Research And Development On The Technology Of River Crab Intercropping With Macrobrachium Rosenbergii In Gaoyou Lake Net Enclosure

This study was carried out to explore suitable density on the river crab intercropping with Macrobrachium rosenbergii.We studied the effects of different feeding baits on the growth of Macrobrachium rosenbergii and water environment,the comparison of growth performance of river crab and Macrobrachium rosenbergii,the effects of intercropping model on fishery resources and economic benefits,and the analysis of amino acids and fatty acids of Macrobrachium rosenbergii.We explored the feasibility of the model of river crab intercropping with Macrobrachium rosenbergii in net enclosure and preliminarily determined the appropriate stocking rate of Macrobrachium rosenbergii.It provided technical support for fishermen to change the breeding models,reduce the breeding risks and increase the incomes in Gaoyou lake area.The main research contents were as follows:1.In order to carry out the single experiment of the Macrobrachium rosenbergii,We setted up a 10 x 667m2 breeding net in zhengdun water area,where the water quality was clear,exchanging well and the dissolve of oxygen was high in Gaoyou Lake.In the early stage,the nets and other fishing gear were used to completely clean the area of the net enclosure.After the plum rain season in July,we grazed 180 tails of 7-8 cm,100 tail/kg postlarvae per 667 m2,a total of about 1,800.After three months of scientific breeding,a total of 1100 tails were caught,The return rate was 61.11%,Average specification was 90 g,The average body length was 13.0 cm,and the largest individual weight reached 150 g.The total investment was 2789.0 yuan,The total output value was 11880.0 yuan,The economic benefit was 9091.0 yuan.So benefit was 909.1 yuan per 667 m2.This experiment showed that,after the flood,breeding Macrobrachium rosenbergii in Gaoyou Lake overwater area was an effective supplementary attempt to make up for the losses caused by high water level crabs.The aquaculture model is completely feasible in terms of technology and efficiency.2.In the Gaoyou Lake set 9 nets,each net area of 8 acres,in each net were 300 Macrobrachium fingerlings around 9.3 5 g.Among the 9 nets,set three processing Group,each group of three replicates,respectively,feeding wild trash fish,wild trash + feed,feed,three months later,weighing after fishing,also the monthly water sample collection,water quality testing and planton observation is acquired.The results showed that the weight gain rate of feed group was higher than that of wild fish group and wild fish+feed group,but the difference was not significant(P>0.05).The fatness of wild fish+feed group was significantly higher than that of wild fish group and feed group(P<0.05).The recapture rate of feed group and wild fish + feed group were significantly higher than that of wild fish group(P<0.05).Economic benefits of wild fish + feed group got highest,but the difference was not significant(P>0.05).The The results of DO,pH,SD,NH4+-N,NO2--N,TN,TP,COD,Chla showed that the effects of these three kinds of bait on the water quality did not show significant difference(P>O.05).The phytoplankton community structure and density analysis showed that the proportion of cyanobacteria in the wild fish group was higher,the diversity index was lower,the degree of eutrophication of the wild fish group was higher and the water quality was worse.From the growth performance of Macrobrachium rosenbergii,economic benefits,the impact on the water environment,the wild fish + feed group is optimal.3.The purpose of this experiment was to explore the suitable density of the river crab intercropping with Macrobrachium rosenbergii in net enclosure and provide technical support for the popularizing cultivation techniques in Gaoyou lake area.In Gaoyou Lake we setted up fifteen 8x667m2 rectangular small net,divided into 5 groups and setted 3 repetitions for each group.After the plum rain season in July,we grazed the specifications of 24 tails per kg river crabs 60 tails per 667 m2 in each small net.Then we grazed the average specification(9.5±0.5)cm.(75.0±5.0)/kg Macrobrachium rosenbergii and the amount of grazing was 80,160,240,320 tails per 667 m2.A blank control group was setted up which did not graze Macrobrachium rosenbergii.We fed granulated feed and small fish daily about three months.We setted up the experiment to explore the growth performance of river crab and Macrobrachium rosenbergii and effects on fishery resources and economic benefits under different stocking density.The results showed that:(1)The yield and rate of weight gain of the crabs in the density of 0 tail per 667m2 were significantly higher than that of the others.The average size of the river crab was decreased with the increasing of the density.The residual limb rate of the river crab was the highest in the density.of 240 tails per 667m2.The yield of Macrobrachium rosenbergii was increased significantly(P<0.05)with the increasing of the density,the average size and the increase rate was the largest in the density of 240 tails per 667m2.The return rate and the fat full of river crab and Macrobrachium rosenbergii was not significant(P>0.05).(2)The total weight of the economic fishes and trash fishes caught in the net gradually were decreased with the decreasing of the breeding density.Under conditions of the river crab intercropped Macrobrachium rosenbergii in low density or only breed river crab,the total amount of economic fish resources in the net was less.But the total amount of prawn resources was significantly more.(3)The economic benefits were highest in the feeding density of 240-320 tails per 667m2.4.We setted the experiment to compare and analyze the Conventional nutrients,Amino acids and Fatty acids of the Macrobrachium rosenbergii muscle from lake farming and pond farming.The results showed that:(1)The coarse fat of the lake farming was lower than the pond farming,and the ash was higher than the pond farming(P<0.05).(2)There was no significant difference between the total amount of amino acid(TAA),the essential arnino acid(EAA)and the fresh amino acid(DAA)in the two breeding models(P<0.05).(3)According to AAS,the Macrobrachium rosenbergii from lake farming and pond farming,the first limiting amino acidswas threonine,the second limiting amino acids were methionine and cysteine.According to CS,the Macrobrachium rosenbergii from lake farming and pond farming,the first limiting amino acids were methionine and cysteine,the second limiting amino acid was threonine.The essential amino acid index(EAAI)of the roche biogas was close under the two farming modes,65.31 and 65.92 respectively.(4)Under the two farming modes Saturated fatty acids(∑SFA),single unsaturated fatty acids(∑MUFA)and polyunsaturated fatty acids(∑PUFA)there were no significant difference(P>0.05).But,both EPA and DHA under lake farming were significantly higher than pond farming(P<0.05).From the perspective of protein nutrition,the lake farming was similar to the pond farming of Macrobrachium rosenbergii.From the perspective of fat nutrition,the lake farming of Macrobrachium rosenbergii was higher than pond farming.