Department of Sustainability and Environment

Documenting the distribution, biology and ecology of Victoria's only threatened estuarine fish species Arthur Rylah Institute for Environmental Research Technical series No. 2008/89

Documenting the distribution, biology and ecology of Victoria's only threatened estuarine fish species

TARMO A. RAADIK JEREMY 5. HINDELL

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

November 2008

In partnership with:

rv1elbourne Water

Arthur Rylah Institute for Environmental Research Department of Sustainability and Environment Heidelberg, Victoria

ill Report produced by: Arthur Rylah lnscirute for Environmental Research Depamm:m of Sustainability and Environment PO Box 137 Heidelberg, Victoria 3084 Phone (03) 9450 8600 Website: www.dse.vic.gov.au/ari ©Slate of Victoria, Department of Sustainability and Environment 2008 This publication is copyright. Apart from fair dealing for the purposes of private study, research, criticism or review as permitted under the Copyright Act 1968, no part may be reproduced, copied, transmitted in any form or by any means (electronic, mechanical or graphic) without the p1ior written permission of the St.ate of Victoria, Department of Su~tainability and Environment. All requests and enquires should be directed to the Customer Service Centre, 136 186 or email [email protected] Citation: Raadik, Tarn10 A. and Hindell, Jeremy S. (2008) Documenting the distribulion, biology and ecology of Victoria's only threatened esruarine fish species: the Pale Mangrove Goby (Mugilogobius placynotus Gunther, 1861). Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008189. Department of Sustainability and Environment, Heidelberg, Victoria

ISSN 1835-3827 (print) ISSN 1835-3835 (Online)

Disclaimer: This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is wi thout flaw of any kind or is wholly appropriate for your panicular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. Front cover photo: Mugilogobi•LS platynows (Tanno A. Raadik). Authorised by: Victorian Government, Melbourne Printed by: PRINTROOM. Preston, Melbourne

iv v Contents LIST OF TABLES AND FIGURES ...... vm

ACKNOWLEDGEMENTS ...... X

S UMMARY ...... l

L"\JTRODUCTION ...... 2

1.1 P ROJECf OBJECTIVES ...... 3

2 R EVIEW OF BIOLOGY/ECOLOGY/TAXONOMY ...... 5

2.1 NAME ...... 5

2.2 OTHER COMMON NAMES ...... 5

2.3 OTHER SCIENTIFICNAMES ...... 5

2.4 D ISTINGUISHING FEATURES ...... 5

2.5 COLOUR ...... 5

2.6 SEXUAL DIMORPHlSM ...... ·········· ...... 6 2.7 SIZE ...... 6

2.8 SIMil..AR SPECIES ...... 6

2.9 D ISTRIBUTION ...... 6

2.10 NATURALHISTORY ...... 6

2.10.1 Habitat ...... 6 2.10.2 Physico-chemical Tolerances ...... 7 2.10.3 Diet...... 7 2.10.4 Behaviour ...... 7 2.10.5 Age and Growth ...... 7 2.10.6 Reproduction ...... 7 2.10.7 Migration/movements ...... 8 2.10.8 Parasites and Diseases ...... 8

2. 11 TRANSLOCA TIONS ...... 8

2.12 CONSERVATION STATUS ...... 8

2.13 TAXONOMY/GENETICS ...... 8

2.14 U SAGE ...... 8

3 REVIEW OF PREVIOUS SAMPLING METHODS ...... 9

4 REVJEW OF THE DISTRIBUTION OF MUGIWGOBJUS PLATYNOTUS IN WESTERN PORT AND PORT P HILLIP BA y ...... 11

4.1 D ISTRIBUTION OF KEY HABITAT (A VICENNIA MARINA) ...... 11

4.2 D OCUMENTED DISTRIBUTION OF MUGIWGOBIUS PLATYNOTUS lN W ESTERN P ORT AND PORT PHILLIP BAY ...... 17

vi 4.3 PREDICTED DISTRIBUTION OF MUGILOGOBJUS PLATYNOTUS JN W ESTERN PORT AND PORT PHILLIP B Ay ...... ············ ...... 18 5 REVIEW OF SMALL AND JUVENILE FISH ASSOCIATED WITH MANGROVES ...... 20

5. 1 VALUE OF MANGROVES TO FISH ...... 20 5.2 A V ICTORIAN PERSPECTNE ...... 20 5.2.1 Bay-wide assessment of fish use of mangroves and mudflats ...... 21 5.2.2 Zonation of fish assemblages within mangroves ...... 2 1

6 SURVEY OF CURRENT DISTRIBUTION AND BIOLOGY OF M UGILOGOBJUS Pl.ATYNOTUS 26 6.1 INTRODUCTION ...... 26 6.2 MATERIALS AND METHODS ...... 26 6.2.1 Survey ...... 26 6.2.2 Size and age structure of Mugilogobius plalynotus ...... 27 6.2.3 Sex structure and fecundity ...... 27 6.3 REsULTS AND DISCUSSION ...... 29 6.3.l Distribution of Mugilogobius platynotus ...... 29 6.3.2 Biology of Mugilogobius platynotus ...... 32 6.3.3 Morphology of Mugilogobius platynotus ...... 32 6.3.4 Fish assemblages ...... 35

7 CONCLUSIONS AND R ECOivlMENDATIONS ...... 38 8 REFERENCES ...... 39

vii List of tables and figures

List of tabJes Table 1. Project tasks to review, describe and update the distribution, biology and ecology of the Pale Mangrove Goby in Port Phillip Bay and Western Port...... 4 Table 2. Number of each species collected in each combination of time of year (summer, autumn, winter and spring) and habitat (mangrove - M, mudflat - UV) across Western Port and Corner Inlet. Data were pooled across bays, sites and sampling gears. From Hindell and Jenkins 2004 ...... 23 2 Table 3. Summary of mean abundances (µN - fish m' ) and lengths (µL- mm), total number 2 of samples, mean water depth, total number of species, abundance (fish m· ) and 2 biomass (g m" ) of fishes among habitats (forest, edge, mudflat). Figures in parenthesis represent standard errors. *only 1 fish caught. J juvenile and A adult lifestages (based on sizes given by Gomon et al. 1994). From HindelJ and Jenkins (2005) ...... 25 Table 4. Summary of sampling locations. ** site sampled, but no mangroves present ...... 29 Table S. Summary of the sex ratio, and average length, weight, number of eggs and percentage gonad to body weight...... 35 Table 6. Summary of total numbers of fish species sampled at each of the study sites. BB - Blind Bight, CI - Churchill Island, DC - Deep Creek, H - Hastings, HC - Hovels Creek, JB - Jacks Beach, KC - Kororoit Creek, SC - Saltwater Creek, SCB - Stony Creek Backwash, SP-Stony Point, T -Tooradin, W - Warneet, WB - Wooleys Beach, RI - Rhyll Inlet, Fin - French island north, Fiw - French Island west, Fle - French Island eac;t, Fln/e - French Island northeast...... 36

List of figures Figure 1. Avicennia marina in the vicinity of Hastings (Jeremy S. Hindell) ...... 11 Figure 2. Summary of the broad distribution of mangrove (Avicennia marina) in Victoria, between the Barwon River estuary and Corner lnlet/Nooramunga...... 12 Figure 3. Distri bution of mangroves (Avicennia marina) in Port Phillip Bay. Red box outlines area for which more detail is given in Figure 4. Filled green circles indicate stands of mangrove not shown in existing habitat maps ...... 13 Figure 4. Distribution of mangroves (Avicennia marina) in Hovells C reek, Limeburners Bay. Mangrove - green shading. Saltmarsh - pink shading ...... 13 Figure 5. Distribution of mangroves (Avicennia marina) in Western Port. Red boxes outline areas for which more detail is given in Figures 6 to 10 ...... 14 Figure 6. Distribution of mangroves (Avicennia marina) in the north-western region of Western Port. Mangrove - green shading. Saltmarsh - pink shading ...... 14 Figure 7. Distribution of mangroves (Avicennia marina) in the north-eastern region of Western Port. Mangrove - green shading. Saltmarsh - pink shading...... 15 Figure 8. Distribution of mangroves (Avicennia marina) in the central-eastern region of Western Port. Mangrove - green shading. Saltmarsh -pink shading...... 15 Figure 9. Distribution of mangroves (Avicennia marina) in the south-eastern region of Western Port . Mangrove - green shading. Saltmarsh - pink shading ...... 16 Figure 10. Distribution of mangroves (Avicennia marina) in the central-western region of Western Port. Mangrove - green shading. Saltmarsh - pink shading...... 16

viii Figure 11. Documented locations (orange circles) from which individuals of Mugilogobius platynotus have been found in Western Port. Numbers as per sites, above...... 18 Figure 12. Proposed locations (blue circles) for sampling Mugilogobius platynotus in Port Phillip Bay (A) and Western Port (B). Mangrove - green shading. Saltmarsh - pink shading...... 19 Figure 13. Location of sampling sites with A) Port Phillip Bay and B) Western Port ...... 28 Figure 14. T he interior region of a forest of A vicennia marina. Note the fyke net set to the left of picture and the seaward edge of the mangroves in the distance. Mugilogobius platynotus were sampled almost exclusively from these types of environments within the mangrove forest. (Jeremy S. Hindell) ...... 30 Figure 15. Upper reaches of Tankerton Creek estuary, French Island, November 2004. (T armo A. Raadik) ...... 3 1 Figure 16. Relationships between length and abundance, number of eggs, fish weight, and gonad-to-fish weight for male and female Mugilogobius platynotus...... 33 Figure 17. M icro-structure of sagittal otolith of Mugilogobius platynotus. Increments are unvalidated, but assumed to represent daily growth rings ...... 34 F igure 18. Opaque growth increments viewed on a sagittal otolith prepared via transverse section. Opaque increments are unvalidated, but assumed to represent yearly growth rings ...... 34 Figure 19. A male Mugilogobius platynotus. (Tarn10 A. Raadik) ...... 35

ix Acknowledgements We would like to thank David Dawson, Andrew Pickworth and Lauren Dodd from the Arthur Rylah Institute for Environmental Research for assistance in the fi eld and laboratory. Thanks also to the Central Ageing Facility, DPI, for analysing otoliths for ageing, to Mike Smith for critical comments on the draft of this document and to Melbourne Water for funding to support this project. Sampling was conducted under the following permits: Victorian Fisheries Research Pennit RP 810, Animal ethics permit no. : ABC 07/24 and Flora and Fauna Guarantee Act Permit 10004327.

