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Harvesting Seaweeds

There are thousands of seaweed species around the world growing in different climates and environments. Different seaweeds grow at different latitudes and at different depths. Like land plants, seaweeds also have seasons so when harvesting seaweeds, understanding seasonality is critical to ensure the natural life cycle of the seaweed is not disrupted.

Hand harvesting seaweeds

Different Ways of Harvesting Seaweeds

There are different ways to harvest seaweeds and this may vary by species and location. Some seaweeds may be able to regenerate whereas others may not. Some of the popular terms or phrases you may hear in connection with seaweed are Beach cast, wild harvested, farmed seaweeds. A little more on each of these follows below.

Beach Cast Seaweed

this is seaweed which is collected from the beach after it’s been washed up by the tide. You can recreationally harvest seaweeds (forage) throughout NZ as long as you are not in a marine reserve. Ensure you choose clean areas of water as seaweed can become contaminated by run off and pollution in the sea.  Once harvested you need to process the seaweed quickly before it starts to break down – we suggest air drying.   Once dried, store in a cool dark and dry place so it doesn’t reabsorb moisture.

Wild Harvested Seaweed

Seaweeds may be cut from where they are growing, ideally in a way which helps them to regenerate and which does not interfere with their natural cycles.  Mechanical harvesting of seaweeds is controversial due to the ‘blunt instrument’ nature of the machines that cut the seaweeds randomly as well as the damage that can be caused to the surrounding environment, which is also destroyed as the seaweed is removed mechanically. Technically, seaweeds which are beach cast are also wild harvested because they are seaweeds which are taken from the ‘wild’ ocean and there has been no human interferance in their growth.

wakame farming

Farmed Seaweeds

Farming seaweed is more common in Asia where typically small-scale, rope grown labour intensive farms are common. There are some research farms already in New Zealand but a lot of work is underway to expand the seaweed farming (aquaculture) space in the future – to date, most of this activity is still in a trial phase and not yet commercially available.  Typically seaweed farms operate under a license and will be monitored and regulated closely. The early life of a farmed seaweed may start in an onshore tank where a small plant is grown and later attached to a rope or some structure in the open ocean to complete its growth, or it may be grown in a tank it’s own life.

In New Zealand all seaweed harvesters who operate commercially are required to be licensed by the Ministry of Primary Industries. Although we have over 1000 species of seaweed only a small number of these are allowed to be harvested.  Kelps are beach cast collected and some seaweeds ( eg, Undaria) are being wild harvested.  There are a few small trials underway to explore farming opportunities, but these are in the early stages.

Globally the seaweed industry faces a challenge as there is a mismatch between seaweed demand and availability of seaweeds which are increasingly being used in new applications such as animal feeds, the biofuel, packaging industries and others. More work needs to be done to understand how larger scale seaweed farms can be established to reduce pressure on natural reserves.  Seaweed grows relatively quickly, requires no fertilisation or water and absorbs enormous amounts of carbon dioxide. The establishment of seaweed farms can reduce carbon footprint, create employment in regional areas and produce high quality products. The key is ensuring that this is done in an ethical, monitored and sustainable way.

The direction of currents is a strong indication of where contaminated waters will flow to and from.

Pacific Harvest only secures seaweeds harvested from ‘clean’, uncontaminated waters. After nearly 20 years of operating, we have a clear understanding of where the clean areas are, and which harvesters operate ethically whilst harvesting seaweeds.

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Our seaweed is sustainably harvested


Processed in approved food grade facilities

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