1. General Conditions
Origin and spread of cage culture techniques; advantages (minimal space requirement, very high production per unit area, facility for towing off in case of pollution, safety from predators, suitability for culturing large variety of species, facility to use areas where sea bed is unsuitable for farming, ease of harvest, etc.) and disadvantages (high demand on oxygen and water flow, dependence on artificial feed, food losses, pollution, rapid spread of disease, risk of theft, conflict with multiple use of natural waters, etc.).
2. Types of cages
Cages occupying the whole water column (from surface to bottom), floating cages, mid-water cages with buoyed "feeding neck" and bottom cages; single and multiple units, rigid and flexible cages; self-supporting and raft-supported cages; selection of type of cage in relation to conditions at farm site.
3. Design and construction
3.1 Selection of site
3.2 Layout
Cages, jetties, walkways, buildings for feed preparation and preparation of fish for market; hatchery and nursery pond (where needed).
3.3 Construction
(a) Framework; materials used (wood, bamboo, galvanized scaffolding, aluminium, etc.); support and lifting ropes; frameless cages; shape of net.
(b) Walls, bottom and roof; mesh netting of natural fibre, synthetic fibre, galvanized chain-link or galvanized weld mesh; site fouling tests with different materials to select the material most suited to the area.
(c) Flotation structure: use of rigid collars of metal or plastic (air-filled, foam-filled or fibre-filled), discrete buoys or polydrums.
(d) Linkage of multiple units.
(e) Mooring and anchoring.
(f) Construction of water-breaking structures.
(g) Shapes and dimensions; determination of shape and size in relation to hydrographical conditions, species to be stocked, stocking rate, production target, etc.; relative merits and demerits of large and small cages.
4. Cultivable species
Indigenous and exotic species of fishes, crustaceans and molluscs suitable for cultivation in cages set in fresh, brackish and marine waters; criteria for selection of species for cage culture.
5. Farming operations
Production or collection of seed; stocking; stocking rates in relation to species and size of cages; monoculture and polyculture; feeding - feeds used, rate and frequency of feeding, feeding methods and conversion rates; growth rates and yield; periodic changing or cleaning of nets; monitoring of water quality; moving cages to new localities in case of unfavourable environment; harvesting; selection of optimum size for harvesting.
6. Relative economics of cage culture
Practicals
Design and fabrication of selected types of cages; experiments in cage farming of local species.