x Distribution, biology and ecology of1he Pale Mangrove Goby

Summary The current project reviewed the taxonomy, biology/ecology and distribution of the pale mangrove goby (Mugilogobius platynotus) in Australia, reviewed their known distribution in Victori a, and defined their potential distribution in two central coastal Victorian embayments. Surveys were then undertaken of their distribution and habitat use at 20 sites throughout Port Phillip Bay and Western Port, and documemed reproductive state and approximate longevity. The review of biology and sampling strategies for M. platynotus provide valuable background information with which to assess the conservation status of this species and plan targeted sampling strategies to document its distribution in the future. The distribution of M . platynotus was determined by sampling with single-wing fyke nets, which also captured other estuarine/marine fish species. M. platynotus were found only in Western Port, with highest abundances caught in the vicinity of Hastings. They were only sampled from mangroves, and were significantly more abundant inside mangrove forest than along the edge. Individuals ranging from c. 30 mm total length appeared to have significant gonadal development, with some suggestion of summer spawning. Otolith-based ageing was ambiguous, with micro-structure suggesting that fish lived for longer than a year but opaque growth rings suggesting some fish may live as long as nine years; growth rings need to be validated in future studies. Notwithstanding the need to better sample mangroves in eastern Victoria (i.e. Comer Inlet), M. platynotus appears to have a very limited distribution in Victoria to a limited area in one coastal embayment, and appears to be largely confined to mangrove­ associated estuaries within Western Port.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 1 Distribution, biology and ecology of the Pale Mangrove Coby

1 Introduction Mangroves play a crucial role in the maintenance of water quality, nutrient processing and sediment stabilisation and are also critical habitat for fish and invertebrates. Only one species of mangrove (Avicennia marina) occurs in Victoria, although there are reports of other mangrove species being planted in the Gippsland lakes. Mangroves have a restricted distribution in Victoria primarily between the Barwon River estuary in the west and Corner Inlet/Nooramunga in the east. They are a significant form of habitat 2 in Western Port, and Comer Inlet, where they cover areas of 15 and 18 km , respectively. Much smaller stands of mangrove are present in the Barwon River estuary, Port Phillip Bay, and Anderson Inlet. Despite their limited distribution, mangroves harbour unique communities of plants and animals, and, until recently, were thought to be critical in the provision of habitat for fi sh, particularly the early life-history stages. Mangrove habi tats are at risk from sea level rise and extraction of freshwater, and there is a need for better understanding of the ecology of these unique ecosystems at the southern margin of their distribution. Despite studies in the tropics documenting the importance of mangroves to fish and invertebrates, especially as nurseries for juvenile stages, little work has been done in Victoria. Work by Hindell and Jenkins (2006) demonstrated the value of mangroves to larger, conunercially valuable fishes in Western Port and Corner Inlet. The gear used in their work was designed to sample larger species, and generally failed to sample smaller cryptic species associated with mangroves - thereby limiting our understanding of the distribution, abundance and species richness of smaller, mangrove associated species. Despite these gear limitations, however, some smaller species were sampled opportunistically when they were trapped among algal mats attached to the nets. Included in these was the Pale Mangrove Goby Mugilogobius platynotus Gilnther, 1861. The Pale Mangrove Goby is Victoria's only threatened estuarine species. It has previously been sampled from only a few locations in Western Port, always in association with mangroves close to freshwater inputs (e.g. tributaries, drainages). It is unclear whether this species occurs throughout the distribution of mangroves in Victoria, or whether it is restricted to small pockets, as already identified. There is a need to document the extent to which this species occurs in areas of mangrove not previously sampled, as well as confirm the presence of fish in areas it has previously been found in Western Port. Melbourne Water has recently expanded the area of responsibility for managing regional drainage, waterways and floodplains to cover the entire Port Phillip Bay and Western Port regions. This includes areas with significant stands of mangroves and, as yet, unresolved distributions of the only FFG-listed estuarine fish - the pale mangrove goby (Mugilogobius platynotus). The collection of data to improve water way condition/value assessments, identification of threatened species, and assessment of the extent of introduced/pest species will directly benefit management by: • Increasing understanding of small, cryptic fish assemblages associated with mangroves in Port Phillip Bay and Western Port, including for extended areas of responsibility. • Providing detailed description of distribution and basic biology of the threatened Pale Mangrove Goby in central Victorian estuarine systems.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 2 Distribution, biology and ecology of the Pale Mangrove Goby

• Improving capacity for advocacy of critical habitats - and habitat requirements of threatened species in estuaries. • Providing valuable baseline data for the assessments of change in the future. • Improving abilities in risk assessment for species and habitat decline with large scale envirorunental perturbations, including reduced freshwater flows and sea level rise.

1.1 Project objectives This project reviewed, described and mapped small (including juvenile stages) and cryptic fish communities using mangrove habitat throughout Western Port and Port Phillip, with a focus on the Pale Mangrove Goby. Specifically, the current project had 3 primary objectives (activities for which are listed in Table 1): 1. Review current knowledge of small (including juvenile stages) and cryptic fish using mangrove habitat in Western Port and Port Phillip Bay, with a focus on describing the distribution, biology and ecology of the Pale Mangrove Goby. 2. Document the current distribution of mangrove habitat in Port Phillip Bay and Western Port, with emphasis on stands of mangrove in the vicinity of drainages and rivers, and identify likely hotspots for further investigation of Pale Mangrove Goby distribution. 3. Complete a targeted sampling regime to confirm current patterns of discribution, biology and ecology of the Pale Mangrove Goby (and including descriptions of all small and cryptic species using mangroves).

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 3 Distribution, biofogy and ecology of the Pale Mangrove Gaby

Table 1. Project tasks to review, describe and update the distribution, biology and ecology of the Pale Mangrove Goby in Port Phillip Bay and Western Port.

Activity Task I. Review Review what is known about the Pale Mangrove Goby in Victoria, including distribution (temporal and spatial), biology and ecology. Document gaps in understanding. Review methods for sampling this species and select a range of techniques for trial. Identify key aspects of the biology and ecology required for effective management*, including how this should be done. Review information on the spatial and temporal variability in abundances of other small, cryptic species using Victorian mangroves 2. Fish and habitat mapping Document spatial distribution of mangrove habitat in Port Phillip Bay and Western Port by: Review/update existing distributional maps for mangroves 'Ground-truth' new and/or expanding stands of mangrove in Port Phillip Bay and Western Port Overlay known distribution of Pale Mangrove Goby on mangrove distribution Identify likely 'hotspots' for further investigation of Pale Mangrove Goby distribution, abundance and habitat use. 3. Field survey Survey size-frequency distribution and habitat use of mangrove-associated fishes (focusing on Pale Mangrove Goby) at 20** sites across Port Phillip Bay and Western Port *** ID fish, collate/analyse data and prepare final report

* Some key aspects may be age, spawning season, egg number, early larval life. ** Final number of sites will depend on activities 1 and 2. ***Data will also be collected, where possible, on key aspects of biology/ecology identified as important for effective management from the review stage of the project.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 4 Distribution, biology and ecology of the Pale Mangrove Goby

2 Review of biology/ecology/taxonomy

2.1 Name Pale Mangrove Goby (Gobiidae: Mugilogobius platynotus, Gunther 1861 ).

2.2 Other Common Names Flatback Mangrove Goby, Mangrove Goby, Palid Goby.

2.3 Other Scientific Names Ellogohius ahascantus, Gobius platynotus, Mugilogohius paludis, Waiteopsis platynotus (Whitley 1930, 1937, Hoese & Larson 1994, Larson 2001).

