Farming methods and management for Eucheumatoids

 Site Selection

Eucheumatoids seaweeds can be grown in different water bodies and water surfaces in ponds, lagoons, coastal fish cages and in islands from a depth of 0.5 - 15 m with different farming methods from fixed-off bottom, floating raft, hanging long-line and net bags. Crops can be grown all year round in places with favorable environmental conditions, especially salinity, temperature and wind, suitable and stable or seasonal (Table 1).

Table 1. Parameter for site selection for Eucheumatoids

Parameters	Value/Description
License/ permit required	Permit required from the local government
Typical farm area per smallholder farmer (in hectare)	Between 1/4 and 1 ha
Typical farm size (by culture line)	1.000 - 10.000 m
Distance from shore	between 0.1 and 3 km
Water depth range	from 0.5m - 15 m at the low tide
Exposure of farm site	Both sheltered and open sea
Substrate beneath farm	Sand, stones, coral, seagrass
Water current	20 - 40 m/minute
Salinity (‰)	> 24ppt and stable
Water temperature	26-29°C

Species Selection

Three common farming species for carrageenan Kappaphycus alvarezii, Kappaphycus striatus and Eucheuma denticulatum. Overall, spinosum requires less attention and is an easier to grow than cottonii. However, farmers prefer to grow cottonii whenever possible, as they get a much higher price. The summaries species selection are shown in the Table 2 and Table 3. 

Table 2. Different species of eucheumatoids seaweeds cultivated around the world, each corresponding farming technique is indicated

Source: (Hayashi, et al., 2017)

Table 3. Market demand and price for two carrageenan species

Scientific name	Commercial name	Carrageenan extract	Farm gate price for dried seaweed in 2022
Kappaphycus alvarezii	cottoni	kappa	0.9-2.88 US$/kg
Eucheuma denticulatum	spinosum	iota	0.42-0.67 US$/kg

Source: (Hatch Innovation Services, 2022)

Sourcing Seeds

Seed production for Eucheumatoids are vegetative propagated via cutting or through micropropagation techniques. About 100-200g of healthy and clean (intact, no scratches, no signs of disease, no sticky algae) is being cut with a sharp knife to prepare new seaweed seedling. The seedling can be directly tied to the cultivation line. Each seedling is 0.20 m apart. Cultivation lines are arranged parallel and 0.2 - 1 m apart on the planting rig. Tying of seaweeds to the cultivation line is carried out on land and must be irrigated or dipped in seawater to avoid drying out. Tying the seedlings to the cultivation line is either done by family members or paid workers, that are paid per piece or line. Women do the majority of tying.

The seedlings mainly from own harvest sometime traded fresh between farmers with the current market price of seaweed. When transferring fresh seaweed from another place to the place, it is necessary to take measures to cover the sun and keep the moisture for the seaweed. If the distance is close and in a short time, after being picked up, the seaweed is put into bags of solid carcass bags during transportation it should be covered to prevent the seaweed from being exposed to the sun, heat, wind, rain and drying. If it is a long distance and the transportation time is long, it is necessary to sprinkle seawater from time to time to keep the seaweed moist and fresh. If transporting 100 km long distance must use trucks with refrigerated containers to keep the seeds at a temperature of 20-22°C.

When you arrive at the planting site, immediately put the seaweed into the water, you can prepare a net to put it under the water to let the seaweed in to keep the seaweed healthy before planting.

Table 4. Seeding Information for Eucheumatoids

Parameters	Value/Description
Source	Mainly own harvest, sometimes neighboring farmers, local collectors or the government
Volume of seed needed	about 100 -200 g/seedlings
Distance between seedlings	0.2-0.3m
Seeding method (Tying)	Nylon cord tie tie directly on rope, Loose loop single, double line method
Distance between cultivation lines	Varies among techniques and locations.
Standard seeding/hour/person	Average 50 m/hour/person (from 30-100 m)

Farming Season

As mentioned in site selection section, Eucheumatoids require stable salinity, temperature, and water flow. In tropical and subtropical regions classification of seasons based on rainfall is either dry and wet, or temperature “cold” winters and “hot” summers seasons. The weather has great influence to seaweed productivity and quality. For example, under suitable - cool season the daily growth rate of the seaweed is from 9-11% and compared to 4% in the hot season (Hayashi, et al., 2017). Season also affects the biochemical compositions of seawater, that influences the carrageenan quantity of the seaweed. Ice-ice disease, predators, epiphytes, and typhon also occur seasonally. Therefore, selection of suitable season is important for the success of seaweed farming.

Tying techniques

The tying technique is to hold or keep seaweed in the farming area, that are (i) seaweed pen, (ii) cage/basket, (iii) tube net, (iv) tie-tie, and (v) quick loops. The seaweed pen and floating basket are mostly used for temporary holding seaweed seedlings. The tubular net bag is reported in Brazin and Tanzania. This technique allows for opportunities for future potential mechanization. The tie-tie method is widely used in seaweed farming. The quick loops uses of 2-3mm rope to tie the seaweed without using raffia string. Thus the plastic raffia will not be mixed with the harvested product. The time to tie and untie the rope is also quicker. However, this method has only been tested in Singapore, and needs to be tested and applied seaweed farms.

