river flow. The estuary also contains a number of islands, several of which are included within the Narawntapu National Park (including Penguin Island, Rabbit Island, Shell Islands).

The waters of Port Sorell Estuary have long been used for recreational and commercial fishing purposes and more recently marine farming. The Port Sorell estuary currently holds 2 marine farming lease areas, operated by a single leaseholder and occupying an area of 48.929 hectares. Both leases farm Pacific oysters ( Crassostrea gigas ). However only a small portion of the oyster lease areas can be effectively farmed due to continuing problems with suitable water depth. In addition, the estuary is prone to frequent flooding events, which increase turbidity for extended periods. The harvesting of oysters for sale during such times is not permitted due to reduced water quality and high bacterial loads (DPIWE, 2001a)

9 Under the Draft Marine Farming Development Plan – Port Sorell Estuary, (DPIWE, 2001a), investigations were made into opportunities for rationalising the existing marine farm leasing areas and finding other suitable growing areas. The Plan has identified a total of 5 marine farming zones covering an area of 43.11 hectares of which the maximum area available for marine farming or maximum leasable area is 24.5 hectares.

Edgar et al . (1999) classified estuaries and associated catchments around Tasmania and assessed the conservation significance of these areas. This was achieved through determination of the similarity in physical attributes of estuaries state wide, the subsequent ranking of the degree of human development within these groups and the assessment of the diversity and conservation status of identified taxa (Edgar et al ., 1999).

As a result of the high population density and the proportion of the catchment that has been affected by human impact, the Port Sorell estuary is considered to be of a degraded nature (Class D) and of low conservation significance. In addition, the intertidal mudflats in the upper reaches of Port Sorell Estuary, and especially the Rubicon River have been severely colonised by rice grass (Spartina anglica). It has been estimated that rice grass is occupying 120 ha of the estuary and has the potential to invade up to 650 ha of intertidal habitat (DPIWE, 2001b). Rice grass is a particularly invasive weed which promotes the accumulation of sediments, changes water flows and alters the amount of available habitat for a range of flora and fauna. The spread of rice grass within the estuary also poses a threat to the intertidal oyster leases by substantially reducing the total area available for intertidal aquaculture and dramatically affecting the volume of water and delivery of nutrients to these aquaculture leases.

Since the introduction of the Rice Grass Advisory Group (RGAG) in 1996 a strategy for the management of rice grass has been developed and implemented through the Rice Grass Management Program. The objectives of the program have been: a) to contain the rice grass infestation south of Eagle Point and; b) to eradicate rice grass infestations north of Eagle Point creating a rice grass free zone. To date the management objectives have been met and the area covered by the rice grass free zone has been increased thus containing the rice grass infestation south of Spalding’s Lane on the western shore, and Eagle Point on the eastern shore of the estuary.

The Rubicon Coast and Landcare Group has provided invaluable information about rice grass in the Rubicon estuary. They have raised the awareness of rice grass as an environmental weed, produced an educational brochure, investigated control techniques and mapped the extent of rice grass infestations in their region. Such groups with encouragement, resources and training are playing key roles in control and monitoring programs. In addition the Port Sorell estuary is the focus of a Masters study into the comparison of the benthic invertebrate community of rice grass infested areas with that of adjacent mudflats which are rice grass free. This involves the assessment of the toxicological impacts of controlled spray events as well as monitoring the recovery of the benthic invertebrate fauna.

Despite the poor rating of the estuary, the waters of Port Sorell have been identified as an important breeding habitat for fish and a designated shark nursery. Forty-two species of fish have been found in the Port Sorell estuary (Table 1). The waters and coastline of the Port Sorell estuary also contain important habitat for bird species, including a number listed as rare, vulnerable or endangered under the Tasmanian Threatened Species Act 1995 (See section 3.3).

10 Table 1. List of marine and estuarine fish species found to inhabit the Port Sorell Estuary (from DPIWE, 2001a)

Scientific Name Common Name Scientific Name Common Name Galaxias brevipinnis climbing galaxias Parablennius tasmanianus blenny Galaxias cleaveri Tasmanian mudfish Platycephalus bassensis sand flathead Galaxias maculatus jollytail Pseudocaranx dentex silver trevally Galaxias truttaceus spotted galaxias Pseudophycis bachus red cod Geotria australis pouched lamprey Raja whitleyi Whitley's skate Lovettia sealii Tasmanian whitebait Rhombosolea tapirina greenback flounder Prototroctes maraena Australian grayling Urolophus cruciatus banded stingaree Pseudaphritis urvillii sandy, freshwater flathead Dasyatis brevicaudatus smooth stingray Retropinna tasmanica Tasmanian smelt Raja lemprieri thornback skate Aldrichettaforsteri Yellow eye mullet Genypterus tigerinus rock ling Arripis trutta Eastern Australian salmon Torquigener glaber smooth toadfish Caesioperca lepidoptera butterfly perch Syngnathus sp. pipefish Cyttus australis silver dory Platycephalus laevigatus rock flathead Galeorhinus galeus school shark Acanthopegasus lancifer sculptured sea moth Gymnapistes marmoratus soldierfish Latridopsis forsteri bastard trumpeter Hippocampus sp seahorse Sillago bassensis school whiting Atherinosoma presbyteroides silverfish Mugil cephalus sea mullet Mustelus antarcticus gummy shark Thyrsites atun king barracouta Myliobatis australis eagle ray Ammotretis elongatus elongate flounder Gobiidae species goby Haletta semifasciata blue rock whiting Hyporhamphus melanochir south Australian garfish Heteroclinus sp. weedfish

Estuarine habitats are highly valued by some sectors of society for their scenic qualities and their high productivity, and the dependent commercial and recreational fisheries. They also can have high conservation value if they provide viable habitat for threatened or endangered flora and fauna. Dunn, (1997) identified a number of issues of concern with respect to the future and management of the Port Sorell estuary. Many of the issues raised relate to management issues in the upper catchment, ie issues affecting turbidity, nutrient levels and flow rates.

In managing the environmental impact of water extraction it is important to have some understanding of the way in which biological risks are linked with the changing impacts arising from water extraction. Currently there is very little information on these biological- risk versus water-extraction relationships for estuaries around Australia. Flows in the Rubicon River are highly seasonal (See section 2.1.7). Lower flows naturally exist in the river from December to March with more elevated base flows during the winter and spring months. Future studies need be undertaken to understand present estuarine physical, chemical, and water quality and sediment transport/geomorphological behaviour. This will then assist in understanding estuarine processes and will provide information for the assessment of the impact of current water use as well as proposed developments in the catchment on the ecological, recreational, consumptive, and aesthetic values of the Port Sorell Estuary.

2.1.7 Hydrology

DPIWE stream gauging data exists for the Rubicon River from June 1967 to the present. The gauging station is located at the tidal limit (GR 463700 5432600) and monitors the outflow from a catchment area of 259km 2. Flows in the Rubicon River are limited by the size of the catchment and are highly seasonal. Almost no flow exists in the river from December through to April. This may suggest limited groundwater storage in the catchment and reflects the large demands on the system by existing users. The seasonality and variability of monthly flows in the Rubicon catchment at the tidal limit is shown in Figure 4, which provides a box

11 and whisker style plot. The plot displays the median (or middle of the data) as a line across the inside of the box. The bottom and top edges of the box mark the first and third quartiles respectively, indicating the middle 50% of the data. The ends of the whiskers show the spread of the data and together enclose 95% of the data. The dots beyond the whiskers indicate the high and low extrema.

The seasonal flow pattern indicates flows peaking in July and August. Lowest flows are experienced between January and March and this period also corresponds to the peak irrigation demand in the river. Flows in the Rubicon River are also variable with occasional high flows occurring throughout the year as confirmed by the range of outliers. This seasonality and variability ensures that many ecological processes essential in riverine and wetland ecosystems are maintained including fish spawning (Beumer, 1980), channel maintenance and flushing flows (Arthington et al., 1992), estuary productivity (Jones et al., 1993; Whitfield, 1996; Davies, 1997a; Loneragan, and Bunn, 1999) and wetland ecosystems (Thomas et al. , 2000).

