1370.0 - Measuring Australia's Progress, 2002  
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Contents >> The supplementary commentaries >> Marine ecosystems

Australia's coastal and marine regions support a large range of species, many of them found only in Australian waters. The marine environment is also important to Australian society and the economy. Many of the ways in which we use our oceans, beaches and estuaries can affect the quality of the ocean's water and the diversity of life within it.

There are very few nation-wide time series data suitable for assessing the progress of Australia's marine ecocsystems. At some time in the future, perhaps, better progress indicators might become available. For the time being, this commentary:

  • recognises the importance of the ocean; and
  • describes some of the important influences on the health of our seas (such as fishing, introduced species and water quality).

However, it does not attempt to assess overall progress among Australia's marine ecosystems.

Australia has one of the longest coastlines of any country. The Exclusive Economic Zone, the area surrounding Australia's coast for which Australia has exclusive responsibilities and to which it has exclusive rights, covers 11 million square kilometres (among the biggest of any country in the world). And so it is perhaps not surprising that beaches, estuaries and wider marine ecosystems play an important role in Australian life.

Our seas also support a vast array of life forms. More than 4,000 species of fish live in Australian waters, and about a quarter of them are found nowhere else (most of these are found in southern waters). Australia has the world's largest and most diverse area of seagrasses, largest area of coral reefs and highest diversity of mangrove species. (SEE FOOTNOTE 1)

There are substantial pressures on Australia's marine environment. Over 80% of the population live within 50 kms of the coast (SEE FOOTNOTE 2) and 97% of the volume of Australian trade is carried by ships. (SEE FOOTNOTE 3) In 1998-99 Australian fisheries produced about 230,000 tonnes of fish valued at over $2b, and over 22,000 people were employed in the fishing industry. (SEE FOOTNOTE 4) Over 516,000 people from overseas visited the Great Barrier Reef in 1995. (SEE FOOTNOTE 5)

Fishing, particularly overfishing, places strains on a number of species, and may also affect other species through disruptions to the food chain or accidental catching of other fish, birds, mammals, and turtles. The release of hydrocarbons, waste water and other nutrients can also disrupt marine ecosystems, while the introduction of foreign species into Australian waters has the potential to cause irreversible harm.

To assess progress within our marine ecosystems one would need information on a broad range of issues, and how they are changing over time. For many areas, information on some of these concerns is not available and so a thorough assessment of progress is not possible. Some data are available for many of the more important concerns and these are discussed here.

The Estuarine Condition Index is an indicator that has recently been developed by the National Land and Water Resources Audit (NLWRA). (SEE FOOTNOTE 6) Time series data are not available yet, but in future this index will go a long way towards summarising progress in our marine ecosystems. The index assesses the condition of about 1,000 estuaries around the Australian coast. Because estuaries occur at the borders of marine and freshwater ecosystems, they are influenced by the tides and also by fresh water from the land. And so measuring the condition of estuaries not only reports on the state of our oceans; it sheds light on how land use around the water that flows into the estuary is affecting the sea. The more modified an estuary the greater the pressures on it; in 2000 the NLWRA assessed estuary conditions as:
  • near-pristine - 50%;
  • largely unmodified - 22%;
  • modified - 19%; and
  • extensively modified - 9%.


In 1999 four of the 30 major Commonwealth fisheries were classed as overfished, with the status of another 15 uncertain. (SEE FOOTNOTE 10) (A fishery - the collective enterprise of taking fish - is usually defined by a combination of the species caught (one or several), the gear and/or fishing methods used, and the area of operation.) Information on Commonwealth and State managed fisheries is below. In terms of tonnage and value, Western Australia has the highest State production, and the combined produce of all States was much more than that of Commonwealth managed fisheries.

Over-fishing can occur when the catch rate exceeds the capacity of the natural population to renew itself through reproduction. A number of species have been, or are in danger of being, over-fished.

