Cultivation of Gelidiella acerosa in the open sea on the southeastern coast of India

Four cultivation methods: raft, bottom net, coral block and cement block were evaluated for the propagation of Gelidiella acerosa in the open sea. Of the 4 methods, the raft method resulted in significantly (p < 0.001) highest daily growth rate (DGR) of 1.11 to 1.31 % and biomass of 973 to 1288 g fresh weight (wt) m(-2). Biomass values showed direct correlation with initial seedling densities. Initial seedling densities >= 500 g fresh wt m(-2) registered maximum yields of 1425 +/- 90 g fresh wt m(-2), while lower initial seedling density (200 g fresh wt m(-2)) showed higher DGR values (0.71 +/- 0.07 and 0.48 +/- 0.06%) during the 1st and 2nd harvests respectively). The 180 d cultivation period registered the highest yield of 367 +/- 45 g fresh wt m(-2), which significantly differed (p < 0.001) from values obtained for the 30, 60 and 90 d cultivation periods. The germplasm collected from Sethukarai (subtidal reef) showed the highest yield (525 +/- 34.6 g fresh wt m(-2), p < 0.001) and DGR (0.54 +/- 0.04%) compared with those collected from Pudumadam (intertidal rock), Ervadi (intertidal reef) and Rameswaram (subtidal rock). The findings of this study indicate that the raft method of cultivation using germplasm from Sethukarai, an initial seedling density of >= 500 g fresh wt m(-2) and a 180 d cultivation period are important criteria for the Successful cultivation of G. acerosa. The augmentation of exploited seaweeds through cultivation practices will help preserve natural biodiversity and ecosystem functioning.