吉富罗非鱼生长过程中氮收支变化的研究

为充实有关鱼类研究数据，提供实际生产理论依据，研究了吉富品系尼罗罗非鱼（Oreochromis niloticus）从鱼种（18 g）生长至成鱼（180 g）过程中氮收支变化。试验为期73 d，每日饱食投喂并收集鱼粪，溶解氧质量浓度为8.0-6.0 mg·L-1，pH为 7.5-6.5，水温为24-30 ℃。在鱼均质量达到50 g、100 g和180 g时测定并计算当前生长阶段氮收支。结果表明，生长氮比例在养殖初期最高（64%），养殖中期最低（47%）；粪氮比例在养殖中期最高（9%），养殖初期和末期分别为5%和4%；排泄氮比例随鱼的生长而逐渐增加。此外，试验期间水中总氮增加速度在养殖中期减慢，养殖末期再次加快。

Nitrogen budget changes of tilapia (Oreochromis niloticus) during growth

We conducted a 73-day experiment to examine the nitrogen budget changes of tilapia （Oreochromis niloticus） during its growth from fry （18 g） to adult （180 g）. In the experiment, we fed the fish fully, collected feces every day in the water with dissolved oxygen from 8.0 mg·L-1 to 6.0 mg·L-1, pH 7.0 to 6.5, and temperature 24 ℃ to 30 ℃. Nitrogen budgets were calculated when fish weighed 50 g, 100 g and 180 g. Results show that, growth nitrogen proportion is the biggest （64%） at the initial grow-stage and the lowest （47%） at the final grow-stage, fecal nitrogen proportion gets the biggest （9%） at the middle grow-stage, and excretion nitrogen proportion increases progressively all the time. In addition, total nitrogen amount in the water increases with the growth of fish, but the increasing speed is slower in stageⅡthan stageⅠand Ⅲ.