Fisheries production, value and employment, by State - 1998-99


. .
2 039

Source: Australian Bureau of Agricultural and Resource Economics.(SEE FOOTNOTE 4)

The Southern Bluefin Tuna is an example: a decline in numbers since the late 1950s resulted in the introduction by Australia, New Zealand and Japan of limits on the amount of fish that could be caught. These limits, together with the collapse in fish stocks, contributed to the decline in catches. Experts in Australia believe there is little chance of numbers recovering given the current global catch, whereas Japanese assessments suggest that a recovery is assured. (SEE FOOTNOTE 11)

A decline in catch can point to increasing scarcity. It can also point to reduced fishing effort. But if catch sizes have remained constant, while the effort required to catch fish has increased, the size of the fish stock may also have decreased. In the Southern Shark fishery the annual catch in the late 1990s was similar to that of the 1970s, yet required two to three times the fishing effort. The increase in catch during the 1980s reflects the lifting of a ban on catching larger school sharks. (SEE FOOTNOTE 11)

Fishing for certain species can result in others being caught by accident (so called non-target catch). Species caught in this way include other fish, seaweed, seagrass, crustaceans, mammals, birds and reptiles. Longline fishing, which involves setting baited hooks along a line up to 100km inlength, is a particular threat to several non-target species, especially seabirds. (SEE FOOTNOTE 13) Species of albatross are particularly at risk, not only because of the number of birds caught, but also because of their breeding patterns. Many are now listed as vulnerable by the Commonwealth Government, which put in place a threat abatement plan in 1998 with the aim of reducing bycatch to one bird per 20,000 hooks set, a reduction of 90% over a five year period, through techniques such as setting baits at night when seabirds are less active.(SEE FOOTNOTE 13)

Southern shark fishery catch
Graph - Southern shark fishery catch


The term aquaculture is used for the farming of any aquatic organisms, including fish, molluscs, crustaceans, and aquatic plants. Australian aquaculture, although growing at quite a fast rate, is still a small industry by world standards. In 1999 prawn farming in Australia produced around 2,400 tonnes. In Thailand production increased from 20,000 tonnes in 1984 to 200,000 tonnes in 1999. (SEE FOOTNOTE 7)

Aquaculture could be a viable way to meet the demand for marine products, given the pressure on some fish stocks. But aquaculture places different pressures on the marine environment. Aquaculture often uses fishmeal to feed farmed species; an estimated 2kg of fishmeal are required to produce 1kg of farmed fish or prawns, which places pressure on the fish species used for fishmeal. (SEE FOOTNOTE 8) Moreover, less than 30% of the protein in aquaculture feed is retained by the species farmed; the rest is either not eaten or excreted. (SEE FOOTNOTE 9) This protein adds to the increased nutrient load in coastal waterways, which in turn contributes to problems such as algal blooms. CSIRO is currently researching alternative feeds. (SEE FOOTNOTE 9)


The importance of some whale and dolphin species to the Australian public is reflected in the popularity of activities such as whale watching. The hunting of whales for meat and oils was common in Australian waters from the early 1800s to the mid-1960s. An estimated 26,000 Southern Right Whales were taken from south-eastern Australia and New Zealand before they were protected in 1935, and over 40,000 Humpback Whales were killed in Australia and New Zealand before they were protected worldwide in 1965. (SEE FOOTNOTE 12)

Whales have low birth rates, and their numbers are slow to recover. But conservation efforts have seen numbers of Humpback Whales grow at 10% per year, moving them in 1998 from a Commonwealth endangered species to a vulnerable one. Other species like Blue and Southern Right Whales remain listed as endangered.


Fishing is not the only human activity that affects the biodiversity of Australian waters. Introduced organisms can place native species at risk from predatory behaviour or competition for food. More than 250 species are known to have been introduced into Australian waters. Most are not believed to pose a large threat, but a few have substantially altered habitats and ecosystems. (SEE FOOTNOTE 17)

The accidental introduction of organisms can occur via ballast water. When a ship's hold is empty, ballast water is taken on board to balance the ship. When the ship next loads cargo at port, the ballast water is discharged along with any organisms living in it. In 2001 Australia introduced new regulations making it mandatory for vessels entering Australian waters to undertake some form of treatment of ballast water before discharging it in any Australian port. These new regulations should help protect our marine environment from pest species entering it in this way.

Although many invasive species are difficult to eradicate, the removal of Black Striped Mussels from Darwin Harbour in 1999 was effective, albeit costly. These mussels grow in dense mats and an individual can produce 50,000 offspring in a month. They were probably transported to Darwin on the hull of a yacht.

