3 What are the pressures?

Pressures on the coast, estuaries and adjacent marine waters result from both land-based and marine-based human activities, as well as broader global influences such as climate change.

3.1 Land-based activities

More than 90% of South Australians live within 50 kilometres of the coast (ABS 2002), and approximately 75% live in greater Adelaide. Many commercial, industrial and recreational activities benefit from South Australia’s diverse coastal and marine resources. This inevitably comes at some environmental cost (see Box 1), in the form of pollution, erosion, degradation of habitats, introduction of pests and unsustainable use of some resources. Unless these impacts are well managed, including for their cumulative impacts, the ability of the coastal and marine environment to sustain the varied economic and recreational benefits may be compromised.

Uses such as recreational boating, shipping traffic and aquaculture are increasing. Most fisheries are fully fished, and some are overfished. The growing number of coastal developments along the coastline includes regional boating facilities, public access points, offshore aquaculture, marinas and boat ramps. Sediments from erosion or run-off, and nutrients or toxins from effluent, stormwater, industry and agriculture persist in the marine environment, entering and changing the food web of the entire underwater world and influencing many biological systems (Figure 6).

Box 1 Water quality

Water quality in coastal and estuarine areas is greatly affected by how the surrounding area is used. Major land uses in coastal catchments that affect estuaries and coastal waters include pastoralism, cropping, horticulture, sea-cage aquaculture and forestry. Additionally, stormwater, wastewater treatment plants, and sewage treatment and effluent disposal systems in coastal towns discharge substantial quantities of nutrients, heavy metals, microbiological loads and organic matter into estuaries and coastal waters.

These pressures have influenced several of the state’s estuaries and coastal waters. For example, breakdown of organic matter in the Inman River estuary sediments and nutrient processing cause high levels of ammonia in the estuary (above 40 milligrams per litre). This is toxic to numerous species, particularly fish species, and can cause algal blooms. The Onkaparinga and Cygnet estuaries also receive excessive amounts of nutrients and organic matter.

Seagrass losses in Nepean Bay and Boston Bay are likely to be due to high nutrient levels. Seagrass and mangrove losses in the Spencer Gulf coastal waters have been attributed to a combination of nutrient enrichment, industrial pollution and climatic conditions. It is also likely that at least some of the seagrass loss in Rivoli Bay (in the south-east) is attributable to discharges of agricultural drainage water from Lake George (Wear et al. 2006).

Conceptual model of typical pressures and impacts on coastal and marine environments. Pressures include human interaction, climate change and erosion.

Figure 6 Pressures and impacts on coastal and marine environments

3.2 Aquaculture

Aquaculture production in South Australia increased from 3883 tonnes in 1997 to 13 548 tonnes in 2002 and 20 549 tonnes in 2010. In 2010–11, aquaculture contributed $90 172 million to the gross state product (Figure 7). Approximately 70% of this was generated in regional South Australia (EconSearch 2012).

There are approximately 650 individual aquaculture licensees farming a variety of marine and freshwater species, including southern bluefin tuna, yellowtail kingfish, abalone, oysters, yabbies and marron, barramundi and algae.

There is evidence that the abundance and distribution of certain seabirds and marine vertebrates have markedly increased because of human activities in the marine environment, particularly refuse discharge and fishery discards (Harrison 2003). As a result of the increase in food entering the water, adverse interactions with marine vertebrates have been reported, albeit rarely.

Wildlife interactions that might occur with some marine farming include interactions with seabirds, sharks and protected marine mammals (Harrison 2003).

3.2.1 Tuna

Southern bluefin tuna accounts for 53% of South Australia’s gross value of production (GVP) from aquaculture (EconSearch 2011). In recent years, production has risen steadily; it is projected to continue to increase by 10% in 2011–12 and 20% in 2012–13 (EconSearch 2011). The pressures on the marine environment from tuna farming include increased nitrification, co-infection from parasites and marine debris.

Australia is a member of the Commission for the Conservation of Southern Bluefin Tuna, which was established in 1993 to protect the species from overfishing. A 2011 stock assessment showed that the spawning stock biomass remains relatively low, but that the outlook for the stock is positive (CCSBT 2011).

Graph of the value and weight of South Australian aquaculture between 1995 and 2010 showing an increasing trend.

Source: Department of Primary Industries and Regions South Australia, Fisheries and Aquaculture, unpublished data

Figure 7 South Australian aquaculture development, 2008–12 and planned

3.2.2 Finfish

Yellowtail kingfish contribute 14% of South Australia’s total aquaculture GVP (EconSearch 2011). Reporting requirements have revealed that escapes of stock can occur from finfish-licensed holding cages. A report by Fowler et al. (2003) concluded that escaped yellowtail kingfish, when recaptured, exhibit poor health and do not seem to survive for long. Therefore, it is not anticipated that escapes have long-lasting ecological impacts. Other pressures from finfish farming are similar to those for southern bluefin tuna farming, described above.

