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The value of estuaries

We have long been attracted to estuaries. The middens of Indigenous Australians consist of shellfish and fish bones and are reminders of human reliance on the estuarine environment (e.g. Sydney harbour had middens 40 m high). Since colonial times, we have used estuaries and their connecting network of rivers for transporting agricultural goods for manufacturing and trade.

Estuaries are valued for their scenic beauty, recreation opportunities and their contribution to our quality of life. Estuaries are also valued as places for ports, shipping and industry, agriculture, tourism, cities, and residential development.

Two distinct forms of capital assets are associated with estuaries:

• natura
• capital; and
• human-made capital.

Natural capital

Estuarine ecosystems services such as:

• habitat, spawning and nursery areas for fish;
• habitat and breeding area for birds and native animals;
• nutrient cycling;
• the natural buffer between the land and the ocean provided by salt marshes and mangroves; and
• sediment and nutrient filtration by melaleuca, saltmarsh and mangrove wetlands providing cleaner water to the estuary and near-shore zones.

The quality of these services depends on maintaining estuarine health. Estuarine habitats include wetland areas (tidal mangrove forests and tidal marshes, melaleuca swamps and floodplains, tidal mudflats, seagrass and algal beds, sandy beaches, rocky shores, and the estuary floor) that support recreational and commercial fishing, and aquaculture.

Human-made capital

Human-made capital assets take advantage of natural assets (e.g. sheltered deep water for shipping movement, protected shoreline for industrial and urban development, effluent disposal and dispersion and natural beauty for locating tourist activities) usually modifying them (e.g. port facilities require dredging of estuaries to facilitate shipping movements) to suit the new land use. Human-made capital can operate without a healthy ecosystem; it can be responsible for damaging the ecosystem to the detriment of both natural as well as other human-made capital assets. Trade-offs are part of estuary management and need to be made in recognition of the benefits and costs of all options.

Monetary value of estuaries

Information on the monetary value of the natural capital, and the goods and services provided by estuaries is limited. One attempt has estimated the value of estuaries to be approximately $39 000 per hectare per year (Costanza et al. 1997). This work was constrained by the level of scientific and valuation studies available. The estimate concentrates on the use values rather than the non-use values.

Indicative values for natural capital can be based on production from selected commercial fisheries and the value of expenditure on recreational fishing; values for human-made capital can be based on the value of ports.

Fisheries

Fisheries value information is based on size of catch over a period of time. Changes in catch due to variability in weather conditions, reduction in estuary condition or fishers moving to another site mean that conclusions are difficult to form. More meaningful interpretation of change in fish catch would be possible if information about catch per unit effort, total fish populations and habitat condition were available.

Fisheries can be estuary dependent or estuary opportunist.

Estuary-dependent fisheries are those where the fish or crustaceans are critically dependent on the estuarine environment for the survival of the species. Their continued survival is dependent on estuaries remaining largely unmodified. The total value of Australian estuarine-dependent commercial fisheries has been estimated as about $432 m each year. Estuary-dependent fisheries include:

• prawn fisheries (e.g. northern Australian prawn fishery);
• oyster fisheries (e.g. Sydney rock oyster, a native species of oyster found along the east coast); and
• barramundi and mud crab fisheries along the north east coast and the Gulf of Carpentaria.

Estuary-opportunist fisheries are those where, although fish and crustaceans spend at least a part of their life cycle in an estuarine environment, they could equally use protected marine waters (e.g. as nursery areas) (Potter & Hyndes 1999). They include some species of crab, the Australian herring, salmon and whiting. Their continued survival is not as threatened by the modification of estuaries as estuarine-dependent species. Estuary-opportunist commercial fisheries are worth approximately $40 m each year.