Water allocations and demands on the river are via Water Licences issued under the Water Management Act 1999. There are 101 licenses situated along the upper and lower reaches of the river and it’s tributaries (Figure 5). Primary water use is for agricultural purposes. Water for irrigation comes predominantly from farm dams. Annual water takes total 4229 megalitres, of which 4077 megalitres is winter storage and the remainder (152 megalitres) is directly pumped during the irrigation season (December to April).

Figure 4: Monthly flow analysis for the Rubicon River

2500

2000

1500

1000 Monthly Flow Monthly (ML/day)

500

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Under the Meander Dam feasibility study, landholders have expressed an interest in gaining additional water via an inter-basin transfer from the Meander River. A postal survey identified 13 properties requiring an additional 4880 megalitres of water from the scheme. (DPIWE – Meander Dam DPEMP 2002).

12 In IFIM studies, the amount of suitable habitat (WUA) is typically assessed under natural flow conditions and compared with that under regulated conditions and attempts are made to minimise the losses in WUA from natural to regulated flow conditions. To estimate the natural monthly volumes, the water licence allocations are added to the stream gauging data. As the water licence data set is for the current irrigation period, water licences have been adjusted downward by 6% each year to reflect the water licence allocations for any particular historic year (Sustainable Development Advisory Council, 1996).

2.2. Site Selection

Bovee (1982) describes a study site as a location on a stream where some characteristics of the habitat are measured. The study site on the Rubicon River was established to measure microhabitat characteristics, which provided a basis for determining a relationship between the total amount of habitat (available to key species) and the discharge in the reach of the river represented by that study site (Bovee, 1982).

Site selection was considered along the entire length of the mainstream. With the exception of some minor tributaries, the mainstream of the Rubicon River and all major tributaries (eg: Bradys, Parrot, Staggs and Gum Scrub Creeks) are affected to some degree by water abstraction (Figure 6). One representative reach was identified on the Rubicon River, based on in-stream habitat diversity, channel morphology including slope, sediment supply, bank materials, substrate, vegetation and flow regime. This reach of the mainstream is also subject to the bulk of water abstraction. Details of the site selected are given in section 2.2.1.

2.2.1 The Rubicon River at Smith and Others Road

The study site is approximately 313m long and is located immediately upstream of the bridge at Smith and Others Rd (TASMAP grid reference 5426100 463300). This site was selected as being representative of the river extending upstream from the study site to where the Rubicon River intersects the Bass Highway (see Figure 2). The river at the study site is a series of shallow runs flowing over sand and gravel substrate interspersed by short riffles dominated by pebble and cobble substrate.

13 14 3. Values

3.1 Community Values

Community and stakeholder participation is crucial in the process of developing environmental management goals for surface waters in catchments throughout Tasmania. The object of this participation is to identify the range of water values appropriate to the particular region via community consultation. In order to determine environmental management goals for surface waters relevant to a particular catchment a sound knowledge of the local water quality and water quantity issues is required.

The community water values for the North Central Coast Catchments and the Greater Rubicon Catchment were determined by a series of public meetings at Ulverstone (23/10/2001), Shearwater (24/10/2001) and Burnie (7/11/2001). The community meetings identified values for determining both Water Quantity Values (WQV's) and Protected Environmental Values (PEVs) for the Rubicon River. Community water values via the PEV process lead to the development of Water Quality Objectives (WQO's) and water management goals through these meetings. Water Quantity Values were identified but were not given a priority, as has been the case for previous catchments. Values that were identified by representatives of various stakeholder groups for the Rubicon catchment are shown in Table 2

Table 2. Community Water Values for the Rubicon catchment

Water Value Categories Specific Water Values 1. Ecosystem • Areas that are free of rice grass ( Spartina anglica ) and other weeds Values • Freshwater lobster and trout • Maintain existing quality • Maintain environmental flows • Maintain areas free of Pacific oysters, specifically swimming areas • Maintain and improve native riparian vegetation • Maintain biodiversity of aquatic and terrestrial plants and animals • Pelicans and other shorebirds • Threatened species • Maintain penguin rookery at the point (Port Sorell) • Shark Nursery – Port Sorell Estuary • Maintain biodiversity – sea birds and waders, sea grass beds, fisheries, marine mammals • Water free from pollutants – sewerage, nutrients • Estuary free of exotic weeds/algae • Riparian zones rehabilitated with local indigenous plants • High water quality

2. Physical • Lower part of the Rubicon is a series of holes and rapids Landscape Values • Intermittent falls and cascades/rapids eg. Eagle Gorge • The Rubicon River has a hard rock base • Islands in the Port Sorell estuary (penguins) • Mud flats in the Port Sorell estuary • Natural coastal dynamics allowed to prevail • Areas without unnatural erosion

15 3. Consumptive • Irrigation and stock watering (agriculture is the lifeline of the greater Rubicon and Non- catchment) Consumptive • Aquaculture – oyster leases Values • Domestic homestead use • Forestry plantations • Dairy washdown from spring-fed instream dams • Ashgrove cheese • Nicholls poultry and processing 4. Recreational • Swimming at the mouth of the Panatana Rivulet Values • Trout fishing in the upper Rubicon • Bream fishing at a hole near the DPIWE weir • Estuary fishing • Water skiing • Boating and sailing • Nature observers – the bush, birds • Tourism • Bushwalking in the National Park • Beach combing • Kayaking • Jet skiing • Swimming • Surfing and Wind surfing 5. Aesthetic • There is good riparian vegetation on the Rubicon River (but not on tributaries) Landscape Values • Backdrop of the Dazzler Ranges • No buildings visible from waterway • Coastal remnants left intact • No forestry clearing visible from waterway Issues/concerns • Pacific oysters • Rice grass • Willows • Weir preventing movement of whitebait • Storm drains flowing into estuaries and beaches • Need for supplementary water to support agricultural activities (Dam?) • Water for limited irrigation and stock use higher in catchment and limited off-river storage • Cumulative effect of in-stream and spring-fed dams • Urban sprawl impacting on aesthetics, introducing weeds, increasing the amount of stormwater etc • Oyster leases impacting on aesthetics and recreational uses (boating and fishing) • No more rock walls in Port Sorell • Erosion from farms and forestry • No jet skis in Port Sorell estuary • No marina in Port Sorell estuary • Marine debris eg. oyster baskets

3.2 State Technical Values

The scientific values required in the assessment of Environmental Flows for a catchment are identified at the State level using technical experts to identify scientific and technical issues such as endangered species, fisheries and wetlands protected under legislation/agreements.

16 The State Technical Committee for Environmental Flows was set up in order to determine scientific values on a catchment by catchment basis, prior to the determination of EWRs. The committee includes representatives from the DPIWE, who provide advice on aquatic ecology, wetlands, geomorphology, riparian vegetation, and estuarine ecology, fisheries biology and ecology. In addition, committee members include environmental representatives from Hydro Tasmania and a researcher from the University of Tasmania with relevant expertise in environmental flows. The committee's terms of reference specifically relating to the identification of scientific values is: To identify water values for catchments from a technical and scientific perspective including the non-negotiable values, which are implicit in various local, national and international agreements and legislation.