3.2.3 Subtidal shellfish

Blue mussels and greenlip abalone are the farmed subtidal shellfish species. Culture techniques for both species vary; they include contained and uncontained longlines, and benthic structures to harbour stock to grow out and harvest. Collectively, the subtidal shellfish culture sector contributes 8% of aquaculture GVP in South Australia. Subtidal shellfish has more than doubled in value since 2003, and the value is projected to grow by approximately 19.5% per year over the next three years (EconSearch 2011). As with southern bluefin tuna and marine finfish, the accidental loss and/or disposal of debris related to subtidal shellfish aquaculture is recognised as an environmental pressure.

3.2.4 Intertidal shellfish

Intertidal shellfish culture is the farming of Pacific oysters. Oyster farms mostly use hanging baskets or, far less commonly, fixed ‘rack and rail’ systems within the intertidal zone to contain stock to grow out and harvest. Collectively, the intertidal shellfish culture sector contributes 18% of aquaculture GVP in South Australia. Intertidal shellfish farming has more than doubled in value since 2003, and the value is projected to grow by approximately 10% per year over the next three years (EconSearch 2011).

Because Pacific oysters are exotic to South Australian waters, concern has been raised over the establishment of wild populations. Small populations of wild Pacific oysters were reported for the first time in Franklin Harbour and Denial Bay in 1990. The pressures from these feral populations include competition for food and space with native oysters (Ostrea angasi) and other filter feeders (Wear et al. 2004).

3.2.5 Land-based aquaculture

Land-based aquaculture in South Australia comprises predominantly abalone, finfish species, yabbies and marron. Pressures from land-based aquaculture include nutrient discharge to coastal or freshwater environments, the potential spread of disease to native flora and fauna populations, and the threat of escape of stock into natural waterways.

3.3 Fishing

During 2009–10, the total volume of production of South Australia’s commercial wild fisheries was 47 581 tonnes, worth an estimated $202 million. This represented an increase in production of 24% (9102 tonnes) since 2008–09 (Knight and Tsolos 2011). Aquatic resources are finite, and there is a risk that continued overexploitation might lead to irreparable damage to the aquatic environment. Fishing also brings economic and social benefits to the state that could be lost if aquatic resources are harvested at unsustainable levels.

Species targeted by commercial and recreational fishing play important roles in their marine ecosystems, and overfishing has the potential to reduce biodiversity and impact negatively on ecosystems. Bycatch of commercial fishing must also be managed to minimise the footprint that fishing places on the aquatic environment.

South Australian commercial fisheries include the following:

  • Snapper: Snapper is highly valued by both commercial and recreational fishers, and South Australia is the major contributor to the national catch. In spite of a large increase in targeted longline effort for snapper, stocks were assessed as healthy and at sustainable levels in 2008–09, except for the southern Spencer Gulf, where the biomass was considered low (Fowler et al. 2010).
  • King George whiting: King George whiting is considered an ‘icon’ species of South Australia, and is heavily targeted by both recreational and commercial fishers. The latest stock assessment report, published in July 2011, stated that the fishery has been stable for several years, and that there is no immediate need to reconsider management arrangements (Fowler et al. 2011). The statewide catch of King George whiting is split evenly between recreational and commercial fishers (Jones 2009).
  • Pipi (Goolwa cockle): The pipi fishery moved to a quota management system in 2007 to address sustainability concerns, following years of increasing catch effort and decreasing catch rates. A limit of 300 tonnes was set for the 2009–10 fishing season, increasing to 400 tonnes for the 2011–12 fishing season.
  • Southern rock lobster: Following a decline in numbers of southern rock lobster, there have been positive signs for recovery of the species in recent years. Effort and fishing days have substantially decreased, while catch per unit effort has considerably increased. Despite this, the fishery faces continuing challenges to ensure healthy levels of recruitment (Linnane et al. 2011).
  • Greenlip and blacklip abalone: The total commercial catch of abalone from South Australian waters is about 870 tonnes per year. The recreational take of abalone was estimated at less than 10 tonnes in
    2007–08 (Jones 2009). Recent catches are at sustainable levels across the fishery (Mayfield et al. 2008, Mayfield and Hogg 2011, Stobart et al. 2011).
  • Australian sardine: The South Australian sardine fishery is the largest South Australian fishery by volume of catch. Evidence indicates that catches are at sustainable levels, with the level of spawning biomass being within the target range (Ward et al. 2010).
  • Western king prawn: Historical reductions in effort, relatively stable catches and increases in prawn size over time suggest that the Spencer Gulf prawn fishery is being fished within sustainable limits (Dixon et al. 2010). The Gulf St Vincent prawn fishery has experienced a decline in biomass, which is likely to have reduced the potential egg production for the fishery (Dixon et al. 2011), and a recovery strategy for the gulf is in place. Spencer Gulf catches have remained stable since the 1973–74 season, with catches ranging from 1048 to 2522 tonnes. West coast fishing is more opportunistic, with annual catches generally less than 200 tonnes since 1990–91.

