Undaria Farm Design

The farm design differs between countries and regions and can generally be categorised in floating raft type or single or double long line systems.

Within these, cultivation lines are either set up in a vertical or horizontal rope method. The benefits of using the horizontal rope method are that the seaweed can receive light evenly and can utilise space efficiently, resulting in higher yields. 

In the vertical rope method, a seeded rope will hang vertically from the floating rope. The advantage of this method is the utilisation of vertical space. The disadvantages are that it is more work intensive and that the seaweed at the bottom receives hardly any light. Depending on the turbidity of a site the main ropes are installed up to 2 m beneath the water surface and will be adjusted during the grow out cycle, depending on the intensity of sunlight.

Horizontal raft type setup of an Undaria farm near Jindo, South Korea.

Undaria farms in Japan use the horizontal longline method, often with double long lines per anchor. In Sanriku, a line length of 100 – 150 metres is most common. Since the substrate beneath the farms varies substantially from farm site to farm site, different types of anchors are used. 

In South Korea, horizontal raft type method is more common, however single lone line systems are used in some region like Gijang, where open ocean conditions prevail. The government is trying to promote more environmentally friendly farm equipment. Especially the floats should all be replaced with proper buoys instead of styrofoam.

In Dalian, the main Undaria producing region in China, pretty much all farms use the horizontal raft type method. Each raft consists of 50 culture lines that are 8 m long and installed horizontally with 1.8 m intervals in between. Thus, each raft holds 400 m of culture lines in total. Here, wooden stakes are commonly used as anchors, since the substrate beneath the farms is mainly mud.