Study On The Effects Of Stocking Density On Growth,Physiological Indexes And Muscle Quality Of Micropterus Salmoides

The green transformation and upgrading of aquaculture mode is an important development trend of aquaculture in China.The zero exchange Juanyang model in pond is an energy-saving and emission-reduction,ecologically efficient model.Stocking density is a very critical factor in aquaculture.Higher stocking density can not only make full use of cultured water,but also increase unit production and reduce production costs.But high stocking density may also cause crowding stress on fish.This in turn leads to negative effects on fish growth,health benefits and muscle quality.It is important to explore the optimal stocking density of largemouth bass(Micropterus salmoides)under the Juanyang model.It is of great significance to the healthy and efficient development of largemouth bass farming in China and the promotion and upgrade of the Juanyang model.Healthy and active largemouth bass were selected for a 180-day breeding experiment.The initial average body weight was 9.71±3.75g,the initial average body length was 7.66±0.98cm,and they were randomly divided into 1000,2000,and 4000 tails/circle(0.42kg/m~3,1.03kg/m~3,1.88 kg/m~3),a total of 3 density groups,respectively recorded as LSD,MSD and HSD,the growth index,blood biochemistry,liver antioxidant performance and muscle quality related indicators of largemouth bass were measured,The main results of the test are as follows:1. The final density of each density group is:17.64±1.63 kg/m~3,32.51±1.49 kg/m~3 and 59.85±4.13 kg/m~3;the survival rate is positively correlated with the breeding density;the growth situation of largemouth bass has stage characteristics,From 0 to 30 days,the body mass,weight gain(WG)and specific growth rate(SGR)of largemouth bass in the HSD group were higher than those in the LSD group;after 30 days,the opposite was true,indicating that the growth rate of the HSD group will be affected inhibition.Compared with the LSD and MSD groups,the HSD group has a lower feed coefficient(FCR);up to 150 d,the body mass variation coefficient(CVw)and fullness(CF)decrease as the breeding density increases,and the visceral index(VSI),Liver body index(HSI)showed the same trend;while the change trend of spleen body index(SSI)was the opposite.2. The effect of high density on the biochemical and antioxidant capacity indexes of largemouth bass serum mainly occurs in the later period of culture,which is manifested as glucose(GLU),albumin(ALB)and triglyceride(TG)in the serum of high density bassfish,Alkaline phosphatase(ALP)and alanine aminotransferase(ALT)increased significantly;total antioxidant capacity(T-AOC),superoxide dismutase(SOD)and catalase(CAT)activities were significantly reduced At the same time,the concentration of malondialdehyde(MDA)increased.3. The breeding density has no significant difference in the nutritional components of largemouth bass muscles,but the crude protein and crude fat content tends to decrease with increasing density;amino acid analysis shows that the total essential amino acid(TEAA)and essential amino acid index(EAAI)index decreased significantly with increasing density;in addition,the muscle texture and hydraulic performance of the HSD group were worse than those of the LSD and MSD groups,which meant that high density had a certain negative impact on the nutrition and meat quality of largemouth bass.In summary,in the early stage of breeding,higher density is conducive to the growth of largemouth bass.When a certain density is reached,growth will be inhibited,and it will also have a certain negative impact on physiological indicators,antioxidant properties and muscle quality.It is recommended that two breeding strategies can be adopted in the actual production process:one is staged and graded breeding,the stocking density during the seedling period can be appropriately increased(>4000 tails/circle),and the stocking density in the middle and late breeding should be controlled at 2500～3200 tails/circle for maximum economic benefit;second,non-graded feeding,at this time,the seedling density should be controlled at 2500～3200tails/circle.