Estuarine dependent commercial fisheries

• The New South Wales oyster industry is estimated to have been worth approximately $29 m in 1999/2000 (valued as landed catch and excluding transport, processing, marketing and retailing of the product). Production between 1997 and 2000 is estimated to have declined by 350 tonnes. Most of this decline is due to poor estuary condition (e.g. bacterial contamination). Exports from the industry are negligible; imports of edible oysters have steadily increased since 1995 to 660 tonnes in 2000 (estimated to be worth over $5 m) (ABARE 2001). The increase in imports of oysters reflects our increasingly limited capacity to cultivate oysters in some New South Wales estuaries due to declining water quality.
• Production of prawns from the northern prawn fishery was worth over $107 m in 1999/2000. Production has declined from 8912 tonnes in 1997/98 to 5605 tonnes in 1999/2000 (ABARE 2001).
• Wild-caught barramundi in 1999/2000 is estimated to have a value (in price paid to fishers at the wharf) of approximately $12 m from the 1800 tonnes harvested from Queensland and Northern Territory. The recreational catch from these areas is about 600 tonnes. At this stage there is no agreement among economists on the correct method to combine the values of commercial and recreational sectors. One approach is to place a value using the equivalent price that commercial fisher would receive. This places a value of about $3. 6 m on the recreational component of the barramundi fishery. Other estimates value the contribution of a single barramundi caught by a recreational fisher to be worth $153 to the economy. This approach would suggest that the recreational fishing of barramundi in Queensland alone could be worth up to $14 m each year.
• Commercial crab production (Queensland, New South Wales, South Australia, Western Australia and Northern Territory) in 1999/2000 was valued at around $42. 3 m. Since 1997/98, the catch has only increased in Queensland and the Northern Territory.

Estuarine opportunist commercial fisheries*

• Queensland: include bream, mullet, snapper, tailor and whiting; valued at $5 m to commercial fishers; production has declined by almost 50% since 1997/98.
• New South Wales: include black and yellowfin bream, Australian salmon, rubberlip morwong, snapper and sand whiting; valued at $6 m; tonnage of harvested fish has declined substantially since 1997/98, from 1039 tonnes to 742 tonnes.
• Victoria: include bream, Australian salmon, King George whiting, pilchards, snapper and sea garfish; valued at $5. 2 m; have remained relatively stable since 1997.
• Tasmania: include Australian salmon, garfish, varieties of morwong and trumpeter fish, school whiting; valued at $1. 5 m; catches have remained relatively stable between 1997 and 2000.
• South Australia: include the Australian salmon, mullet, Australian herring, King George whiting, yellowfin whiting, pilchards, snapper and garfish; estimated to be worth over $14 m.
• Western Australia: include cobbler, sea mullet, yelloweye mullet, Australian herring, Australian salmon and whiting; valued at $4. 5 m.
• Northern Territory: include jewfish, snapper and threadfin salmon; valued at $2 m.

Recreational fisheries

Recreational fisheries values are based on expenditure on fishing activity rather than production (as for commercial fisheries). Australia's recreational fishing industry is worth over $2. 9 billion each year with at least 60% occurs within estuaries. This means that expenditure on recreational fishing in Australian estuaries, excluding flow-on impacts, is approximately $1. 7 billion each year.

• Queensland: fishers are estimated to spend approximately $1000 each year on their fishing activities, including tackle, boats, travel and accommodation. Using these estimates, the contribution to the Queensland economy from individual fishers is approximately $880 m with about $528 m of this attributable to fishers in estuaries.
• Northern Territory: a total of 430 000 days are fished annually by recreational fishers responsible for an estimated $30 m each year of direct expenditure. Information is not available to identify what part of the catch was sourced from estuaries. The most popular recreational species in the Northern Territory, barramundi, is estuarine dependent.
• Western Australia: estimated to contribute over $500 m each year to the State's economy. Approximately 600 000 people or 34% of the population are estimated to fish. The coastal area between Kalbarri and Augusta attracts the highest level of recreational activity in the State with around 380 000 anglers responsible for a catch of between 400 and 500 tonnes each year.

Indigenous fishing

Information about the volume of fish caught in estuarine areas by Australia's indigenous populations is not available. The National Recreational and Indigenous Fishing Survey has been commissioned with the results expected to be released in early 2002.

Port infrastructure and annual revenue

Shipping is an important estuary use with the largest ports located close to State and Territory capitals (Table 20).

• Port Melbourne is the biggest port in Australia, handling $50 billion of trade annually and contributing $5 billion each year to the Victorian economy.
• The value of foreign trade handled at Queensland ports exceeds $14 billion each year.
• Marine-based tourist activities from these key ports are estimated to be in excess of $5 billion each year.

The location of large ports on estuaries has often required substantial dredging of the estuary to facilitate access for large shipping. Industrial waste from shipping has severely damaged the estuarine environment.

Table 20: Estimated value (including property, plant and equipment held by a number of port authorities and operating revenue from these authorities)of some major Australian ports 1999/2000.

Port Authority	Operating revenue ($ m)	Property, plant and equipment ($ m)
Sydney Port Authority	107	485
Melbourne Port Corporation	77	535
South Australian Port Authority	38	85
Fremantle Port Authority	55	88
Port Hedland	12	162
Port of Brisbane Corporation	79	480
Gladstone Port Authority	86	294
Hobart Ports Corporation	16	52
Darwin Port	6	56
Total	476	2237

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