In this instance the State Technical Committee has determined the State Technical Values for Environmental Flows on a regional rather than a catchment basis, though a number of issues relevant to the Rubicon catchment have been identified as follows:

• Maintenance of flow to protect species listed in the Tasmanian Threatened Species Act 1995 or the Threatened Species Protection Order 2001 (see section 3.3 ). • Provision of flows for the maintenance of wetland habitat for the Green and Gold Frog (Litoria raniformis). • Maintain in-stream habitat for the giant freshwater lobster ( Astacopsis gouldi), and Australian grayling (Prototroctes maraena) populations within the catchment . • Protect riparian flora listed in the Tasmanian Threatened Species Act 1995. • Protect native fish populations • Protect trout fisheries

From these issues the Water Assessment and Planning Branch of the DPIWE has identified a range of scientific values pertinent to the determination of ecological requirements for flow within the Rubicon River. These values are provided in Table 3

Table 3: Rubicon catchment Water Assessment and Planning Branch scientific values. Those values marked with an asterix (*) were targeted for detailed and specific assessment

Ecosystem Values • Maintain suitable flow for the protection of Australian grayling and the giant freshwater crayfish, which are both listed as vulnerable in the Tasmanian Threatened Species Act 1995 . • Maintain suitable flow for the protection of wetland habitat for the Green and Gold frog which is listed as vulnerable in the Tasmanian Threatened Species Act 1995 . • Maintain habitat for: Australian grayling ( Prototroctes maraena ), shortfinned eel ( Anguilla australis )*, river blackfish ( Gadopsis marmoratus )*, freshwater flathead ( Pseudaphritis urvillii ), spotted galaxias ( Galaxias truttaceus ), climbing galaxias ( Galaxias brevipinnis ), common jollytail (Galaxias maculatus )*, Tasmanian mudfish ( Neochanna cleaveri ), Tasmanian whitebait (Lovettia sealii ) and Tasmanian smelt ( Retropinna tasmanica ), • Maintain rearing and/or spawning habitat for shortfinned eel, giant freshwater crayfish and Australian grayling. • Maintain in-stream woody debris as habitat for giant freshwater crayfish and native fish species. Recreational Values • Maintain fish stocks of brown trout ( Salmo trutta ). • Maintain habitat for brown trout* • Maintain in-stream woody debris as habitat for brown trout

17 3.3 Endangered species

Nine animal species listed in the Tasmanian Threatened Species Act 1995 are known to occur within the Rubicon catchment. Details of these species are provided in Table 4 below (Source – PWS GtSpot database). A species is regarded as endangered when the causal factors relating to its decline continue operating and ultimately reduce the long term survival prospects of that species (Bryant and Jackson, 1999). Alterations to the natural flow regime have the potential to impact on these species either directly or indirectly.

Table 4. Current listing of threatened species recorded within the Rubicon catchment including the Port Sorell Estuary.

Species Listing Habitat/occurrence Australian Grayling Vulnerable Occurs in lower reaches of the Rubicon River. (Prototroctes maraena ) Prefers slow flowing, or still freshwater with good water quality and good riparian vegetation and macrophyte cover Green and gold frog Vulnerable Occurs in permanent or temporary water ( Litoria raniformis ) bodies with surrounding vegetation (eg. streams, swamps, vegetated pools and farm dams). Prefers shallow water and dense vegetation for breeding. Giant freshwater lobster Vulnerable Occurs in the Rubicon catchment. Typically (Astacopsis gouldi ) found in well-vegetated catchments of several stream sizes, where woody debris, pools and undercut (not eroding) banks are present and water temperature <18 oC, high dissolved oxygen levels and clear of sediment. Wedge-tailed eagle ( Aquila Vulnerable Occurs throughout the catchment in audax fleayi ) association with remnant vegetation but may also be found foraging over improved pasture. White-bellied sea-eagle High Conservation Occurs in the Port Sorell estuary (Haliaeetus leucogaster ) Significance Fairy tern Rare Occurs on sand and shingle beaches in the Port (Sterna nereis ) Sorell estuary Hooded plover High Conservation Occurs on beaches in the Port Sorell Estuary, (Thinomis rubricolis ) Significance nesting above the high tide mark.

New Holland mouse Rare Occurs in dry coastal heathland and open (Pseudomys heathy forest. novaehollandiae ) Little penguin High Conservation Breeds in colonies located on the coastline. (Eudyptula minor ) Significance Their burrows are dug into dunes, surrounded by tussock or other vegetation

Bryant and Jackson (1999) also identify suitable habitat throughout the catchment where additional ‘listed’ endangered animal species may occur. Those species that are listed as threatened in the Tasmanian Threatened Species Act 1995 which are likely to occur within the catchment include, the spotted tailed quoll ( Dasyurus maculatus maculatus ), the eastern quoll (Dasyurus viverrinus ), the eastern barred bandicoot ( Perameles gunii ) and the Grey goshawk (Accipiter novaehollandiae ). These species rely on terrestrial riparian habitat that may be indirectly influenced by excessive de-watering. However the influence of altered flow regimes on riparian vegetation and associated faunal communities are beyond the scope of

18 this report and may be examined under a more comprehensive holistic assessment of the catchment. It should be noted that this section aims to identify endangered species currently known to or expected to occur within the catchment. It may be likely that in the future further species will become of conservation significance within the catchment, particularly those species where threatening processes continue to operate.

4. Methodology

The method used to assess the flow requirements of key species (see Table 6.) was the Instream Flow Incremental Methodology (IFIM), originally described by Bovee (1982). In this process, the preferences of key species for velocity, depth and substrate parameters are combined with transect-derived hydrologic data at specific discharges. This data is then incorporated into a suitability index, which is a function of available depth, velocity and substrate. This suitability function is then summed over the study reach to give the Weighted Useable Area, or WUA (refer to Jowett, 1992).

Hydraulic simulation is used to generate velocity and depth data for each transect at the discharges for which data are not available. The outcome is a plot of WUA against discharge for each species or lifestage (see Figure 3). An analysis of the flow levels that will provide varying degrees of risk to the ecosystem is then possible. The software package used for this process was the RHYHABSIM (River HYdraulics and HABitat SIMulation) program developed by Jowett (1992).

4.1 Physical Habitat Data

Transects were established at the site, according to the protocol detailed by Bovee (1982). Within the study reach, a number of distinctive sub-reaches were identified on the basis of hydraulic characteristics and substrate. Transects were established within each of these sub- reaches, perpendicular to the channel.

At each transect, a semi-permanent datum (or header peg) was established by driving a mild steel star picket deep into the upper section of the bank. Header pegs for this site were set on the 10 th October 2000. All measurements were taken perpendicular to the direction of flow, to a point on the opposite bank at a similar height above water level. Water surface elevation relative to the elevation of the header peg was recorded at each transect.

On the 11 th October 2000, depth, average water velocity and substrate composition were measured and recorded at regular intervals evenly distributed across the channel with a minimum of 10-15 wetted points. In this way each transect was divided into regular ‘cells’ by collecting all data at the same distances from the header peg. Depth and velocity at 0.6 of the depth from the surface were recorded at each of these points using a pre-calibrated Flowmate meter and wading rod. Percentage substrate composition was also recorded at each location using the following categories: aquatic vegetation; mud; sand; gravel; pebble; cobble; boulder and bedrock. Substrate particles were characterised by the following modified Wentworth scale:

R = Bedrock B = Boulder >256 mm C = Cobble 64 - 256 mm P = Pebble 8 - 64 mm G = Gravel 2 - 8 mm S = Sand 0.06 - 2 mm M = Silt/Mud <0.06mm

19 Three calibration gaugings were carried out at a suitable location within the study reach to determine discharge. The height of the water surface from the datum peg was measured at each transect at the same time. The data collected from these sites were entered into an Excel  spreadsheet in the format required by the RHYHABSIM program.

4.2 Biological Data

4.2.1 Invertebrates

A total of 18 biological samples were taken at the study site on the Rubicon River. The sampling occurred on the 12 th October 2000.

Sampling effort was stratified to fully represent the range of depths, velocities and substrates at the site. Stratification was carried out on the habitat data from the study site, using the methodology described by Davies et al. (1997b). Sampling for macroinvertebrates was carried out by disturbing the substrate within a 1m2 quadrat upstream of a 250 µm kick net. The preserved samples were later sub-sampled to 20% (or a minimum of 200 animals) and invertebrates were identified to the lowest taxonomic level possible using the most up-to-date taxonomic keys.