2.4 Distinguishing Features Small to moderately large, slender, flat-headed goby; bead wider than deep (especially in maJes); mouth large and subterminal, slightly oblique, jaws reaching past posterior border of eye in adult males (to below anterior half of eye in females); eye small, tongue tip blunt to rounded; teeth on both jaws; eyes lateral and high in head; snout broad and rounded; interorbital broad and flat; caudal peduncle laterally compressed; gill openings usually extending forward to under opercle; body mostly covered with cycloid scales, except before ventral fin s and on head; firs t and second dorsal fin s, and anal fin , low, generally rounded, first dorsal with flexible spines; pectoral, pelvic and caudal fins rounded. (Whitley 1930, 1937, Kuiter 1993 , Hoese & Larson 1994, 2008, Larson 2001). Dorsal Fin: V-VI; 1.8- 10 (usually VI; l.9) Anal Fin: T. 8-10(usually1.9) Caudal Fin 15-17 (usually 16) (segmented rays) Pectoral Fin: 13-17 (usually 16) Pelvic Fin: 1.5 Longitudinal Scales: 45-59 (mean 53) Predorsal Scales; 0-21 (mean 4) Gill Rakers: 2+5 to 4+6 (on first arch)

2.5 Colour Head and body dull brownish grey, darker above, pale on belly; head usually darker. Scale margins dark brown. Sides of the body, and top and sides of head with indistinct scattered brown mottling and fine vemliculation; tending towards a series of midlateral dark brown spots near or on caudal fin. Eye marbled brown and gold with distinct gold rim around pupil. Dorsal fins with broad submarginal yellow band, lower portion of fins light greyish brown; first dorsal fi n with two longitudinaJ dark brownish grey streaks and an intense black blotch at rear margin; second dorsal fin with two rows of vertically orientated dark brown spots. Anal fin yellowish grey with narrow white margin; caudal, pectoral and pelvic fins plain yellowish grey (Kuiter 1993, Hoese & Larson 1994, 2008, Larson 2001, Allen et al. 2002).

Arthu r Rylah Institute for Environmental Research Technical Report Series No. 2008/89 5 Distribution, biology and ecology of the Pale Mangrove Coby

2.6 Sexual Dimorphism Mature males with larger mouth, wider head and longer first dorsal fin spines than females. Male genital papilla elongate, flattened and with a blunt tip; in females short, rounded and bulbous. Females similar in colour to males, but paler (Hoese and Larson 2008, Larson 2001).

2.7 Size To 65 mm (total length - TL) and 4.0 g, usually to 50 mm (TL).

2.8 Similar Species May be confused with Tamar Goby (Afurcagobius tamarensis) and Eastern Bluespot Goby (Pseudogobius sp.).

2.9 Distribution Endemic to Australia, widely distributed in tidal estuaries and marine inlets from southern Queensland (Coomera Island, Moreton Bay), through New South Wales into eastern Victoria ( Morton et al. 1987, Larson 2001 ), including near shore islands. A recently discovered population in South Australia, ori ginally identified as M. platynotus, has been reconfirmed as the morphologically similar species Blackspot Mangrove Goby Mugilogobius stigmaticus, with which M. placynotus is found in sympatry towards the north of its range in NSW and QLD (Hammer 2006, Bertozzi & Hammer 2007). In Victoria, currently only known from Western Port (Larson 2001, Raadik unpublished data). Specifically known from the western, northern and eastern perimeter of Western Port, including Tankerton Creek and Mosquito Creek on French Island (Raadik unpublished data) and Stony Point (Hindell & Jenkins 2004, 2005; Figure 11).

2.10 Natural History The biology and ecology of the Pale Mangrove Goby is poorly known across its range.

2.10.1 Habitat Usual ly found in clear to slightly turbid shallow water areas of tidal estuarine or flowing fresh reaches of coastal rivers and creeks and marine environments in bays, inlets and coastal lagoons. Found in close association with saltmarsh and mangroves on soft- mud or sand/mud substratum, among organic debris or in tunnels of other species (Maguire & Bell 1982, Bell et al. 1984, Burchmore et al. 1984, Morton et al. 1987, Morton et al. 1988, Gee and Gee 1991, Pollard & Hannan 1994, Saintilan & Williams 1999, Hindell & Jenkins 2004, Mazumder 2004, Hinde)] & Jenldns 2005). Mugilogobius platynocus have also been recorded from a Lidal pool on a rocky foreshore in NSW (Ivey 1951), but are generally absent from seagrass areas (Allan et al. 1985, Ferrell & Bell 1991, Ferrell et al. 1993, Griffiths 2001, Rotherham & West 2002, Saintilan et al. 2007); a record of their presence in seagrass on the north coast of NSW is probably erroneous and most probably refers to the morphologically similar species Mugilogobius stigmaticus (Gray et al. l996). M. platynotus also appear to be absent from small estuaries which are only intermittently open to the ocean.

Arthur Rylah lnstitULe for Environmental Research Technical Report Series No. 2008/89 6 Distribution, biology and ecology of the Pale Mangrove Coby

Populations can be patcbiJy distributed but high in abundance, and can be the dominant species in mangrove hahitati; in some estuaries (Mazumder et al. 2005). Abundance can vary seasonally, with high abundance recorded in mangrove and saltmarsh habitat in Botany Bay (NSW) during autumn and spring (Mazumder 2004, Mazumder et al. 2005). Abundances also vary strongly among microhabitats within mangroves (Hindell & Jenkins 2005), with more fish present within the mangrove forest than along the seaward edge or adjacent mudflat. Habitat usage during low tide is unknown. Fish may occupy tidal creeks within mangrove patches, or reside within mangrove forests by burying in mud or seeking refuge in crab/fish burrows and other areas of surface water. Work of Hindell, Jenkins and students(2005, unpublished data) suggests that M. platynotus does not follow tidal fronts to subtidal waters.

2.10.2 Physico-chemical Tolerances Physico-chemical tolerances are poorly known except that the species generally has a very broad tolerance to salinity, can cope with lowered dissolved oxygen levels, and has been found in water up to 27.5 °C. They have been recorded from fully marine environments (around 56 000 µIS cm) to lower reaches of freshwater streams just upstream of tidal influence at a salinity of 1 300 µ/S cm (Tankerton Creek, French Island) (Raadik unpublished data). Specific salinity tolerances, particularly in relation to newly shed eggs and hatched larvae, and short and long- term exposure to differing salinity levels, is unknown. Appears to also be tolerant of low dissolved oxygen levels, with fish performing aerial surface respiration (ASR) at oxygen levels below 0.9 g/L (Gee & Gee 1991). Fish usually 'beach' themselves on the substrate just below the water surface, with the head arched upwards so that the mouth is in the surface waters, or after some time, 'hang' vertically in the water column with their mouth at the surface (Gee and Gee 1991). As dissolved oxygen levels fall, fish gulp a bubble of air and hold it in their mouths for less than a minute before exchanging it, and also increase their gill ventilation rate (Gee and Gee 1991).

2.10.3 Diet Mainly carnivorous and diet changes seasonally. Found lo consume algae, culicid larvae, other insects (e.g. dipterans), arachnids, crustacean (crab larvae and adults, copepods, amphipods and prawns), juvenile fish, algae and detritus (Morton et al. 1988, Larson 2001, Mazumder 2004, Mazumder et al. 2006).

2.10.4 Behaviour Is able to leap out of water, and also to remain alive out of water for a considerable length of time (Ivey 1951, Larson 2001). Some evidence of fish burying in mud during low tide (Hindell personal observation).

2.10.5 Age and Growth Unknown, though Ivey (195 1) kept fish in an aquarium for 14 months and recorded very little growth.

2.10.6 Reproduction Largely unknown. Juvenile fish (22.5 mm TL) have been recorded in an upper estuarine/lower freshwater reach on French Island (VIC) in early November, indicating a possible winter spawning. Small juveniles have been collected in NSW

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 7 Distribution, biology and ecology of the Pate Mangrove Goby during mid October (Ivey 1951) and very young juveniles were noticed in an aquarium at the end of June, the result of an unobserved captive spawning (Tvey 1954).

2.10.7 Migration/movements Unknown. As tides fall and expose the shallow water areas associated with mangrove stands, it is unknown whether M. platynotus remain or move. Fish may possibly: • move long distances into more marine environments to remain in shallow water; • move up into the lower reaches of any inflowing tributaries; • burrow into the substratum; • move into exposed invertebrate burrows; • withstand air exposure; • inhabit tidal pools; or, • undertake a combination of the above. Specific migrations for spawning are unknown.

2.10.8 Parasites and Diseases Unknown.

2.11 Translocations None known. 2.12 Conservation Status Considered a threatened species in Victoria and listed on the Victorian Flora and Fauna Guarantee Act 1988. Listed as vulnerable in Victoria (DSE 2007).

2.13 Taxonomy/Genetics Taxonomy of the genus and species has recently been reviewed and revised (Larson 2001). Popul ation genetic structure of the species across its range, and within Victoria, has not been undertaken, though mtDNA analysis of one Victorian and one southern NSW population indicated little difference (Bertozzi & Hammer 2007).

