Sustainability
Updated December 2023
Ascophyllum nodosum (rockweed) grows in the intertidal zone of the Atlantic coast. It is rich in nutrients and has many applications in agriculture, animal feed, cosmetics, and biotechnology. Sustainable harvesting is crucial to ensure the longevity of this valuable resource.
Figure 1. A healthy rockweed bed, harvested annually in Argyle Sound, NS.
According to a study published in the Journal of Applied Phycology, the commercial harvesting of Ascophyllum nodosum in eastern Canada has been sustainable for over 25 years (Lauzon-Guay, Ugarte & Morse, 2021).
Tidal Organics is committed to sustainable seaweed harvesting methods that ensure the health and regeneration of the seaweed and the ecosystems it supports. Our methods include:
Using appropriate tools that are both approved by the minister and minimize damage to holdfasts & substrate. Our hand harvesters use rakes equipped with guards that help control harvest. Alternatively, our mechanical harvester is size-selective for larger fronds of rockweed cutting at an average height of 50 cm above the substrate. Neither harvest method targets plant holdfast and stays well below the by-weight regulations. Data collected to date shows holdfast removal with mechanical harvesting as the lowest in the industry.
Leaving enough seaweed for regrowth. Our harvesters prune the seaweed fronds carefully and leave 20±5 cm of rockweed. This allows the seaweed to grow back quickly and maintain its productivity. The average length post-harvest is approximately 80cm.
Sector-based management of rockweed leases means they are managed in subunits defined geographically by the Nova Scotia Department of Fisheries and Aquaculture (NSDFA). These sectors can range from <1 hectare to 16 hectares. Each of these sectors are assessed for area coverage of rockweed using ground truthing, aerial, and satellite photography. Direct sampling of the biomass is conducted using quadrat sampling (Figure 2) along metered transects.
Figure 2. A sample quadrat.
Other sector information is recorded such as substrate, average plant length, epiphytes, Ascophyllum clump density, other algal species, and macrofaunal species that are present in the area in order to ensure the health of the rockweed beds. Quotas are established for each of the sectors based on regrowth and accessibility to a maximum exploitation rate of 20% annually.
Monitoring and recording harvest. We keep track of the amount of rockweed harvested, as well as the incidences of holdfast. We use this data to assess the health of the seaweed resource and adjust our harvesting practices accordingly. We monitor the landings very closely and inform the rockweed harvesters that the closure of the sector is imminent.
Close collaboration with the NSDFA. Monthly harvest reports are submitted to keep the department informed of progress being made on our quotas. Pre- and post-season meetings provide an opportunity to discuss the resource. End-of-season reports provide the province with yearly harvest data.
Figure 3. A group of harvesters hand raking.
The harvesting of rockweed in Nova Scotia has a long history. Commercial harvesting began in Lobster Bay in 1959.
Mechanical harvesting and manual harvest methods existed during the development of the harvest. The resource base has been well managed by all leaseholders.
The distribution and abundance of rockweed has been very stable in the long-term history of these harvests. Furthermore, the management of rockweed has improved year over year throughout the past 30 years.
For additional inquiries, please use the form on the Contact Us page.
Related articles
Lauzon-Guay, JS., Ugarte, R.A., Morse, B.L. et al. Biomass and height of Ascophyllum nodosum after two decades of continuous commercial harvesting in eastern Canada. J Appl Phycol 33, 1695–1708 (2021). https://doi.org/10.1007/s10811-021-02427-x