If established, they could have threatened the biodiversity of surrounding waters, had a major impact on aquaculture, commercial and recreational fishing and could potentially have affected the local port and shipping industries, through the fouling of wharves, marinas and vessels. The mussels' freshwater cousin which behaves similarly, the Zebra Mussel, caused very significant economic and ecological damage to the North American Great Lakes. The removal operation involved treating three infected marinas and numerous vessels that were thought possibly to be infected. (SEE FOOTNOTE 18)


Handfish are found only in Australia and 'walk' on their pectoral and pelvic fins rather than swim. The Spotted Handfish, found only around the lower Derwent River in Tasmania, was once commonly seen and was among the first Australian species known to science. They are now considered to be vulnerable to extinction. The Northern Pacific Seastar, introduced to our waters through either ballast water or hull fouling, feeds on handfish eggs and is a possible cause of their decline. CSIRO is undertaking captive breeding trials and a monitoring program to try to protect the handfish. (SEE FOOTNOTE 14)


Seagrasses are flowering plants growing in marine or estuarine areas, and Australia is home to over half the world's known seagrass species. Although there are few accurate data, experts estimate that some 50% of our seagrass beds have been lost since 1788, though patterns vary around the country. In NSW an estimated 50% of seagrass beds have been lost in recent decades; (SEE FOOTNOTE 1) and at Cockburn Sound in Western Australia, 97% of seagrass beds have been lost. (SEE FOOTNOTE 19) Turbidity, from soil erosion, is believed to be one factor behind the decline (the soil prevents sunlight from reaching the sea bed).

Seagrasses provide food for many marine organisms including green turtles and swans, as well as habitats and nursery areas for many fish and cetaceans. Large scale destruction of seagrass areas could have impacts on the commercial viability of the surrounding fisheries. Dugongs are particularly at risk from the loss of seagrasses, which are the sole source of food for this large marine mammal. The loss of seagrasses, as well as accidental capture in mesh nets, has led to the dramatic decline of some populations of dugongs since 1800. (SEE FOOTNOTE 20)


Australia has two major coral reefs: the Great Barrier Reef, which at 2,500 km long is the largest coral reef system in the world, and Ningaloo Reef in Western Australia which stretches for 230 km. Both are diverse marine systems that are home to many organisms, and provide commercial benefits to Australia, mainly through tourism.

Coral reefs are potentially at risk from international as well as domestic influences. Rising sea temperatures (linked in part by some scientists to greenhouse gases) could place coral reefs at risk from bleaching, which occurs when water temperature exceeds a certain threshold, usually just over 300C. At this threshold algae in the coral tissues are expelled, allowing the white skeleton to show through the clear tissue cover. If the temperature remains high for more than a few weeks the coral will die. Once a reef dies, the habitat it provides for a vast variety of biodiversity is lost. Such an event occurred in 1998, and although Australia was not affected as badly as other regions, bleaching was concentrated in certain areas. For example on Orpheus Island (of the Central Grear Barrier Reef) over 80% of coral became bleached. However, five weeks later, less than 20% of the coral had died. On Pandora Island, 10 km away, there was almost 100% mortality. (SEE FOOTNOTE 15)

Domestic sources placing the Great Barrier Reef at risk are sediment and nutrient runoff (often from land use practices far inland), commercial and recreational fishing, and the coral-eating Crown of Thorns Starfish, which periodically explodes in numbers. Scientists are still unsure what triggers the booms and declines in the starfish's population cycle, although some theorise that overfishing of the starfish's natural predators or increased nutrient levels in the water from pollution are to blame. (SEE FOOTNOTE 16)

Oil spill sightings and national plan responses
Graph - Oil spill sightings and national plan responses

The environmental impact of oil spills depends largely on the location of the accident and prevailing weather conditions at the time: oil spills close to the coast or near areas of high conservation value are likely to cause the greatest damage. Between 1994-95 and 1999-2000 there were almost 2,000 oil spill sightings in Australian waters. Over 90 of these were large and environmentally damaging enough to warrant a National Plan Response (a nationally coordinated cleanup plan).


Experts on the State of the Environment Committee have indicated that the maintenance or restoration of water quality, particularly in coastal waters, is a critical marine environmental issue in Australia in 2001. Although they assess that many coastal areas have excellent water quality, they also assess that many areas do not. (SEE FOOTNOTE 20) Poor water quality can be attributed to many sources, sometimes land use practices far inland that add nutrients to inland waters (such as land clearance or overgrazing which can enhance erosion or the use of agricultural chemicals). Nitrogen and phosphorus are found naturally in inland and coastal waters, but in large quantities they contribute to the increase in estuarine algal blooms. Toxic algal blooms kill fish, and plants can die because of decreased sunlight. They also affect human health by making seafood unsafe to eat and water unfit for recreational purposes.

Sewage discharged into seas releases nutrients and, sometimes, disease-causing micro-organisms, which can make water dangerous to swim in or seafood dangerous to eat. High levels of disease- causing bacteria and viruses can cause problems such as gastroenteritis, respiratory infections and hepatitis.

