盐度对尼罗罗非鱼低温耐受性影响的研究

为提高尼罗罗非鱼的抗寒能力，本试验采用室内水族箱养殖方法研究了尼罗罗非鱼在0‰、5‰、12‰、25‰ 4个盐度梯度下的低温耐受性。结果表明：就温度而言，死亡率随着温度的降低呈先上升后下降的趋势，温度达到9.1℃时，死亡率达到最大值，为38.7%；就盐度而言，盐度为5‰时的死亡率最低，当盐度上升至25‰时罗非鱼的死亡率最高，50%的个体的成活时间(ST50)由长至短排序为5‰＞12‰＞0‰＞25‰；在不同的盐度梯度下，尼罗罗非鱼的低温耐受性都有所增加，当温度在8℃~11℃，盐度为12‰时，死亡率小于50%，当温度低于8℃时，死亡率急剧升高，在7℃时全部死亡；经统计分析，盐度为12‰时的半数致死低温显著低于其他3组。以上结果说明，一定的盐度可提高罗非鱼的低温耐受性。

The Effect of Salinity on its Cold Tolerance of Oreochromis niloticus

In order to improve the ability of cold resistance of Oreochromis niloticus, in this experiment, we did some researches on low-temperature tolerance of Nile tilapia under 0, 5, 12, 25‰ four salinity gradients with indoor aquarium farming methods. The results showed that, as for temperature, the mortality rate showed a trend of increased and then decreased as the temperature decreases, When the temperature reached at 9.1°C, the mortality rate reaches its maximum of 38.7%; in terms of salinity, salinity is 5 ‰ when mortality rate was the lowest, when the salinity increased to 25 ‰, means the highest mortality, according to Salinity, the survival time of 50% of individuals ranked as follows: 5‰＞12‰＞0‰＞25‰; Under different salinity gradients, the low-temperature tolerance of Nile tilapia has increased, when the temperature reached at 8℃-11℃, salinity 12 ‰, the mortality rate did not reach half of the total, when the temperature was below 8°C, the death rate rised sharply, they all died at 7℃; with statistical analysis, half of the lethal low temperature at the salinity of 12‰ was significantly lower than the other three groups. These results suggested that a certain degree of salinity could increase the low-temperature tolerance of Oreochromis niloticus.