Grow Out

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 includes 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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Undaria is only farmed in the winter months. Grow out lines are deployed starting from October to November and the grow out period lasts until March to April the following year. The exact timing depends on the region and weather. 

Throughout the grow out period the farmers revisit the farm site to check on the structure of the rig and the growth of the crop. When the density of seedlings on the seeded rope is too high, the cultivation lines need to be thinned by scraping off seedlings. This process is absolutely necessary for high quality crops. Farmers also need to clean the lines to remove any other algae, fouling shellfish or other foreign matter.

Furthermore, farmers who use the horizontal raft and long-line methods need to manage the water depths of the ropes. Cultivation lines are typically hung deeper (1.5 metres) at the start of the growing period and raised closer to the water’s surface during grow out.

High densities during grow out, poor nutrition and poor light can cause diseases. Farmers reported that when a disease occurs, the only way to prevent more damage is to harvest the affected Undaria plants before the disease can spread

In areas with low nutrient content and slow ocean currents in China, fertilisers are sometimes applied to ensure growth and disease resistance of the seaweed. The fertiliser is ammonium nitrate or ammonium chloride and is applied using different methods. In Japan and South Korea these types of growth enhancers are not used.

Technology use

Most Undaria farmers base their farming decisions on intuition and experience. The large corporate farms will use conventional spreadsheets to keep track of their production. 

Communication regarding farm operations is most commonly done through verbal instructions and instant messaging services.

Explore another seaweed species:
Eucheumatoids  |  Saccharina |  Undaria  |  PyropiaGracilaria

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