Depending on the type of seaweed, the reproduction process differs and therefore the complexity of obtaining seed material does as well. The seeding method is the process of bringing the seed material on to the line used for grow out. The method for attaching these seeded lines to the farm site is called deploying.
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In South Korea dedicated seed companies supply seed material to the farmers. In Japan, the Cooperatives run centralised hatcheries. In Northern China, farms are usually integrated companies and have their own hatchery facilities, sometimes even more than one.
Due to the complex life cycle of Saccharina a dedicated hatchery is required to produce seed for cultivation at scale. In the hatchery process, zoospores from the mature plants will be collected on either seed frames or curtains made from palm fibre or vinolyn fibres. The production of these ‘seed collectors’ is very time-consuming and labour intensive and currently mostly done by hand.
In Japan and South Korea, a common method of attaching the seed material to the culture line is by inserting small pieces of the seed string (2-3cm) into the culture line. Roughly 70% of the farmers already use a machine that automatically cuts and inserts 2-3 cm of seed strings into the culture line. The seeding machine enables old ropes to be reused, because it can work with different rope sizes/strengths.
In China, the seedling material is grown at the nursery site until they reach about 15 – 20 cm and they are then clamped onto the rope and cultivated at the grow out site. This process is done manually and consequently it is very labour intensive.
Another method that is sometimes used in Japan and South Korea is twine seeding, in which the seedling rope is wrapped around the cultivation rope without the manual attachment of individual seedlings. However in this method, seedlings are easily damaged and final yields tend to be lower.
The seeded lines with young sporelings will be moved to a nursery site when the temperatures at sea drop below 20°C before being deployed at the farm site.
In South Korea and Japan, the seed material will be produced between early June till October (while sea water temperatures are above 20°C). In China, the hatchery season can start as early as mid/late August in Shandong province and last into mid November in Fujian.
Saccharina was the first seaweed species for which artificial breeding in indoor systems over summer was developed. These seedling rearing technologies have since been used for other seaweed species.