| Siniperca chuatsi is an important and famous freshwater carnivorous fish in China.It grows fast and has high quality meat.However,there are some problems such as unstable breeding efficiency,serious disease and other high risks in traditional pond culture of Siniperca chuatsi.These problems seriously hinder the healthy development of the Siniperca chuatsi culture industry in China.In this study,we explored the effects of different stocking density of Siniperca chuatsi on their growth,nutrition,water quality and breeding benefit in water circulating pond aquaculture system,aiming to construct new culuter model for Siniperca chuatsi and providing the basic data for Siniperca chuatsi culture in water circulating pond aquaculture system in China.1.Dynamic changes of water quality in water circulating pond aquaculture system for Siniperca chuatsiThe culture unit was constructed at a ratio of 6%of the pond area,and the remaining 94%of the water was used as the tail water purification unit to construct a compound breeding system including aquatic plants.In June 2018,the stocking of the Siniperca chuatsi was carried out and three culture density gradients of 20,30,40 individuals/m2 were set in triplicate.From June to September,the total phosphorous,total nitrogen,ammonia nitrogen and COD in the tail water and purified water were determined.The results showed that:(1)the highest nitrogen in high density culture group reached 3.58mg/L.It was 0.47mg/L and 0.89mg/L higher than the medium density culture group and low density culture group respectively.The metabolic intensity of the high density culture group was significantly higher than that of the medium density and low density culture group.(2)The purification zone has a good removal effect on the total phosphorus in the water.Behind the purification area,the TP in the tail water of different density groups were decreased from 1.14mg/L-1.96mg/L to 0.73mg/L-1.20 mg/L.The removal rate of TP in water was 39.2%-75.4%,and the overall removal rate of TP was first high and then low during the experiment.(3)Behind the purification area,the ammonia nitrogen values in the tail water of different density groups were decreased from 0.64mg/L-0.91mg/L to 0.33mg/L-0.55mg/L.The removal rate of ammonia nitrogen in the tail water of different density groups in the purification area increased rapidly and then slow decreased during the experiment,and the highest removal rate was in the low density group.(4)The COD removal rate in the tail water of different density groups increased rapidly in the early stage,and it fluctuated slightly around 50%in the low density group,and it fluctuated between 40%and 50%in the medium and high density group,and gradually decreased in the later stage(after mid-September).The COD removal rates of the three culture density groups were 47.18%,40.64%and 35.58%,respectively.2.Effects of different culture densities on the growth and the content of nutrient components in the muscle of Siniperca chuatsiThe experiment method was the same as experiment one.The growth rate,the feed coefficient and the content of nutrient components in the muscle of Siniperca chuatsi in different culture densities were measured.The results showed that:(1)with the increase of culture density,the average daily gain decreased from 4.86g to 4.19g,the survival rate decreased from 92.88%to 86.49%,and the feed coefficient increased from 3.77 to 4.34.(2)A total of 17 amino acids were detected in the muscles.The TAA content ranged from 76.06 to 80.89 g/100g,and the EAA content ranged from 30.39 to 31.28g/100g.Nutrients in the muscle including TAA,EAA and NEAA,did not change regularly with the changes of stocking density.3.Effects of different culture densities on the immunity of Siniperca chuatsiThe traditional pond cultured Siniperca chuatsi was used as the control group.The contents of superoxide dismutase,alkaline phosphatase,acid phosphatase and lysozyme in the serum of Siniperca chuatsi under different culture densities were determined.The results showed that:(1)the serum SOD activity of the high density group was significantly lower than that of the medium and low density groups.By the end of experiment,the SOD activity in the blood of the three experimental groups was 4.6%,13.5%and 44.3%lower than that of the control group,respectively.(2)The alkaline phosphatase activity was lower than that of the medium,low and control group.By the end of experiment,the AKP activity in the blood of the three experimental groups was 20.9%,25.5%and 45.1%lower than that of the control group,and there was no significant difference among the three experimental groups.(3)The acid phosphatase activity in high density group was lower than that of the medium,low density group and control group.By the end of the experiment,the ACP activity in the blood of the three experimental groups was 33.3%,42.5%and 49.9%lower than the control group,and there was no significant difference among the three experimental groups.(4)The lysozyme content increased first and decreased soon with improving of stocking density.The lysozyme content increased in each experimental group within the first 30 days of the experiment.However,with the increase of breeding time,the lysozyme content decreased slowly,indicating that the Siniperca chuatsi have a certain tolerance to high-density culture.4.Analysis of yield and benefit of pond circulatory aquacultureThe growth rate,yield,benefit and input-output ratio of Siniperca chuatsi under different culture densities were analyzed.The results showed that Siniperca chuatsi in the low density culture group had the highest growth rate and in high density culture the slowest growth rate.The unit area yield and output increased with the increase of culture density.The profit per unit area was the highest in the medium density group(17,583.8 yuan).There was the highest input-output ratio in the medium density culture group(1:1.72),and the input-output ratio in low density and high density culture groups were 1:1.69 and 1:1.54,respectively. |
PDF Full Text Request