1. General considerations
Mollusc biology as related to culture; general description of the various systems of mollusc culture (bottom, rack, tray, raft, pole and long line cultures) and their relative efficiencies; hydrographic conditions favouring high production; importance of pollution-free water, adequate water flow, health regulations relating to molluscs and local availability of brood stock.
2. Criteria for selection of site (see Chapter II - Selection of Sites for Aquaculture)
3. Species suitable for cultivation
Indigenous and exotic species of oysters, mussels, clams, scallops and cockles, suitable for cultivation.
4. Procurement of seed
4.1 Hatchery production
Techniques of hatchery spawning of molluscs; genetic modification of stocks.
4.2 Collection of spat
Methods, place and time of collection; types of collectors used (see page 4); measures required for avoiding fouling.
5. Bottom culture
5.1 Special pre-requisites
Firm bottom; adequate tidal flow to prevent silt deposition, for removal of excreta and for supply of oxygen.
5.2 Shell beds
(a) Advantages (easy and cheap maintenance; possibility of using seed culled from other systems) and
Disadvantages (silting; predator attack; relatively poor growth; low yield).
(b) Preparation of bed: type of bottom required; improvement measures, perimeter ditching; construction of low earthen or brush dikes to prevent incursion of sand and sediment; spreading of shell or cultch; levelling; settling.
(c) Culture operation: collection of spat; importance of timing; laying of spat; routine maintenance (raking, washing with water jets; spraying of water on exposed waters, cleaning of ditches, use of lime, etc.); harvesting; grading and cleaning of crop.
5.3 Rock beds
(a) Advantages (ease and inexpensiveness; ease of culling) and
Disadvantages (difficulties in preparing bed; weed and pest growth; low yield).
(b) Construction: type of rocks used; artificial substitutes; weight and size of rocks; consolidation of ground where necessary; piling of rocks; spacing; construction of walkways and puntways.
(c) Culture operation: spatfall, inspection, culling, routine maintenance (turning of rocks, clearance of weeds and other unwanted organisms, seasonal cleaning and repair of beds); harvesting; grading and cleaning of crop.
6. Intertidal and shallow water culture
6.1 Rack culture
(a) Advantages (possibility of using readily available building materials; ease of re-laying; efficiency in catching spat; ease of culling and harvesting, reduced silting, lesser infestation of pests) and Disadvantages (constant demand on time, labour and materials).
(b) Construction: different types of racks; suitable woods; use of bamboos, logs or rough sawn timber; tarring of sawn timber; arrangement and spacing of racks - single line, double line and quadrangular stockades; positioning and fixing of pillars and horizontal beams; attachment of collectors.
(c) Culture operation: timing of spat collection; re-racking of settled collectors; culling, setting out of dislodged shells; routine maintenance; (inspection, refastening, moving of racks to new areas when necessary; replacement of faulty timbers); harvesting; grading and cleaning of crop.
6.2 Tray culture
(a) Advantages (as in rack culture above) and
Disadvantages (need to obtain spat from elsewhere, need for constant maintenance and frequent replacement of wire and wood).
(b) Construction: construction of racks, their spacing and arrangement to carry trays; construction of trays - frames, ends, mesh materials, size of mesh, fastening and stretching, tarring, draining and weathering of wire mesh trays.
(c) Culture operation: setting out of trays, spreading of seed; culling; respreading; routine maintenance (inspection, patching and renewal of fastenings).
6.3 "Bouchot" or pole culture
(a) Advantages (local collection of seed, intensive use of intertidal land, high yield) and
Disadvantages (infestation by borers, susceptibility of crop to predation and theft, need for daily inspection).
(b) Construction: frames and ropes for seed collectors; poles suitable for bouchots; sheathing of bottom of poles in smooth plastic (to prevent predators); size, arrangement and spacing of poles; insertion of poles; perimeter fencing.
(c) Culture operation: collection of seed; transplantation; preparation of "boudins" (tubes of seed); attachment to poles; inspection and culling; routine maintenance (scraping and cleaning); storage cages; harvesting; grading and cleaning.
7. Deepwater culture
7.1 Raft culture
(a) Types: ropes, poles and rens.
(b) Advantages (high yield, use of water column, freedom from silting and pests) and Disadvantages (high cost, need for boat, and fouling of ground).
(c) Construction: construction and/or assembly of basic platform, buoys, anchors and moorings; attachments of poles, ropes, netting tubes, rens, etc. to raft; methods of attachment.
(d) Culture operation: collection of spat; attachment of seed; culling; harvesting; special vessels and equipment required.
7.2 Long lines
(a) Advantages (use of open water, ability to operate under rough conditions) and Disadvantages (difficulty in servicing).
(b) Construction: assembly of constituent parts - anchors, pennants, buoys or drums, longlines and growing lines (hanging rens); methods of attachment.
(c) Culture operation; preparation of rens with seed settled in other areas; stringing on longlines; inspection and culling; harvesting; washing and grading.
8. Depuration of molluscs
Necessity for depuration of molluscs; methods of depuration; bacteriological standards, etc. (see page 28).
9. Economic aspects of different types of mollusc farming
Comparative labour and capital requirement; rates of production; marketability.
Practicals
Collection of oyster and mussel spat; designing of intertidal and deepwater culture devices; experiments in oyster farming.