2.14 Usage None known. Possibly as a hardy estuarine aquarium fish.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 8 Distribution, biology and ecology of the Pale Mangrove Ooby

3 Review of previous sampling methods Various gear types have been used to collect M. platynotus, including: • Fyke nets • Pop nets • Seine nets • Bait Traps • Dip nets • Electrofishing The most quantitative method of sampling fishes from Victorian mangroves has been by pop nets, though Mazumder (2004) compared pop nets and fyke nets in saltmarsh and mangrove in Botany Bay (NSW) and found pop nets caught fewer individuals and less species. The methods used in the construction and sampling using pop nets are described in detail by Hindell and Jenkins (2005). Pop nets provide excellent estimates of fi sh density, even in highly structured habitats such as mangroves, however, they are difficult and time consuming to set; only 2 to 3 nets can be fished on a particular day. Pop nets have proven to be the most successfu l method of sampling M. platynotus within mangrove forests, however, this method would not be feasible in establishing the extent of distribution over many sites. Fyke nets have been used by Hindell and Jenkins (2004) to sample fi sh associated with mangroves throughout Western Port and Corner Inlet, however, it is critical that Fyke nets are set properly. Hindell and Jenkins (2004) attempted to set fyke nets from the front of a small boat at high tide, but this limited the nets to being set along the mangrove fri nge and did not enable the bottoms of the nets to be set firmly against the substratum. Given the benthic nature of gobies, and the propensity for M. platynotus to be more abundant inside the mangrove forest (HindelJ & Jenkins 2005), the method for setting fyke nets employed by Hindell and Jenkins (2004) is likely to have underestimated abundances of small fish inside the mangrove forest. Future work should ensure (1) that fine mesh fyke nets are set inside the forest, and (2) that the bottoms of the nets are set into the substratum. Seine nets are not a suitable method of sampling fish associated with structurally complex habitats such as mangroves. While it is difficult but not impossible to find a clearing within a mangrove forest to set the net, it is almost impossible to keep the bottom of the net on the substratum as it rises over, and also 'snags' on pneum atophores while being hauled. This allows small benthk fish such as gobiids opportunities for escape underneath the net. Seine nets may possibly be used over clear, harder substrates (e.g. sand, sand/mud) adjacent to structurally complex mangrove habi tats. Dip nets are rarely used in estuarine/marine studies, probably because many fish can escape, especially in open, structurally complex environments. Dips nets will be limited in their effectiveness within mangrove forests because of the difficulty in sampling benthic fishes hiding among pnewnatophores, lhrough which the dip net is difficult to push. Bait traps have shown some promise in sampling small and juvenile fish associated with structurally complex habitats in estuaries, including seagrasses and Phragmites,

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 9 Distribution, biology and ecology of the Pale Mangrove Coby and have been used to capture M. platynotus (French Island). Bait traps warrant further tria11ing in a more considered way within mangroves forests. Of specific interest will be the value of adding bait and light sticks to attract fishes. Another benefit of bait traps is that many samples can be taken over a short time, and the gear is easy to set and retrieve. Electrofisbing is wholly restricted in its application to waters of very low salinity, and will not be useful for high-tide periods in much of Victoria's mangrove habitat. The exceptions are situations in the higher tidal zones, where there is significant input of low-conductivity (fresh) water (< 1500 µIS cm). M. platynotus were successfully electrofishcd from the lower reaches of Tankerton Creek on French Island (Raadik unpublished data). Pit-fall traps are a novel but largely untested method of sampling fishes from aquatic environments. They have some potential merits in sampling fishes from shallow, draining habitats such as intertidal mangroves and mudflats, where fi sh move into small drainages or tunnels at low tide to avoid exposure. Like the bait traps, pit fall traps should be tested further to assess which species of fish are most likely to be sampled, and which design constraints require consideration.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 10 Distribution, biology and ecology of the Pale Mangrove Coby

4 Review of the distribution of Mugilogobius platynotus in Western Port and Port Phillip Bay

4.1 Distribution of key habitat (Avicennia marina) Of the approximately 38 species of mostly tropical mangrove found in Australia (58 % of the world total), only a single species (Avicennia marina) grows in the temperate state of Victoria (Figure 1). This species grows here at the southernmost latitude of any mangrove in the world (38° 45' S) and trees are stunted, 1 - 4 m in height compared with = 30 m for A. marina on Hinchinbrook Island, tropical Australia (Harty 1997). In Victoria, A. marina has been cleared for agriculture and urbanisation, used as building materials, and burnt to make Jime and soap (Harty 1997), however, A. marina forests still cover around 41 km2 of intertidal mudflat (almost 30 % of the total intertidal mudflat along Victoria's 1720 km coastline), between the Barwon River estuary in the west and Nooramunga in the east. The value of mangroves as habitat for marine animals, especially fish, has been transferred in theory from tropical systems, where it is relatively well studied, to temperate latitudes. Unfortunately, there is little empirical data on which fish species, when, and at what life stages, use mangroves at their most temperate latitudes.

Figure 1. A vicennia marifla in the vicinity of Hastings (Jeremy S. Hindell).

Mangroves are far less abundant in Port Phillip than Western Port (Figure 2 to Figure 5). The most significant stand of mangroves in Port Phillip Bay is in the upper estuarine reaches of Hovells Creek, Limeburners Bay (Figure 4). Recent habitat

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 11 Distribution, biology and ecology of the Pale Mangrove Coby mapping underestimates the true extent of mangroves, missing significant stands in the Stony Creek backwash and the mouth of Kororoit Creek. There are also repo11s of much smaller (less than 10s of individual trees) stands of mangrove in Swan Bay and on Mud Island, although reports suggest that Parks Victoria may have removed mangroves from the latter (David Ball, Fisheries Victoria, DPI, Queenscliff, pers. comm.) Avicennia marina in Western Port covers an area of approximately 15 km2 (Figure 5 to Figure 11). Individual mangrove trees grow to a substantially larger size (3-4 m) in Western Port compared to those further to the east (e.g. Comer Inlet 1-2 m) and these stands are 'broken' by intertidal mudflats up to 500 min width. There appears to be little difference in the degree and frequency of inundation of mangroves across Western Port, with different microsites within the forest flooded at similar stages of the tidal cycle. Mangrove habitats within the tropics in Australia and overseas are characterised by channels that funnel water from the mangroves as the tide recedes, but channels are largely absent from the mangrove habitat in Western Port.

\/ie10ri• l .. I

Poll Phllllp 8~

100 Mllomtttra ~~iiil!!~~~iiiiiiiiiiii

Figure 2. Summary of the broad distribution of mangrove (A vicennia marina) in Victoria, between the Barwon River estuary and Corner InJet/Nooramunga.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 12 Distribution, biology and ecology of the Pale Mangrove Goby

II Mangrovos o sa111narsh >----1-- 0 Intertidal mudll

30 0 30 60 l

Figure 3. Distribution of mangroves (Avicennia marina) in Port Phillip Bay. Red box outlines area for which more detail is given in Figure 4. Filled green circles indicate stands of mangrove not shown in existing habitat maps.

144 41

2 0 2 4 IOlometers l!!!!!!!!!!!!!!!!!!!!!!!!!Siiiiiiiiiiiiiiiiiiiiiiiiil!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!~iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiil

Figure 4. Distribution of mangroves (Avicennia marina) in HoveUs Creek, Limeburners Bay. Mangrove - green shading. Saltmarsh - pink shading.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 13 Distribution, biology and ecology of th e Pale Mangrove Goby

i. Mangroves D Saltmarsh ~;.-:.....:...L---~_;,~~~::::![L__ ~ .,_----l.:::__..._J 0 Intertidal mudll

s

0

Figure 5. Distribution of mangroves (Avicennia marina) in Western Port. Red boxes outline areas for wbicb more detail is given in Figures 6 to 10.

0 5 10 i!!!!!!!!!!!!!!iiiiiiiiiiiiiiiiiiiiiiiil!!'!!!!!!!!!!!!!!!!!!!!!!!!!!!'!Siiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii l

Figure 6. Distribution of mangroves (Avicennia mari11a) in the north-western region of Western Port. Mangrove - green shading. Saltmarsh - pink shading.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 14 Distribution, biology and ecology of the Pale Mangrove Goby

2

38 29

O 5 10 Kllometera ~!!!!!!!!!!!!!!liiiiiiiiiiiiiiiiiiiiii~!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!liiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiil

Figure 7. Distribution of mangroves (A11icennia marina) in the north-eastern region of Western Port. Mangrove - green shading. Saltmarsh - pink shading.

3836

5 O 5 10 Kilometers l!!!!!!!!!!!!!!!liiiiiiiiiiiiiiiiiiil~~~!!!!!!!!!!!!liiiiOiiiiOiiiiiiiiiiiiiiiiiiiiiiiiiiiii

Figure 8. Distribution of mangroves (Avicennia marina) in the central-eastern region of Western Port. Mangrove - green shading. Saltmarsh - pink shading.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 15 Distribution, biology and ecology of the Pale Mangrove Coby

l!!!!!!!!!!!~;;;;;;;;;;;;;;;;;;;;;;;;;l!o !!!!!!!!!!!'!!!!!!!!'!!!!!!!!'!!!!!!!!'!!!!!!!!'!!!!!i5;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;iiiil10 Kllomotors

Figure 9. Distribution of mangroves (Avicennia marina) in the south-eastern region of Western Port. Mangrove - green shading. Saltmarsh - pink shading.

