Polus frontalis

例句：

1. 1.The fish had a long, thin body with a prominent dorsal fin.
   这条鱼身体长而细，有一个突出的背鳍。
2. 2.The angler caught the fish by feeling its dorsal fin.
   钓手通过触摸鱼的背鳍来捕捉它。
3. 3.The dorsal fin is used to sense water currents and help the fish swim more efficiently.
   背鳍用于感知水流并帮助鱼类更有效地游泳。