Biomass and height of Ascophyllum nodosum after two decades of continuous commercial harvesting in eastern Canada

Abstract

With the increasing demand for seaweed resources worldwide, management must ensure that the harvest of wild seaweed stocks is sustainable. We evaluate the impact of over 25 years of commercial harvesting of Ascophyllum nodosum in eastern Canada by comparing the biomass and height of the seaweed in the late 1990s to the late 2010s over a broad spatial scale spanning the provinces of Nova Scotia and New Brunswick. There has been no significant decrease in the biomass of A. nodosum in either province, and biomass has increased in some regions of New Brunswick during that period. The average height of A. nodosum has decreased by 7.8 cm in Nova Scotia while it increased by 13.8 cm in New Brunswick. Biomass of A. nodosum in unharvested sectors was 7% higher than that in harvested sectors while height of A. nodosum in unharvested sectors in New Brunswick is similar to the values observed in harvested sectors. Over the same period, water temperature has increased in both provinces and, in recent years, has at times exceeded the optimal growing temperature for A. nodosum within bays in Nova Scotia. We conclude that the current management and harvest of A. nodosum in eastern Canada are sustainable and maintain the biomass and height of A. nodosum beds but that control sites are necessary to offer adequate comparisons as environmental conditions are changing.

A novel approach reveals underestimation of productivity in the globally important macroalga, Ascophyllum nodosum

“…Ascophyllum nodosum is commercially harvested in several countries (mainly Canada, Ireland, Norway, Iceland, USA, Scotland, and France). Regulations vary between countries; for example, the maximum harvest rate in New Brunswick, Canada, is set at 17% of the standing stock (Ugarte and Sharp 2001;Lauzon-Guay et al 2021). According to previous productivity estimates based on the most apical growth segment (Cousens 1984), it was estimated that this harvest rate represented between 15.1 and 18.7% of the annual A. nodosum production in southern New Brunswick (Ugarte et al 2006).…”

“…These yearly air bladders have also been used to calculate yearly growth and productivity estimates for the species (Baardseth 1970;Cousens 1984;Vadas et al 2004). Ascophyllum nodosum is commercially harvested on both sides of the North Atlantic (Mac Monagail et al 2017), and quotas are often determined based on productivity estimates of the species to ensure recovery (Ugarte and Sharp 2001;Lauzon-Guay et al 2021).…”

Current Insights into the Molecular Mode of Action of Seaweed-Based Biostimulants and the Sustainability of Seaweeds as Raw Material Resources

“…Kelly et al [ 57 ] reported that sites in Ireland at Clew Bay and Connemara demonstrate almost complete recovery of A. nodosum 11- and 17-months post-hand harvesting, respectively. In Canada, 2 to 5 years was suggested for A. nodosum biomass recovery ([ 86 ] and references therein), which was observed within 3 years post-removal of 50% of the biomass ([ 86 , 87 ] and references therein). Rapid recovery may be due to stimulation of growth and branching of the suppressed shoots of the clumps [ 88 ].…”

“…Rapid recovery may be due to stimulation of growth and branching of the suppressed shoots of the clumps [ 88 ]. A. nodosum is harvested in Canada from small boats using a hand-held cutting rake [ 87 ].…”

Seaweeds and microalgae: an overview for unlocking their potential in global aquaculture development

“…The existence of vast marine areas suitable for seaweed farming makes champions of seaweeds envision a forthcoming "Seaweed Revolution". 5 There is a growing consensus that wild resources will not be able to supply enough seaweeds to satisfy future demand despite the robust management strategies in many areas (Steen et al, 2016;Monagail et al, 2017;Lauzon-Guay et al, 2021). Aquaculture is the primary means to ensure safety and traceability and to help unlock the great potential of seaweeds.…”