Optimal Culture Capacity of White Shrimp (Litopenaeus vannamei) and Razor Clam (Sinonovacula constricta) in a New Series-Connection Culture Model

To construct an effective circular mix-culture model and investigate its culture capacity, we established one small and one large systems, with white shrimp ( Litopenaeus vannamei ) and razor clam ( Sinonovacula constricta ) cultured in separate ponds. The culture water from the L. vannamei was pumped to the S. constricta , and the culture water from the S. constricta overflowed back into the L. vannamei via gravity. In trial I, we tested four culture densities (groups 1–4), and monitored water quality, growth indices, and digestive and immune enzyme activities. From the results, the nitrogen and phosphorus levels generally increased then declined after 56 days, and were lower in groups 1 and 2. The specific growth rate of group 2 was the highest. After 56 days, activities of four digestive enzymes were increased in group 2, and lysozyme activity was significantly decreased in S. constricta in groups 1–4; Alkaline phosphatase activity of L. vannamei was increased in group 3, but decreased in S. constricta in groups 2–4; Acid phosphatase activity was significantly higher in groups 1–3 ( P < 0.05), while SOD and CAT activities were significantly elevated in group 2 ( P < 0.05). Thus, we applied group 2 density for trial II. In trial II, nitrogen and phosphorus concentrations declined significantly during the latter stages, and growth indices were higher than the control ( P