Details on other fisheries are available from the Department of Primary Industries and Regions South Australia (PIRSA) (Knight and Tsolos 2011, Knight and Vainickis 2011).

PIRSA Fisheries and Aquaculture classifies the stocks of commercially exploited species (Table 5) into three categories:

  • Underfished—underutilised and has the potential to sustain harvest levels higher than those currently being taken.
  • Fully fished—harvest levels are at, or close to, optimum sustainable levels. Current fishing pressure is considered sustainable.
  • Overfished—harvest levels are not sustainable and/or yields may be higher in the long term if catch or effort levels are reduced in the short term, or the stock may still be recovering from previous excessive fishing pressure. Recovery strategies will be developed to reduce fishing pressure and ensure that stocks recover to acceptable levels within agreed timeframes.
    Table 5 Fisheries stock status for selected species



    Source: PIRSA (2006)

    Pipi (Lakes and Coorong)

    Fully fished

    Southern Zone southern rock lobster

    Fully fished

    Northern Zone southern rock lobster


    Southern garfish


    Southern calamari

    Fully fished

    King George whiting



    Fully fished

    Giant crab

    Fully fished

    Blue crab

    Fully fished


    Fully fished

    Gulf St Vincent prawn


    Spencer Gulf prawn

    Fully fished

    Southern Zone abalone

    Fully fished

    Central Zone abalone

    Fully fished

    Western Zone abalone

    Fully fished

Fishing activities can interact with threatened, endangered or protected species. Some species have been listed as protected and/or of conservation concern under the Fisheries Management Act 2007 and other environmental legislation, and must not be taken or deliberately interfered with. From data submitted voluntarily by commercial licence holders to the South Australian Research and Development Institute (SARDI), there were 582 incidents involving interactions with 1921 threatened, endangered or protected species in South Australian–managed fisheries during 2009–10 to 2011–12. Of these, 1802 animals were released or escaped, and 119 died. Dolphins accounted for 609 of the animals and 917 individual pinnipeds were involved in interactions. The latter figure is skewed by a large number of seals interacting with fishing in the Lakes and Coorong during 2009–10 and 2010–11. Over the three-year period, 97% of all the encounters involved trawl or net operations (Tsolos and Boyle 2013).

Fishing activities also have the potential to damage habitat. Potential impacts include deployment of illegal artificial reefs, mooring over seagrass beds and damage to reefs from anchors.

3.4 Marine debris

The Environment Protection and Biodiversity Act 1999 (EPBC Act; Cwlth) lists marine debris as a key threatening process: ‘Injury and fatality to vertebrate marine life caused by ingestion of, or entanglement in, harmful marine debris’. Harmful marine debris refers to all plastics and other types of debris from domestic or international sources that might cause harm to vertebrate marine wildlife.

Marine debris continues to be a persistent pressure on the South Australian marine environment. It includes land-sourced plastic garbage (e.g. bags and bottles), ropes, fibreglass, piping, insulation, paints and adhesives; derelict fishing gear from recreational and commercial fishing activities; and ship-sourced, solid, nonbiodegradable floating materials lost or disposed of at sea.

For marine species, entanglement in debris can restrict mobility, leading to starvation. It can also create wounds, infections, and damage to body and limbs, and can facilitate drowning. Debris (e.g. plastic bags, rubber, balloons, plastic fragments and food wrappers) can be ingested by marine wildlife that mistake the debris as prey species. This can affect their digestive systems, causing physical blockage, internal scarring and injuries that lead to starvation and death.

3.5 Pest plants and animals

South Australia’s coastal waters are under increasing threat from a range of marine pest species, resulting from increased vessel traffic. Marine pests can outcompete native species for habitat and food, thereby adversely affecting the ecosystems on which fishing and aquaculture industries depend. Once a pest is well established, eradication is rarely possible, and control is expensive. Biosecurity programs are in place to identify, assess and respond to all pests that pose a threat to our fish stocks and their habitats, and to raise awareness of pests. These pests and the programs to manage them are outlined in the Biodiversity chapter.

Commercial shipping is one of the most commonly recognised marine pest vectors. Recent research by Hewitt and Campbell (2010) suggests that vessel biofouling is a larger contributor (60%) to the translocation of marine pests than ballast water from commercial shipping (24%) in Australia.

