Seaweed Innovations for Blue Swimming Crab Aquaculture: Improving Molting, Growth, Feed Conversion Ratio, and Survival Rates

This study evaluated the effects of hot-water Sargassum extract and Kappaphycus biofilm application on molting success, growth, feed conversion ratio (FCR), and survival of juvenile Portunus pelagicus. A total of 288 crablets (40–100 mg) were used in two consecutive 30-day experiments. In Experiment 1, Sargassum extract was incorporated into feed at 0 (control), 4, 8, and 12 g/kg. The 4 g/kg dose, which showed the best molting results, was selected for Experiment 2. In this phase, Kappaphycus biofilm was added to the feed at 0, 1.2, and 3 g/kg to assess its role in enhancing extract retention and efficacy. Results showed that Sargassum extract significantly improved molting success (100% vs. 94.44% in control) and growth performance, with 8 g/kg being optimal for growth and 4 g/kg for molting stimulation. The addition of Kappaphycus biofilm further enhanced growth, molting, and FCR efficiency, with optimal effects at 1– 2 g/kg. All treatments resulted in 100% survival. From the results of this study, it is recommended to use a dose of Sargassum of 4-8 mg/kg of feed and coat it with Kappaphycus gel as much as 1-2 mg/kg of feed.