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

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.