How to harvest seaweed sustainably

Algae are among the fastest growing organisms on the planet and are very regenerative if harvested correctly. The number one rule for sustainable harvesting is: don’t tear the algae from the rock. Always leave part of the seaweed attached and harvest by size. Here are some key considerations for ensuring a sustainable harvest.


In order for the algae to grow back, it must not only be harvested leaving part of the algae attached to the rock, but also cut in the right place. The best place to cut the algae will depend on the species. Most algae will not regenerate if their stipe (stalk-like structure) is cut. In many algae, new growth occurs in the part of the lamina (leaf-like structure) closest to the stipe. Leaving this part intact and leaving several centimeters (or more for large algae) of the blade is important so that the algae can regenerate. Additionally, many algae have distinct reproductive structures that must be left intact to ensure that they can reproduce. Still other algae are long-lived perennials and require special attention. It is also important to know the ecological role of algae in the areas where you plan to harvest. Take a course and learn about the specific algae you want to harvest in the wild.

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Also, depending on where you are harvesting, a license may be required.


Only harvest a particular type of seaweed if it is abundant in the area where you plan to harvest.

Only take what you need and can handle

Seaweed takes up a lot of space to dry out. Be sure to only harvest what you need and what you can dry or process in your space.

Harvest by recovering

Salvage harvesting is a great way to be sustainable. Where I live, we regularly have high winds and ocean swells, which rip healthy seaweed and deposit it on the beach like treasures waiting to be discovered. To determine if the seaweed is still fresh and of good enough quality to eat or use in the bath, use your senses. It should smell brackish and fresh, it should not be viscous to the touch but should be lubricated and gelatinous, and the color should be uniform and vivid. For elusive species, or those found only in deep water, scavenging is often the only way to harvest them.


Practicing reciprocity is essential to sustainability. In healthy ecosystems, there is a balance of trade-offs and trade-offs between all living organisms. When you harvest algae, you become part of their ecosystem. The organisms that make up an ecosystem work together as a whole, so it is essential to listen to the ecosystem and be sensitive to its needs. What can you give back to an ecosystem after taking something, in order to restore balance? Giving back is personal and can be done in many ways. Acting on local threats to the ecosystem where I harvest and global threats to the wider ocean ecosystem are ways in which I choose to give back. Sharing the love and wonder you have for an ecosystem with your community is a great way to engage people and build support for protecting the health and integrity of local ecosystems.

Photo by Chris Adair.

Commercial harvest

In the province of British Columbia where I work and live, a commercial seaweed harvester is legally required to harvest by pruning and is only allowed to harvest by hand, cutting the seaweed a minimum distance from the spike or stipe, which varies according to the species. As a commercial harvester, I feel very fortunate that our local regulations help ensure harvesting is done in a sustainable manner.

Where to harvest

Seaweed that is harvested for food must come from clean water. Urban centers and areas near sewage outfalls are not safe places to harvest. Since algae are masters of the concentration of minerals in the water in which they grow, they should be harvested away from industrial areas such as pulp and paper mills, mines, shipyards and other industrial sites that release chemicals or heavy metals into the ocean or highlands. watercourse. Areas with strong tidal currents are better than areas with more standing water because the currents regularly bring in water from the open ocean and wash away old water.

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Listening to the ecosystem

As I prepared to harvest bull kelp one day, many years ago, I had a very strong feeling that today was not an appropriate day to “take”. I questioned myself and went to harvest anyway. As I emerged from the ocean with a heavy bag full of kelp, a wave lifted me up and crushed my masked face into the sand. I slowly got to my feet, feeling shocked and disoriented, and started reaching for my kelp bag. Although I searched the area for a while, I never found it. Since then, I take a moment before harvesting to listen to the ecosystem. I ask permission. When I’m done harvesting, I look at the kelp forest or intertidal kelp garden and say, “Thank you.”

Wild Watercress, Kelp and Cauliflower Soup with Crispy Fermented Jerusalem Artichokes

Photo by Laura Jany.

“This is a beautiful, vibrant, green spring soup that comes together quickly and is simple to make. Wild watercress has a refreshing, clean, peppery flavor that’s balanced by the deeply savory umami taste of kelp, while cauliflower lends its silky texture to this mineral-rich spring soup. Prepare the fermented Jerusalem artichokes at least three days in advance. —Laura Jany, wild food forager, Kelowna, British Columbia


Crispy Fermented Jerusalem Artichokes
3–4 Jerusalem artichokes
2 tbsp. (30 ml) pickling spice
6 garlic cloves
1 C. (15 ml) Himalayan sea salt Garlic salt to taste
Olive oil

Wild watercress, kelp and cauliflower soup
1 medium onion
2 medium carrots, peeled
2 stalks of celery 1 leek
3 tablespoons (45ml) unsalted butter
1 cup (250 mL) cauliflower florets
3-5 strips of dried kelp
3 bunches of fresh wild watercress, coarsely chopped
Sour cream or coconut milk (optional)
Salt (optional)


Note: Jerusalem artichokes do not need to be fermented before roasting. However, it adds a tart flavor and aids digestion. If you prefer to skip the fermentation process, simply wash the Jerusalem artichokes, then proceed to the roasting steps.

To ferment: Gather enough Jerusalem artichokes to fill a small jar. Wash the tubers but do not peel them. Add 2 tablespoons (30ml) pickling spice and 6 garlic cloves to a medium jar. Add the tubers, leaving a 2.5 cm (1 inch) space at the top.

Dissolve the Himalayan sea salt in 4 cups (1 L) of filtered water, then pour into the jar, making sure the tubers are covered. Close the jar and leave at room temperature until fermentation begins, about 3 to 4 days. When the contents are actively bubbling, store the jar in the refrigerator until ready to use. (Fermented Jerusalem artichokes will keep for up to 1 month.)


Preheat oven to 425 F (220 C) and line a baking sheet with parchment paper.

Peel and coarsely chop the onion, carrots, celery and leek. In a large saucepan, melt the butter and add the onion, carrots, celery, leek, cauliflower and kelp strips. Stir and cook until the onion is translucent, 5 to 6 minutes. Add enough water to cover the vegetables and bring to a boil, then reduce the heat to low and cover. Simmer until the vegetables have softened, about 15 to 20 minutes.


While the soup cooks, thinly slice the raw or fermented Jerusalem artichokes using a mandolin. Use a paper towel to pat the slices dry. Toss the slices with garlic salt and a drizzle of olive oil until coated. Roast on prepared baking sheet until edges begin to brown and fries are crispy, about 20 minutes, stirring occasionally to ensure even roasting.


Remove the soup from the heat, add the watercress and cover. Allow the greens to wilt gently, about 2 to 3 minutes. Use an immersion blender to purée the soup until smooth.

Ladle the pureed soup into bowls. Stir in a dollop of sour cream or coconut milk, if using. Add salt to taste if needed (bull kelp often provides enough salt and additional salt may not be necessary). Garnish with crispy fermented Jerusalem artichokes.

Excerpted with permission from The Science and Spirit of Seaweed: Discovering Food, Medicine, and Purpose in the Pacific Northwest’s Kelp Forests by Amanda Swinimer (Harbour Publishing, April 26).