!s !!!!!!!'!~!!!!!§;;;;;;;;;;;;;;;;;;;;;;;;;io !!!!!!!!!!!!!!!!!!!!!!!!!!!!!is;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;iiiil10 Kiiometer•

Figure 10. Distribution of mangroves (Avicermia marina) in the central-western region of Western Port. Mangrove - green shading. Saltmarsh - pink shading.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 16 Distribution, biology and ecology of the Pale Mangrove Goby

4.2 Documented distribution of Mugilogobius platynotus in Western Port and Port Phillip Bay Mugilogobius platynotus is currently only known from Western Port (Larson 2001, Raadik unpublished data) (Figure 11). Specifically, the locations (and dates) within Western Port from which M. platynotus has been recorded, include: 1. Stony Point, south of Hastings (2003, 2005) 2. BUnd Bight Swimming Hole, Blind Bight (1992) 3. Western Contour Drain, South Gippsland Highway (1989) 4. creek near Grantville (1989) 5. Reef Island, north of Bass River (1970) 6. French Island (1972) 7. Tankerton Creek, Coast Road, French Island (2004) 8. Mosquito Creek, Overpass Road, French Island (2004) 9. Renison Bight, Newhaven (2004) Hindell and Jcnlcins (2004, 2005) provide the most rigorous assessment of local abundances of fi sh at particular sites, but this work is highly restricted in space, with only 3 si te sampled in Western Port. Key findings include: 1. Densities of Mugilogobius platynotus of up to almost 2 fi sh per 10 m2 at Stony Point. 2. General restriction of fish to the interior regions of mangrove forests (but see Hindell and Jenkins, 2004). Raadik (unpublished data) also collected many fish from French Island during early November 2004. M. platynotus were electro.fished at the upper Limits of a small, mangrove-lined estuary (Tankerton Creek), and also collected by bait trap in the upper tidal reach of Mosquito Creek, well upstream of mangroves and saltmarsh. This indicates that, at least at these sites, fish are using low saline waters towards the upper tidal 1imj ts. In both cases, the sites sampled have some direct freshwater input via small tributaries. At least some sampling effort should be given to assessing whether freshwater inputs to areas of mangroves is an important predictor of fi sh abundances.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 17 Distribution, biology and ecology of the Pale ManRrove Goby

• Mangroves o sa11marsh 0 1n1ertldal mudn

s

1!!0 !!!!!!!!!iiiiiiiiiiiiiiiiiiiiiiiol!!!!!!!!!!!!!!!!!!!!lil;i;O iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~:zo Kilometero

Figure 11. Documented locations (orange circles) from which individuals of Mugilogobius platynotus have been found in Western Port. Numbers as per sites, above.

4.3 Predicted distribution of Mugilogobius platynotus in Western Port and Port Phillip Bay At this preliminary stage we have little data with which to differenti ate the likelihood of sampling fi sh across mangroves in either Western Port or Port Phillip Bay. Hence, all mangroves should be considered to harbour populations of fish. We have chosen 20 potential sampling points across both bays to cover as wide an area of mangroves as possible (Figure 12, see Section 6).

Arth ur Rylah Inslilule for Environmental Research Technical Report Series No. 2008/89 18 Distribution, biology and ecology of the Pate Mangrove Goby

A

• Mangroves ~----1-- O SallmarSh 0 Intertidal mudn _w*N r s

30.~!!!!!!!!!!!!liiiiiiiiiiiiiiiiiiiiiiiiiiiiiioi!'!!!!!!!!!!!!!!!!!!!!!!!!!!!~30;;.-iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~60 Kllometora

1!!0!!!!!!!!!!!1iii-iiiiiiiiiii!0!!!!!!!!!!!!!!!!!!!!!'!!1i;;Oiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~20 Kll ometers

Figure 12. Proposed locations (blue circles) for sampling Mugifogobius platynoflls in Port Phillip Bay (A) and Western Port (B). Mangrove - green shading. Saltmarsh - pink shading.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 19 Distribution, biology and ecology of the Pale Ma rig rove Coby

5 Review of small and juvenile fish associated with mangroves

5.1 Value of mangroves to fish Mangrove forests are highly productive, unique ecological environments that support rich assemblages of species via the provision of both a physical habitat and a source of nutrients (Hogarth 1999, Little 2000, Kathi resan & Bingham 2001). Peumatophores, prop roots and trunks increase the available hard substratum for colonisation by unicellular diatoms (e.g. bluegreen cyanobacteria), micro/macro algae (e.g. Rhodophyta) and faunal epibionts, and may trap sediments and organic material (Chapman & Underwood 1995, Hogarth 1999). Crustaceans and molluscs are considered to be the most abundant and conspicuous invertebrate fau na in mangrove habitats (Hogarth 1999), and together with the epibiota, support diverse assemblages of fish, many species of which are linked directly, or indirectly, to valuable fisheries (Robertson & Duke 1990). Mangrove habitats contain diverse and abundant assemblages of fish. Marine species appear to be the most common species of fish sampled in mangroves, estuarine species are the next most abundant, and freshwater species generally make up less than 10 % of the species collected (Pinto & Punchihewa 1996). Species richness and abundance of juvenile and adult fishes is often greater in mangrove habitats compared with alternatives such as unvegetated sand, seagrass or mudflats (Laegdsgaard & Johnson 1995, Clynick & Chapman 2002, Nagelkerken & van der Velde 2002), although the larger numbers of fish in mangroves than mudflats recorded by Clynick and Chapman (2002) were driven by a single species of gobiid. These patterns, however, depend strongly on the lifestages (size-classes) of the fishes sampled (Robertson & Duke 1987, de la Moriniere et al. 2002) and the species (Nagelkerken et al. 2000). One of the strongest paradigms in mangrove ecology promotes the role of mangroves in the provision of nursery habitat for juvenile fish and crustaceans. This paradigm is based on the observations by many studies of a tich fauna of juvenile fish in mangroves (Kathiresan & Bingham 2001), greater species richness and abundance of juvenile fish in mangroves compared with alternative habitats such as mudflats and/or seagrass (Nagelkerken & van der Velde 2002), post-settlement life-cycle migration from mangroves to alternative habitats such as coral reefs (de la Moriniere et al. 2002), and, in the few experimental assessments, the provision of food and reduction of predation by structural aspects of mangrove habitat (Laegdsgaard & Johnson 2001). Mangroves also appear to be valuable to older Jifestages, some of which have juveniles in other habitats (de la Moriniere et al. 2002). Larger fishes use mangrove habitats for feeding and shelter (Katbiresan & Bingham 2001), and many species are targeted by artisanal (de Boer et al. 2001) and commercial (Ley et al. 2002) fishers. These lines of evidence have helped to strengthen the resolve to protect these habitats, particularly in the tropics.

5.2 A Victorian perspective There has been some intermittent, small-scale, opportunistic sampling of fish in Victorian mangroves, but the most extensive sampling of fi sh from mangroves has been conducted in Western Port (Hindell & Jenkins 2004, 2005).

Arthur Rylah Institute for Environmental Research Technical Reporr Seri es No. 2008/89 20 Distribution, biology and ecology of the Pale Mangrove Goby

Hindell and Jenkins (2004) have completed two large studies of fish in mangroves within Western Port: 1. Bay-wide assessment of fish use of mangroves and mudflats 2. Zonation of fish assemblages within mangroves

5.2.1 Bay-wide assessment of tis~ use of mangroves and mudflats The first study used fyke, mesh and seine nets to identify species and quantify abundances in mangroves and adjacent mudflats within Comer Wet and Western Port (within which three locations were sampled: Hastings, Warneet and Newhaven). Forty-one species were sampled across the embayments (Table 2). Marine, estuarine and freshwater species represented 78, 17 and 5 % respectively of the total species sampled. Juvenile stages from 17 species (41 % of all species) were also caught. Eighteen species (44 %) of commercial/recreational interest were sampled from mangrove and mudflat habitat, of which 44 % were juvenile stages. With the exception of a few species of gobiid (including Mugilogobius platynotus), about whose ecology we know little, few other species of fish sampled could be considered to be residents of the mangroves. Several species of fish (Urocampus carinirostris, Hyporhamphus regularis, Mugilogobius platynotus, Myxus elongatus, Platycephalus Laevigatus, Aracana ornata) were only sampled over mudflats, while five species (Pseudaphritis urvillii, Atherinid postlarvae, Eubalichthys mosaicus, Cirella tricuspidata, Arripis trutta) were only sampled in mangrove habitat. Although the focus of this study was on teleost/chondrichthyian fishes, juveniles of a species of loliginid squid (Sepioteuthis australis, Quoy & Gaimard 1833) were also sampled from mangroves. The fyke net sampled at least 28 species, the second greatest diversity (but the highest number of individuals) of fi shes sampled by any gear in the study. The majority of these were juvenile stages, although adults from several species (eg Macquaria colonorum and Hyporhamphus melanochir) were also caught. Semi-pelagic fishes, such as Arripis truttaceus, Aldrichetta forsteri and Hyperlophus vittatus were commonly sampled with fyke nets, as were benthic gobiids and senti-demersal tetradontids. The gill nets were most effective at sampling larger fishes (SL> 15 cm), and no fish smaller than 10 cm were sampled with this gear. The seine net sampled mostly early post-settlement and juvenile stages of fish from at least 29 species. Most of these fishes were benthic (e.g. species from the family Gobiidae), although there were also semi-demersal species of atherinids and a sillaginid sampled.

5.2.2 Zonation of fish assemblages within mangroves A second study by Hindcll and Jenkins (2005) used pop-nets to sample fish assemblages across different mangroves zones: forest, edge and adjacent mudflat. The pop nets collected 15 species of fish from 9 families (Table 3). Benthic fishes such as gobiids (6 spp) dominated (42% of all fish caught), but semi-pelagic species (e.g. Atherinasoma microstoma, Sillaginodes punctata, Aldrichetta forsteri, Arripis trutt, Arripis truttaceus) were also sampled. Many of the fishes, particularly the gobiids, were adult/subadult stages, but juvenile stages of Sillaginodes punctata,

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 21 Distribution, biology and ecology of the Pale Mangrove Goby

Rhombosolea tapirina, Aldrichetta forsteri and the arripids were also colJected (Tab1e 3). The assemblage structure of fish differed strongly among microhabitats. Fish assemblages collected with the pop nets in the forest were different from those along the edge and mudflat. The same five species (Pseudogobius sp., Atherinasoma microstoma, Mugilogobius platynotus, Tetractenos glaber and Favonigobius lateralis) explained at least 88% of the differences between forests and the other zones (edge and mudflat), 50% of which was due to Psudogobius sp. The strong difference in assemblage structure between edge and mudflat was dri ven by four of the species from above, but M. platynotus was replaced by Arenigobius frenatus. Fish abundances and species richness differed among zones, but fi sh biomass did not. Fish abundances were greater in the forests and along the edge than in mudflats, but not different between edges and forest. Species richness was greater along edges than in forests or mudflats, but differed little between forests and mudflats, although the species composition was markedly different (see above).

