Gracillaria, a red seaweed, classified under the Division Rhodophyta is considered the most promising source of refined agar. It is macroscopic in form, characterized by elaborate thallus under the plant body with more or less red color due to the presence of phycoerthrin. It is soft and fragile and can be easily removed from its muddy substrate by strong waves during monsoon rains. These seaweeds grow luxuriously in protected coves and bays.
Gracillaria in its raw form is mainly used in vegetable salads or processed into agar or "gulaman". Agar extract is used for food, and stabilizer for canned foods in confectionary, jelly preparations, marshmallows, and candies for candy filler. Food grade agar which is another processed product from agar is applied to food processing and directly as food. Industrial agar (agarose) is used in biochemical technology for protein separation mainly in analytical laboratories. Bacteriological agar is used in microbiological applications in medicine and pahrmaceuticals. Agar is also used in tissue culture.
Four major Gracillaria species will be propagated. These are: G. firma (= G. fisher), G. fastigiata, G. cylindrica (= G. changii), and G. tenuispitata. All of these species have agar quality and good growth.
Generally, in an open sea or bay, the area need to be protected from strong current and wind and avoid areas with heavy freshwater runoff. There should be a good water movement, a water depth of not be less than 0.5 M at low tide and more than 2.5 M at high tide. The ground should be firm and stable enough to permit easy installing of stakes. The substrata and water conditions should be in accordance with the preference of the Gracillaria species to be farmed, an area with natural Gracilaria species stock. Before setting up a farm in an unknown location a test plant plot (2.5 × 5.0 meter) or a raft should be set to determine the feasibility of the area. For pond culture, brackishwater extenseive or semi intensive culture fishponds with good water flow could be used. Shrimp (P. monodon) culture ponds are recommended. Polyculture with shrimp/milkfish and crabs have been reported to be succesful.
Three environmental conditions have been identified in the project area for the farming of Gracillaria species. These are : low salinity, semi-clear water with muddy substrate; high salinity, semi-clear water with sandy-mud substrate; and, high salinity, clear water with firm substrate.
Seedling selection. Careful selection of cuttings is important. Choose healthy and strong branches for planting. These are usually found at the center and near tips of a healthy plant. Use a clean to cut branches to keep a smooth surface.
The healthy seedlings stock from the wild would give better production. Healthy seedlings from farmed lines can be used. Stock seedlings are maintaned in a net pen, net cage or floating raft. The two common farming methods are discussed below:
a. Fixed Bottom Monoline. A cheap and easy method to establish and maintain which is not prone to surface weather conditions. In this method, the only materials needed are the bi-filament polyethylene twine No 5 or No 6 and mangrove stakes. The seeds plants are inserted between the twines. A 10 × 10 m plot is fixed at the bottom of substrata at approximately 32 cm apart. The lines are stretched and tied to the stakes which are approximately 5 or 10 meters apart. It is positioned either prallel or perpendicular to the water current and must not be exposed to air during the low tide. The lines with seedlinggs should be at least 25 cm submerged in water during low tide.
The seedlings, approximately 50 grams are inserted between the bi-filament No 5 or 6 twine. A 5 meter line can accommodate 16 plants. The lines with seedlings is towed to the site where the stakes are set up. The lines are tied to the stakes.
b. Floating Raft Monoline. A floating bamboo raft with lines and plants submerged at 30 cm in water is constructed. Recommended size of the raft is 2.5 × 5.0 meter and weight allowance of seaweed at harvest time is considered. The raft is anchored either at the bottom with a stone or tied to a bamboo pole. It should be positioned either parallel or perpendicular to the water current. This method is prone to surface weather conditions. However, there may be sites which are suitable only for this type of method, such as unfavourable tidal range and water depth but protected areas with suitable environmental condition.
The No 5 or No 6 line bi filament polyethylene twine is used. The seedlings of 50 to 75 grams are inserted between bi filament lines. In one line about 16 plants can be inserted.
Please refer to Annex 1 for a diagram of Farming Methods.
A growing period (fixed bottom monoline and floating raft monoline) of between 40 and 50 days is required for first harvest. Generally, daily percentage growth rate is high at 16% during the initial 7 to 14 days. The daily growth rate (%) declines to approximately 4 to 7 % after 40 to 50 days. The daily growth rate of less than 1% is expected after 45 days.
An average daily growth rate percentage recorded within 50 days of growing period in optimum environment for the Gracillari species are as follows: G. fastigiata- 9%; G. firma- 8.7%; G. cylindrica = % and G. tenuispititata = 6.2%.
Before starting a farm, the site should be cleaned and undesirable marine benthic animals ( sea urchin, starfishes, sea grasses and other specie of seaweeds), rocks, and other foreign materials are removed. The line should be inspected every day. Missing plants, stakes and broken or lose lines should be shaken to get rid of the sediments settling on the plants. A glass bottom underwater viewer with which planted lines can be observed from a banca is a useful equipment for inspection of farmed lines.
Harvest the plant when individual plant weigh approximately 500 grams. This is done after 45 to 50 days. Always use sharp, stainless steel knife when harvesting. Cut the selected branch carefully and stock them in net bag or basket. When harvesting the plant for drying, break their thallus from the tying material and put them in the basket and stock in banca. Nothing should be left on the monoline.
Spread the harvested plant over a suitable area. Never dry directly on sand or soil to avoid contamination. Use coconut leaves as flooring to facilitate gathering when necessary. In the absence of continous sunlight, drying may take 3 or more days.
After drying, the product is packed in gunny sacks and sold to traders who will deliver the product to processors or exporters.
Or, housewives can process dried seaweeds into local food item, e.g. “gulaman”. Simply boil previously dried and bleached seaweed materials. While hot, separate gel from water by using a piece of flour cloth as strainer and then allow gel to cool in the desired form.
Initially, the six (6) cooperatives will start with a 1 hectare Seaweed Farm. A farm house/shed will be constructed near the farm. It will also be used as a drying and storage facility. The chosen site must be proximate to the highway for transport efficiency.
The farms will operate for 4 cropping season. Harvest is estimated at 4 tons after 60 days.
Please refer to Annex 2 for the location map.
