Development trend and strategy of artificial breeding technology for marine fishes

Introduction: at present, the international research on the breeding technology of Shanghai aquatic fingerling mainly focuses on the establishment of small ecosystem (physical environment and biological environment) of larva and the nutrition enhancement of larva and juveniles In order to achieve the goal of safety, stability and sustainable development of artificial breeding and aquaculture of marine fish, combined with the current situation and special situation of the development of marine fish aquaculture in China, some suggestions on the development trend and development strategy of this major are put forward in the following aspects Establishment of a good microbial environment: in the process of intensive high-density seedling cultivation, the large-scale propagation and growth of harmful bacteria often directly cause the growth retardation, a large number of deaths and diseases in the early stage of the fry In the process of intensive artificial seedling raising in highly artificial environment, the current seedling raising technology promotes the selection of microbial community in water body to the direction of pathogenic bacteria The effective way to adjust the composition of microbial community to solve this problem is to actively select the benign microbial community (using the mature water body of microorganisms) or directly add beneficial bacteria to the water body of seedling Recently, microbial mature seawater has been widely used in research and seedling production abroad The selection of bait Series in the early stage of juveniles and juveniles: whether the bait series of juveniles and juveniles are correct or not is directly related to the survival and growth of juveniles and the quality of seedlings and the cost of seedling cultivation If we want to get an ideal bait series, we must study the feeding behavior, feeding selection and feeding amount of the juveniles in detail, which will have great guiding significance for the production of sea water fish At present, the widely used technology of using rotifer and juvenile nauplii as opening and early bait has been in operation for many years In the early stage of larval feeding, the density, species and size of biological bait are important factors affecting the growth and survival of larval Unsuitable bait organisms usually lead to slow growth, malnutrition and frequent and large-scale death of larval, and sea water fish When selecting food, larva like fish not only depends on the characteristics of the food organisms, such as the size and swimming speed of the food organisms, but also depends on the density of the food organisms in the water body The method of transition from biological feed to granular feed: generally, most of the fish larvae and juveniles are difficult to accept granular compound feed when the feed type is changed, and there are a large number of deaths However, under the condition of reasonable use of "weaning" method, healthy fry groups can successfully pass through this dangerous period without causing a large number of deaths At present, the general view is that it is better to start the bait transformation early, because with the continuous growth of the fry, the fry instinctively need to eat larger bait, and the rapid growth of the fry also makes it difficult for the nutrition of the nauplii to meet the needs of the highly unsaturated fatty acids of the fry Nutrition enhancement of juveniles and juveniles: juveniles need more highly unsaturated fatty acids than adults to meet their needs of rapid growth, in which DHA plays a more important role than EPA There have been many reports on the importance of DHA content in diets for the normal development and growth of juveniles and juveniles Feeding DHA alone can promote growth and increase the growth rate, while feeding diets with low DHA content leads to fry Low vitality The proportion of EPA / DHA in the diet led to the decrease of survival rate of freshwater fish It was also found that DHA in nerve tissue of Paralichthys olivaceus with normal pigment deposition was more than that of albino fish Flow through system: at present, the flow through system is the main one in the sea water fish nursery in China, and the system configuration is constantly improved and improved in the process of seedling production However, the automation level of the system is not high, the special equipment for seedling cultivation is insufficient, and there is still a lack of professional personnel engaged in the research and development work in this area The key of the flow through seedling system is the design of the seedling pond In this respect, experts and many production units have made great cooperation and achieved gratifying results Closed cycle system: closed cycle system started late in China, but the current international popular is the cycle runway system The water quality treatment capacity of the circulating system, especially the ability to degrade ammonia nitrogen and kill pathogenic microorganisms, is very strong In addition, it can also remove the suspended organic particles in the water Hybrid sterility: hybrid breeding, especially interspecific hybridization, can produce sterile offspring Although these offspring have the disadvantages of sterility, they can often show significant advantages: (1) there will be no genetic hybrid between hybrid species and parent groups, which is conducive to the maintenance of parent purity and the protection of species diversity in the natural sea area; (2) it is conducive to the cultivation density And scale control and management (3) is also conducive to the protection of intellectual property rights Polyploid sterility: as we all know, triploid is generally sterile, and its gonad development is blocked, so it is very important for mariculture, so that the breeding objects do not need to consume the energy and materials for reproduction, improve the survival rate, growth speed and meat quality in the reproductive period, and prevent pollution to the natural sea area The production practice shows that it is difficult to use the method of direct induction of triploid by medicine in large-scale production, and interspecific hybridization and the culture of tetraploid parent fish will be the effective way to apply the triploid breeding technology to seedling production, especially the cultivation of tetraploid parent fish.