Freshwater aquaculture site selection
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Introduction
The selection of a suitable site together with a good supply of high quality freshwater are essential components for a freshwater aquaculture facility. The majority of production comes from purpose built earthen ponds which can be completely drained. Ponds can vary in shape and size but generally they are rectangular or square to facilitate the management of the water quality and harvesting of the crop. Pond depths and sizes vary with the species being cultivated. Most ponds operate on a 'static' system where water is only exchanged to manage water quality and algae blooms.
The important factors to consider in site selection include:
- Soils;
- Water;
- Topography;
- Environmental considerations; and
- General site location
Soils
Soils need to be impervious (more than 20% clay) to eliminate or minimise the loss of water by seepage. These impervious soils should be close to the surface and extend deep enough to facilitate the construction of both ponds and discharge channels. Soils that have high silt and sand components or contain organic matter may leak, erode easily and present construction problems where pipes are installed through the banks. Soils that contain gravel or sand layers or rock strata formations should be avoided. This also applies to dispersive soils which can lead to wall failure due to erosion and tunnelling. It is preferable to have soils with a neutral pH (6.5 - 7.0). Soils that are acidic or have the potential to be acidic (acid sulphate soils) should be avoided. Soil surveys are advisable before planning pond layouts.
Water
A large volume of good quality water is essential to support an aquaculture operation. Normal sources include farm dams, rivers, impoundments, irrigation channels and underground (bore) water. Chemical laboratories can test samples to determine if the source is of an appropriate quality for aquaculture.
Seasonal changes in the quantity and quality of water should also be considered. Care must be taken with water used from surface sources to ensure that there are no toxic chemicals, such as pesticides, herbicides or heavy metals, present in the water. Water containing high levels of organic matter should also be avoided.
Bore water, and sometimes artesian water, can be excellent for aquaculture. The water is generally free of pathogens, predators, pollution and has a relatively constant temperature all year. However, some bore water can contain excess levels of nitrogen, carbon, total dissolved salts and harmful gases such as methane and minerals such as lead, zinc and iron. Storing and aerating the water can remove the gas (usually carbon dioxide) problems.
Generally, water that is safe for livestock or supports wild fish populations is safe for aquaculture. Domestic water supplies can contain chlorine which is toxic to fish.
Chemical characteristics of water that are desirable for good animal growth include:
- pH - 6.5 to 8.5
- Total Alkalinity - 75 to 250 mg/L (less than 500mg/l as CaCO3)
- Total Hardness - 75 to 250 mg/L (less than 500mg/l as CaCO3)
- Total alkalinity and hardness should not be below 20 mg/L. Freshwater crayfish can be grown successfully above the high levels of hardness and alkalinity listed above.
For more detailed information about Water Quality Parameters for Aquaculture Species refer to DPI&F Notes ISSN - 0155 - 3054 (Nov 2002)
Topography
Pond design (width, depth, orientation) and farm layout (growout areas, building sites, settlement and holding dams) will be influenced by the topography of the land. Pond construction costs can be minimised by building on land with a gentle slope (1% - 3%). The steeper the land the more works that are required and the higher the water pumping costs. With very flat land it is more difficult to design and operate a farm because of the need to have slopes on the pond bottoms to allow complete drainage and to ensure discharge drains from the ponds can transfer water to settlement ponds and holding dams. This water can then be recirculated through the farm or used for irrigation purposes. Land should be above flood levels to prevent the loss of the crop or the translocation of species, which may be non-indigenous to the area, into the natural river system. Land that floods more than one year in 100 should not be considered for growout ponds.
All pond construction should be above 5 metres Australian Height Datum
Environmental considerations
The proximity of the farm to sensitive areas such as national parks, other aquaculture and rural activities and urban development should be considered before selecting a site as these may have an influence on regulatory controls of the activity.
Aquaculture is an Environmentally Relevant Activity and will require an Environmental Authority or approval from the Environmental Protection Agency (EPA) to authorise activities, in particular, but not limited to the discharge of waste water. Developments with less than 5 hectares of ponded surface area and do not discharge wastes to waters of the state do not require this approval. If EPA approval is required EPA will act as a concurrnce agency during the Development Authority application process as defined under the Integrated Planning Act 1997
Water that is drained from ponds during normal water exchanges or from pond harvests contains dissolved nutrients (nitrogen and phosphorus), algae and suspended solids. If this water is discharged directly to waterways it can create problems for that environment. Any discharges to waters of the state would be subject to licence conditions for water quality control. For this reason and for the purposes of water conservation, it is recommended that the water be drained into holding dams on the farm and then be reused or used for irrigation. It is recommended that wastewater is stored in a settlement pond before returning to the holding dam to remove the majority of the suspended particles. The site needs to be large enough to allow for the construction of these settlement ponds and dams.
Buffer zones need to be considered before purchasing or developing a site as these requirements will reduce the effective area for pond development. Developments near agricultural or horticultural areas may need buffers over 1000 metres to minimise the risk from spray drift. Buffer widths adjacent to residential estates should be a minimum of 150 metres. Buffers should be left in their natural vegetated state or revegetated with suitable species.
General site location
Factors which should also be considered when selecting an aquaculture site include:
- Previous land use - potential for chemicals in soils (eg organochlorine pesticides). Chemical residues and contaminants may affect production, saleability and safety of aquaculture product. Chemical testing should be carried out by a NATA accredited laboratory. These chemical tests are not always conclusive. More information is available: Aquaculture - policies, guidelines, protocols and other publications. (Guidelines)
- Surrounding land use - urban and agricultural activities (sewage plants, crop spraying);
- Predators - birds and other predatory animals;
- Road access - all-weather for supply of goods and services;
- Electricity - access to three phase power; and
- Market access for products.
Further information
If you require further information contact:
- DPI&F Business Information Centre - 8.00am to 5.00pm, Monday - Friday, (telephone 132523 for the cost of a local call within Queensland; interstate callers 07 3404 6999) or email callweb@dpi.qld.gov.au
This DPI Note is also published on the DPI&F's Prime Notes CD-ROM.
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last updated 18 January 2007
