Abstract:Polyculture of sea cucumber Apostichopus japonicus and Gracilaria lemaneiformis was conducted in land-based enclosures at orthogonal design during May~July，2010. A. japonicus was cultured at densities of 15,20,25 ind/m2 without feed,and G.lemaneiformis was cultured at densities of 0,180,360 g/m2. The growth and survival of A. japonicus and G.lemaneiformis were compared for different treatments and the changes of environmental nutrient were also detected. The results showed that the final average weight (Wf) , daily weight gain (Mdwg) and Specific Growth Rate (SGR) of A. japonicus were significantly affected by the density of A.japonicus . Wf, Mdwg and SGR of A. japonicus were not significantly affected by the density of G. lemaneiformis. The highest Wf, Mdwg and SGR of A. japonicus were obtained when the density of A. japonicus and G. lemaneiformis were 15 ind/m2and 360 g/m2 respectively. The highest yield of G. lemaneiformis was acquired when the density of A. japonicus and G. lemaneiformis were 25 ind/m2 and 360 g/m2 respectively. The highest SGR of G. lemaneiformis was obtained when the density of A. japonicus and G. lemaneiformis were 25 ind/m2 and 180 g/m2 respectively. The analysis of water quality showed that the content of total nitrogen and total phosphorus in mud declined most sharply when the density of A. japonicus was 15 ind/m2. In summary, polyculture of A.japonicus and G. lemaneiformis could improve water quality and increase the SGR of A. japonicus.
