Construction Of Recirculating Aquaculture System For Apostichopus Japonicus And Exploration Of Carbohydrates In Feed

In recent years,the aquaculture area of Apostichopus japonicus in China has been increasing,and A.japonicus aquaculture has become a new growth point of fishery economy.However,at present,the breeding methods of A.japonicus in China are mainly near-seabed sowing and pond breeding.These traditional open breeding modes are easily disturbed by the external environment,resulting in a breeding loss of up to 10 billion yuan per year due to extreme weather.In addition,A.japonicus has the habit of narrow temperature and narrow salt.The sudden change of salinity will promote the emergency response of A.japonicus and increase the hidden danger of disease.Too high or too low water temperature will make it enter a dormant state,which makes the optimal growth period of A.japonicus in the natural state only 4 months and a half.Although the indoor factory static water inflatable breeding and flow water breeding mode of A.japonicus are relatively controllable.However,it is necessary to clean up the pollution by manual regular pouring,and the work intensity is very high.In addition,the research on the nutrition of A.japonicus is still in its infancy,and the configuration of compound feed lacks standards and basis.The commercially available A.japonicus compound feed has a mixed formula and uneven quality,which is difficult to fully meet the nutritional needs of A.japonicus,resulting in the slow promotion of high-quality A.japonicus compound feed.Therefore,it is of great significance to promote the sustainable development of A.japonicus culture industry by improving the culture mode,developing efficient and clean recirculating aquaculture,and exploring the nutritional needs of A.japonicus feed.In order to promote the healthy development of A.japonicus culture industry,in view of the above problems,this study constructed a set of dual-channel self-cleaning circulating water culture system suitable for A.japonicus factory culture,and explored the effect of A.japonicus culture of the system and the system’s decontamination function and water purification ability under different material mud ratios.By designing the types and levels of different carbohydrates in the feed of A.japonicus,the growth,body composition,digestive enzyme activity and other indicators of A.japonicus were determined,and the appropriate levels and types of carbohydrates added to the feed during the culture of A.japonicus were explored.The specific results of the test are as follows:（1）In order to solve the problems of short suitable growth period,difficult cleaning of aquaculture ponds,and serious harm caused by extreme weather,this study constructed a set of double-channel self-cleaning circulating aquaculture system suitable for industrial aquaculture of A.japonicus through the development of double-channel sewage discharge and self-cleaning attachment base of A.japonicus.The system consists of three parts:self-cleaning aquaculture pond,automatic control system and water treatment unit.The aquaculture process can realize automatic water treatment and water exchange of aquaculture wastewater.In addition,the system can also maintain the suitable water temperature for the growth of A.japonicus,relieve the influence of temperature on the growth of A.japonicus,and operate the self-cleaning attachment base in the aquaculture pond.The self-cleaning function of the culture pond can be realized,which greatly reduces the consumption of human and material resources in the process of A.japonicus culture.（2）In order to explore the decontamination ability and breeding effect of the constructed recirculating aquaculture system,the factory recirculating aquaculture experiment of A.japonicus was carried out,and the growth status of A.japonicus and the change of water quality in the system under the condition of long-term feeding of different feed mud ratio bait were explored.The results showed that during the 120 days of culture,even in the case of long-term high mud-to-feed ratio,there was no siltation in each pond.The concentrations of NH4₊^-N and NO₂^-N in the culture system were within the safe concentration range suitable for the growth of A.japonicus,and the average weight gain rate of A.japonicus could reach 43.70%,which indicated that the constructed recirculating aquaculture system had good culture effect and good cleaning function and water purification ability.In addition,this study also found that increasing the proportion of sea mud in the feed can contribute to the feeding,digestion and defecation of A.japonicus,but excessive sea mud content may cause the intestinal burden of A.japonicus,resulting in a decrease in the activity of trypsin,amylase and lipase in the intestine.In the recirculating aquaculture system,the A.japonicus fed with 1:3 and 1:2 feed mud ratios grew better.（3）In order to explore the appropriate amount of carbohydrates in the diet of A.japonicus and the effect of different carbohydrate levels on the growth of A.japonicus,this study used the initial weight of 54.26±14.25 g of A.japonicus to feed four groups of different carbohydrate levels（25.48%,34.51%,43.22%,57.37%）with corn starch as the sugar source.The experimental results showed that the crude protein content of the body wall of A.japonicus was not affected by the carbohydrate level in the diet,but it could promote the deposition of body wall fat,and with the increase of carbohydrate level in the diet of A.japonicus.The final body weight,BWG and SGR of A.japonicus increased first and then decreased,and the growth of A.japonicus was the best when the carbohydrate level in the feed was 43.22%.（4）In order to further explore the suitable sugar sources and sugar levels in the diet of juvenile A.japonicus,and the effects of different sugar sources and sugar levels on the growth performance of juvenile A.japonicus,glucose（monosaccharide）,sucrose（disaccharide）and dextrin（polysaccharide）were used as sugar sources in this study.Four supplemental levels（0%,6%,12%,18%）were designed to feed juvenile A.japonicus with an initial body weight of 5.32±0.05 g.The results showed that there was no significant difference in the survival rate,specific intestinal length and intestinal body ratio of juvenile A.japonicus（p>0.05）.However,the final body weight,BWG and SGR of juvenile A.japonicus increased first and then decreased with the increase of dietary sugar level,and the growth efficiency of polysaccharide group was significantly higher than that of monosaccharide group（p<0.05）.Although different carbohydrate sources and carbohydrate levels in the diet could promote the deposition of A.japonicus body wall proteins,this deposition effect was not significant（p>0.05）.The crude fat content of A.japonicus body wall increased with the increase of dietary sugar level,while the content of monosaccharide group（glucose）was significantly higher than that of polysaccharide group（dextrin）（p<0.05）.In addition,the amylase activity in the intestine of A.japonicus increased with the increase of dietary sugar level.The polysaccharide group increased significantly（p<0.05）,which proved that adding a certain amount of carbohydrate to the A.japonicus diet could promote the secretion of intestinal amylase.In conclusion,under the conditions of this experiment,the utilization efficiency of polysaccharides（dextrin）in diet was higher than that of monosaccharides（glucose）,and the growth effect of A.japonicus fed with 12%dextrin diet（carbohydrate content 31.22%）was the best.