The resulting habitat preference information was used for the creation of WUA-Q curves for key macroinvertebrate species as well as total abundance (an index of benthic fish and platypus standing crop) and macroinvertebrate diversity. Key species were selected on the basis of:

• not having rare or patchy abundance; and • exhibiting clear preferences for depth, velocity and substrate

4.2.2 Fish

Habitat preference curves used for adult brown trout, early young of the year, or 0+ were developed from data collected in March 1990 - 1993 by Davies and Diggle (unpublished data) and preference curves for brown trout adults were developed by Bovee (1978). Habitat preference curves were also taken for shortfinned eels, and jollytail (Jowett and Richardson 1995) and blackfish (Koehn 1986).

The transfer of habitat preference curves between different catchments is regarded by many ecologists as an acceptable practice for the above species. Examination of curves for brown trout by previous workers has generally found that these curves are similar between rivers both in Australia and overseas (Dr Peter Davies, Freshwater Systems, pers. comm), shortfinned eels, climbing galaxias and jollytails are also regarded as comparable between rivers (Jowett and Richardson, 1995). Given the agreement among these ecologists in the transfer of these curves, these preference curves have been adopted for use in this assessment.

4.3 Hydraulic Simulation

From the habitat data of both sites combined, and the biological samples collected, values of useable habitat area (called Weighted Useable Area or WUA) were generated in m 2/m of stream channel for each species or lifestage at a range of discharges. The protocol for generating these WUA-Q curves is that described by Jowett (1992), using the RHYHABSIM hydraulic modelling and simulation package. A single Excel  data set, containing:

20 • velocity, depth and substrate data at every offset for each transect; • locations of all water edges ; • inter-transect distances; and • stage-discharge relationships for each transects.

This information was used to generate velocities and depths at discharges from 0.06 to 5.55 cumec. Davies and Humphries (1996) describe the protocol used for the hydraulic simulation.

Jowett (1992) describes the WUA-Q curve generation in detail. Habitat preference data were combined with simulated velocity and depth data and the measured substrate data, so as to calculate habitat suitability for each cell. The values for all cells from all transects were combined to generate a species’ total habitat area (WUA) in m 2/m or % of stream area for the whole site for each discharge value. This process was used to generate WUA curves for both sites, for all the key species and life stages.

4.4 Risk Analysis

The risk analysis used in this study is a modification of that developed by Davies and Humphries (1996). Risk is based upon changes in useable habitat ( ∆WUA) relative to a reference flow. In this study the reference flows used (Qm) were the median monthly flows at each site for the period 1968-1996 adjusted to account for irrigation takes (ie. the median monthly flows at each site that would have occurred without abstraction). In this case there are three risk categories (see Table 4), and six variables. The variables include:

1 WUA for Salmo trutta adults. 2 WUA for Salmo trutta early young of the year (0+) 3 WUA for Gadopsis marmoratus 4 WUA for Galaxias maculatus. 5 WUA for Anguilla australis. 6 WUA for key individual macroinvertebrate taxa (see Table 6. for a list of these species). 7 WUA for macro-invertebrate abundance. 8 WUA for macro-invertebrate diversity.

Table 4. Criteria for assigning risk levels to different values of change in habitat ( ∆WUA) relative to the reference flow (Q m) for the key ecological variables in this study. Derived from Davies and Humphries (1996).

Risk Category I II III Variable No Risk Moderate Risk High Risk ∆WUA for trout, jollytail, short- >85% WUA cf Q m 60-85% WUA cf Q m 30-60% finned eels, blackfish platypus, WUA cf Q m Invertebrate diversity, Invertebrate abundance (Variables 1-5, 7&9) ∆WUA for individual <10% taxa with ≥10% of taxa with >25% of taxa with macroinvertebrate taxa <75% WUA cf Q m <75% WUA cf Q m <75%WUA (Variable 6) & <25% of taxa cf Q m with <75% WUA

The risk assessment was conducted as follows for each of the above variables:

• WUA as it varies with Q is normalised so that at the maximum (Qm), (WUA m) is 100% • Qn can then be read directly from the relevant percentage of WUA n on the graph where: WUA n = Weighted Usable (habitat) Area for month of concern (pre-offtake median flow) Qn= Boundary flow for risk level during month of concern ( n )

21 A worked example of Risk Analysis.

To determine the flow at which there is no risk to adult trout at North Esk River, Watery Plains reach in December (some values excluded for brevity):

1. RHYHAB gives values for WUA as it varies with Q:

Flow WUA 2 (Qm) (m /m) 0.05 0.94 0.45 2.95 0.85 3.93 1.25 4.63 1.65 5.31 2.05 5.91 2.45 6.2 2.85 6.37 3.25 6.47 3.65 6.53 3.85 6.55

NB: the maximum flow given (3.85 cumecs) would be the pre-irrigation median monthly flow for December and the corresponding WUA value is then normalised in the next step.

2. This is then normalised so that at the maximum Q m, WUA m, is 100%:

Flow Normalised (Qm) WUA 0.05 14.35 0.45 45.04 0.85 60.00 1.25 70.69 1.65 81.07 2.05 90.23 2.45 94.66 2.85 97.25 3.25 98.78 3.65 99.69 3.85 100.00

3. Q n can then be read directly from the relevant percentage of WUA n on the graph where:

WUA d = Weighted Useable (habitat) Area for December (pre-offtake median flow) Qn= Boundary flow for risk level during month of concern ( n )

22 WUA m Dec WUA/Q

100 90 85 80 70 60 50 40

NormalisedWUA (m2/m) 30 20 10 0 0.0 0.5 1.0 1.51.8 2.0 2.5 3.0 3.5 4.0

Qn

Flow (cumec)

ie. to get the low risk flow, the percentage WUA above 1.8 cumec, there should be low risk to trout adults in the North Esk River at the Watery Plains reach in December.

5 Results

5.1 Physical Habitat Data

Hydrologic and substrate information was collected at the site for the discharge of 0.97 cumec on 11/10/2000. Subsequent gauging visits were carried out when the discharge was 0.06 cumec (7/12/00) and 3.36 cumec (24/10/01). Ranges of depth, velocity and substrate at the site are presented in Table 5.

Table 5. Ranges of depth, velocity and substrate for the Rubicon River at Smith and Others Road.

Variable Value Depth (m) 0-1.02m Velocity (m/s) 0-1.39 m/s % Silt cover 0-100% % Sand cover 0-100% % Gravel cover 0-85% % Pebble cover 0-75% % Cobble cover 0-60% % Boulder cover 0-80% % Bedrock cover 0-80%

23 5.2 Biological Data

Eighteen (18) invertebrate samples were successfully taken across the IFIM reach, on the Rubicon River at Smith and Others Road. WUA-Q curves were developed for each of the key taxa listed in Table 6. These curves are provided in Appendix 1.

Table 6: Selected taxa for which WUA curves were developed

Type Common name Taxon Lifestage (s) Fish Brown trout Salmo trutta adults and late 0+ Jollytail Galaxias maculatus adults Blackfish Gadopsis marmoratus adults Shortfinned eel Anguilla australis adults Insects Mayflies Nousia spp (total) larvae Koorrnonga spp.(total) larvae Tilyardophlebia spp (total ) larvae Tasmanocoenis spp.(total) larvae Baetidae (total) larvae Stoneflies Cardioperla spp.(total) larvae Leptoperla spp. (total) larvae Caddisflies Ecnomus spp. (total) larvae Notalina spp.(total) larvae Helicopsyche murrumba larvae Taschorema complex larvae Midges Chironominae larvae Orthocladiinae larvae Tanypodoninae larvae Flies Austrosimulium spp. (total) larvae Ceratopogonidae spp (total) larvae Bugs Micronecta spp.(total) larvae Beetles Austrolimnius spp (total) larvae Austrolimnius spp (total) adult Molluscs Freshwater snails Hydrobiidae (total) Freshwater mussels Pisidium casertanum Crustacea Amphipods Austrochiltonia spp.(total) Paramelitidae (total) Freshwater shrimp Paratya australiensis Worms Oligochaeta Freshwater Mites Hydracarina

24 5.3 Risk Analysis

Results of the Rubicon River risk assessment for the study reach, covering the summer (irrigation) months are provided in Table 7. In addition, curves of the relationship between Weighted Usable Area vs Flow for each species investigated are provided in Appendix 1. Note that the highest monthly flow necessary to provide the required quantity of habitat for any variable has been chosen as the flow for each category to ensure that all values are protected.

