ESTABLISHMENT OF SUITABLE CULTURE SITES FOR THE PRODUCTION OF HIGH QUALITY SEAWEED (Gracilaria sp.) AT COX’S BAZAR

Abstract

The study conducted a thorough assessment of agar-enriched Gracilaria sp. production in the coastal district Cox’s Bazar, performance, and chemical composition in two distinct aquaculture systems: floating raft net culture and off-bottom long-line culture, over the period from October 2022 to April 2023. Within the Monkhali study area, a total of 69 seaweed culture plots were established, comprising 54 off-bottom long-line systems and 15 floating long-line systems. In the Salsa Beach study area, there were 32 seaweed culture plots with 25 off-bottom long-line systems and 7 floating long-line systems. These plots were managed collaboratively in partnership with local coastal communities. Throughout the cultivation period, Gracilaria sp. was partially harvested every 15-30 days once it reached a length of 30-40 cm. The off-bottom long-line system exhibited significantly superior average biomass production compared to the floating raft net culture system, showcasing a remarkable 699% increase in Monkhali and a substantial 445.2% increase in Salsa Beach. Furthermore, Monkhali demonstrated superior performance to Salsa Beach in both off-bottom long-line culture (542% higher) and floating raft culture (548% higher). Notably, Gracilaria sp. harvested from the off-bottom long-line culture was exceptionally clean, predominantly free from encrusting organisms and impurities, and featured an attractive reddish coloration. Multivariate analysis indicated that the growth of Gracilaria sp. was positively influenced by high salinity, dissolved oxygen levels, and nutrient concentrations, while high temperature, turbidity, and total suspended solids had adverse effects. Furthermore, Gracilaria sp. exhibited elevated levels of protein and lipids. This study demonstrated the potential of off-bottom long-line-based culture systems as a promising technology for Gracilaria sp. production in coastal regions of Bangladesh and similar geographical areas.