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 22 Distribucion, biology and ecology of the Pale Mangrove Goby

Table 2. Number of each species collected in each combination of time of year (summer, autumn, winter and spring) and habitat (mangrove - M, mudflat - UV) across Western Port and Corner Inlet. Data ll'ere pooled across bays, sites and sampling gears. J:t'rom Hindell and Jenkins 2004.

Summer Autumn Winter Spring Specieos M UV M UV M UV M UV

Banjo shark (Trygonorrhina guanerius)

Eastern Blue.-.pot goby (P.m1dogobius sp.) 48 8 138 13 4 13 28 43 Blue-spot spotted stingarec (Uroloph11s pa11cimac11lat11s) 2 Bridled lealherjacket (Acamhaluteres spi/0111e/a11unis) 2

Cobbler (Gynmapistes mamw ra1us) 2 Congolli (Pseudaphritis urvillii) 2

E.~tuary perch (Macquaria colonomm) 3 3 6

Common Galaxia~ (Galaxias nU1Culatus) 7 26 Girdled goby (Nesogobius sp l) 33 9 7 2 3 5 GI.ass goby (Gobioprems semivestiws) 101 14 29 33 8 3 2 Globefish (Diodon nicthemems) 3 2 2 2 Greenback flounder (Rhombosolea tapirina) 6 6 3 6 18 45 Hairy pipefish (Urocampus carinirostris) 2 2 Halfbridled goby (Arenigobiusfrenatiu) 26 5 l3 8 25 King George whiting (Sillogi11odes ptu1ct11ra) 2 4 5 4 2 Longfin goby (Favonigobi11s laterolis) 9 9 46 5 16 4 42 Longsnout flounder (Ammotrt!tis rostrat11:) 2 2 2 Luderick (Gire/la tricuspidata)

Mosaic leatherjacke1 (Eul>alichrhys mosaicus)

Orna1e cowfish (Aracana nmata)

Pale mangrove goby (Mugllogobius platy11orus) Pike-bead hardyhead (Kt!stratherina esox) 20 5 2 2 Prickly toadfish (Conrus11s brevicaad11s) 3 12 6 Ri ver garfish (Hyporhampl111s regularis) 5

Rock fla1head (Plarycephalu.s lae11igat11s) 4

Sand mullet (My.ms elongnr11s)

Sanely sprat (Nyperloplws virratus) 446 31 412 2

Sea mullet (M 11gil cephaltu)

Senator wrasse (Pictilabrus faticlavius)

Shortfi.n eel (Anguilla a11stro/is)

Silver fish (leptatherina presbyteroides) 2062 580 183 4 404 9 185 460 Smooth toacltish (Tetractcnos glaber) 263 125 93 43 139 102 137 137

Southern calamary (Sepioteuthis australis) 4

Southern sea garfoh (Hyporhamplu1s melanochir) 4

Spotted pipetish (Srigmatopora argus) Tailor (Po111atom11s saltatrix) 2 2 Eastern Austral ia salmon (Arripis trutto) Western Australian salmon (Arripis rr11rrace11s) 5 3 6 4 5

Widebody pipefi ~ h (Stigmaroporo nigm) 6 16

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 23 Distribution, biology and ecology of the Pale Mangrove Coby

Yank tlathead (Pla1ycepha/11s speculator) 4 3 Yellow eye mullet (Aldrichenaforsten) 69 I 17 493 78 114 57 168 139 Monacanthi d poo;tlarvae Atherinid ptlarvac 3 Gobiid postlarvae 28 19 4 9 Odacid postlarvae 4

Total fish 3144 966 14 11 273 69 1 215 589 922

Total species 28 24 23 24 13 14 16 20

Arthur Rylah lnstitule for Environmental Research Technical Report Series No. 2008/89 24 Distribution, biology and ecology of the Pale Mangrove Coby

2 2 Table 3. Summary of mean abundances (µN - fish m" ) and lengths (µL - mm), total number of samples, mean water depth, total number of species, abundance (fish m· ) 2 and biomass (g m· ) of fishes among habitats (forest, edge, mudflat). f<'igures in parenthesis represent standard errors. "' only I fish caught. J juvenile and A adult lifestages (based on sizes given by Gomon et al. 1994). From Hindell and Jenkins (2005) Pop net

Forest Edge MudAat Species µN µL µN µL µN µL Aldricheua forsterl

Arenig(lbi11sJrer1atus' A 0.029 (0.017) 36.2 (1.7) 0.09 1 (0.037) 38.7 (3.2) 0.063 (0.027) 43.4 (3.1) Arripis truttaJ 0.006 (0.006) 75.0 (*) Arripls mmaceus' 0.006 (0.006) 65.0 Atherinasoma microstoma' '- 0.246 (0.099) 20.4 (0.5) 0.154 (0.078) 20.1 ( I.I)

Fa1•011igobiuslareralis J " 0.126 (0.050) 30.8 (2.4) 0.120 (0.033) 29.9 (2.2) Gobioptems semivestitus" 0.011 (0.011) 19.0 (1.0)

Mugilogobius plat;.·1wt11l.A 0.171 (0.035) 27.8 (1.3) 0.006 (0.006) 40.0 (8 )

1 Nesogobi11s~p. 1 " - 0.017 (0.017) 17.0 (0.6) Omobri111ch11sa11 0//11.1" 0.006 (0.006) 54.0 (*) Pseudogobius sp.'• 1.480 (0.273) 20.9 (0.2) 0.714 (0.310) 20.7 (0.3) 0.011 (0.01 1) 23.0 (2.0)

Rhombosolea 1apiri11a•A 0.017 (0.008) 20.7 (2.3) 0.029 (0.011) 36.0 ( 1.6) 0.023 (0.017) 22.9 (2.3) Sillaginodes punctata1 0.080 (0.023) 27.S (l.2) 0.034 (0.024) 115.5 (4.2) Sipliaemia cephatores" 0.006 (0.006) 41.0 (*)

Terrammos glaber" 0.023 (0.012) 98.5 (2.4) 0.1R3 (0.081) 85.8 (3.6) 0.120 (0.062) 98.8 (2.5)

Total "amples 7 7 7 Mean water depth (cm) 0.6 (0.3) 0.9 (0.2) 0.9 (0.2) Tomi Species 8 12 6 2 Total Abundance (fi~hm· ) 13.8 9.9 2.6 2 Total Biomass (g m' ) 8.4 32.5 28.4

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 25 Distribution, biology and ecology of the Pale Mangrove Coby

6 Survey of current distribution and biology of Mugilogobius platynotus 6.1 Introduction The material presented in Se.ctions 1 to 5 of this report provided detailed information on what is currentl y known of the taxonomy, biology and ecology of Mugilogobius platynotus in southeastern Australia. This section provides information on the current distribution of M. platynotus in Port Phillip Bay and Western Port, based on targeted sampling. This section also provides some preliminary findings on the age, sex structure and fecundity of M. Platynotus collected from Western Port.

6.2 Materials and methods

6.2.1 Survey All fish surveys were done between November 2007 and May 2008. Earlier studies demonstrated that fyke and pop nets were best suited to sampling Mugilogobius platynotus. Additionally, the success of bait traps in sampling M. platynotus was evaluated, as was the effects of net orientation for fyke nets. The results of these evaluations indicated that bait traps did not catch M. platynotus, regardless of where within a mangrove forest they were set. However, the orientation of the fyke net strongly influenced the catches of fish, with nets set perpendicular to the shoreline catching around twice the number of fish as those set parallel. Subsequent sampling used fyke nets set perpendicular to the shoreline with the entrance of the net facing shoreward. Fish assemblages, focussing on Mugilogobius platynolus, were sampled using fine­ mesh, single-wing fyke nets set at 18 of the 20 previously selected potential sites (see section 4.3); four in Port Phillip Bay and 14 in Western Port (Table 4). Three sites (Saltwater Creek, Mordialloc Creek and the Werribee River) did not have mangroves, and, of these, only Saltwater Creek was sampled (Figure 13; Table 4). Each fyke net consisted of four aluminium rings with a D-shaped entrance ring and were made from 5 mm knotless mesh. A single, two-tiered design was used to address questions about I) broad-scale (bay­ wide), and 2) fine-scale (within mangrove forest) di stribution patterns of Mugilogobius platynotus. First, to assess broad-scale distributions, fyke nets were set wi thin patches of mangrove forest at all 18 sites (Table 4). Second, to assess fine­ scale distributions, at 10 of the sites (only in Western Port) fyke nets were also set along the seaward edge of the mangrove forest (Table 4). Four or five fyke nets were set and retrieved two hours before and after high tide, respectively at each site. Each net was separated by at least 30 m. One site was sampled on a given day. The timing of net-sets between sites varied between sites because of changes in the timing of high tides, but most sites were sampled between midday and early evening. All fish caught in the nets were identified to species and counted.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 26 Distribution, biology and ecology ofth e Pale Mangrove Coby

6.2.2 Size and age structure of Mugilogohius platynotus The total length (nun) and weight (0. l g) of indi viduals were measured and recorded where possible. Otoliths were dissected from the fish and sent to the Central Aging Facility in Queenscliff for aging. Based on other studies of goby ageing we assumed that Mugilogobius platynotus were most likely around 1 year of age. Therefore, we initially investigated daily growth rings on sagittal otoliths for 20 samples (individual fish). The micro-increments were clear for the first 50-60 rings, but difficull to count after this period, raising some uncertainty as to whether the rings we were counting were daily rings. We then decided to prepare otoliths by transverse sectioning (which was not easy with otoliths so small). This preparation revealed opaque growth increments which looked as if they were being laid down on a cycle, which may or may not be annual.

