Effects Of Pond Culture Density On Growth Performance Of Eriocheir Sinensis And Aquaculture Water Environment

As an important economic aquaculture animal in China,the Chinese mitten crab Eriocheir sinensis plays an increasingly important role.The cultivation of the crab in Jiangxi Province also has developed rapidly and has become the fifth largest production area in China in recent years.However,due to the influence of different water environment,the suitable aquaculture modes may be different.And the research on the culture technology of the Chinese mitten crab is still rare in Jiangxi Province.In this study,the main important point is revealed the effects of the culture density on growth performance of Eriocheir sinensis and aquaculture water environment under the field ponds culture of the Chinese mitten crab in Poyang Lake area of Jiangxi Province.The result is as follows:?1?During the period of culture experiment?169d?,the crab has grown and molted four times.The weight growth multiples of crabs with different densities ranged from 11.71 to 14.93,and the average fatness coefficient ranged from 51.65 to55.72%.The analysis showed that there was a significant negative correlation between BW and culture density?P<0.05?,and significant or extremely significant negative correlation with GB_BW,GB_CLL and GB_CW.The results showed that GB_BW,GB_CLL and GB_CWW decreased with the increase of culture density significantly.And in the pond of 1200ind/mu,the crab had the maximum average breeding specifications,the largest average coefficient of fatness?CF?,and the minimum average coefficient of variation?CV?.?2?In the muscle tissue of Eriocheir sinensis,the moisture content was77.68-79.63%,the crude fat content was 2.86-4.09%,and the crude protein content was 13.43-14.56%.In the hepatopancreas tissue of Eriocheir sinensis,the moisture content was 39.27-51.67%,the crude fat content was 38.97-51.55%,and the crude protein content was 5.67-6.59%.With the increase of culture density,crude fat and crude protein in crab muscle and hepatopancreas decreased.The correlation coefficient R was negative,but no significant correlation was detected.The results showed that the contents of crude fat and crude protein were the highest and the CV was the lowest in the two tissues of the pond of 1200ind/mu.The amino acid composition analysis of the two tissues after acid hydrolysis showed that all 17 water-soluble amino acids were detected.In muscle tissue of Eriocheir sinensis,total amino acid?TAA?content was 12.92-16.41g/100g,essential amino acid?EAA?content was 5.04-6.46g/100g,delicious amino acid?DAA?content was 6.15-7.76g/100g,EAA/TAA was 38.03-40.11%,DAA/TAA was 46.98-47.91%.In hepatopancreas of Eriocheir sinensis,TAA content was 5.08-5.39g/100g,EAA content was 2.04-2.20 g/100g,DAA content was 2.39-2.48 g/100g,EAA/TAA was40.07-42.06%,DAA/TAA was 46.01-47.59%.With the increase of culture density,the contents of TAA,EAA and DAA in muscle of Eriocheir sinensis decreased,and there was a significant negative correlation?P<0.05?.However,there was no significant correlation between culture density and the evaluation indexes of amino acids in hepatopancreas of Eriocheir sinensis.The maximum value of TAA,EAA and DAA and the minimum value of CV also were found in the muscle tissues of Eriocheir sinensis in the pond of 1200ind/mu;EAA/TAA in the two tissues had the maximum value in 1000ind/mu,and DAA/TAA in two tissues had the maximum value in800ind/mu.Therefore,the crabs in medium and low density ponds may have better levels of TAA,EAA,DAA,EAA/TAA and DAA/TAA.?3?The pond of 800 ind/mu were used as control group,significant low expression levels of immune signal recognition related genes?LGBP?,immune signal transduction related genes?Dorsal,Tube?and immune effect related genes?PPAE,GST and SOD?were found in the pond of 1200ind/mu and 1400ind/mu;and all seven immune-related genes were detected have significant or extremely significant high expression levels in hemolymph of Eriocheir sinensis in high density group?1600ind/mu?.The correlation coefficient R between culture density and relative expression of all immune-related genes in haemolymph of Eriocheir sinensis was positive,and had a significant positive correlation with GPx gene?P<0.05?.The results showed that the hemolymph of Eriocheir sinensis in the high culture density test pond?1600ind/mu?had relatively high expression levels of immune-related genes.It was speculated that high culture density might have some adverse effects on Eriocheir sinensis.?4?In the aquaculture experiment,the water quality of the pond is mostlywithin the water quality reference standards of fishery aquaculture and surface water class III,which indicates that the influence of the culture activities of Eriocheir sinensis on the water environment was not serious.The results showed that the indicators of TN?Total Nitrogen?,TP?Total Phosphorus?and COD_Mn?Permanganate Index?increased with the increase of culture density.And TN,TPand COD_Mnn were the main water quality indicators exceeded the standard limits???.The indicator of TN also had the highest over-standard rate and over-standard multiple.The results showed that there was a significant negative correlation between culture density and mean pH?P<0.05?,and there was a significant positive correlation between DO and pH?P<0.01?;there was a significant positive correlation between culture density and TN?P<0.05?;also there was a significant correlation between TN and NO₂-N?P<0.01?;and there was a significant or significant positive correlation between NO₂-N and NH₃-N,TP and COD_Mn.In conclusion,high culture density can adversely affect the growth rate,the nutrient accumulation,the immune gene expression of Eriocheir sinensis,and the quality of culture water.In this experiment,the crab from the pond of 800ind/mu had the maximum growth rate.But the crab from the pond of 1200 ind/mu had the largest average breeding specifications,the largest average fatness coefficient?CF?,the better level of crude nutrition and amino acid composition,the lower level of relative expression of immune-related genes and the smallest coefficient of variation?CV?.And the water quality was also better under the culture density of 1200 ind/mu.Therefore,it is suggested that the suitable culture density should be about 1200ind/mu in this area.