The improvements in the disposal and treatment of sewage at Sydney's sewage outfalls saw a reduction in levels of certain bacteria, called coliforms, between 1989-90 and 1998-99. None of the 23 beaches tested had a coliform density above health guidelines in the summer of 1998-99. In 1989-90, 11 had exceeded the limit. (SEE FOOTNOTE 21)


1 Zann, L. 1995, Our Sea, Our Future: Major Findings of the State of the Marine Environment Report for Australia, Great Barrier Reef Marine Park Authority for the Department of the Environment, Sport and Territories, Ocean Rescue Program 2000, Townsville.

2 Australian Bureau of Statistics, 1996 Census of Population and Housing, ABS, Canberra.

3 Commonwealth Department of Environment and Heritage 1998, Australia's Ocean Policy, Caring, Understanding, Using Wisely, DEH, Canberra.

4 Australian Bureau of Agricultural and Resource Economics 2000, Australian Fisheries Statistics 1999, ABARE, Canberra.

5 Blamey, R., and Hatch, D. 1998, Profiles and Motivation of Nature-based Tourists Visiting Australia, Bureau of Tourism Research Occasional Paper no. 25, BTR, Canberra.

6 National Land and Water Resources Audit 2002, Estuaries, National Land and Water Resources Audit, Canberra.

7 Preston, N., and Rothlisberg, P. 2000, "Aquaculture; Environmental Impacts'', in Outlook 2000, Oceans Policy, Fishing and Aquaculture, Australian Bureau of Agricultural and Resource Economics conference 29 February to 2 March 2000, Vol. 1, pp. 255-261, ABARE, Canberra.

8 World Resources Institute, United Nations and World Bank 2000, World Resources 1998-99 . A guide to the Global Environment, Oxford University Press, Oxford, New York.

9 Commonwealth Scientific and Industrial Research Organisation, 1998 Information - Aquaculture in Australia, CSIRO. URL: http://www.csiro.au/index.asp?type=faq&id=AquacultureInAustralia&stylesheet =divisionFaq last viewed 19 February 2002.

10 Caton, A., McLoughlin, K., and Staples, D. (eds) 2000 Fishery status reports 1999: Resource Assessments of Australian Commonwealth Fisheries, Bureau of Rural Sciences, Canberra

11 Bureau of Rural Sciences 2000, Fishery Status Report, 1999, BRS, Canberra.

12 Environment Australia 2001, Coasts and Oceans - Marine Species - Whales, Environment Australia, Canberra. URL: erin.gov.au/coasts/species/cetaceans/ whale.html last viewed 19 February 2002.

13 Environment Australia 2000, Threat Abatement Plan for the Incidental Catch (or Bycatch) of Seabirds During Oceanic Longline Fishing Operations, Biodiversity Group, Environment Australia, Canberra.

14 Commonwealth Scientific and Industrial Research Organisation 1998, CSIRO - Information - Australia's First Endangered Marine Fish (Handfish),CSIRO. URL: http://www.csiro.au/index.asp?type=faq&id=SpottedHandfish&stylesheet=divisionFaq last viewed 19 February 2002.

15 Wilkinson, C. (ed.) 2000, Status of Coral Reefs of the World, Global Coral Reef Monitoring Network, Cape Ferguson. URL: http://www.aims.gov.au/pages/research/coral-bleaching/scr2000/scr-00.html last viewed 19 February 2002.

16 State of the Environment Advisory Council 1996, Australia - State of the Environment Report 1996, CSIRO Publishing, Melbourne.

17 Environment Australia 2000, Joint SCC/SCFA National Taskforce on the Prevention and Management of Marine Pest Incursions, Environment Australia, Canberra. URL: http://www.ea.gov.au/coasts/imps/report.html last viewed 19 February 2002.

18 Environment Australia 2000, The Effectiveness of Australia.s Response to the Black Striped Mussel Incursion in Darwin, Australia, Environment Australia, Canberra.

19 Kirkman, H. 1997, "Seagrasses of Australia", in Australia: State of the Environment Technical Paper Series (Estuaries and the Sea), Department of the Environment, Canberra.

20 State of the Environment Committee 2002, Australia - State of the Environment Report 2001, CSIRO Publishing, Melbourne.

21 NSW Environment Protection Authority (NSW EPA) 1999, Beachwatch Annual Report 1998-99, NSW EPA, Canberra. URL: www.epa.nsw.gov.au/beach/annual.htm=divisionFaq last viewed 19 February 2002.

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