关键词: 海马齿, 生态浮床, 覆盖率, 石斑鱼养殖, 投入产出比, S. portulacastrum L., ecological floating beds, coverage rate, Yunlong grouper, input-output ratio

Abstract: The intensive aquaculture relying on exogenous feed intensifies the eutrophication of seawater and leads to the increase of aquaculture diseases, which is the main factor restricting the sustainable development of mariculture. In this study, by constructing an integrated closed mariculture system combined Sesuvium portulacastrum L. with Yunlong grouper, a hybrid of E. lanceolatus (♂) and E. moara (♀), the effect of S. portulacastrum L. ecological floating bed (EFB) on grouper culture was investigated under simulated conditions, and the optimal coverage rate of EFB in culture water was explored. The results showed that after 22 days of culture, there was no significant difference in the survival rate of S. portulacastrum L. among groups (P>0.05), and a positive linear correlation between the plant weight gain rate and the EFB coverage rate was revealed (R2=0.994, P = 0.048 5), implied that the intensive fish activity could decrease the growth of S. portulacastrum L. by root damage. The survival rate, specific growth rate (SGR), feed conversion rate and output-input ratio of fish in the EFB treatment group were significantly higher than those in the control group (P<0.05), and there was no significant difference among the EFB treatment groups (P>0.05), which indicated that 15% coverage of S. portulacastrum L. EFB could improve the economic benefits of E. grouper culture tremendously. Except for T1, the weight gain rate (WGR), residual feed and fecal yield of fish in EFB treatment groups were higher than those in the control group (P<0.05), and there was no significant difference among EFB treatment groups (P>0.05), that’s to say, the fish WGR would be improved obviously as long as 30% of the water was covered with S. portulacastrum L. EFB. Similarly, the total feed quantity varied among groups, and the trend was expressed as T3> (T2, T1)>CK; in other words, S. portulacastrum L. EFB could increase the amount of feed intake and T3 (45% coverage) worked the best. What’s more, the nitrogen content of residual feed and feaces in T3 was lower than that in other groups (P<0.05), while phosphorus content stayed at the same level between groups (P>0.05), showed that feed protein utilization of fish increased in S. portulacastrum L. EFB treatment groups. Taken together, the S. portulacastrum L. EFB has obvious promoting effect upon the survival, growth and aquaculture benefit of Yunlong grouper, of which 30% coverage is the priority.