Abstract: Conducting exercise training of habitat adaptability before the enhancement and releasing of aquatic organisms is one of the key links to improve the survival rate of larval and juvenile fishes in the wild. To investigate the suitable exercise strengthening techniques before releasing, we examined survival rate (SR), condition factor (CF), hepatosomatic index (HSI) and cardiac index (CI) of Takifugu obscurus under different training intensities (0, 0.75, 1.5 BL·s^-1) and training time (7, 14, and 28 days) in the upstream training experiments. The changes of lysozyme (LZM), cortisol (COR), superoxide dismutase (SOD), lactate dehydrogenase lysozyme (LDH), and glycogen (Gn) levels in the serum of T. obscurus were measured. The results showed that the SR in the 0.75 BL·s^-1 training group was higher than that of the control group and the 1.5 BL·s^-1 training group after 28 days. The contents of LZM, COR, SOD, LDH, and Gn in all training groups were significantly higher than that in control group (P<0.05), without significant variations among the training groups (P>0.05). Moreover, the contents of LZM and COR first increased and then decreased with the extension of training time. The content of LDH also increased with the extension of training time. In summary, the appropriate upstream training (training intensity of 0.75 BL·s^-1 with 14 days) can effectively improve the immune enzyme activity of T. obscurus, and enhance the survival rate and efficiency of releasing.

Key words: Takifugu obscurus, upstream training, enhancement and release, immune performance