6.2.3 Sex structure and fecundity Using samples that had been collected previously (Raadik, T.A., ARI collection), the sex of M. platynotus individuals wac; determined using a combination of macro­ features of gonads (e.g. presence of eggs) and external morphological features (e.g. genital papilla - see Section 2.6). The genital papillae were assessed for shape and degree of pigmentation. Male papillae were elongate and appeared to be more heavily pigmented; female papillae were shorter, with a rounded, blunt end, and they were generally less pigmented. Gonads were then dissected from fish and identified as male or female. The sex category given to each fish from evaluating the gonad structure was then compared to that defined by the genital papillae. There was 100% agreement between the two methods. Female gonadal material was then weighed and recorded (Table 5). Female gonadal weights were expressed as a percentage of total fish weight (from Section 6.2.2 above). Where possible, the number of eggs within each gonad was counted.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 27 Distribution, biology and ecology of the Pale Mangrove Coby

A

e Not sampled

I!!!! Mangrove$ Q Sallma<•h J------t-- 0 lntortidal mudfl

O 30 60 Kiiometers 1!!!!!!!!!!!'!!!!!!5iiiiiiiiiiiiiiiiiiiiiiii!!!!!!!!!!!!!!!!!!!!!'!!!!!!!'!!!~iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii~

10 0 10 20 l

Figure 13. Location of sampling sites with A) Port Phillip Bay and B) Western Port.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 28 Distribution, biology and ecology of the Pale Mangrove Gaby

Table 4. Summary or sampling locations. *"' site sampled, but no mangroves present. Mangrove Bay Sampled Site Edge Forest Pon Phillip Hovells Creek .,/ .,/ Kororoit Creek .,/ Stony Creek Backwash Stony Point .,/ .,/ Western Port Blind Bight .,/ .,/ .,/ Churchill Island .,/ Deep Creek .,/ French Island - east French Island - north .,/ French Island - northeast .,/ French Island - west .,/ .,/ .,/ .,/ Hastings .,/ .,/ Jacks Beach .,/ .,/ Rh yll Inlet Tooradin ./ .,/ Warneet ./ .,/ .,/ .,/ Wooleys Beach Saltwaier Creek**

6.3 Results and Discussion

6.3.1 Distribution of Mugilogobius platynotus Mugilogobius platynotus were primarily sampled from within mangrove forests (Figure 14), and only found in Western Port. They were uncommon along the seaward edge of mangroves, despite all other mangrove-associated species being present in this habitat. These data suggest that non-edge areas of mangroves are a critical habitat for this threatened species, and the fragmentation of mangrove habitat is likely to reduce overaH habitat for M. platynotus as a consequence of increased perimeter-to­ area ratios. Of the 14 sites sampled in Western Port (Table 4), Mugilogobius platynotus were found only at sites on the western and northern shores (including the northwestern area of French Island, Table 6). M. platynotus were not found in mangroves on Phillip Island nor were they sampled from Saltwater Creek (also on Phillip Island). Previously a single M. platynotus was sampled from mangroves in the vicinity of Newhaven on Phillip Island (Hindell unpublished data), however re-sampling of this area in the current study did not find any fish. Previously, Jenkins and Hatton (2005) used pop nets to assess whether M. platynotus were present in mangroves of Comer Inlet/Nooramunga, however, they were not able to find any fi sh, and could not refute the proposition that M. paludis (platynotus) occurs only in Western Po1t (within Victoria). Similarly, Hindell and Jenkins (2004) also noted an absence of M. platynotus from samples taken from mangroves of Corner

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Inlet over a two year period (although they only captured a single fish over unvegetated mud in Western Port). Given that no fish were sampled from Port Phillip Bay in the current study, previous studies and the data presented here suggest that M. platynotus has a very limited distribution, and is currently only known from a reasonably restricted area of a single embayment in central coastal Victoria.

J!'igure 14. The interior region of a forest of A vicenni.a marina. Note the fyke net set to the left of picture and the seaward edge of the mangroves in the dis tance. Mugilogobius platynotus were sampled almost exclusively from these types of environments within the mangrove forest. (J eremy S. Hindell)

The current study strongly suggests that mangrove forests, and not the edges of this habitat, are important for M. platynotus. This pattern is consistent with previous work by Hindel1 and Jenkins (2005), which found that Mugilogobius platynotus occurred almost exclusively within the forested area of mangroves, and were unconunon in adjacent habitats and along the mangrove fringe. Recent work by McGuckin (2008), together with sampling by Raadik (unpublished data) in 2004, however, indicate that

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 30 Distribution, biology and ecology of the Pale Mangrove Coby

M. platynotus may be among the most common fishes using areas of shallow water within saltmursh-dominated areas landward of mangroves (Figure 15).

Figure 15. Upper reaches of Tankerton Creek estuary, French Island, November 2004. (Tarmo A. Raadik).

Additionally, the fish sampled in the present study were all reasonably small, with lengths rarely exceeding 30 mm (Table 5). This is in contrast to fish sampled by McGuckin (2008), and Raadik (unpublished data), where individuals ranged in size up to ac least 60 mm. Local distributions of M. platynotus may not be as habitat­ specific as the present study indicates, and there may be some age- or size-based change in habitat association through time, whereby younger/smaller fish reside primarily within the mangroves, and larger/older fish inhabit waters within saltmarsh dominated areas (or at the saltmarsh/mangrove interface). Additional work on micro­ habitat preferences of this species would improve understanding of the degree to which both saltmarsh and mangrove dominated habitats support this species.

Specific habitat attributes in the direct vicinity of each net, such as sediment structure, length and density of pneumatophores, and overgrowth of pnuematophores by algae, were not recorded in the present study. However, general observations indicated that M. platynotus were found in habitats ranging from solid sandy substratum, in which pneumatophores were generally short (< 10 cm long) to very fine, muddy sediments where pneumatophores were long (> 20 cm) and covered by algae and grazing invertebrates. These anecdotal data suggest that while M. platynotus prefer mangrove forests to adjacent habitats, they may be more flexible about very fine-scale (meters) habitat structure.

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6.3.2 Biology of Mugilogobius platynotus The present study focussed on mapping the distribution of Mugilosobius platynotus in Western Port and Port Phillip Bay, however, opportunities to advance understanding of the basic biology for this species were also taken. Specifically, samples of M. platynotus were dissected so that their reproductive condition could be qualified (based on egg counts and gonad-to-weight ratios) and their age (yet to be validated for otoliths) measured.

More female fish were sampled in the present study than males (~ 19 :&' 12). As in Section 2.6, the genital papillae appear to be a strong indicator of sex for this species. Average lenglhs and weights of male fish were slightly greater than those of females (Figure 16), although length-to-weight distributions were generally overlapping for samples collected in the present study. Anecdotally, the lengths of fish measured in the present study appear to be significantly shorter than those of Raadik (unpublished data), and McGuck.in (2008). Female gonads may have up to 2000 eggs, with up to 25% of their weight contributed by gonadal material (Figure 16), however, it is not clear from static egg counts how fecundity might be di spersed over a season. The higher egg counts were seen in females collected from November through to February, suggesting a summer spawning period for this species, however we have not assessed reproductive condition of fish caught at other times of the year. If we assume that the increments observed from the transverse sectioning of otoliths are being laid-down on an annual cycle (Figures 17 & 18), then the largest fish for which otoliths were prepared (::::: 45 mm in length) was estimated at 9 yrs. Previous work on the ageing of gobies indicates that this is an unusually long longevity for gobiids of any species. There is a need to look at the otoliths of larger fish to assess whether there is some consistency in the age estimate for the single large individual assessed here. Additionally, some level of validation of the daily growth rings would help to resolve whether it is likely that these fish could possibly be surviving to ages up to nine years.

6.3.3 Morphology of Mugilogobius platynotus Specimens of M. platynotus were examined in greater detail to refine external morphological characteristics that could distinguish between the sexes. in addi tion to those provided in section 2.6. SpecificalJy, the flexible spines of the first dorsal fin extended from 2 to 4 mm above the fin membrane connecting the spines in the first dorsal fin for males, while the first dorsal fin spines extended only around 1 mm above the fin membrane in females (see Figure 19 for a photograph of a male Mugilogobius platynotus). In addition, the previous description of male and female spawning papilla in (Larson 2001) can be expanded to: male genital papilla moderately to heavily pigmented, elongate and triangular, flattened and with a pointed, slightly bi-lobed posterior tip; in females lightly pigmented, short and bulbous, with a rounded posterior end.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 32 Distribution, biology and ecology of th e Pale Mangrove Coby

4 3 I .s:::. (/) I :;:::: a Female e Male zci l __ 2500

2000 • tJ) O> O> 1500· (I) • zci 1000 500 .••

--~ 2.5 § 1: 2.0 I O> ~ I ·~ 1.5 j .s:::. ~ n1 • 0 010.5 L • ...... s ~· •• ., 1: 30 O> a> 25 3 ~ I .c (/) 20 15 .9 • • 'Oco 10 c 0 • g> SL _j 0~ • ....- 2.5 .- . § 1: 2.0 ~ • ~ O> 'Ci) 1.5 I ~ .s:::. (/) 1.0 ~ (ij 0.5 ••• .....0 .... 0 10 20 30 40 50 60 Standard length of fish (mm)

Figure 16. Relationships between length and abundance, number of eggs, fish weight, and gonad· to-fish weight for male and female Mugilogobi.us platynotus.

