Ecology, Distribution And Feeding Habits Of Bottom Sowing Culture Apostichopus Japonicus In Qiansan Island, Haizhou Bay

Apostichopus japonicas is a kind of aquaculture species with important economy value. The research on the relationship between the distribution of bottom sowing culture population of sea cucumbers and the habitats has the great significance in the natural enrichment, protection and recovery. Research has been conducted focusing on the relationship between the sea cucumber(Apostichopus japonicas) and the habitats from three points of view in the area around the Ping island in Qiansan Island as the study area. First, the bottom sowing culture population of A.japonicus’ s seasonal variation of the weight structure around the Ping island was investigated by the diving transect survey method,and the density of A.japonicus in different habitats was compared. Besides, the juvenile A.japonicus ’s habitat selection was surveyed in a typical bay by the diving transect survey and the underwater video in summer and winter, and the PCA(principal component analysis) was adopted to study the comprehensive impact of the habitat factors to the distribution of juvenile A.japonicus. Finally, the eukaryotic composition in the gut content of A.japonicus was detected by the high-throughput sequencing, to analysis the composition of the food source and the difference among the samples in different seasons and locations. Major finding are as follows:1 The density of A.japonicus in North Ping island ranges from 0.4 ind./m2 to 1.33 ind./m2 and biomass ranges from 42.69 g/m2 to 103 g/m2. The A.japonicus population is relatively stable, the weight showed an increasing trend in spring and winter yet decreased in summer and winter. It showed that A.japonicus has different distribution patterns in various habitats. The density of A.japonicus in the reef area with algae distribution is significantly higher than that in the reef area with no algae distribution and sediment area.2 In the summer the juvenile A.japonicus in the southeast bay of Ping Island aggregated at the rochy reef near the coast. In the winter however, the A.japonicus had a relatively wide distribution. The A.japonicus had an obviously selectivity to the habitat with rocky sediments and higher algae coverage. Compere to winter, the A.japonicus tend to be more habitat selective and aggregate in summer. The underwater video and the PCA method can be used to give a comprehensive evaluation to the habitat selection to the A.japonicus.3 The result of high-throughput sequencing of the gut content of A.japonicus showed that the gut content of A.japonicus mainly contain the Pyrrophyta, Diatomea, Arthropoda, Mollusca, Cercozoa and some macrophytic algae. There was significant difference in the gut content of A.japonicus, in winter the gut content were mainly made of Pyrrophyta, Diatomea, but in the summer the Arthropoda, Mollusca were being the important component of the gut content of A.japonicus. In the same season, no difference in got content of A.japonicus was detected between two different bays.