This study investigated metabolic responses of acute and chronic exposures of tilapia, Oreochromis niloticus, to different levels of salinity. Fish were transferred from freshwater to water with different salinity concentrations (0, 6, 12, 18 and 24 g/L), and oxygen consumption and ammonia excretion were measured at various exposure times (1, 3, 6, 12, 24, 48, 72, 96 h and 30 days). Estimates of metabolic oxygen consumption rate (MO₂), metabolic ammonia excretion rate (T_amm), ammonia quotient (AQ) and oxygen-to-nitrogen ratio (O:N) were computed. The results showed that O. niloticus could not tolerate sudden transfer from freshwater to water with salinity concentration of 24 g/L. The best survival rate was recorded from fish cultured in 12 g/L salinity, while the best weight gain was recorded in fish cultured in 6 g/L and 12 g/L salinities. The study revealed that both salinity and time had significant effects (p < 0.050) on MO₂, T_amm, AQ and O:N. MO₂ was observed to decrease significantly (p < 0.050) with increasing salinity for almost all the exposure times, which suggested that less energy was spent by O. niloticus to maintain a balanced osmoregulation as salinity levels increased. It was also revealed that protein metabolism played a minor role in the maintenance of a balanced osmoregulation in the fish since its rate was seen to significantly decrease (p < 0.050) with increasing salinity and time. Protein metabolism was estimated to contribute not more than 14.74% of the total energy used for osmoregulation in O. niloticus.

中文翻译：

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尼罗罗非鱼（Oreochromis niloticus）急性和慢性暴露于不同盐度的代谢成本

本研究调查了罗非鱼（Oreochromis niloticus）急性和慢性暴露于不同盐度水平下的代谢反应。将鱼从淡水转移到不同盐度浓度（0、6、12、18 和 24 g/L）的水中，并在不同的暴露时间（1、3、6、12、24、48 、72、96 小时和 30 天）。计算了代谢耗氧率 ( MO ₂ )、代谢氨排泄率 ( T _amm )、氨商 (AQ) 和氧氮比 (O:N) 的估计值。结果表明，O . 尼罗罗非鱼不能容忍从淡水突然转移到盐度浓度为 24 g/L 的水中。在 12 g/L 盐度下养殖的鱼记录到最佳存活率，而在 6 g/L 和 12 g/L 盐度下养殖的鱼记录到最佳增重。研究表明，盐度和时间对M O ₂、T _amm、AQ 和 O:N都有显着影响（p < 0.050）。在几乎所有暴露时间内，随着盐度的增加，观察到M O ₂显着降低（p < 0.050），这表明O消耗的能量更少。 尼罗罗非鱼随着盐度水平的增加，保持平衡的渗透调节。还发现蛋白质代谢在维持鱼的平衡渗透调节方面发挥了次要作用，因为其速率随着盐度和时间的增加而显着降低（p < 0.050）。据估计，蛋白质代谢对O 中用于渗透调节的总能量的贡献不超过 14.74% 。 罗非鱼。