sailfish       
noun [ C ] uk/ˈseɪl.fɪʃ/ us/ˈseɪl.fɪʃ/  sailfish
 旗鱼
a fish with a long, narrow, pointed mouth and a very high fin on its back that looks like a sail (= a sheet attached to a pole on a boat that makes the boat move)
  The sailfish is found worldwide, at the edge of coastal waters and in the open sea. 旗鱼分布于世界各地,在沿海水域的边缘和公海中都有它们的踪影。 
 - More examples
 - Currents swirling around the ship could stir up nutrient-rich water to attract larger fish, such as dolphin, wahoo and sailfish.
 - He was the first known fly fisherman in the world to catch Atlantic sailfish, Pacific sailfish and all five species of marlin on a fly.
 - Commercial and sport fishing, notably for shark and sailfish, are economically important.
 - As the sailfish's quick burst of speed ends, it erects its "sail" to prevent it from rolling.