Table 7. Flows for each risk category, Rubicon River at Smith and Others Rd.

January Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.03 0.03 – 0.01 < 0.01 0+ S. trutta > 0.04 0.04 – 0.02 < 0.02 G. maculatus > 0.01 0.01 – 0.005 < 0.005 G. marmoratus > 0.04 0.04 – 0.02 < 0.02 A. australis > 0.01 0.01 – 0.005 < 0.005 Macroinvert. taxa > 0.04 0.04 – 0.01 < 0.01 Taxon abundance > 0.01 0.01 – 0.005 < 0.005 Taxon diversity > 0.01 0.01 – 0.005 < 0.005 Flow > 0.04 0.04 – 0.02 < 0.02 February Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.02 0.02 – 0.01 < 0.01 0+ S. trutta > 0.02 0.02 – 0.01 < 0.01 G. maculatus > 0.01 0.01 – 0.005 < 0.005 G. marmoratus > 0.02 0.02 – 0.01 < 0.01 A. australis > 0.01 0.01 – 0.005 < 0.005 Macroinvert. taxa > 0.02 0.02 – 0.01 < 0.01 Taxon abundance > 0.01 0.01 – 0.005 < 0.005 Taxon diversity > 0.01 0.01 – 0.005 < 0.005 Flow > 0.02 0.02 – 0.01 < 0.01 March Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.08 0.08 – 0.06 < 0.06 0+ S. trutta > 0.03 0.03 – 0.01 < 0.015 G. maculatus > 0.01 0.01 – 0.005 < 0.005 G. marmoratus > 0.03 0.03 – 0.01 < 0.01 A. australis > 0.01 0.01 – 0.005 < 0.005 Macroinvert. taxa > 0.03 0.03 – 0.01 < 0.01 Taxon abundance > 0.01 0.01 – 0.005 < 0.005 Taxon diversity > 0.01 0.01 – 0.005 < 0.005 Flow > 0.08 0.08 – 0.06 < 0.06 April Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.10 0.10 – 0.06 < 0.06 0+ S. trutta > 0.15 0.15- 0.09 < 0.09 G. maculatus > 0.07 0.07 – 0.05 < 0.05 G. marmoratus > 0.14 0.14 – 0.08 < 0.08 A. australis > 0.01 0.01 – 0.005 < 0.005 Macroinvert. taxa > 0.01 0.10 – 0.07 < 0.07 Taxon abundance > 0.01 0.01 – 0.005 < 0.005 Taxon diversity > 0.01 0.01 – 0.005 < 0.005 Flow > 0.15 0.15 – 0.09 < 0.09

25 Table 7 (cont.)

May Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.20 0.20 – 0.08 < 0.08 0+ S. trutta > 0.11 0.11 –0.07 < 0.07 G. maculatus > 0.06 0.06 – 0.04 < 0.04 G. marmoratus > 0.21 0.21 – 0.10 < 0.10 A. australis > 0.07 0.07 – 0.05 < 0.005 Macroinvert. taxa > 0.38 0.38 – 0.35 < 0.35 Taxon abundance > 0.20 0.20 – 0.07 < 0.07 Taxon diversity > 0.08 0.08 – 0.05 < 0.05 Flow > 0.38 0.38 – 0.35 < 0.35 June Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.25 0.25 – 0.08 < 0.08 0+ S. trutta > 0.12 0.12 –0.08 < 0.08 G. maculatus > 0.04 0.04 – 0.03 < 0.03 G. marmoratus > 0.14 0.14 – 0.08 < 0.08 A. australis > 0.06 0.06 – 0.04 < 0.04 Macroinvert. taxa > 0.84 0.84 – 0.68 < 0.68 Taxon abundance > 0.70 0.70 – 0.09 < 0.09 Taxon diversity > 0.09 0.09 – 0.06 < 0.06 Flow > 0.84 0.84 – 0.68 < 0.68 July Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.10 0.10 – 0.07 < 0.07 0+ S. trutta > 0.15 0.15 –0.09 < 0.09 G. maculatus > 0.03 0.03 – 0.02 < 0.02 G. marmoratus > 0.15 0.15 – 0.09 < 0.09 A. australis > 0.05 0.05 – 0.04 < 0.04 Macroinvert. taxa > 0.68 0.68 – 0.43 < 0.43 Taxon abundance > 0.90 0.90 – 0.10 < 0.10 Taxon diversity > 0.10 0.10 – 0.07 < 0.07 Flow > 0.90 0.90 – 0.43 < 0.43 August Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.08 0.08 – 0.06 < 0.06 0+ S. trutta > 0.18 0.18 –0.11 < 0.11 G. maculatus > 0.03 0.03 – 0.02 < 0.02 G. marmoratus > 0.17 0.17 – 0.09 < 0.09 A. australis > 0.05 0.05 – 0.03 < 0.03 Macroinvert. taxa > 0.60 0.60 – 0.42 < 0.42 Taxon abundance > 0.96 0.96 – 0.11 < 0.11 Taxon diversity > 0.10 0.10 – 0.07 < 0.07 Flow > 0.96 0.96 – 0.42 < 0.42 September Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.12 0.12 – 0.07 < 0.07 0+ S. trutta > 0.22 0.22 –0.12 < 0.12 G. maculatus > 0.04 0.04 – 0.03 < 0.03 G. marmoratus > 0.14 0.14 – 0.08 < 0.08 A. australis > 0.05 0.05 – 0.04 < 0.04 Macroinvert. taxa > 0.68 0.68 – 0.50 < 0.50 Taxon abundance > 0.87 0.87 – 0.10 < 0.10 Taxon diversity > 0.10 0.10 – 0.07 < 0.07 Flow > 0.87 0.87 – 0.50 < 0.50

26 Table 7 (cont)

October Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.27 0.27 – 0.08 < 0.08 0+ S. trutta > 0.12 0.12 –0.08 < 0.08 G. maculatus > 0.05 0.05 – 0.03 < 0.03 G. marmoratus > 0.15 0.15 – 0.08 < 0.08 A. australis > 0.06 0.06 – 0.04 < 0.04 Macroinvert. taxa > 0.87 0.87 – 0.70 < 0.70 Taxon abundance > 0.70 0.70 – 0.09 < 0.09 Taxon diversity > 0.09 0.09 – 0.06 < 0.06 Flow > 0.87 0.87– 0.70 < 0.70 November Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.20 0.20 – 0.08 < 0.08 0+ S. trutta > 0.12 0.12 –0.08 < 0.08 G. maculatus > 0.06 0.06 – 0.04 < 0.04 G. marmoratus > 0.22 0.22 – 0.10 < 0.10 A. australis > 0.07 0.07 – 0.05 < 0.05 Macroinvert. taxa > 0.32 0.32 – 0.26 < 0.26 Taxon abundance > 0.12 0.12 – 0.06 < 0.06 Taxon diversity > 0.08 0.08 – 0.05 < 0.05 Flow > 0.32 0.32 – 0.26 < 0.26 December Risk Category Low Risk Moderate Risk High Risk Adult S. trutta > 0.08 0.08 – 0.06 < 0.06 0+ S. trutta > 0.15 0.15- 0.09 < 0.09 G. maculatus > 0.01 0.01 – 0.005 < 0.005 G. marmoratus > 0.14 0.14 – 0.08 < 0.08 A. australis > 0.07 0.07 – 0.05 < 0.05 Macroinvert. taxa > 0.12 0.12 – 0.09 < 0.09 Taxon abundance > 0.09 0.09 – 0.06 < 0.06 Taxon diversity > 0.08 0.08 – 0.05 < 0.05 Flow > 0.15 0.15 – 0.09 < 0.09

