用不同密度（12、20、32、40、52 和 60尾·m-2）饲养克氏原螯虾体重（2.4±0.2）g 2个月，分别求得其相对生长率、成活率和残肢率，测定其血细胞吞噬活性和血清中酸性磷酸酶（ACP）、溶菌酶（LZM）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活性，旨在探讨饲养密度对克氏原螯虾生长、成活和抗病力影响的机制。结果表明，随着饲养密度的增加，克氏原螯虾的相对生长率、成活率、血细胞吞噬活性及血清中ACP、LZM活性均呈逐渐下降趋势；残肢率呈逐渐上升趋势；血清中SOD、CAT活性呈先升高后下降趋势。本研究认为，随着饲养密度的增加，克氏原螯虾个体用于应对环境胁迫的能量消耗增多，对空间资源的竞争加剧，为了争夺自己的领地空间和生存资源不惜自相残杀；机体对自由基的清除能力下降，使“自由基稳衡性动态”被打破，导致抗氧化系统紊乱，机体受到氧化损伤，细胞免疫和体液免疫水平均显著下降，可能是克氏原螯虾生长速度减缓、成活率逐渐降低、死亡率逐渐升高的主要原因。考虑到既要能充分利用水体资源又要获得最大的生长率和成活率，20 尾·m-2的饲养密度为此规格克氏原螯虾适宜的饲养密度。
To observe the influence of stocking density on the growth and survival rate of P. clarkill and to investigate the suitable stocking density of P. clarkill at the size, Procambarus clarkill Girard (initial weight of 2.4 g±0.2 g）were reared at different stocking densities of 12, 20, 32, 40, 52 and 60 individuals·m-2 for two months. The relative growth rate, the survival rate and the limb loss rate were calculated. The activities of ACP, LZM, SOD and CAT in serum and the phagocytic activity of blood cells were determined after 60 days feeding period in order to observe the influence of stocking density on the growth and survival rate of P. clarkill, to investigate the probable reasons and confirm the fitting stocking density of P. clarkill at the size. Results showed that the relative growth rate, the survival rate and the activities of ACP and LZM in the serum showed a declining trend and the limb loss rate presented a gradually rising trend with the increasing stocking density. The activities of SOD and CAT in the serum were first increased and then decreased with the increasing stocking density. We concluded that the decreased growth rate, reduced survival rate, and increased mortality rate as the increasing stocking density of P. clarkill might be caused by the increased competition for the energy resources and territorial space among the individuals. The free radical scavenging ability was decreased, and the "free radical homeostasis in dynamic" was broken, which resulted in the antioxidant system disorder, the organism oxidative damage, cellular and humoral immunity declined in the body of P. clarkill. Twenty individuals·m-2 might be a suitable stocking density of P. clarkill at the size of 2.4 g±0.2 g, considering the growth rate, the survival rate, and adequately utilized water resource.