South Australia’s shipping industry is an important contributor to the economy—some 500 vessels traverse our waters, making more than 1000 port calls and carrying more than 26.8 million tonnes of product. During 2010–11, South Australia’s commercial ports had a total of 1509 port calls by cargo ships (Figure 8).

Little penguin killed by marine debris at Troubridge Island

Dr Jane McKenzie

Graph of the number of calls of cargo ships at South Australian ports over 10 years to 2011 showing a relatively stable trend over time and 25 per cent increase from 2009–10 to 2010–11.

Source: BITRE (2012)

Figure 8 Number of port calls by cargo ships in South Australia, 2001–02 to 2010–11

Globally, there is a trend towards larger ships that require deeper channels and larger berths, but are more efficient and require fewer trips for any given freight task. The average size of large vessels, including bulk carriers and container vessels, visiting Adelaide has increased (BITRE 2012).

The Australian Government, through the National System for the Prevention and Management of Marine Pest Incursions, and the shipping industry play important roles in preventing the spread of marine pests. Pests are contained primarily by managing ballast water according to Australia’s mandatory ballast water management requirements, and by minimising the amount of biofouling on vessels.

Thirteen of the 99 pest species reported in South Australia since the 1800s are currently listed as trigger species in the marine pest monitoring manual, which means that they are regarded as species of particular concern (Wiltshire et al. 2010). More detailed information on these species is provided in the pest species section of the Biodiversity chapter.

A comprehensive set of management arrangements for domestic ballast water is being developed to complement the existing requirements for international vessels. These arrangements will be consistent with the International Maritime Organization’s International Convention for the Control and Management of Ships’ Ballast Water and Sediments.

The Australian Government is also investigating new biofouling management requirements for vessels arriving in Australian waters. In developing these requirements, the Australian Government has been working with stakeholders to ensure that implementation arrangements are both practical and effective in minimising the biosecurity risk posed by biofouling.

With an expected increase in shipping traffic due to mineral exports and natural growth in other trades, there will be continued focus on risk-based management of the coastal waters.

3.6 Coastal and offshore exploration and production

Coastal and offshore exploration activities include mineral and petroleum exploration and production. Offshore mining has the potential to alter patterns of sediment movement, and affect ecological processes and associated biodiversity. A large number of mineral exploration licences and production leases are located onshore near the coast, and several of the salt and gypsum extraction tenements extend into inland waters. A substantial amount of Spencer Gulf is covered by 16 mineral exploration licence applications. There is one inshore petroleum licence covering most of Gulf St Vincent, but little exploration has occurred under the licence to date, and none in the marine part of it. One application is pending for petroleum exploration in part of Spencer Gulf. A geothermal exploration licence also covers part of Spencer Gulf and a small portion of Guichen Bay in the south-east.

A major offshore seismic survey is being undertaken in the Great Australian Bight. Further seismic exploration is expected, as well as drilling of five deepwater petroleum wells in 2013–14. Seismic surveys have the potential to impact on whales. Baleen whales might be more affected than toothed whales, as their acoustic range is thought to operate in the same frequency as the air-gun pulses used in seismic exploration. Seismic operations are regulated by Commonwealth legislation and guided by the Australian Government’s Guidelines on the application of the Environment Protection and Biodiversity Conservation Act to interactions between offshore seismic operations and larger cetaceans (Environment Australia 2001; revised in 2007) and EPBC Act Policy Statement 2.1—Interaction between offshore seismic exploration and whales, (DEWHA 2008).

Oil-well drilling has the potential to cause spills, which can have major environmental impacts on marine and coastal ecological communities. Lessons have been learnt from past disasters in the Gulf of Mexico and north-west Australia that could reduce the chances that this type of disaster could occur in South Australia.

Pearson Island

Dr Jane McKenzie

3.7 Climate change

Global sea level has risen 0.21 metres over the last century and is continuing to rise (Climate Commission 2013). Coastal infrastructure is particularly vulnerable to the risks of sea level rise caused by climate change. Recognising this, South Australia has led the nation in developing strategic responses to climate change impacts in coastal areas. The Coast Protection Board’s 1991 sea level rise policy (Policy on Coast Protection and New Coastal Development 1991) was incorporated into the Planning Strategy for South Australia and local government development plans in 1994. This policy is currently being updated to reflect more recent projections and analysis.

The consequences of sea level rise could include increased seawater flooding risk, increased coastal erosion, changing distribution of tidal plant communities and rising coastal groundwater levels.

Although changes in sea level are relatively well understood, there is limited information available about the South Australian impacts of other changes in the ocean environment, such as changes in acidity, salinity and temperature due to climate change. Various research initiatives are addressing this gap in knowledge.

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