Effects of seaweed Sargassum muticum on growth of sea cucumber( Apostichopus japonicus) and some water environmental factors

At water temperature of 7. 0-19. 5 ℃,and a salinity of 28. 7-30. 9,sea cucumber( Apostichopus japonicus) with body weight of( 25. 2 ± 1. 21) g and seaweed( Sargassum muticum) were reared in a 1 m3 tank at various initial densities including 200,400 and 600 g / m3 for sea cucumber and 0,1 000 and 2 000 g /m3 for seaweed to study the appropriate farming capacity and density of sea cucumber and seaweed in certain water volume,and the effects on water environmental factors. The results showed that the mean daily weight gain rate( Mdwg) and specific growth rate( SGR) of sea cucumber and seaweed were significantly affected by their density( P 0. 05). The minimal Mdwg and SGR of sea cucumber were observed in the group A1,B4。While the maximal Mdwg and SGR were found at groups of C8 and C9. The maximal SGR of seaweed was observed at group A2,and the minimal SGR of seaweed found at group C9. NH4+-N,NO3--N,NO2--N and PO43--P contents in the water were affected significantly by the densities of sea cucumber and eaweed( P 0. 05). There were relatively high NH4+-N、NO3--N,NO2--N and PO43--P contents in the water in groups of A1,B4. The low nutrient levels were found at groups of A3,B6 and C9. The results indicated that seaweed( Sargassum muticum) could fully utilize the nutrients in the water and the density played a significant effect on sea cucumber growth( P 0. 05). In this experiment,the group of C8( Apostichopus japonicus: 200 g / m3;Sargassum muticum: 1 000 g / m3) and C9( Apostichopus japonicus: 200 g/m3; Sargassum muticum: 2 000 g/m3)is recommended due to the better ecological and growth effects.