METHODS OF COASTAL AQUACULTURE AND MARICULTURE

Introduction• Coastal aqua culture- pond culture; Open sea- cage culture

• Shellfish culture- Off bottom, bottom

• Culture methods- Rafts, long lines and stakes

pond culture Raft culture

Pond cultureSite selection

• Based on the species to be cultured and technology to be adopted

• Points to consider- Agro chemical conditions, access to market, roads and communication, protection from natural disaster, labour availability, public utilities

• Meteorological and hydrological information, soil characteristics, quantity and quality of available water, ease of filling and drainage

• Astronomical information- tides

• Land slope- not more than 2%- good

• Extensive area- for future expansion and farm facilities

• Pollution, legal and social aspects, environmental constraints

Criteria to locate a good coastal farm site

• Average air temperature of 26 degrees C for tropical fish and crustaceans

• Average pond temperature of 30 degrees C.

• Salinity of 10 t0 35 ppt (optimum would depend on the species selected for culture)

• Brackish/seawater of good quality and high natural productivity- optimum water quality will depend on the species to be cultured.

• Away from all sources of pollution (urban, agricultural and industrial).

• Low flood risk• Land of suitable elevation to enable easy

drainage of water from the ponds• Clay or clayey loam soil• Soil with relatively higher pH (>6.0)• Good electricity connection and supply• Good availability of labour• Road and transportation• Availability of communication• Availability of supplies• Proximity to markets• Availability of seed for stocking

CRITERIA TO SELECT A GOOD COASTAL FARM SITE

Design• Site physiography, source and nature of water supply, type of stock enclosure to be

used, organisms to be cultured and techniques of management

• Seasonal variation in salinity of available water and availability of fresh water

• Tidal ponds- information on tides, ground elevation

• Size and shape- imp- quantity of water & extent of land available, technology to be followed (extensive, semi intensive or intensive)

Water supply system

• Quantity of water- depend on soil and climatic conditions

• Water supply- also depends on species to be cultured

• Separate supply of water and drainage canals, separate inlets and outlets for operational safety and efficiency

CAGE CULTURE

• Originated in kampuchea

• Salmons- Norway; yellowtail- Japan; Groupers and sea bass- in Hong Kong and Singapore

• Floating unit, a framework & flexible mesh net suspended under it

• Floating units- Styrofoam, Polyethylene pipes or ready made pontoons of plastics or metal

• Framework- impregnated wood, bamboo spars, galvanized scaffoldings or welded aluminum bars

• Nylon –net; weldmesh or even woven split bamboo is also used

• Cage flotillas - provide sager working conditions and enable storage of feed on site, as well as installation of automatic feeder

Site selection for cage culture

• Considerations for cage farming site -Reasonably sheltered areas, sufficient water movement, the occurrence of typhoons, hurricanes and cyclones in the area, the vulnerability of the sites

• In cold climates, areas that receive safe heated water effluents are preferred- higher water temperatures generally improve growth and productivity.

• Accumulated wastes-decompose -oxygen depletion or generation of methane or other toxic gasses under anaerobic conditions

• Cages also increase deposition of silt on the bottom of the site

• So, important to have enough movement of clean water below the floating cages

• Carrying capacities -avoid overcrowding of cages

• The most sophisticated design of cages -Norway for salmon

• Cages of size 100 to 500 m3 are used. S simple unit holds a net of four vertical sides and is rectangular in cross section

• Mooring cages to a jetty with direct access to a quay, in order to facilitate work and reduce labour cost

• Feed dispensers are installed above each cage; or, manual feeding has to be done

• Most of the presently available cages are designed for use in protected bays and fjords

• In order to utilize more open waters and high seas, special cages with a flexible rubber framework have recently been developed.

PENS

• Pens - transitional structures between ponds and cages• Yellowtail in Japan, milkfish in the Philippines and salmon in Norway – use pen

culture• The success of pens - hydrobiological conditions of the site• The design- base on - adequate knowledge of water quality, floods, waves and

currents and prevalence of predatory animals

• Pens - formed by net barriers to partition off areas of an open water body, such as intertidal areas of the sea, bays or lagoons

• Enclosure is formed one side of the shore and on the other three by a wall of nylon netting hung from pole driven into the bottom

• Net barriers may be hung from steel cables stung between the poles or the concrete of steel piles

• In some cases, two walls of netting are used, the outer one to protect the enclosure form floating debris and to prevent escape of fish if the inner wall gets damaged

• The net barrier is fixed by a rope along the sea bed for 1m, until it terminates in a lead line

• The net embed itself in the sand or silt at the bottom. As a further precaution to prevent fish escaping heavy rubble is piled up at the bottom

CULTURE METHODS FOR OYSTER, MUSSELS AND SEAWEEDS

OYSTERS• On bottom culture: followed on fairly firm bottom, protected from wave action

and predators. Oyster spats are sowed and harvested when grown to marketable size- cheaper, but siltation over oysters beds can cause problems

• Off-bottom culture:1. Pole /stick culture:

• Wooden or bamboo sticks are installed in rows in shallow muddy regions of the intertidal zones

• Sheltered areas free from strong waves, wood boring organisms are selected

• Seed oysters are attached to the poles using degradable nets, or sting on which oysters are collected are strewn round the poles for fattening and final harvest

Pole /stick culture

2. Raft/string culture:

– string/trays are suspended from floating rafts or long lines

– Raft are use in protected areas, strings in more exposed areas

– Rafts/longlines are supported by buoys

– Trays are made of wood or wire screens

– Spat oysters are placed in trays and suspend for grow out

Raft/string culture

SEAWEEDS

• Raft and long line culture - growing seaweeds• Spores are collected on nets from areas rich in spores and they are transferred to

on growing areas for culture to marketable size• floating frames, fabricated as nets with ropes of hemp fibers, palmyra fibres or

synthetic twines which serve as suitable substrata. The culture frames are suspended in the sub-littoral zone from poles driven into the bottom in such a way that the flat surface of the net is close to water surface even during low tides. Fragments of plants are twisted into the ropes and allowed to grow to harvestable quantity