Tube net cultivation of Kappaphycus alvarezii in floating high density polyethylene raft - a feasibility study in exposed coastal waters in Northeastern Indian Coast

Commercial-scale seaweed production in exposed coastal waters has failed due to the absence of appropriate culture methods. In the present study a novel tube-net based seaweed cultivation in floating high-density polyethylene (HDPE) raft structure was developed for exposed and deeper coastal waters. The design prototype was evaluated by culturing Kappaphycus alvarezii , in the northeastern Bay of Bengal Sea, off the Visakhapatnam coast, India, for its structural stability, seaweed culture potential, and economic feasibility. A square-shaped HDPE raft of 3 × 3 m, was tied with ten tube nets of each 3.0 m length and 0.32 m dia, made of HDPE net. A cluster of 25 rafts deployed as a single unit and the entire system was stabilized by a multipoint mooring system. The raft structure with seaweed, along with the anchoring system endured the high waves (1.34 ± 0.08 m) and wind speed (11.5 ± 0.62 km h -1 ) and had supported for seaweed growth. Four different initial seeding biomasses (3, 5, 7.5, and 10 kg tube-net -1 ) were assessed for growth in a total of six cycles with a culture duration of 45 days cycle -1 . The growth parameters were observed to be significantly higher (p