The Environmental Water Requirements for all risk categories are governed by the flow requirements for brown trout and blackfish during months of low flow (December to April). The maintenance of habitat for brown trout was identified as a recreational value in a regional context. In a statewide context, however, the recreational trout fishery in the Rubicon River is not considered, to be significant (S. Chilcott, Inland Fisheries Service pers comm ). During months of higher flow (May to November), the Environmental Water Requirements are determined by the flow requirements for macroinvertebrates. The macroinvertebrate taxa that have determined the EWRs for these months include: Hydrobiidae spp., Austrolimnius spp ., Tilyardophlebia spp ., Pisidium casertanum, Ecnomus.spp, Ceratopogonidae spp, and Oligochaeta . While it is important to consider the implication of different flow regimes on individual taxa (macroinvertebrate and fish), it is important to adequately protect the endangered giant freshwater crayfish, Astacopsis gouldi and Prototroctes maraena. It is recommended that flows remain in the ‘low risk’ category to ensure these values are maintained.

27 6 Discussion

Before discussing the implications of the risk analysis , it is important to re-iterate the caveat stated at the beginning of the report. This is that the flows are only appropriate for the individual months for which they have been recommended. However, hydrological processes operating throughout the year dictate the ecological integrity of rivers, and further assessment will be required if there is further development of the water resource.

It should also be stressed that an essential part of setting an environmental flow is the monitoring of compliance and environmental benefit. Further assessment may need to be undertaken in the future if monitoring highlights values that are not being met by the negotiated flow regime. Any risk assessment must be made relative to some reference period. In this study the reference flows were calculated for the Rubicon River by adding offtakes to existing median monthly flow data for the period 1967 – 2001. In other words, the reference flows were estimations of the median monthly flows without abstraction. Medians have been used for the risk analysis rather than means due to the effect of high flow events skewing means upward and away from a true measure of the central tendency of the data.

The net volume of water taken during the summer irrigation period is high compared to the summer flow. This is due primarily to abstraction for irrigation. Abstraction during the summer months is likely to temporarily place this river ecosystem under stress and may adversely impact a number of ecosystem values identified by both the catchment community and the scientific values proposed for this catchment by the State Technical Panel. Other risks to the catchment include in-stream dams and the stream-gauging weir on the Rubicon River. The weir presents a formidable barrier to fish passage, whilst the increase in instream dams has the potential to hydrologically isolate large sections of the catchment.

It is likely that very little risk is posed to the environmental values during July and August as flows during these months are sufficiently high to ensure that many ecological processes essential in riverine and wetland ecosystems are maintained.

6.1 Vertebrate Fauna

6.1.1 Mordacia mordax and Geotria australis

Requirements for the maintenance of rearing and spawning habitats for lampreys ( Mordacia mordax and Geotria australis ) are described in Koehn (1990). Mordacia mordax enters fresh water to breed, migrating upstream to headwaters between November and March (Potter, 1996). Actual spawning occurs between July and September. Newly hatched ammocoetes larvae live in soft mud. Downstream migration to the sea usually occurs in spring about three to four years after hatching. This species has no known distribution records for the catchment.

Geotria australis lives in seas for an undetermined period thought to extend for several years. Breeding occurs in freshwater following upstream migration, which may last sixteen months. Spawning takes place in relatively shallow, relatively fast flowing waters on gravel bottoms, probably in small headwater streams and is thought to occur in late spring from October to December (Koehn, 1990). The adults do not feed while in fresh waters and die shortly after spawning. Lamprey larvae live buried in soft-bottomed sediments and live in freshwater for about three to four years. The young lampreys then transform to the adult stage and migrate downstream to the sea. G. australis was recorded in the Rubicon River below the weir.

28 The spawning requirements of both these species are likely to be unaffected by the current water demand in the Rubicon River as these lifestages occur outside of the period of high water demand.

6.1.2 Gadopsis marmoratus

Gadopsis marmoratus is a strictly freshwater fish which occurs throughout south eastern Australia and Tasmania (Waters, 1991). Spawning of G. marmoratus occurs in spring to early summer. Fecundity is low for the species with each female only depositing between 20- 500 eggs (Waters, 1991). The number of eggs deposited being dependent of female size (Jackson et al. , 1996). The preferred spawning sites for G. marmoratus are within hollow logs, which are actively protected by the male parent (Waters, 1991). The use of such hollows allows egg development and hatching of larvae to occur within relatively stable areas of low water speed (McDowall, 1996d). Sufficient resources however were not available to include an assessment of the habitat requirements for spawning in this report. The assessment of the habitat requirements of individual age classes of blackfish (eg: (0+) years and adult) was also beyond the scope of this study as insufficient information is available on the habitat requirements of different fish size classes. It is known that variations in habitat utilisation occur between age classes of G. marmoratus (Koehn, 1986). Blackfish prefer to occupy areas where accumulations of coarse woody debris occur and water speeds are less than 0.2 ms -1 . The depth at which G. marmoratus is found is dependent on fish size, with the larger fish preferring deeper water, such as that associated with pools. Juveniles can be found in shallow habitats usually amongst leaf litter associated with the substrate, where boundary effects have reduced water speed (McDowall, 1996d).

While woody debris is indeed important as habitat for blackfish, it is beyond the capacity of this assessment to ensure their maintenance. Other issues outside the management of water quantity, such as riparian zone management and coarse woody debris retention, will have greater influence on this value. The single record for blackfish in the Rubicon River is from the Avenue Plains.

6.1.3 Pseudaphritis urvillii

Few details of the life history of freshwater flathead ( Pseudaphritis urvillii ) are available, but the adults appear to migrate downstream to spawn in estuaries from late April to August (Andrews, 1996). Their preferred freshwater habitat is usually slow flowing water around log snags, under overhanging banks or among leaf litter. As little is known of the spawning requirements of the freshwater flathead, the assessment of the influence of flow on their spawning was beyond the resources of this study. The only record for freshwater flathead in the Rubicon River is below the weir at the bottom of the catchment. Further studies will need to be carried out to determine the extent of their distribution within the catchment.

6.1.4 Galaxias truttaceus and Galaxias maculatus

The spotted galaxiid ( Galaxias truttaceus ) is similar to the common jollytail ( Galaxias maculatus ), in that both species have a marine juvenile stage and a diadromous life cycle. Non land-locked populations migrate downstream to estuaries during autumn-spring tides where spawning and hatching occurs. The newly hatched larvae are swept out to sea and the juveniles eventually migrate back to shore and enter freshwater streams during late winter or spring (Fulton, 1990). Both species form a large part of the whitebait runs at this time. Flow requirements have not been assessed for the whitebait run. In addition, habitat preference information is not available for any lifestages of G. truttaceus and therefore the assessment of their flow requirements is outside the scope of this study. Both G. truttaceus and G.

29 maculatus have been recorded from Port Sorell Estuary. However neither of these species have been recorded above the weir.

6.1.5 Galaxias brevipinnis and Neochanna cleaveri

The climbing galaxiid ( Galaxias brevipinnis ) is a secretive and solitary species that prefers clear, bouldery headwaters and can also be found in lakes and their tributaries. Breeding occurs during autumn and winter, with the eggs usually laid amongst litter and detritus. Diadromous populations of newly hatched larvae are thought to be swept downstream into the sea, where they live for 5-6 months (McDowall and Fulton, 1996). Similarly, Tasmanian mudfish ( Neochanna cleaveri ) spawn during winter (Oct.-Nov.) with the newly hatched larvae moving to sea for a brief period of a few months. Both species of juveniles return as whitebait during the spring, migrating first into river estuaries, then slowly making their way upstream to find suitable rearing and feeding habitats (McDowall and Fulton, 1996. Assessment of the flow requirements of G. brevipinnis and N. cleaveri was deemed outside the scope of this study.