Figure 1. Tying techniques

Table 5. Seaweed tying techniques and its advantages and disadvantages.

#	Tying techniques	Advantages	Disadvantages
i	Seaweed pen	A seaweed pen protects the seaweed from being eaten by fish.	Expensive and take time to setup
ii	Cage/basket	Varieties of cages are possible, advantage to tackle the epiphytes, sustain in the bad weather conditions	Expenses are higher in terms of implementation, maintenance, possibilities of biofouling etc.
iii	Tube net	Lower risks weather conditions, uniform growth rate, useful in deep water with minimum infrastructure	More seedling requirement, not user friendly, ecofriendly and economic method
iv	Tie-tie	Widely used in seaweed farming. Easy to use.	Time consuming in tying propagules  and tie-tie separation. Risk of softie contamination to the harvested seaweed
v	Quick loops	Faster in tying propagules  and tie-tie separation. No risk of softie contamination to the harvested seaweed	New methods, needs to be tested and applied in seaweed farm.

Basic cultivation techniques

Water depth is the main criteria to determines the cultivation techniques beside other site conditions, price and availability of equipment needed on a seaweed farm. Five main cultivation techniques are named as follows (i) fixed-off bottom, (ii) bamboo floating raft, (iii) (iii) hanging long-line, (iv) multiple raft long-line, and (v) spider web. The advantage and disadvantage of these techniques are presented in Table 6.

The fixed-off bottom and bamboo floating raft techniques remain the simplest and suitable for shallow water of 0.5 - 5 m at low low tide. The hanging long-line, multiple raft long-line, and spider web techniques are suitable for more than 5 m water depth at low low tide (Others modified techniques are adapted to suit the local conditions while increasing productivity also presented. Fixed-off bottom and hanging long-line and techniques are most commonly use techniques. The cultivation lines should be arranged in the same direction of the water current of the site (Figure 2).

Figure 2. Illustration of different four main cultivation techniques

Table 6. Seaweed cultivation techniques and its advantages and disadvantages

	Cultivation techniques
	Fixed off-bottom	Bamboo floating raft	Hanging long-line	Multiple raft longline	Spider web
Water depth (m)	0.5-1	1-5	1-10	>10	>15
Distance between cultivation lines	1	0.15	2 (double lines)	1	0.5
Length per cultivation line (m)	20	3	10	20	3
Distance between tie (m)	0.2-0.3	0.2-0.3	0.2-0.3	0.2-0.3	0.2-0.3
Anchor	Wooden stake	Wooden stake, sand sack, stone		Metal anchor, concrete block
Floater	Not use/ PET bottles	Bamboo	PET bottles, Styrofoam	Bamboo, plastic buoys	Plastic buoys
Other materials	Plastic raffia and various sizes of polyethylene ropes
Advantages	Low investment cost. Easy to handle	Environmental and user-friendly. Easy to set up	Simple, low cost, and effective.	Useful for large scale production, more economic, user friendly	Higher productivity, possible polyculture (oyster)
Disadvantages	Vulnerable to bad weather, epiphytes	Sensitive to weather changes, no uniform growth	Sensitive to weather changes (high temperature).	Higher investment cost and maintenance	Epiphytic risks, sensitive to weather changes

Based on five cultivation techniques, other modified cultivation techniques are showed in the below figure.

Figure 3. Modified cultivation techniques to suit the local conditions

Farm Design

A typical seaweed farm should include several components to support the farming plots. They are (1) storage room, (2) working shack, (3) seed holding cage or pen, (4) seaweed seedling banks; (5) several farming plots to rotate planting and harvesting every weeks, (6) boat, (7) drying platform/systems, and (8) warehouse to store dried seaweed while waiting for transport to market. The functions and description of different farm’s components are described in the Table 7. The layout of the farm is illustrated in Figure 4.

Table 7. Farm components and their functions

Components	Functions/description
1. Storage room	To keep planting materials
Plastic raffia	-  To tie seaweed propagule
Various sizes of polyethylene ropes	-  To setup cultivation lines and anchor ropes
Recycled PET bottles	-  To float  cultivation lines
Wooden stakes/ anchor bar or block	-  To anchor the cultivation lines
Tools and equipment	-  Kinfe, scissor, hammer, measuring tape…
2. Working shack	To: - Prepare seaweed cultivation lines - Select of good seaweed seedlings - Tie propagules - Tie-tie separation - Rest for worker/people
3. Seed holding cage or pen	- To holding seaweed seedlings
4. Seaweed seedling banks in multiple sites and farming techniques	- To ensure quality available seaweed for successive farming cycles
5. Farming plots multiple rotatting plots. E.g 5-7 farming plots to rotate planting and harvesting every weeks.	- To grow seaweed. Seaweed weight should increase 5-6 times after 45 days. - To have constant harvest and income as seaweed farming must be done every day, but may not take whole day!
6. Boat (which not always required)	- To transport and tie cultivation lines to farming plots - To visit farm daily to remove floating debris, predators (sea urchins, crabs, sea stars), ice-ice disease - To transport of seaweed from farm sites to drying area - To transport the dried seaweed to buying station
7. Drying platform/systems with raised plastic cover at night or during raining day	- To dry seaweed and keep away from contamination with dirt and other materials - The seaweed will dry in 3 days when it's sunny and 5 days when it's cloudy or sometimes it rains.
8. Warehouse	- To pack, weight, record and store dried seaweed while waiting for transport to market

