Screening, Culture And Application Of High Quality Food For Abalone Larval

This paper concluded studies about the community composition and the law of the changment of benthic diatoms attaching to the substrates in abalone hatcheries of Haliotis diversicolor supertexta and Haliotis discus hannai in Dongshan and Zhangpu, Fujian Province from September 2005 to December 2007. The relationship between the reasons of the "delinking of the board" of abalone larval and the benthic diatom community was discussed. And the five common benthic diatoms attaching to the substrates during the early breeding period were isolated and cultured. Meanwhile the five benthic diatom were actual applicated in abalone breeding pools, and comparatived analysis of the advantages and disadvantages of the five benthic diatom were done. Finally a simple and effective method were found to improve the survial rate of abalone larval. The results were showed as following:1.Totally 61 benthic diatom species (including varieties) belonging to 30 genera were identified in benthic diatom community in the substrate of abalone breeding pool. These species were mainly from 5 genera: Nitzschia(8 species), Navicula(8 species), Achnanthes(4 species), Amphora(5 species) and Cocconeis(5 species). The number of Cocconeis species was less other genera species, but the percent of the Cocconeis density was more than other genera in most benthic diatom community.2.The species of benthic diatom community attaching to the substrate of abalone breeding pools were mainly made up of microdiatom and nanodiatom in size, the growth type was mainly attachment in type; the attachment form were mainly shell attachment and the slit shell attachment. And the algaes moving weakly were in majority. It was indicated by comparative analysis of different larval breeding abalone effect on the attachment of the benthic community in the composition of diatoms, that serious from the board of the benthic community diatom species composition of the movement stronger ability of the density of algae in general was higher than the corresponding percentage of the same batch Breeding has not from the board of algae cell percentage, usually in the range of 14.28% to 23.04%.3. In August to December, 2006. a full experiment of the four abalone breeding was done, and the results were showed :â‘ the continous changment of benthic diatom community attaching to the substrate was obvious. The diversity of the middle stage of abalone breeding is higher than both other stages. Although the dominant species had several differences in the different culture time. Cocc. scutellum var. minutissima was the dominant species of the benthic diatom community, particularly in the late abalone breeding stage the percentage of the density was generally more than 90 percentage. And Amphora coffeaeformis, Achnanthes citronella, Navicula ramosissima, Cylindrotheca clostetium only appeared in the early stage or the mid-stage.â‘¡the abalone larvae growth rates was different in different propagation, but at the end of the experiment, the averages of shell length were all up to 3.38cm, and there were no significant difference (P>0.05),â‘¢At the end of the experiment, the difference of abalone larvae survival rate was great different.and there was very significantly (p<0.05). and the abalone larvae survival rate was higher with the benthic diatom community more stable.4. Success or failure of abalone breeding production may have relationship with the community structure and its stability at the same time. The coefficient of variation in the diversity of benthic diatom communities for the success abalone larval breeding was more than that for the failture abalone larvae breeding. And the percentage of the domaint species in the benthic diatom community varyed greatly in the former abalone larvae breeding stage. But in the last abalone larval breeding stage, they had a common domaint species, that was Cocc. scutellum var. minutissima.5. Comparation between different abalone breeding periods of the benthic diatom community attaching to the substrates was done. The conclusion was showed as follow:â‘ the diversity index of the same batch abalone breeding in the late stage was lower than that in the early stage. And the diversity index of benthic diatom community attaching to substrate in Haliotis discus hannai breeding pools was higher than in Haliotis diversicolor supertexta breeding pools.â‘¡the richness is generally higher than that in the early stage and in the late stage. And that in Haliotis discus hannai breeding pools was still higher than in Haliotis diversicolor supertexta breeding pools.â‘¢the changment trend of the dominance ratio and the evenness ratio is contrast to the richness ratio, they were higher in the early stage and in the late stage, however the dominance ratio index of benthic diatom community attaching to substrate in Haliotis diversicolor supertexta breeding pools was higher than in Haliotis discus hannai breeding pools,the evenness ratio was contrast.6. The analysis results were showed: the gut content of abalone larval showed that the features of different shell length abalone larvae were closely related to the biofilm's vertical structure. That was abalone larvae feeding benthic diatom species which were on the surface of the biofilm. And then feeding the sec-surface species of the biofilm. The main species with the content of the gut of abalone larvae were basically the same as the advantage species of the benthic diatom communities, which was showed that the feeding of abalone larvae has no selectivation.7. A test of N(NaNO₃), P(NaH₂PO₄·H₂O), Si(Na₂SiO₃·9H₂O), Fe(FeC₆H₅O₇·5H₂O) four elements on the growth rate of the five benthic diatoms and its extracellular polysaccharide content in Orthogonal experiment, and then in turn draw the best combination of nutrients. The results showed N elements played a major role among four elements. Taking the characteristics of life abalone larvae into account , select five benthic diatoms in the attachment polysaccharide (Exopolysaccharide ) the best combination of nutrients as the optimization of their respective medium. The study show that the optimization of medium could promote the abalone larvae adhesion.8. In October to December, 2006. five species of benthic diatom (Cocc. scutellum var. minutissima, Amphora coffeaeformis, Achnanthes citronella, Navicula ramosissima, Cylindrotheca clostetium) were assayed to evaluate their food value for the postlarvae of Haliotis discus hannai, the result was that: the shell length of abalone larval cultured five single benthic diatoms had no obvious difference ,and the difference was not significant (P<0.05) at the end of the experiment. However, in the survival rate area, five single benthic diatoms cultured abalone larval were obvious by significant test, significant differences (P>0.05), especially Cylindrotheca clostetium was more obvious. Meanwhile, in the density of algae area, in the early breeding stage, the changment of the density of five benthic diatom was little. But in both other stages, the density of five single benthic diatom have varying degrees of decline, and the order was Cylindrotheca clostetium > Navicula ramosissima > Amphora coffeaeformis > Achnanthes citronella > Cocc. scutellum var. minutissima.9. In September to December, 2007, the practical application of research were held with optimization training methods of five benthic diatoms in Haliotis diversicolor supertexta breeding pools and in Haliotis discus hannai breeding pools. Meanwhile natural mixed benthic diatom group was contrast, the results showed:â‘ In the late breeding stage of both abalone larval, although the attachment density of abalone larval had difference in all groups. The effects of five benthic diatom are superior to the natural group.?During both the abalone larvalbreeding stage, the average growth rates have differences in all experimental groups. However, the analysis showed that there was not obvious.10. The results showed that Cocc. scutellum var. minutissima ,as a dominant species of benthic diatom community attachmenting to the substrates was a most simple and effective method of increasing survival rate of abalone breeding. Taken the polyethylene plastic film was still as the substrate of abalone larval in majority of abalone breeding factories in account.