Effect Of Stocking Density On Growth And Blood Parameters Of Juvenile Hybrid Sturgeon

In factory farming process, stocking density is a key and complicated management factor. It can leed to chronic stress and effect the growth, physiological condition and behavior of fish, through water, space and interaction of each other. So it is very important to make further study on the mechanism of the environment stress to the fish, which can help to master appropriate rearing density and improve the fish breeding efficiency.To evaluate the influence of stocking density on the growth performance,muscle composition and blood biochemical parameters of juvenile hybrid sturgeon (Acipenser baerii♀×Acipenser schrenckii♂), the study was conducted in 12 flow-through tanks for 90 days. Sturgeon(251.11± 0.59g,31.55±1.50cm)were randomly distributed into four different initial stocking densities, Gl(5.50kg/m3,200fish/pond), G2(8.27kg/m3,300fish/pond), G3(11.01kg/m3,400fish/pond), G4(13.80kg/m3,500fish/pond). Moreover, the study tested the parameters of water. The results are as follows:1. The Dissolved oxygen concentration of the same density was different at different time one day. Also, the dissolved oxygen content of four stocking densities was significantly different at the same time(P<0.05). As study went on, the dissolved oxygen content of four stocking densities showed a decreasing trend and the temperature showed an increasing trend, although they were different at different time. The temperature of water didn’t show any difference. However as the experiment went on, it rose up. The ammonia nitrogen content of different stocking densities fluctuated and ascended, with no significant difference among different stocking densities. The pH didn’t show any clear trend in whole experiment. It stayed around 7.6.2. The results showed that stocking density had significant effects on the growth performance of juvenile hybrid sturgeon(p<0.05). The daily food reduced during the whole study, however the food conversion ratio and feeding ratio declined. The parameters of feed were significantly different between four stocking densities. The final body weight, specific growth rate (SGR) and condition factor (CF) decreased with the increase of stocking density, while the food conversion ratio (FCR) showed an opposite tendency. At the end of the experiment, the survival rate was 99.33%,97.67%,95.33%,92.80%, respectively. The moisture content in muscle of juvenile hybrid sturgeon increased significantly with the increase of stocking density, while the crude lipid content in muscle decreased significantly(P<0.05). However, there were no significant difference in the ash content and crude protein conten(P＞0.05).3. The study also examined the effects of stocking density on bloodbiochemical parameters of juvenile hybrid sturgeon. The results showed that the red blood cell content rose first and then declined, and there were no significant difference(P>0.05). However, the hemoglobin and white blood cell content rose continuously. The bigger stocking density was, the bigger they were. Moreover, Differences between stocking densities were also registered for glucose and total protein at the end of the study (P<0.05). The glucose、total protein、albumin、aspartic transaminase and alkaline phosphatase content were in a dynamic balance with small change ranges. The significant differences between stocking densities only occurred in a certain period(P<0.05). The alanine aminotransferase content showed an increasing firstly and decreasing secondly then increasing trend. The cortisol content showed no significant difference between stocking densities, however the content of G4 stocking density was higher than Gl all along the experiment.