Effects of stocking density on nitrogen and energy budget of gibel carp | 养殖密度对异育银鲫氮和能量收支的影响

Chinese. 在（28±1）℃、自然光照条件下,设计4种养殖密度饲养异育银鲫（Carassius auratus gibelio）。第1种处理为对照组,在体积为70cm×55cm×36cm、水深为18cm的水族箱放入23尾鱼（平均体重6.82g.尾-1）,试验鱼占用1个水箱,折算养殖密度为407g.m-2,第2、3和4种处理中试验鱼分别占用1/2、1/4和1/8水箱（其余空间空置）,养殖密度分别为对照组的2倍、4倍和8倍,4种密度分别以C、D1/2、D1/4和D1/8表示。每天9：00和16：00过量投喂配合饲料2次,2h后回收残饵,同时用虹吸法收集粪便,70℃烘干。试验持续28d。结果显示,随着养殖密度上升,生长氮和生长能的比例显著下降,排泄氮、排泄能和代谢能的比例显著上升;粪氮的比例有所下降,而粪能的比例无显著变化。高密度下鱼体增重的下降与氮及能量的利用效率下降有关。[著者文摘]

English. In order to investigate the nitrogen and energy budget of gibel carp （ Carassius auratus gibelio） in different stocking densities, a 28-day growth trial was conducted at four stocking densities in condition of （28 ±1）℃ and the natural photoperiod. In the first group （ control group）, 23 fish with the initial average hody weight of 6.82 g・ind. 1 were cultivated in a whole tank（70 cm ×55 cm ×36 cm,water depth 18 cm） ,and the stocking density was 407 g. m. 2. In the second to fourth groups, the tanks were divided into 2,4 and 8 parts, and the fish occupied 1/2, 1/4 and 1/8 water volume respectively in each. Tank, and other water volumes were empty. Therefore, the densities of the second, third and fourth groups were as 2, 4 and 8 times as control group＇s, and the four densities were marked as C, D1/2, D1/4 and D1/8. Diet were fed to satiation twice a day （at 9：00 and 16：00） and being fetched out after 2 h. Feces were siphoned out at 11：00 and 18：00 and dried at 70℃. The results showed that, with increasing stocking density, the proportions of growth nitrogen and growth energy decreased significantly, and the proportions of excreted nitrogen, excretion energy and metabolizable dnergy increased significantly. The proportions of fecal nitrogen decreased, while the proportions of fecal energy were unaffected by density. In conclusion, the lower nitrogen and energy utilization efficiency lead to lower percent weight gain.