Integration of white shrimp (Litopenaeus vannamei) and green seaweed (Ulva prolifera) in minimum-water exchange aquaculture system

Ulva prolifera is one of the most common macroalgae and is distributed widely off the coast of China. It is well known for its rapid growth rate and good reproduction and it has fast nitrogen removal efficiency. Integration of seaweed cultivation in shrimp farming water is considered a potential aquaculture practice since seaweeds can convert dissolved inorganic nitrogen into biomass and the biomass can be harvested easily. This study investigated the effect of integrating green seaweed (Ulva prolifera) with Litopenaeus vannamei (500 shrimp m−3) at varying levels of water exchange daily on water quality and shrimp growth performance. The four daily water exchange quantities were 5% (T1), 10% (T2), 15% (T3), and 20% (T4). The appropriate range of the stocking density of U. prolifera was 800 mg L−1. No significant differences were observed in total ammonia nitrogen (TAN) concentration between T2 and T3 (P > 0.05) from beginning to end. The concentrations of nitrite and nitrate in all treatment remained constant at low levels from beginning to the end. On day 35, there were no significant differences in survival rate of shrimp among T2, T3, and T4. No significant differences in FCR were observed in group T2, as compared to T1, T3, or T4. No significant differences in cumulative weight of U. prolifera were observed among T1, T2, and T3; however, they were significantly larger than that of T4. The study demonstrates that integrating U. prolifera (800 mg L−1) with L. vannamei (500 shrimp m−3) with 10% water exchange can control the water quality and enhance shrimp growth.