The Stress-influences Of Rearing Densities On Juvenile Amur Sturgeon, Acipenser Schrenckii

This dissertation investigated the regulations of stocking density on growth performance and physiological system of Amur sturgeon, Acipenser schrenckii. The short-term and long-term effects of rearing densities on blood physiological, biochemical parameters, severel non-specific immune factors, and growth rate were studied.1. The effects of short-term crowding stress on Amur sturgeonBlood cortisol and FT3 level verid significanly during short-term (15 d) crowding stress. The results showed that plasma cortisol level would elevate when fish was exposed to the stressors. While, plasma FT3 level decreased significantly with the increase of the exposrure time to crowding stress was the discovery of this experiment. Meanwhile, plasma T₃,T₄,FT₄ levels changed significantly in a shorter time.Short-term (15 d) crowding stress caused elevated plasma GLUCOSE, CREA, AST level during whole time (15 d), while plasma TP, TRG, T.BILI changed significantly in a shorter time, and D.BILI, CHOLESTEROL, UREA did not changed. These substances were correlated with energy metabolism. It hinted that these changes probably supplement the enhancement of energy demands, and it reflected that some injury on viscus or obstacles on metabolic ways.Some changing parameters could recover to the initial level, including T₃, FT₄, TP, TRG and T.BILI, which suggested that there might be one homeostatic system to modulate the metabolism in Amur sturgeon. Some parameters, including T4, FT3, GLUCOSE, CREA and AST, changed significantly at the end of the experiment comparing to the initial value, reflected that crowding stress influenced Amur sturgeon during a 15 days period.2. The effects of long-term (60 d) crowding stress on Amur sturgeonA 60-day experiment was conducted to study the effects of three stocking density, high stocking density (HSD), middle stocking density (MSD), and low stocking density (LSD) on the growth, feeding rate, digestibility, several non-specific immune parameters and several plasma biochemical parameters on juveniles Amur sturgeon.It showed that higher density had significant negative influences on feeding rate and digestibility. The specific growth rate (SGR) and daily weight gain (DWG) significantly decreased with the increase of rearing density. Net yield (NY) was increasing with the increase of the rearing densities. Digestibilities of LSD and MSD were significantly higher than that of HSD, while the level of the digestibility of MSD was nearly equal to that of the LSD. Feeding rate of MSD was significantly lower than that of HSD, while...