两种养殖密度对刀鲚当年鱼种生长性能、消化及非特异性免疫能力的影响

为研究中、高养殖密度对刀鲚当年鱼种生长、存活、消化及非特异性免疫能力的影响，本实验采用池塘培育方式，以同批次人工繁育的刀鲚当年鱼种 (0.88±0.26）g和（0.55±0.20)g]为研究对象，进行为期96d的养殖试验。结果显示：中密度养殖塘(62#，6尾/m2)刀鲚的体长和体质量增长速度均显著大于高密度养殖塘(56#，11尾/m2) (P<0.05)，其中体长相对增长率是56#塘的3.4倍，体质量相对增长率是56#塘的6.5倍；肥满度和存活率均大于56#塘，分别为0.290g/cm3，83.5%和0.278g/cm3，79.7%。养殖期间，62#塘淀粉酶(AMS)活力均显著大于56#塘(P<0.05)，并随养殖时间呈先升高后降低的趋势；而胰蛋白酶(TPS)活力表现出先降低后升高的变化，除养殖中期时与56#塘无显著差异外，其他时间均显著大于56#塘(P<0.05)。62#塘胃蛋白酶(PPS)活力在养殖前中期均明显大于56#塘(P<0.05)，之后降低至显著低于56#塘(P<0.05)，而56#塘PPS活力随时间无显著变化。62#塘脂肪酶(LPS)活力随养殖时间逐渐升高，至养殖中期时与56#塘无显著差异，其他时间均显著小于56#塘(P<0.05)。两塘间的超氧化物歧化酶(SOD)活性均无明显差异(P>0.05)，但随养殖时间逐渐降低。62#塘谷胱甘肽过氧化物酶(GSH-PX)和过氧化氢酶（CAT）活力随养殖进行均显著大于56#塘(P<0.05)，其中CAT活力随养殖时间显著升高，GSH-PX活力无明显变化；56#塘的CAT呈先升后降趋势，而GSH-PX随养殖时间而逐渐降低。因此，在本实验条件下，高密度对刀鲚幼鱼的生长速度、消化能力和免疫系统产生一定的负面影响，而中密度养殖塘刀鲚鱼种的生长、消化及免疫性能均优于高密度，更适合刀鲚鱼种的培育和规模化养殖。

Effects of two stocking densities on growth performance, digestion and non-specific immunity of the current year Coilia nasus

The experiment was conducted to study the effects of medium and high aquaculture density on the growth, survival, digestion and non-specific immunity of the current year Coilia nasus. A 96 days aquaculture experiment was conducted in the same batch of artificially bred Coilia nasus(0.88±0.26)g and (0.55±0.20)g] using pond culture methods. The results showed that the growth rate of body length and body mass in medium density pond (62#, 6/m2) was significantly higher than that in high density pond (56#, 11/m2) (P<0.05), in which the relative growth rate of body length was 3.4 times than that in 56# pond, the relative body mass growth rate was 6.5 times than that in 56# pond. The fatness and survival rate were also greater than those of 56# pond (0.290 g/cm3 and 83.5%, 0.278g/cm3 and 79.7%, respectively). During the aquaculture period, the amylase (AMS) activity in 62# pond was significantly higher than that in 56# pond (P<0.05) and showed a trend of increased first and then decreased with the aquaculture time, while the Trypsin (TPS) activity showed a change of decreased first and then increased. Except that there was no significant difference between 62# pond and 56# pond in middle stages of aquaculture, the other time was significantly greater than 56# pond (P<0.05). The pepsin (PPS) activity in 62# pond was significantly higher than that in 56# pond (P<0.05) and then gradually decreased to significantly lower than in 56# pond (P<0.05), while PPS activity in 56# pond did not change significantly change with time. The lipase (LPS) activity in 62# pond increased gradually with culture time, and was not significant different from that in 56# pond in middle stage, and was significantly smaller than that in 56# pond at other times (P<0.05). There was no significant difference in the activity of superoxide (SOD) between two ponds (P>0.05), but it decreased gradually with the time of aquaculture. The activity of catalase (CAT) and glutathione peroxidase (GSH-PX) in 62# pond was significantly higher than those in 56# pond (P<0.05). The CAT activity increased significantly with the aquaculture time, and GSH-PX activity did not change significantly. The CAT activity in 56# pond showed a trend of increased first and then decreased, while GSH-PX activity gradually decreased with aquaculture time. Therefore, under the experimental conditions, high-density aquaculture has a certain negative impact on the growth rate, digestive ability and immune system of juvenile Coilia nasus, while the growth, digestion and immunity of coilia nasus cultured at medium density are superior to those at high density, which is more suitable for the cultivation and large-scale aquaculture of coilia nasus.