6.1.6 Prototroctes maraena

The reproductive period for the Australian grayling ( Prototroctes maraena ) is from late summer to early autumn although Fulton (1990) suggests that spawning in Tasmania may take place from late spring to early summer. Each female produces about 25,000 to 68,000 eggs that sink to the bottom just downstream of the spawning site (McDowall, 1996a). Newly hatched larvae are thought to be swept down to estuaries where they remain for about 6 months before returning to freshwater to complete their lifecycle. As little is known of the spawning requirements of the grayling, the assessment of the influence of flow on their spawning was beyond the resources of this study. This species has been recorded from the Rubicon River directly above the weir.

6.1.7 Lovettia sealii and Retropinna tasmanica

The Tasmanian whitebait ( Lovettia sealii ) forms the basis of whitebait shoals entering estuaries and rivers during late winter and spring. It is during this time that the previous years hatch migrate from the sea to spawn. The whitebait adults die once they have spawned, and it is generally rare for two year classes to spawn at the same time (McDowall, 1996b;1996c). Eggs are attached to submerged logs and rocks from where the larvae are swept and go to sea, although little is known of the complete life history (Fulton, 1990).

The Tasmanian smelt ( Retropinna tasmanica ) is similar to L. sealii in that both species spend a large portion of their life cycle at sea. Smelt migrate into coastal rivers during spring and along with L. sealii form the basis of shoals of whitebait. Retropinna tasmanica like L. sealii migrates into the estuaries and lower reaches of riverine habitats to spawn (McDowall, 1996b;1996c). Smelt can be of at least two-year classes upon migration, and return to the sea following spawning. The larvae go to sea for a period of time before returning to spawn, however little is known of the complete life history and the length of the marine stage has not been determined.

Distribution of these species within the Rubicon catchment is restricted to the Port Sorell Estuary. Further studies will need to be carried out to determine the extent of their distribution within the catchment.

30 6.1.8 Anguilla australis

Sexually mature adults of the short-finned eel ( A. australis ) migrate downstream to the sea. Anguilla australis then follow the Eastern Australian Current to the vicinity of the Coral Sea where they are believed to spawn (Fulton, 1990). Larval eels (leptocephali) utilise the Eastern Australian Current over summer to return to Tasmania and as they near the coast, metamorphose into elvers (glass eels). During February to April the glass eels move into the estuaries and become pigmented elvers. The elvers of A. australis move considerable distances upstream over several years and are often located within upper catchment reaches. A. australis has been recorded throughout the Rubicon catchment. This suggests that this species can negotiate the weir.

6.1.9 Salmo trutta

One species of introduced salmonid, brown trout ( Salmo trutta ) has been identified from the Rubicon catchment. S. trutta is widely distributed within the catchment occuring throughout the mainstream. S. trutta spawn in late autumn, with eggs being deposited in gravel nests or egg pockets (redds) in streams. The eggs are deposited only when sufficient depth and velocity of water occur over a redd and take from 6 to 20 weeks to develop (Davies and McDowall, 1996). Following hatching the young stay in the gravel for some time (September to November) and it is at this time that they are susceptible to high mortality rates from low flow levels (Davies, 1989, Davies and McDowell, 1996). During November the young leave the gravel beds to form shoals which feed in areas of low hydrological variability, such as the shallows along stream edges and backwaters.

6.1.10 Nannoperca australis and Perca fluviatilis

Southern pygmy perch ( Nannoperca australis ) are a protracted or multiple spawner, with breeding occurring between September and January, when temperatures are over 16 oC (Kuiter, et al , 1996). They prefer covered vegetated habitat in slow flowing or still waters. Hatching takes around three weeks and juveniles mature at around one year of age (Bryant and Jackson, 1999). Southern pygmy perch have been recorded from the mid- to upper reaches of the Rubicon River.

Redfin perch ( Perca fluviatilis ) was introduced into Tasmania from Europe in 1861. Redfin perch is regarded as a pest species due to its ability to out-compete native fish, and in some cases seriously reduce or even eradicate populations. It inhabits still or slow flowing waters, especially where there is abundant aquatic vegetation (Allen et al ., 2002). Spawning occurs in the spring. The eggs hatch in 1-3 weeks and the young form schools for some time before taking up a solitary existence. The single record for redfin perch in the Rubicon River is from the Avenue Plains.

Habitat preference information is not available for any lifestages of Nannoperca australis or Perca fluviatilis and therefore the assessment of their flow requirements is outside the scope of this study.

31 6.2 Invertebrate Fauna

6.2.1 Astacopsis gouldi

There is a lack of habitat preference curves relating to Astacopsis gouldi and it was beyond the scope of this study to develop such information. However, the protection of this species is an important community and State technical value. Hamr (1990) documented the reproductive biology of A. gouldi , and he found that females mate and spawn in autumn (April – May) and carry eggs over winter. Females mature after 14 years of age and then breed every two years (Bryant and Jackson, 1999). The young hatch in January and remain attached until well into the following summer (Bryant and Jackson, 1999). A. gouldi juveniles and adults are most active during summer and early when flows are naturally lowest within the Rubicon River (refer to Figure 4). Further reductions in flow have the potential to further reduce habitat availability for this species. In addition critical periods for key events in the lifecycle of this species occur during the irrigation season (hatching and detachment of juveniles) and this could be an issue given the extremely low flows in the river at this time. Differences in habitat utilisation have been noted for varying age classes of this species with adults typically being in pools containing snags and coarse woody debris and juveniles in shallow riffles or smaller stream zones. Though both favour habitats within reaches with an intact cover of riparian vegetation. The habitats used by A. gouldi are most at risk of becoming unwetted during periods of low flows, which has implications for water regulation for the river. It is beyond the scope of this study however to determine the effect of low flows on this species as sufficient data to determine habitat preference curves are not available. The species is known to occur within the middle reaches of the mainstream, though it is likely to occur throughout the Rubicon catchment, wherever suitable habitat exists. A. gouldi is listed as vulnerable under the Tasmanian Threatened Species Protection Act 1995 and it is recommended that flows in the ‘low risk’ category presented in Table 7 should remain in the river for its protection. This is to ensure that:

• a range of size of pools are maintained for adults and subadults; • boulder riffles are maintained for juveniles; and • base flows are maintained at sufficient levels to keep water temperatures at a level conducive to survival of all age classes (below 18 °C Forteath, 1987).

6.3 Flow Recommendations

This section offers a summary of Environmental Water Requirements that will provide certain, defined risks to the maintenance of ecological values for the Rubicon River at the reach at Smith and Others Road. Given the comparatively high water demands within the Rubicon catchment during the irrigation period, it is likely that current flows during this period will impact on a number of community and scientific values. However, spawning and rearing of the above fish species is largely outside the summer low-flow period so these values are unlikely to be affected at present. However, substantial reductions in flows may cause dewatering of the preferred habitats of many of these fish species, making the fish more vulnerable to predation. In addition, although the spawning of the above fish species occurs during spring, autumn and into winter, at times that are largely outside of the irrigation season, provisions should also be made to ensure adequate flows to enhance the recruitment success of these species. This may mean ensuring that high or flushing flows, which may serve as cues for spawning and migration, are not severely attenuated by excessive development of in-stream dams.

