Floating cage system for seaweed mariculture: Design and site suitability in the dynamic coastal environment of Bangladesh

The monsoonal climate with varying hydrodynamic conditions, prevalence of traditional cultural practices, and difficulties in suitable area identification are the main obstacles to the growth of seaweed farming activities in Bangladesh. The present study introduces an innovative floating net cage system to improve seaweed mariculture techniques, specifically for cultivating Gracilaria. This system was tested in the Moheshkhali Channel waters of Bangladesh to alter the hydrodynamic forces within the cage, thereby enhancing seaweed growth. The production system successfully reduced ~28% sea surface current velocity inside the cage and yielded 1.77–3.50 kg m−2 per month at 10.37–14.65% daily growth rate during the period of November to April. Moreover, this study attempted to develop a seaweed site suitability index (SSI) model using suitability functions for different environmental variables in order to predict suitable seasons and potential areas for seaweed aquaculture development in Moheshkhali Channel. A large array of environmental datasets was created to feed the SSI model, with monthly sampling conducted across 56 geospatial locations within the ~52 km² area of the Moheshkhali Channel. The monsoon showed the highest environmental variability, differing from other seasons. Winter and post-monsoon were identified as the most suitable seasons, when 32–39 km2 area of the channel was predicted as suitable (SSI score > 0.70) for seaweed aquaculture development. The findings of the study on the new production system and suitable area identification can aid in the horizontal expansion of seaweed culture and contribute to enhance seaweed production in Bangladesh.