Construction Of "Container+Ecological Pond" Efficient Aquaculture And Efficient Wastewater Treatment System In Ankang Area Of Shaanxi Province And Its Effect On The Quality Of Cultured Fish

The"container+ecological pond"aquaculture model is a new technology of"partitioned aquaculture and ex-situ treatment".It is a breeding model in which the container is used as a breeding unit,and the wastewater is purified and then returned to the container for recycling or up to standard discharge.In order to accelerate the green and high-quality development of the aquaculture industry,in July 2020,the"container+ecological pond"high-efficiency aquaculture and wastewater high-efficiency treatment technology was included in the ten leading agricultural technologies of the Ministry of Agriculture and Rural Affairs.In April 2022,the Shaanxi Provincial Department of Agriculture and Rural Affairs issued the"Notice on the Implementation Plan of the"Four Actions"for Green and Healthy Aquaculture in 2022,in which the container model is also included.Ankang area,as an important water source conservation area in the"Middle Route Project of South-to-North Water Diversion Project"located in the upper reaches of the Han River,puts forward higher requirements for the development of fishery industry in water environmental protection.In recent years,the local government and industry have actively introduced new technologies and promoted the upgrading and transformation of traditional farming models.On August 12,2020,three fish farming containers arrived at the Ankang Fisheries Experiment and Demonstration Station of Northwest Agriculture and Forestry University,marking the official"settlement"of the container farming system in Shaanxi.Based on the actual situation in Ankang area,this study carried out the construction and breeding experiment of the"container+ecological pond"aquaculture system,and explored the growth of fish and the effect of wastewater treatment.At the same time,based on the relevant reports that the container culture mode can provide the most suitable breeding environment,thereby effectively improving the product quality,the quality characteristics of the cultured fish such as grass carp and carp are evaluated.The main results are as follows:Trial 1,Ankang area"container+ecological pond"efficient breeding and wastewater efficient treatment system construction.The hardware construction of the system lasted 62days,mainly including two parts,one is the design and installation of standard breeding containers,intake and drainage systems,sterilization systems,oxygen supply systems,water quality monitoring systems,etc.A total of three containers（25m³/unit）were installed,the second is the design and transformation of ecological wastewater treatment ponds,including the use of dry and wet separation,physical precipitation,filler filtration,aeration and microbial purification of multi-stage wastewater purification processes,and the implementation of standardized"three pools and two dams"pond transformation Project（total area 473.8m²）,and completed the construction of sedimentation tank,aeration tank,ecological purification tank,overflow dam and filter dam.Subsequently,grass carp,framed mirror carp and koi were cultured in containers,and a 120-day trial operation of the"container+ecological pond"system was carried out.During the operation of the system,water samples are regularly collected and tested at the three sampling points of the first-level sedimentation tank,aeration tank and ecological purification tank.The water quality indicators tested include p H,nitrite（NO₂^--N）,ammonia nitrogen（TAN）and Dissolved Oxygen（DO）.At the end of the breeding test,the three containers produced839.2kg of grass carp with an average weight of 1.46kg,434.6kg of frame carp with an average weight of 288.8g,and 66.6kg of koi carp with an average weight of 108.6g;the results of water quality testing showed that the wastewater treatment The ecological pond can effectively remove ammonia nitrogen（TAN）and nitrite（NO₂^--N）,with an average removal rate of 44.74%and 33.12%,respectively,realizing the recycling of water resources and the effect of zero discharge of aquaculture wastewater.Trial 2,the effect of the"container+ecological pond"model on the quality characteristics of grass carp and carp.Using pond cultured grass carp and framed mirror carp as controls,cultured for 91 days and 110 days,respectively,to explore the effect of container culture mode on fish body index,nutritional composition and quality characteristics.The test results are as follows:（1）The Condition factor,Intraperitoneal fat index,Hepato somatic index and Viscero somatic index of grass carp in container culture mode were significantly higher than those in control pond（P<0.01）.Intraperitoneal fat index and Hepato somatic index of container mirror carp were extremely significant and significantly higher than the pond group,respectively（P<0.01,P<0.05）;（2）The muscle moisture of grass carp cultured in container was significantly lower than that of pond group（P<0.05）,the crude lipid of whole fish and muscle was significantly higher than that of pond group（P<0.01）,and the ash content of whole fish was significantly lower than that of pond group（P<0.01）;The muscle moisture and crude protein of the container carp were significantly lower than those of the pond group（P<0.05）,the whole fish and muscle crude lipid were significantly higher than those of the pond group（P<0.01）;（3）The adhesive force,adhesiveness,gumminess,maximum shear force and p H of container grass carp meat were significantly lower than those in pond group（all P<0.01）,and chewiness was significantly lower than that in pond group（P<0.05）.The hardness,adhesiveness,springness,gumminess and p H of container mirror carp meat were significantly lower than those of pond group（P<0.01）.The cohesiveness and maximum shear force were significantly lower than those of pond cultured box carp（P<0.05）;（4）The redness（a）,yellowness（b）and saturation（c）of the lateral line of container grass carp were significantly lower than those in the pond group（P<0.01）,and the redness（a）of the abdomen of grass carp was significantly lower than that in the pond group（P<0.01）;The redness（a）of the back of container mirror carp was significantly lower than that of the pond group（P<0.05）,the redness（a）and yellowness（b）of the lateral line were extremely significantly lower than that of the pond group（P<0.01）,and the saturation（c）was significantly lower than that of the pond group（P<0.05）;The lightness（L）and yellowness（b）of container grass carp meat were significantly lower than those in pond group（P<0.01,P<0.05）;The yellowness（b）and saturation（c）of container mirror carp meat were significantly lower than those of pond group（P<0.01）.The color of the container group is light,blue-green.In summary,"container+ecological pond"efficient aquaculture and wastewater efficient treatment system was successfully constructed in Ankang,Shaanxi Province.The operation of the system shows that the ecological pond has a good removal effect of ammonia nitrogen and nitrite in the wastewater of container aquaculture;It was found that in terms of quality characteristics,the muscle nutrients,most muscle texture,and meat color of container-farmed fish were lower than those of pond-farmed fish,indicating that the related technical model needs to be further improved.This study provides a new reference model for the high-quality development of ecological fisheries in Ankang area.