The potential species of marine suitable for culture in floating netcages are classified as following :
Serranidae (groupers, coral trouts)
Epinephelus tauvina (estuarine grouper)
E. malabaricus (malabar grouper)
E. fuscoguttatus (mottled grouper)
Plectropomus leopardus (Leopard coral trout)
P. maculates ( Spotted coral trout )
Cromileptes altivelis ( humpback seabass )
Lutjanidae (snappers)
Lutjanus sanguineus (red snapper)
L. sebae (emporer snapper)
L. argentimaculatus (mangrove snapper)
L. Johni (John's snapper)
Latidae (seabass)
Lates calcarifer (seabass)
Carangidae (jacks, crevalles, travalles,
pompanos, scade amberjacks, yellow tails)
Caranx sexfasciatus (six-banded jack)
Crangoides chrysophrys
C. malabaricus
C. armatus
Siganidae (rabbit fishes, spinyfoots)
Siganus javus
S. canaliculatus
S. guttatus
S. spinus
Successful of seafarming depends to a great extent upon the proper selection of sites. Common to all species group are risk factor and environment conditions.
2.1.1 Risk factor
Risk factors that may impact on the subsequent culture operation are exposure, pollution and conflicting activities of the sites.
Exposure involves safety of the culture facilities and culture stock. Information on sea conditions including wind and wave actions and strengths, tidal current speed and direction and other pertinent conditions associated with these variable obtainable from the sources are evaluated.
Pollution sources related to domestic, agricultural and industrial sources are considered. Details and location of the pollution sources that may impact on the sites are given in Chapter 6.
Conflicting activities of the “common users” of the sea such as navigation, oil drill, and other industrial activities that may produce harmful effects on seafarming operations through the introduction of various industrial wastes are also taken into accounts.
2.1.2 Ecological criteria
The ecological criteria used for the assessment of the potential sites are salinity, water transport, turbidity, nutrient, dissolved oxygen, chlorophyll a and topography.
2.1.2.1 Salinity
Salinity requirements for the species suitable for culture in floating netcages vary from species to species. The seabass can be raised in salinity ranging from 0 to 33 parts-per-thousand (ppt) whereas the carrangids prefer to thrive under oceanic conditions. The estuarine grouper (Epinephelus tauvina) and certain rabbit fishes (Siganus spp. ) tolerate between 15 and 30 parts-per-thousand.
2.1.2.2 Current
Water transport are extremely dynamic in their transport. Normally it is generated by wind, tides, coastal currents and seasonal water masses. In sheltered area tidal current plays an important role in dictating the design of floating rafts and netcages and the mooring systems. Water movement serves to flush out metabolites and replenish the level of dissolved oxygen. The frequency and duration of the minimum currents generally determine the maximum biomass carrying capacity in the floating netcages. In the absence of currents to flush out the cages, high density of animals can reduce the dissolved oxygen concentration of the water to dangerously low level in very short periods of time. This is particulary important when grouping cages or considering large cages with high density of fish. A good site should have consistent mild currents, and very short intervals of slack water conditions.
The fast current generates high drag forces. It requires considerably stronger facilities, special mooring arrangements, and greater wastage of feeds. By average, greater than 90% of the total food intake would be expended for locomotion and other activities in coping with this much vigorous environment. It is generally recommended that tidal water speed should be within 20–40 cm/sec.
2.1.2.3 Turbidity
The turbidity of water serves as a suitability of the site. If it is too high, it implies that the sediment action of solids on the netcage takes place at a high rate thereby clogging the meshes and reducing the flow-through of tidal waters in the thinning out of the trapped metabolites and in raising the level of dissolved oxygen. It is recommended that a potential site should have suspended solids less than 400 mg/l.
2.1.2.4 Nutrient
One of the key assessments of the overall water quality of a site is nitrate, phosphate (total), ammonia, chlorophyll a and dissolved oxygen. The critical value of the various parameters should not exceed or fall below the following critical values :
| Parameter | Upper | Lower |
| Nitrate (mg/cu.m) | 75 | - |
| Phosphate (mg/cu.m) | 70 | - |
| Ammonia (mg/cu.m) | 100 | - |
| Dissolved oxygen (%) | - | 55 |
| Chlorophyll a (mg/cu.m) | 9 |
Chiu et al (MS,b) showed that the interactions among these variable were closely associated with the well-being of the confined fish stocks especially during periods of slack tidal movements abrupt rise in ammonia, drop in pH and dissolved oxygen and increase in solid loads. The phenomena can lead to mass fish kills.
2.1.2.5 Topography
The potential site should be located in area which should provide a 5-meter bottom clearance from the seabed. This serves a number of practical purpose. First, trapped nutrients once released from the seabed may not immediately affect the waters inside the cages, and the dissolved oxygen values are therefore not serious affected. Second, any chemical processes that take place in substrate would not be immediately transferred to cages. Third, it provides a free flow of sub-surface and bottom current thereby optimising the given oxygen budget.
The potential area suitable for finfish culture in floating netcages are found in Weh island, Sabang, Lhok Sudu bay, Simeulu island in Aceh; Batam island and Bintan island in Riau; Siberut island, Sipora island and Pagai island in West Sumatra; Nipah Panjang, Kg. Laut, Kuala Tungkal in Jambi; Bangka island in South Sumatra; Hurun bay, Lampung bay in Lampung; Banten bay in West Java, Grajagan Bnyuwangi, Gili Genteng bay, and Madura in East Java, Pajarakan in Bali; Lombok and Sumbawa in West Nusatenggara; Ujung Pandang, Pinrang, Barru, Selayar in South Sulawesi; Ambon in Maluku and Sangihe in North Sulawesi; Terakan Berau, Bontang, Sangkulirang and Adang bay in East Kalimantan. The estimated total area is about 3 600 ha (Table 2).