32 Examination of risk categories for individual taxa (Table 7) indicates that EWRs for the Rubicon River are influenced by the higher flow requirements for brown trout during months of low flow (December to April). During months of higher flow (May to November), the Environmental Water Requirements are determined by the flow requirements for macroinvertebrates. Those individual macroinvertebrate species that were found in this assessment to have a narrow range of tolerance to changes in flow conditions included Hydrobiidae spp., Austrolimnius spp ., Tilyardophlebia spp ., Pisidium casertanum, Ecnomus.spp, Ceratopogonidae spp, and Oligochaeta. Both fish and macroinvertebrates were identified as prominent ecosystem values by the community and by the scientific panel for ensuring that adequate water was provided to maintain in-stream habitat for various aquatic faunas. It should also be noted that healthy macroinvertebrate populations provide an essential and highly significant portion of the diets of many game (recreational fishery) and forage (native) fish and serve a crucial role in the processing of energy in lotic ecosystems (Davies and Cook, 2001, Gore, 1987). In addition, many macroinvertebrates have been shown to have narrow ranges of tolerance to changes in flow (Gore, 1977). Therefore ensuring flow regimes that protect habitats is an integral step in maintaining the viability of both fish and macroinvertebrate populations, and the maintenance of ecological and recreational fishing values (for brown trout) in the Rubicon River.

It is also important to consider the role that river flows play in influencing the ecological and hydrological processes in estuaries. Riverine and estuarine food webs appear to be linked through ecological processes. This involves the transport of carbon and nutrients from upstream reaches during high river flows and the incorporation into benthic and pelagic food chains (Arthington, 1996). In order to develop an understanding of the ecological processes governed by the river's flow regime and the transport of materials and energy into estuarine waters, further research is required in this area. Freshwater flows are not only a major stimulus for estuarine and marine productivity and associated fishery production (Whitfield, 1996), but also provide a signal for breeding and migration in many marine and estuarine species (Loneragan & Potter, 1990, Adam et al ., 1992, Edgar et al ., 1999). While it is understood that productivity levels and recruitment in key species of estuarine fauna are influenced by freshwater inputs, the quantification of the river flows that will provide the essential environmental conditions for productivity are also yet to be defined. Studies have, however found that on-stream dams create a significant barrier to the downstream transfer of catchment derived nutrients, organic matter and sediment, which may influence river and estuarine ecosystem processes downstream (Bunn & Loneragan, 1998). The presence of dams and weirs also disrupt fish communities through the prevention of migration of diadromic fishes including eels ( Anguilla australis and Anguilla reinhardtii ), lampreys (Mordacia mordax and Geotria australis ) and Australian Grayling ( Prototroctes maraena ). Flushing processes that provide large flow events and freshwater plumes into estuaries are also important for maintaining water quality as well as preventing closure of estuary entrances, reducing anoxic conditions and mixing of saline and fresh waters. Although this study has not specifically addressed the issues of providing freshwater flows for estuaries, it is important that estuarine requirements are considered as an important component of any future water management and development plan for the catchment. While it is difficult to identify the magnitude of flow events required to maintain ecological processes in the estuary and estuarine productivity, it is clear however from previous studies that the maintenance of variability of flow is important for these processes (Schlacher & Wooldridge, 1996).

It is recommended that a study addressing holistic EWRs is undertaken for the Rubicon catchment. This should address issues such as flushing flows, channel maintenance and flow requirements for Port Sorell Estuary. Until such time such a study is completed, it is recommended that any consideration of water resource development in the Rubicon catchment that a flow regime that "mimics" the natural flow variability in the river is preserved. The retention of medium and large flood events in the catchment should therefore

33 ensure the maintenance of both freshwater processes governed by flood events and ecological processes in the estuary.

Secondly, it is recommended that an investigation to identify fish passage issues at the weir and possible solutions, taking into account the potential natural barrier of the gorge section below Smith and Others Road.

6.3.1 Rubicon River at Smith and Others Road

Table 8 provides a summary of Environmental Water Requirements that will provide defined risks to the maintenance of ecological values in the Smith and Others Rd reach. These risks only apply to this reach (see section 2.2.1 for details of the extent of the reach). It is recommended that flows in the "low risk" range should remain in the river for maintaining instream habitat for aquatic animals including giant crayfish and Australian grayling populations .

Table 8. Environmental Water Requirements for each risk category,

Risk Category Low risk (EWR) Moderate risk High risk Month Cumecs ML/Day Cumecs ML/Day Cumecs ML/Day January > 0.04 >3.5 0.04 – 0.02 3.5 - 1.7 < 0.02 <1.7 February > 0.02 >1.7 0.02 – 0.01 1.7 - 0.9 < 0.01 <0.9 March > 0.08 >6.9 0.08 – 0.06 6.9 - 5.2 < 0.06 <5.2 April > 0.15 >13.0 0.15 – 0.09 13.0 - 7.8 < 0.09 <7.8 May > 0.38 >32.8 0.38 – 0.35 32.8 - 30.2 < 0.35 <30.2 June > 0.84 >72.6 0.84 – 0.68 72.6 - 58.8 < 0.68 <58.8 July > 0.90 >77.8 0.90 – 0.43 77.8 - 37.2 < 0.43 <37.2 August > 0.96 >82.9 0.96 – 0.42 82.9 - 36.3 < 0.42 <36.3 September > 0.87 >75.2 0.87 – 0.50 75.2 - 43.2 < 0.50 <43.2 October > 0.87 >75.2 0.87 – 0.70 75.2 - 60.5 < 0.70 <60.5 November > 0.32 >27.6 0.32 – 0.26 27.6 - 22.5 < 0.26 <22.5 December > 0.15 >13.0 0.15 – 0.09 13.0 - 7.8 < 0.09 <7.8

34 7. References

Adam, P., Burchmore, J., Chrystal, J., Creighton, C., Downey, J., Geary, M., Hughes, P., Leadbitter, D., Llewellyn, L. & Patten, J., (1992). Estuary management manual . New South Wales Government, October.

Allen, G. R., Midgley, S. H. and Allen, M. (2002). Field guide to the Freshwater Fishes of Australia. West Australian Museum, Perth 394pp

ANZECC, (1992). Australian Water Quality Guidelines for Fresh and Marine Waters. National Water Quality Management Strategy.

ARMCANZ and ANZECC, (1996). National Principles for the Provision of Water for Ecosystems, Sustainable Land and Water Resources Management Committee, Subcommittee on Water Resources, Occasional Paper SWR No. 3.

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38 APPENDIX 1 Habitat area (WUA) – Discharge (Flow) relationships for all species, taxa and life stages of fish and macroinvertebrates at the Rubicon River at Smith and Others Road study site

700 Notalina sp.(total)

600 Ecnomus sp. (total)

500 Taschorema complex spp. 400 Leptoperla sp. (total) WUA ∆ ∆ ∆ ∆ 300 Cardioperla sp.(total) 200 Micronecta sp.(total) 100

Tasmanocoenis 0 sp.(total) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Discharge (cumecs)

200 Koorrnonga sp.(total) 180

160 Nousia sp.(total) 140 Tillyardophlebia 120 sp.(total)

100 Atalophlebia

WUA sp.(total)

80 Baetidae (total) 60 Chironominae 40

20 Orthocladiinae

0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Discharge (cumecs)

39 Smith and Others Road reach (cont)

500 Tanypodinae 450

400 Austrosimulium sp. (total) 350 Ceratopogonidae 300 (total)

250 Austrolimnius

WUA sp.(Larva)

200 Austrolimnius sp.(Adult) 150 Paratya australiensis 100

50 Paramelitidae (total)

0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Discharge (cumecs)

900 Austrochiltonia 800 sp.(total)

700 Hydracarina

600 Oligochaeta 500

WUA 400 Pisidium casertanum

300 Hydrobiidae (total) 200

100 Nematoda

0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Discharge (cumecs)

40 Smith and Others Road reach (cont)

120

100

80

60

WUA Total Abundance

Diversity 40

20

0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Discharge (cumecs)

300 Gadopis marmoratus (Koehn 1986) 250

S. trutta adults (Bovee 1978) 200

S. trutta 0+ (Davies 150 and Diggle unpub WUA data)

100 Galaxias maculatus (Jowett & Richardson 1995)

50 Anguilla australis (Jowett & Richardson 1995) 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Discharge (cumecs)

41