Farm Design
The cultivation method and farm design – which are highly influenced by the individual site conditions – determine what type of equipment is needed on the seaweed farm. Anchors, ropes, culture lines and floats are essential equipment for all cultivation taking place at sea.The material the farmer chooses for each will not only depend on the site conditions, but also on the price and availability of equipment.
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Eucheumatoids
Water depth is the main indicator that determines the cultivation methods and equipment used for growing Eucheumatoids.
In shallow areas (0.3 – 2 metre depths during the lowest lowest tide) the fixed off-bottom method is very common, where wooden or steel stakes hold suspended lines in place below the water’s surface. In deeper waters, the hanging long-line, floating rack and multiple raft long-line methods will be used.
The farmers we interviewed operated in farm sites with a maximum depth of 15 meters. Farming in deeper waters is not only more expensive, since more material and boat fuel is used, but also exposes the farm to higher risks, due to typically increasing wave height.
Fixed off-bottom cultivation
Hanging long-line cultivation
Illustrations adapted from University Malaya
Floating raft cultivation
60 meter long floating long lines in 8-10m deep water in South Sulawesi, Indonesia.
Fixed off-bottom method in shallow water in Nemberala, Rote Island, Indonesia.
Fixed off-bottom method in high density, due to short distance between culture lines Nemberala, Rote Island, Indonesia.
The different farming methods of eucheumatoids have different material requirements or needs for equipment.
There are at least a handful of other cultivation techniques and many unique design variations to grow Eucheumatoids in the Coral Triangle region.
In the fixed off-bottom and floating rack method the line length usually does not go beyond 10 metres. However in the floating/ hanging long line method the length of each culture line can be much longer and vary quite a bit, depending on the farm location. Less exposed areas can have longer lines, however farmers reported that the handling of a longer line can be a limitation.
Different anchors
Wooden stakes are mainly used for anchoring the farming rig across Indonesia, the Philippines and Malaysia.
They are usually rammed into the bottom of the sea using pure manpower. In waters over head height, this requires skilled free divers in the community.
Wooden stake anchors are in some regions preferably made out of mangrove wood because of their durability in the water. However, by law, mangroves in the Philippines and Indonesia are protected. In Indonesia, the leaders of coastal communities have a consensus to protect mangrove forests and do not allow mangroves to be used as stakes for seaweed farming.
In most fixed off-bottom farm setups, each culture line will be attached with two wooden stakes.
It takes a lot of strength to hammer the anchor stakes into the sea ground. Once well placed they would last up to two years under normal conditions.
Iron bars are more expensive but usually last much longer than other anchors (approximately 5 years).
Rope material
The culture lines are typically between 4 and 7 mm in diameter. In floating long line systems, the lines connected to the anchor (rig lines) are often stronger (10-14 mm).
The strength of all ropes used depends both on the farm design and exposure of the site.
The lines are a substantial cost in setting up a farm and in most cases farmers buy universal polyethylene ropes (PER), which are sold in local stores or provided by local dealers.The prices for a roll of 200m rope are somewhere between 10 and 15 USD. Under normal conditions, these ropes can last up to 5-8 years. Frequent cleaning of the culture line after each cycle will help to keep them intact and also reduce disease and epiphytes across crop cycles.
Preparation of a new culture line consisting of 6 mm polyethylene rope and nylon cord to tie the seedlings. Taytay Bay, northern Palawan in the Philippines.
The culture lines can be reused many times if kept in good conditions. Sabah, Malaysia
New seedlings are tied into culture lines and ready to be deployed at sea.
Biofouling on floaters is the main reason they will need to be replaced after a few cycles.
Floats
To keep the cultivation lines with seaweed close to the water surface at all times, used PET (polyethylene terephthalate) bottles are most commonly used as floats. Farmers reported large differences in how long these bottles last them. Depending on the type of PET bottle, they have to be replaced a minimum of every 2-3 cultivation cycles.
There have been some initiatives to introduce manufactured floaters (rubber floats) from more durable materials dedicated for seaweed farming. However, most farmers reported that they prefer the PET bottles since they are cheap and practical. They noticed that the surface of the manufactured floaters enables more biowaste to attach and the additional weight sinks them faster. The PET bottles on the other hand have a cleaner surface, where this process happens much slower.
PET bottles ready to be deployed as floaters in Honda Bay, Palawan in the Philippines.
Because almost all PET bottles can be used for seaweed farming, they will be collected from the general trash and traded at a fairly high price in seaweed farming regions.
To reduce the pollution from the PET bottles or Styro Foam used as floaters, the government in Malaysia has introduced various new types of floaters, that are also supposed to last longer.
However a big problem with these floaters is the accumulation of biowaste that makes them sink faster.
Styro Foam floaters are probably the worst option for the environment as they slowly disintegrate into small pieces that never completely decompose.
Usually the fixed off bottom method does not require any floaters. However in some cases they are attached so the seaweed lines will stay closer to the surface at high tide. Oenggaut, Rote Island, Indonesia.
Explore another seaweed species:
Eucheumatoids | Saccharina | Undaria | Pyropia | Gracilaria
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