The species Orcinus orca, generally known as orcas or killer whales, is made up of many genetically distinct populations called ecotypes. Each ecotype indicates an ecological specialization with its own ecological and phylogenetic characteristics.

The North Pacific is home to three known ecotypes of killer whales, called the transient, resident, and offshore ecotypes. While transient ecotype killer whales are mammal-eating, the resident and offshore orcas are fish-eating.