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Figure 17. l\ilicro-structure of sagitta.l otolith of Mugilogobius plaJyJZotus. Increments are unvalidated, but assumed to represent daily growth rings.

Figure 18. Opaque growth increments viewed on a sagittal otolith prepared via transverse section. Opaque increments arc unvalidated, but assumed to represent yearly growth rings.

Arthur Rylah Institute for En vironmental Research Technical Report Series No. 2008/89 34 Disrriburion, biowgy and ecology of the Pale Mangrove Goby

Figure 19. A male Mugilogobitts platynotus. (Tarmo A. Raadik)

Table S. Summary of the sex ratio, and average length, weight, number of eggs and percentage gonad to body weight. Sex Measure F M Number of fish 19 12 Total Length (mm) (Avg (range)) 30.6 (22-41) 33.5 (24-48) Fish Weight (g) (Avg (range)) 0.3 (0. 1-0.6) 0.5 (O. l-1.9) Number of Eggs (Avg (range)) 1009 (465-1996) % Gonad to Body Weight (Avg (range)) 6.9 (0-25.9) 1.0 (0.3-2.9)

6.3.4 Fish assemblages In sampling Mugilogobius platynotus, a range of other species were collected (Table 6). These fish were identified to species and counted to improve information on which other species of fi sh may use mangroves in Port Phillip Bay and Western Port. The range of fish sampled in the present study matched those sampled previously by Hindell and Jenkins (2004, 2005). Smooth toadfisb (Tetractenos glaber), Glass Goby (Gobiopterus semivestitus), Eastern bluespot goby (Pseudogobius sp.), and Bridled/Half-bridled gobies (A renigobius spp.) were the most common fishes sampled from mangroves, regardless of whether effort was focussed along the edge or the interior. These species were also common in both embayments. Most of the species sampled were small bodied adults or juvenile stages. As in Hindell and Jenkins (2004, 2005), very few of these species, with the exception of some of the gobiids, are likely to be residents in the mangroves. Eight species sampled from the mangroves support fisheries.

Arthur Rylah Institute for Environmental Research Technical Report Series No. 2008/89 35 Distribution, biology and ecology of the Pale Mangrove Goby

Table 6. Summary of total numbers of fish species sampled at each of the study sites. BB - Blind Bight, CI - Churchill Island, DC - Deep Creek, H - Hastings, HC - Hovels Creek, JB - Jacks Beach, KC - Kororoit Creek. SC - Saltwater Creek, SCB - Stony Creek Backwash, SP- Stony Point, T -Tooradin, W - Wameet, WB - Wooleys Beach, RI - Rhyll Inlet, Fin - French island north, Flw - French Island west, Fie - French Island east, Fln/c- French Island northeast.

Port Western Phillip Port Bay

Data ~ a OC H D ~ D T W WB RI Fin Flw Fie Finfe SCB HC KC Total

Smooth roadfah (Tetracte1ws glaber) 39 101 0 22 8 0 0 8 2 22 4 26 2 1 0 0 0 236 Yellowcye mullet (Aldrichetla forsteri) 2 73 0 3 3 0 0 0 15 0 l 1 6 5 3 0 9 0 121 Rough 1oadfish 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (Contuws brevica11d11s) Globefish 0 0 0 0 0 0 0 0 0 0 0 0 0 (Diodon nicrhemems) 0 0 0 0 0 0

Gla5.~goby (Gobiopterus semivestitus) 7 21 96 51 l 0 0 88 34 2 20 0 0 5 0 0 0 628 953 Eastern bluespot gohy 25 0 I 0 21 34 1449 5 6 20 42 27 9 46 2 I 0 157 1n 1977 (Pse11dogobi11ssp.) Pale mangrove gohy 3 0 I 6 8 0 0 9 14 9 0 0 14 0 0 0 0 0 64 (Mugilogobius platy11otus) Bridled goby 22 0 I 2 0 0 1 4 3 (Arenigobius bifrenatus) 0 6 14 4 0 0 0 0 0 57 Half bridllld goby 15 0 1 5 9 0 0 10 15 13 2 0 0 0 0 0 0 0 70 (Are11igobi11sfre110111s) Shortfin eel 10 1 0 I 0 0 0 J 0 0 0 0 0 0 0 0 0 0 13 (A11g111//a a11srralls) Shortlin .eapike 0 0 0 0 0 0 0 0 0 0 I 0 0 0 0 0 0 0 (Sphyraena 11ovaeholla11diat) Smallmoutb hardy head 0 0 0 0 0 1766 2 2 0 21 6 0 97 (Atherinosoma microsroma) 0 0 0 211 0 2 105

Sandy ~pral 0 4 0 I 0 0 0 0 0 0 0 0 0 0 5 (Hyperlophus vi"aws) 0 0 0 0 Westcm Aus1raliun salmon 0 2 0 0 0 0 0 I 0 (A rripis truttacea) 0 0 0 0 0 0 6 Aachead gudgeon 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 I 21 22 (Philypnt>don grandiceps) Black brt:am 0 0 0 0 I 0 0 0 0 0 0 0 0 0 0 0 I 4 6

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(Acat1thopagrus b111cheri) Oyster blenny 0 0 0 0 5 0 0 I 3 I 0 I 2 0 0 0 0 0 13 (Omobmnchus anoli11s) Ulue sprat 0 0 0 0 0 0 0 0 I 0 0 0 0 0 (Sprarelloides rob11st11s) 0 0 0 0 King George whiting 0 0 0 0 7 0 0 0 0 0 7 (Sillagi11odes pum:tata) 0 0 0 0 0 0 0 0 Skipjack trevally (Pseudocaranx wrighti) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Yellowtin goby 3 0 0 0 0 0 0 0 3 (Aca11thogobi1isjlaviman11s) 0 0 0 0 0 0 0 0 0 0 Silverfish 0 0 0 (uptatherina presbyteroides) 0 0 0 0 6 135 5 0 2 0 0 0 0 0 0 148 Girdled goby I 0 0 0 I 0 0 0 3 0 0 0 0 0 0 0 0 5 (Nesogobius sp. l) 0 Greenback flounder (Rhomboso/eo rapirina) 0 0 0 0 I 0 0 0 0 3 0 0 0 0 0 0 0 0 4 Tamar river goby 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (Af11rcagobi11stamorensis) Australian anchovy 0 0 0 0 0 0 0 0 0 0 0 (Engra11lis a11srralis) 0 0 0 0 0 0 0 0

Eastern Gambu~ia I 0 0 0 0 0 0 0 0 0 0 0 (.Qamb11sia/10/brooki) 0 0 0 0 0 0

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7 Conclusions and Recommendations The present study provides a snapshot of fish assemblages using mangroves during high tide periods, and in doing so provides a basis for assessing the distribution of Victoria's onJy threatened estuarine fish, Mugilogobius platynotus, in Port Phillip Bay and Western Port. Mugilogobius platynotus was only found associated with mangroves in the western and northern regions of Western Port in the present study, though it has previously been recorded in the east and south-east of the embayment. More specifically, this species wao;; predominantly found within mangrove forests, and was uncommon along the edges of mangroves. The relatively small range over which M . platynotus has been found, together with their apparent preference for specific areas within a single habitat type (i.e. mangroves forests or shallow water within saltmarsh), make this species highly susceptible to habitat degradation. Future studies should assess the degree to which M. platynotus move within and among sheltered pools in mangroves and adjacent saltmarshes. The high affinity for areas within mangroves forests means that this species will be particularly susceptible to habitat fragmentation and Joss of mangroves in Western Port. The present study reiterated that male and female Mugilogobius platynotus may be separated by gross external morphological features, supporting the separation based on genital papillae. Differences in the height and structure of the first dorsal fin also differentiate sexes. Females appear to be ready to spawn in summer, and individuals may carry up to 2000 eggs at a time. The assessment of age from otolith rnicro­ structure and opaque growth rings suggested that fish were more than a year old with longevity possibly up to 9 years. This longevity is uncommon for small fish such as gobiids, and additional studies need to be undertaken to validate the cycles over which micro-structural rings and opaque zones are laid down. Future work on tbis species should focus on: • Assessing their presence and abundance in areas outside of this present study (i.e. Corner lnlet-Nooramunga, Barwon River estuary), • Re-assessing their presence and abundance in the south and south-east of Western Port with more intensive sampling, • Deciphering seasonal changes in abundance, • Identifying specific sources of refuge during low tidal periods, • Investigating linkages and movements across habitats of mid to high intertidal regions, and • Validating ageing. The reproductive behaviour of this species, especially with regards to egg production and distribution, and larval ecology would also provide much needed information to inform conservation measures for this species. The listing of Mugilogobius platynotus as a threatened species under the Victorian Flora an.d Fauna Guarantee Act 1988 is a valid and much needed mechanism of protection for a species with specific and localised preferences for habitat such as mangroves (and saltmarshes). This is particularly pertinent as these habitats are under increasing pressure from urbanisation, industrial development, pollution and sea level rise.

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