Relationships with the Land and Seascape
The Natural Capital of Bays, Inlets and Estuaries
Management Themes
Management Responses

Relationships with the Land and Seascape
Bays, inlets and estuaries are semi-coastal waters where freshwater inputs from catchments blend to varying extents with marine waters. In Victoria, these features are found from the Glenelg River estuary in the west to Mallacoota Inlet in the east. They have biophysical characteristics that distinguish them from riverine and oceanic areas and together they form one of Victoria’s significant bioregions. They have a range of salinity from virtually fresh water to fully marine, lower wave energy than the open coast, restricted water exchange patterns and their floors are generally covered in soft sediments. A number of habitats occur within these systems including sand flats, mud flats and associated drainage channels, seagrass beds, and mangroves. Larger embayments also contain sandy beaches, rocky reefs and islands. Mangroves and intertidal flats only occur within the bays, inlets and estuaries.

There are pronounced differences between the various estuaries, inlets and bays depending on their topography and hydrology. The largest Victorian marine embayment is Port Phillip Bay, which covers 1950 square kilometres and has 250 kilometres of coastline. Sand covers the sea floor along the eastern, western and southern sides, with a large mud area in the middle. Intertidal flats and seagrass beds occur predominantly along the western shore from Altona to Swan Bay. The southern section near Port Phillip Heads has more oceanic characteristics. Western Port covers 680 square kilometres, has two entrances and contains several large islands. It is also a large tidal bay with extensive mudflats and seagrass beds occurring in the north and south-east. Corner Inlet and the Nooramunga are marine barrier island inlets with extensive tidal mudflats, seagrass beds and the southern-most occurrence of the White Mangrove, Avicennia marina, in the world. The Gippsland Lakes, Victoria’s largest estuary, are a series of interconnected lagoons that drain several catchments. A permanent artificial entrance to the estuary was created in 1889.

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The Natural Capital of Bays, Inlets and Estuaries
The flora and fauna vary according to the biophysical characteristics of each bay or inlet. The benthic assemblages in the muddy central region of Port Phillip Bay are distinct from those in adjoining sandy areas to the west and east. The turbid conditions in Western Port allow many subtidal animals to live in shallower water than is usual. A highly diverse intertidal community has developed on the soft basalt reefs near San Remo.

In Port Phillip Bay and Western Port the dominant seagrasses are Zostera muelleri and Heterozostera tasmanica. Posidonia australis occurs in Corner Inlet and the Nooramunga. The small riverine estuaries in western Victoria have an impoverished benthic fauna compared to the larger estuaries with wind-mixed lagoons and lakes in the east. The estuaries of far eastern Victoria are also distinguished by the presence of several warm temperate species, for example peneid prawns and the seagrass Zostera capricorni.

The bays and inlets support a rich invertebrate, fish and bird fauna. For example over a hundred species of fish have been recorded from Victorian bays, inlets and estuaries. Some fish, such as Black Bream, are normally found only in bays, inlets and estuaries, whereas other fish only use these areas during part of their life cycle. Bays, inlets and estuaries are important breeding and nursery areas for several fish of commercial and recreational importance. Islands within the bays support important breeding colonies for species of birds and seals. Intertidal flats and adjacent shorelines provide feeding areas and sheltered roost sites that are needed by large numbers of migratory and resident wading birds and waterfowl. Many of the wetlands are of international significance for migratory birds and nationally important for Australian waterfowl species.

Of the threatened species and ecological communities in this bioregion there are:

• two listed opisthobranchs, neither of which has an Action Statement;
• one listed community has an Action Statement.

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Management Themes
The living resources of our bays, inlets and estuaries were first utilised by indigenous peoples who collected shellfish and trapped fish. Fish and shellfish also nourished the early European settlers. Flat oysters were the target of an early dredge fishery and were over-exploited in many areas. Near shore, fish were caught with hand-hauled seine nets. Commercial fishing expanded with the increasing population and the development of ferry and rail links. By 1890 there was a thriving industry in all major Victorian bays and inlets. Catch levels of these fisheries have been quite variable over this century, with peaks and declines occurring at different times in different inlets. Fishing effort has shifted towards more profitable species as market preferences have changed. Dredging for scallops started in Port Phillip Bay in 1963 but ceased in 1996 due to concerns about the environmental effects of this technique. The main commercial fishing methods currently used in bays and inlets include haul seining, purse seining, mesh (gill) netting, long-lining and hand collection of various invertebrates by divers.

Approximately 14 per cent of Victorians over the age of 14 currently fish for recreation in the major bays and inlets at least once a year. The participation rate has declined in recent years; however, continued improvements in fishing technology and knowledge have probably led to an increase in the overall fish catching capacity. The recreational catch of a number of bay and inlet species (flathead, whiting, garfish, calamari squid, snapper, bream) is potentially equal to or greater than the commercial catch. Illegal harvesting and/or sale of shellfish and illegal netting are thought to be major problems in some of our bays and estuaries.

The farming of blue mussels is the major current significant aquaculture development in the bays. Culture of abalone, flounder and scallops is being developed but attempts to cultivate flat oysters and other species have not so far been as successful as hoped. Aquaculture is expected to increase with improved technology. Environmental impacts from poorly managed aquaculture can include nutrient enrichment at the local to regional scale, pollution from the use of pesticides and therapeutic chemicals, the establishment of feral populations of exotic species, and interference with seabirds and mammals.

