fishes Article Effects of Different Densities of Sea Grape Caulerpa lentillifera on Water Quality, Growth and Survival of the Whiteleg Shrimp Litopenaeus vannamei in Polyculture System Khanh Van Ly, David Kamau Murungu * , Dung Phuong Nguyen and Ngoc Anh Thi Nguyen Department of Coastal Aquaculture, College of Aquaculture and Fisheries, Can Tho University, 3/2 Street, Ninh Kieu District, Can Tho City 94000, Vietnam;
[email protected] (K.V.L.);
[email protected] (D.P.N.);
[email protected] (N.A.T.N.) * Correspondence:
[email protected] Abstract: The integrated aquaculture-seaweed system has been identified as a bio-mitigation strategy to overcome environmental damage, improve the efficiency of nutrient use, maintain good water quality, and ensure the system’s sustainability. This study was conducted to determine the appro- priate density of sea grape (Caulerpa lentillifera) in polyculture with whiteleg shrimp (Litopenaeus vannamei) in the same culture tank. Five treatments were randomly designed in triplicate tanks where shrimp was monocultured (without sea grape) as a control treatment and four polyculture treatments with different seaweed density levels (0.5, 1, 1.5, and 2 kg m−3) for 56 days. The results showed that polyculture of shrimp and sea grape significantly reduced the concentrations of total − − 3− ammonia nitrogen (TAN), nitrite (NO2 ), nitrate (NO3 ), and phosphate (PO4 ) in the rearing tanks and significantly improved (p < 0.05) the growth rate (6.67–6.76% day−1), survival (73.3–78.5%), Citation: Ly, K.V.; Murungu, D.K.; and production of shrimp (3.44–3.87 kg m−3) compared to monoculture (6.24% day−1, 54.8%, and Nguyen, D.P.; Nguyen, N.A.T.