Worm found inside of wahoo
It is Giant Stomach Worm (Hirudinella Ventricosa).  

It is a platyhelmith parasitic to Wahoo fish, feeding on its blood and found inside the stomach. It makes 98% of Wahoo's parasitic infections.


  It is a fleshy worm that varies in size and shape; with extended worms the size of a mans finger and contracted ones about the size of a walnut. 


It requires two hosts to complete its lifecycle; a snail and a wahoo fish.

A picture from National Geographic Society

Source: lahaina news

Note: A youtube video shows this worm moving.