Isistius is a genus of dogfish sharks in the family Dalatiidae.

They are particularly notorious for biting small chunks off of a prey animal in passing.

Large prey, such as swordfish and cetaceans, may bear several healed wounds from such bites.

[4] Weaker prey may be injured enough to be weakened until they are unable to swim properly.

Isistius species can eat half of their own body weight at a time.