Farming plots are the key component of the seaweed farm. Water depth is key criteria to design farming plots and select appropriate cultivation techniques (see section 8). It is important to have the right anchor to hold the farming plot. Experience and local knowledge on wind, current, wave drift forces and sea bottom type composition are important to decide weight and type of anchor. General rule the length anchor rope should be 4-6 times the depth of water. The total weight of the anchors should be twice that of the combined weight of the farm and the seaweed. 

Managing of Grow-out Farms

Eucheumatoids are reared in cycles of 30 to 45 days (sometimes up to 60 days) and most farmers visit their farm daily. Besides setup new lines and harvesting, farmers also adjusting depths, remove sediments and filamentous algae. In some regions, a lot of sediment tends to accumulate on seaweed, after heavy rains and freshwater runoffs.

Spinosum (Eucheuma denticulatum)  is easier to farm and more resistant to ice-ice syndrome than Cottonii (Kapphaphycus spp.). When the season is not ideal for growing cottonii, farmers can consider growing spinosum instead. The grow out information for Eucheumatoids is showed in Table 8.

Figure 4. Illustration of a seaweed farm layout

Table 8. Grow out information for Eucheumatoids

Parameters	Value/Description
Grow out time (until harvest)	30-45 days (sometime up to 60 days)
Tasks at sea during grow out	Adjusting depths, remove sediments and filamentous algae
Frequency of farm visits	Almost every day
Best season to grow	All year around production, but cooler months are best (24-29°C)
Maximum water temperature	30°C
Biofouling (Epiphytes, Epibionts)	Seasonally and regionally shellfish attaching, filamentous algae
Pests and diseases	Ice-ice syndrome (seasonally)
Grazers (natural predators)	Mostly rabbit fish and surgeon fish
Monitoring equipment	Regularly monitors with portable sensors, record farm activities
Production planning tools	Intuition, tidal cycle, pen and paper

Adapted from (Hatch Innovation Services, 2022)

Common Diseases and Prevention

The incidences of disease and epiphytic infestations are on rise in recent times which have severely affected biomass production, as well as the yield and product quality (carrageenan). Since efforts in producing/selecting disease resistant seedling or commercial extract to treat seaweed disease are not available for commercial scale yet. The selecting appropriate cultivation methods, suitable site, season and management are still widely apply by farmers. The common disease, and practical remedy and prevention are presented in Table 9 and Figure 5.

Table 9. Common disease, and practical remedy and prevention

Common disease	Effect	Practical remedy	Prevention
(i) ice-ice disease: stresses due to changes in temperature and/or salinity	Loss of color and consequently, disintegration, and die-off	Remove the affected parts, harvest, or do seedling and transfer to other locations	Keep seaweed in deeper water
(ii) Epiphytes: aquatic marine plant attached to the cultured seaweeds	Competes space, sunlight, nutrients, and can damages seaweed tissues		Choosing favourable season
(iii) Seasonal grazing: school of juvenile rabbit fish appear in certain season	Graze the skin of seaweed and kill it	Evaluate the situation and harvest immediately if needed	Avoid grazers fish spawning seasons
(iv) Territorial grazing: bigger fish	Big bites, even faster than seaweed can growth	Trap the fish or scare them away	Careful in select farming location
(v) Others: Mollusc spat attached, domestics wastes and natural contaminants	Makes it prone to infection and disease	Regular cleaning of the seaweed farms	Select other farm site if possible

Source: (Hatch Innovation Services, 2022)

Figure 5. Illustration of the common disease/problems

References

CD-CAAM, 2016. Basic manual seaweed farming, post-harvest improvement and marketing, Mindanao: Community Development in Conflict-Affected Areas in Mindanao.

Hatch Innovation Services, 2022. Seaweed Insights. [Online]
Available at: https://seaweedinsights.com/
[Accessed 25 May 2023].

Hayashi, L. et al., 2017. The Cultivation of Kappaphycus and Eucheuma in Tropical and Eucheuma in Tropical . In: A. H. e. al., ed. Tropical Seaweed Farming Trends, Problems and Opportunities. Springer International Publishing, pp. 55-90.

Johnson, B. et al., 2017. Economic analysis of farming and wild collection of seaweeds in Ramanathapuram District, Tamil Nadu. Indian Journal of Fisheries, 64(4), pp. 94-99.

Teitelbaum, A. & Lesire, S., 2003. Farming seaweed in Kiribati:A practical guide for seaweed farmers. New Caledonia: Secretariat of the Pacific Community.

VUSTA, 2022. A guide to growing eucheuma seaweed with oyster. [Online]
Available at: https://www.youtube.com/watch?v=f3McHlO1Fcs
[Accessed July 2023].