Feasibility of farming the agarose-yielding red alga Gracilaria dura using tube-net cultivation in the open sea along the Gujarat coast of NW India

Abstract

Despite some perceptions of economic risk, the global aquaculture industry continues to attract new entrepreneurs and investors. However, to sustain this trend, innovative and cost-effective strategies are needed. In recent years, algal farming has been shown to be a sustainable activity in the global Blue Economy. In 2015, harvests of the red algal agarophyte genus Gracilaria surged to over 114,100 tons dry weight which constituted ca. 91% of the total raw material for industrial agar production. We carried out a trial of experimental farming of the agar-yielding alga known as Gracilaria dura using a tube-net method along the Gujarat coast, India. The mean daily growth rate (DGR) of this agarophyte ranged from 1.88 ± 0.23% day −1 to 3.30 ± 0.25% day −1. Similarly, the mean yield varied between 0.62 ± 0.03 kg and 1.05 ± 0.02 kg fresh wt m −1 of tube-net. A Pearson correlation showed that both DGR and biomass yield were positively correlated with temperature. In addition, the DGR was significantly positively correlated with air temperature (r = 0.916; p < 0.01) whereas biomass yield was also positively correlated with surface seawater temperature (r = 0.986; p < 0.001). The economic projections for four harvests per year revealed that the value of the product was US$5577, while the investment required for the necessary tube-net infrastructure was US$1797 thereby providing US $1890 as profit to single farmers, a significant amount in the coastal communities of Gujarat. Thus, undertaking commercial farming of G. dura in Indian waters could diversify the livelihood of artisanal, coastal fishermen and further encourage the indigenous production of agarose.

Recent advances in seaweed seedling production: a review of eucheumatoids and other valuable seaweeds

“…Due to the high demand and profitability of eucheumatoids and Gracilaria, new techniques in seaweed farming have been used to increase the quality and productivity of the seaweed farms, including the use of floating cages in open-sea farming over the conventional longline method to protect seaweeds from grazing predators such as fish and turtles (Kasim and Mustafa 2017). Another novel technique for seaweed cultivation is tube-net cultivation, which was used for Gracilaria dura in open-sea farming along the Gujarat Coast of North West India (Mantri et al 2020). This method has several advantages, including being less affected by the propelling waves, taking less time to seed, protecting seedlings from drifting, and allowing the depth of planting to be adjusted based on location and season (Mantri et al 2017a).…”

“…This method has several advantages, including being less affected by the propelling waves, taking less time to seed, protecting seedlings from drifting, and allowing the depth of planting to be adjusted based on location and season (Mantri et al 2017a). The economic projections for gross revenue from four harvests per year using this method are US$5,577, while the investment required for the tube-net and related infrastructure is US$1,797, resulting in an estimated profit of US$3,780, or US$11.81 per farmer per day (Mantri et al 2020).…”

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

“…Public support (including financial incentives) is also needed to support the development and commercialization of innovations that tend to have significant technical, economic, environmental and/or social benefits. Examples of such innovations include, among others, (i) tube-net technique suitable for growing warm-water red seaweeds in areas with strong currents (Mantri, Shah and Thiruppathi, 2020); (ii) land-based tank culture systems that provide better-controlled environment conditions to optimize the quality, safety and traceability of seaweed products (Gadberry et al, 2019); (iii) species diversification and crop rotation that tend to help reduce the risk of disease, deter grazing by herbivores and improve crop yield (Grebe et al, 2019); (iv) technologies to prevent the contamination of non-target species in large-scale open systems of microalgae cultivation; (v) technologies that reduce the high cost of harvesting microalgae in large-scale cultivation, which has been a major constraint deterring investments in large-scale microalgae cultivation; (vi) resourceefficient biorefinery technologies that convert algae biomass into different products (Lange et al, 2020); (vii) product improvement, such as the removal of undesirable tastes, better texture, more appealing appearance and longer shelf-life; and (viii) integration of seaweeds in local cuisine and innovative recipes.…”

An Individual-Based Model of the Red Alga Agarophyton chilense Unravels the Complex Demography of Its Intertidal Stands

“…Seaweeds are the most efficient primary producers on the planet (Creed et al, 2019). In coastal waters, they often sustain the food web (Kang et al, 2008;Cordone et al, 2018;Momo et al, 2020), structure the community (Arkema et al, 2009;Momo et al, 2020) and are of commercial interest for mankind (Bustamante and Castilla, 1990;Guillemin et al, 2008;Lawton et al, 2013;Veeragurunathan et al, 2015;Mantri et al, 2020). Some algal species turned invasive, disrupting the functioning and balance of native communities (Staehr et al, 2000;Yamasaki et al, 2014;Davoult et al, 2017).…”