Devil Fish (known as Ichtyion in Super Nova) is one of the "paired" bosses (same boss in 2 different zones) of Darius Force. Interestingly enough, in the special boss endurance mode he is called "Ichtyion" instead of Devil Fish.
His attack patterns depends on the zone where you encounter him.
Zone G (red)
All his fire power is based on lasers. When the battle starts, he charges and shots a paser-based spread shot from his nose-like cannon, and grenades from his head. He also has a huge tentacle (just as Mudy Crystal) that makes serpent-like moves, but it won't regenerate after you destroy it. The tentacle, the cannon and his forehead are the first Devil Fish's weak points. When the three are destroyed, it will show up a blue spot (his last weak point) on his forehead, from where he will shot small laser bullets to your Silver Hawk.
Zone I (gray)
Same as the former. The difference is that his first attack, besides of his grenades, is a normal gun (normal from enemy's perspective) and the blue spot will shot normal-based spread shots.