Environmental factors that influence site selection
You should consider the following environmental factors when selecting a site for your land-based marine aquaculture operation.
Conduct a soil survey before choosing a site. Soils must be impervious (more than 20% clay) to ensure minimum water is lost through seepage. Clay or clay-loam soils are ideal.
Avoid soil types:
- with gravel/sand layers or rock strata formations
- that are permeable with high silt, sand or organic matter that may erode
- that are acidic, which often occur in saltpan and low areas next to mangroves.
Most marine aquaculture activities occur near the coast or estuarine rivers, although inland sites where saline water is an agricultural problem are being developed.
The salinity level of waters near a site will determine what species you can successfully farm. Seawater normally has a salt concentration of about 35 parts per thousand. In river systems, areas of brackish or estuarine water decrease in salinity further upstream.
Salinity and water quality also changes with the size of tides, the size of the river at low tide (large tides means some creeks can be dry at low tide), rainfall, flooding and artificial barriers. Other factors include ocean currents and water depth, suspended solids such as clay and organic matter, dissolved nutrients and toxic chemicals. While some species prefer brackish water (barramundi and banana prawns), others demand higher salinity and better coastal water (reef fish and snapper).
An adequate supply of freshwater is also necessary for some hatcheries and processing plants. Sources include dams, freshwater waterways, run-off, irrigation channels and underground bores.
Avoid the following types of water:
- domestic water (which may contain chlorine, and can be expensive)
- water containing high levels of organic matter
- bore water with excess levels of nitrogen, carbon, total dissolved salts, minerals and gases.
Site topography influences the design and layout of ponds. A well-drained, gently sloping site (1-3%) is best because it allows easy construction of sloping ponds.
On a very flat site, you must build pond walls well above the high water mark and slope the pond bottoms (to allow complete drainage into settlement ponds before discharge).
Check the site is above flood level to reduce the risk of losing fish during floods or transferring non-native species into the ocean or river. Land should be 2m above the highest astronomical tide.
Sites near sensitive areas like national or marine parks require certain regulatory controls, especially to discharge drained pond water (which contain nutrients and algae).
Check requirements for buffer zones from houses or farms, which reduce the amount of land available for aquaculture.
Check for chemical contamination
Research the previous use of a site to make sure there is no contamination risk from chemical residues. These may affect the production, saleability and safety of your product.
Read or download Site identification for aquaculture - assessment of chemical contamination in site selection, a practical 11-step approach to determining site suitability and safety.