Survey on the roles and impacts of seaweeds and aquatic plants in the improved extensive black tiger shrimp farms in Bac Lieu province

A survey was conducted to assess the roles and impacts of seaweeds and aquatic plants on the production and financial efficiency of black tiger shrimp in improved extensive farms through direct interviews with 60 farmers from Dong Hai district, Bac Lieu province. The householders were divided into two groups based on the presence of natural seaweed and aquatic plant, including group 1: the presence of different seaweeds and aquatic plants but the absence of red seaweed (mixed vegetation) and group 2: the presence of red seaweed dominates over the mixed vegetation. The surveyed results showed that group 2 had an average shrimp yield of 268.6 kg/ha/year with a profit of 58.4 million VND/ha/year, which was higher than that of group 1 (shrimp yield of 203.1 kg/ha/year and profit of 43.0 million VND/ha/year). Almost all farmers agreed that seaweeds and aquatic plants acted as important roles in improving water quality, providing natural food and shelter for shrimp, crab, and fish. Farmers, on the other hand, claimed that their excessive growth (high biomass) increased water transparency, limited living space, and hampered the activities of shrimp, crab, and other organisms, as well as reduced shrimp growth and production and polluted water after seaweed died off. Notably, the farm that maintained vegetation coverage ≤50% obtained higher shrimp production and profit than pond with coverage >50%. Moreover, 46.7% of farmers preferred red seaweed over other seaweed and aquatic plant species in their farms.