Marine aquaculture

You will need:

• a resource allocation authority for aquaculture
• development approval for aquaculture.

You may need development approval if your proposed development:

• disturbs or destroys marine plants
• impacts a declared fish habitat area
• requires tidal works.

Our industry plans identify pre-assessed locations and guidelines for:

• oyster farming in Moreton Bay
• rack, line, and sea-ranching farms in the Great Sandy Marine Park.

A permit is required to collect broodstock and culture stock from Queensland waters.

Water quality

In river systems, areas of brackish or estuarine water decrease in salinity further upstream. While some species prefer brackish water (such as barramundi), others demand higher salinity and better coastal water (reef fish and snapper).

Salinity levels and water quality can be affected by:

• the size of tides
• rainfall and flooding
• ocean currents and water depth
• suspended solids such as clay and organic matter
• dissolved nutrients and toxic chemicals.

Rack systems

Rack culture in Australia is predominantly used to grow edible rock oysters. The Sydney rock oyster is the main oyster species currently farmed in Queensland waters, with some smaller-scale growth of Blacklip rock oysters.

Design

The industry standard for rack aquaculture in Australia is an adjustable system where oysters are enclosed in plastic mesh bags. These bags are hung from lines suspended between wooden or plastic posts.

Oyster bags are suspended high in the intertidal water column so natural processes can take place beneath.

Adjustable longline systems allow you to raise and lower the oyster bags on the line, allowing the farmer to control shell growth, condition and cleaning.

Environmental impact

Rack culture has minimal impact on the surrounding environment, but the correct location and design is important. Structures should be narrow and well-spaced, so light can penetrate to reduce the impact to seagrass and other benthic (bottom) plants and animals.

Sea cage systems

Sea cages are used for intensive marine aquaculture of:

• barramundi
• cod
• cobia
• coral trout
• lobster
• mulloway
• snapper.

Design

Cage nets are commonly made of nylon mesh. Semi-rigid PVC coated polyester, brass and galvanised steel netting are also used and may be more resistant to biofouling and to prevent predation from sharks and other marine animals.

The type, size and design of cages depends on the species, site conditions and environmental factors.

Sea cage aquaculture has been successful and shown significant economic benefits domestically. In Tasmania and South Australia, financial and technical innovation applied to sea cage culture has allowed the salmon and tuna fish farming industries to expand rapidly.

Environmental impact

Sea cage fin fish culture is considered an ecologically sustainable system when the farm is closely managed and good husbandry practices are followed to minimise effects on the local environment.

Sea ranching production system

These systems are suitable for:

• sea cucumbers (beche de mer)
• scallops.

Scallop and sea cucumber sea ranching is only viable if the:

• culture area is closed to commercial trawl fishing while the animals grow
• animals remain in the specified culture area until harvest.

Scallops are normally grown in deep water and harvested using trawl boats. Sea cucumbers are normally harvested by hand, either by diving or hand-harvesting at low tide in shallow water.

Design

In a sea ranching production system, juveniles (also called spat) feed naturally with no input from the farmer. The environment will provide the animals with all the food they need.

Hatchery-produced or wild-caught juveniles are placed into the natural environment where they are allowed to grow without containment structures. Juveniles are placed on the sea bed, usually in the form of slurry, by a length of pipe or by hand.

Surface line systems

These systems are suitable for:

• pearl oysters
• scallops
• mussels
• tunicates
• seaweeds
• sponges.

Design

In a surface line production system, filter-feeding animals are grown on structures placed in the water column.

These structures are made up of a series of parallel ropes buoyed at the surface with floats and anchored to the sea bed. Animals are grown in panel-style baskets, small cages or on ropes that are suspended below floating surface lines.

Rows of lines and floats are normally visible on the surface but are usually coloured so that they blend into the surroundings.

Environmental impact

Surface line aquaculture is designed to reduce any negative impacts on aquatic wildlife. Lines are kept taut and are well spaced to reduce the risk of entanglement.

The sea bed remains free of obstacles (except for anchor points) and natural processes can take place beneath the farm. If placed correctly, the lines should be adequately spaced to minimise benthic (bottom) disturbance.

Subsurface line systems

These systems are suitable for:

• pearl oysters
• scallops.

Design

In subsurface line systems, the horizontal mainlines and suspended culture panels are positioned well below the surface of the water. Since the mainlines are submerged, vessels are able to move freely over the top of the farm.

The culture panels are held off the seabed by a series of floats along the mainline. The lines and supporting floats are submerged, meaning the only structures visible on the surface are site corner markers, and optional intermittent buoys to mark the location of submerged lines and anchors.

Environmental impact

Submerged lines help protect the cultured animals from the effects of swell and wave action.

As with surface line systems, lines are kept taut and well spaced to allow aquatic wildlife to move freely and reduce the risk of entanglement. Wide spacing of lines allows for flushing and good light penetration to the seabed, so natural processes can take place beneath the lines.