腹鳍

例句：

1. 1. The fish swims with its tail held high, displaying a beautiful dorsal fin.
   这条鱼游动时，尾巴高高翘起，展示出美丽的背鳍。
2. 2. The scientist studied the behavior of fish using underwater cameras to capture images of their fins.
   这位科学家使用水下相机研究鱼类的行为，以捕捉它们的鳍部图像。
3. 3. The fisherman used a net to catch the fish, which he then released into the water with its tail still attached.
   渔民用网捕获了这条鱼，然后带着它的尾巴一起将其释放回水中。