Other uses of the bays and inlets include tourism, recreational diving, boating and other water sports and ports and shipping. Ecology based tourism operators offer a range of wildlife watching experiences, particularly in southern Port Phillip Bay. It is likely that tourists will increasingly seek out the experiences of our diverse biodiversity assets and new industries will evolve. Boat ownership in Victoria has doubled in the last 20 years. The effect of boating on sensitive habitats or water quality has not been quantified.

There are four major ports and numerous minor ports and jetties along the Victorian coast, many of which are contained within the bays and inlets. Environmental impacts from shipping and related activities include dredging of the sea floor to maintain channels, the discharge of dredge spoils, the use of toxic antifouling paints, the accidental release of hydrocarbons, the cleaning of fouled ship hulls, and the disposal of ballast water. Shipping activities have introduced numerous species from foreign ports, from hull fouling and the release of ballast water. Over 90 introduced marine plants and animals are now known from Port Phillip Bay, some of which have become pest species. The use of the toxic antifouling paint tributyl-tin has been banned on vessels less than 25 metres long. The in-water cleaning of ship hulls within Victorian ports has also been banned recently.

The major sewerage discharge into our bays is from the Werribee treatment complex into Port Phillip Bay which handles 65 per cent of the domestic sewage from Melbourne. Industrial discharges also occur from several outfalls into Port Phillip Bay and Western Port. There is also runoff pollution from unsewered urban areas, stormwater drains and inappropriate land use practices. High toxicant levels in the sediments of several sites around Port Phillip Bay are a legacy of past industrial pollution. These are likely to decrease with time.

Inadequate management of the associated catchments has compromised the health of our inlets and estuaries. Increased levels of nutrient from sewerage and agricultural practices have led to eutrophication in some areas. Sediment from erosion and urban development has been washed down the rivers and streams to smother seagrass and alter the natural topography. The hydrological regime has been altered in many estuaries by the creation of entrances to the sea through the outer sand bars and the diversion of water from the catchment rivers to agriculture and urban centres. This has led to increased salinity levels and decreased the natural flushing of the inlets. The spread of introduced pests (e.g. Carp, marine fanworms) and weeds (Spartina, Broccoli Weed) have compounded these problems. Poor environmental conditions pose a major threat to the biodiversity of these systems. The large bays appear better able to absorb the increased input of nutrients, although a progressive decrease in nitrogen levels has been recently recommended for Port Phillip Bay.

The bays and inlets are largely in public ownership. Alienated sea floor is confined to areas around some ports and marinas. Leases, licences and similar arrangements cover a range of commercial activities, such as aquaculture, fishing and shipping channel maintenance. Areas have been reserved or proclaimed as Protected Areas in Port Phillip Bay, Shallow and Corner Inlets and the Nooramunga. Fishing is permitted throughout all bays, inlets and estuaries except in the tiny Popes Eye reserve in southern Port Phillip Bay. Current reserves are not comprehensive, adequate or representative of bay and inlet habitats. In recognition of their wetland values, extensive areas in Port Phillip Bay, Western Port and Corner Inlet and the Nooramunga are listed for protection under international agreements such as the Ramsar Convention.

Natural habitats have been modified in many areas. Fringing mangrove and saltmarsh habitats have been cleared. There have been significant declines of various seagrasses in Swan Bay, Western Port, Corner Inlet and the Nooramunga. Soft sediment habitats were extensively disturbed in the past by dredging for scallops and oysters. Localised areas are also affected by dredging and spoil disposal for navigation and beach nourishment purposes.

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Management Responses
Victoria’s bays, inlets and estuaries support a rich diversity of flora and fauna. The public ownership of most of the area allows for the strategy of maintaining the essentially intact ecological processes in these areas. The Victorian Coastal Strategy (1997) provides the framework for management of this bioregion, and the Environment Conservation Council’s investigation will make recommendations on marine park reservation and a range of activities that affect the area.

Like aquatic systems on land, these near-shore areas are affected by the use of land in the catchments that empty into them. Therefore a key management approach is to improve the quality of water that enters the sea from land. Catchment management is as important for these marine areas as it is for the terrestrial bioregions in which it occurs.

There is a strong focus on research into the distribution, conservation status and management requirements of the species and ecological communities that rely on these environments, as they are not as well understood as most terrestrial systems. The recent four year scientific study of Port Phillip Bay is the most comprehensive investigation carried out in this bioregion to date. As such information is gathered, environmental management plans and guidelines for the ecologically sustainable use of the areas and the natural resources they support can be improved.

The early detection and control of introduced plants and animals is a key threat management activity in this bioregion, as it is almost impossible to control infestations in such areas. Efforts to prevent the introduction of exotic organisms through the release of ballast water are also significant in this respect.

The priority management responses for land and water managers and planners are the following:

• Restore the health of our inlets and estuaries through improved catchment management.
• Prevent the establishment and control the presence of noxious marine species.
• Reduce theft and illegal fishing methods through education and enforcement.
• Increase understanding, protection and monitoring of vulnerable habitats, particularly seagrass, mangroves and saltmarsh.
• Promote ecologically sensitive tourism that is based on maintaining the long-term health of the biological assets and minimising disruption to populations (e.g. dolphin watching).
• Increase the understanding and protection of vulnerable and threatened species, and significant sites such as seabird breeding locations.
• Ensure the ecologically sustainable harvesting and management of fisheries resources.
• Encourage the non-extractive use of our living marine resources
• Plan for oil spill contingencies in all bays and inlets
• Improve the environmental quality of the bays and inlets by minimising industrial waste and progressively improving sewage treatment standards.
• Progressively improve dredging and spoil disposal.
• Encourage sustainable and environmentally sensitive aquaculture.