The time it takes for seaweed to grow from deployment to harvest varies significantly between tropical and temperate species. Seaweeds are low trophic species and generally do not need to be fed during the grow out process. Yet once the lines are in the water, some species require more attention than others. Risks during the grow out phase include epiphytes, diseases, pests, aquatic animal grazing and even strong weather events. Technology usage for production planning, communication or monitoring indicates how widespread digital solutions are.
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Saccharina is only farmed in the winter months. Cultivation lines are deployed starting from early November to December and grow out period lasts until March to April the following year. The exact timing depends on the region.
In the North of Japan, the grow-out time at sea starts around the end of October and usually takes around 10 months. The harvest takes place between mid June and mid August. In South Korea and most locations in China, the grow-out period is usually not longer than 5 months, from October til February or March.
The deployment of the cultivation lines is highly weather dependent and time-critical. In Northern China, there are typically can be millions of lines to be deployed on large farms, which can easily take up to 2 months.
Between January and April, when the water temperature and light intensity rises, the depth of the culture lines needs to be adjusted regularly using additional floats. Such work is typically done by two people per boat and is a fairly repetitive and heavy task.
Furthermore, throughout the grow-out time, regular ‘thinning out’ will need to be done, to ensure good growth of high quality blades. This means, small blades will be cut out manually. In South Korea this happens on a much more regular basis. Japanese farmers usually wait for two months until the blades have grown up to one metre until they conduct the first selection. In March the second selection or thinning out will take place. Farmers also need to clean the lines from any other algae, fouling shellfish or other foreign matter.
Most Saccharina farmers base their farming decisions on intuition and experience. The large corporate farms use conventional spreadsheets to keep track of their production.
Communication regarding farm operations is mainly done through verbal instructions and instant messaging services.