| From October 2011 to April 2012, outdoor experiments were conducted to investigate the sea cucumber(Apostichopus japonicas Selenka) in earthen ponds, according to the breeding cycle of sea cucumber in the south. Four kinds of shelter(scallops cage, woven bags, sunshade nets and hollow brick) in the sea cucumber pond, the species of benthic algae and the effect of changes in cell number and biomass to sea cucumber’s growth and survival were investigated.Afterwards, research on the changes of sediment organic carbon and sulphide content to explore the effect of sea cucumber’s breeding to purifying sea cucumber aquaculture sediment.1) The benthic algae which attached to the four kinds of shelter were collected as sample once a month. The species were identified and the number of the sample was counted under the microscope, and the content of chlorophyll was determined to obtain the biomass of benthic algal.The results show that: there were 3 phyla, 20 genera and 49 species in the benthic algae,including 18 genera and 47 species in Bacillariophyta at the dominant. The species composition of benthic algae on scallop cage, woven bags and sunshade net are similar, and the ratio of large benthic algal growth on hollow brick is slightly larger than the other 3 kinds of shelter. During the test, the average number of benthic algae cell were 30.9×104cells/cm2 on scallops cage,11.2×104cells/cm2 on woven bag, 22.3×104cells/cm2 on sunshade net and 22.4×104cells/cm2 on hollow brick, and correspondingly the average lever of benthic algal biomass were 3.46μg/cm2,2.46μg/cm2, 2.77μg/cm2 and 3.82μg/cm2. The adhesion of benthic algae to shelter during the first half of the experiment, hollow brick and scallop cage are superior to woven bag and sunshade net.2) After 154 days of growth, the survival rate of sea cucumber on 4 kinds of shelter(Sr), the mean rate of daily weight gain(Mdwg) and specific growth rate(SGR)were mensurated, and the yield was calculated. The results show that: there is significant difference of sea cucumber’s growth and survival among the 4 kinds of shelter. The growth of sea cucumber on hollow brick was the slowest, but the survival rate of it was significantly higher than the others(66.5%), so the yield was the highest(192.8g/m2).The yield of sea cucumber on scallop cage was 169.8g/m2,and the survival rate of it was 48.7%, which were only next to hollow brick. The yield and surviver of sea cucumber on woven bag or sunshade net were low. So according to the results of breeding, hollow brick among the 4 kinds of shelter was the best, and the scallop cage followed.3) The biomass of benthic algae on the shelter is closely related to sea cucumber’s growth and survival, so the assessment of sea cucumber’s surviver rate and yield is in accordance with the lever of the benthic algae biomass.Based on the comprehensive analysis of shelter’s material,shape and color, hollow brick is most suitable to sea cucumber’s growth, scallop cage is in the middle, sunshade net and woven bag are the worst.4) Through the monthly sampling, the organic carbon and sulphide content of the breeding group and control group was compared, to explore the impact of sea cucumber breeding to sediment in pond. The results showed that: Compared with the background survey, the organic carbon mean content of breeding group increased by 0.01%, while the control group increased0.04%; and the sulphide mean content of breeding group decreased slightly, while the control group decreased more slightly(mean values were-14.7mg/kg and-6.42mg/kg).The differences between the breeding group and control group at the qualitative change of organic carbon and sulphide content value of the sediment was not significant(P>0.05). And there is only one experimental pool which the changes of organic carbon content can reflect the purification effect of sediment in sea cucumber. |
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