Some clearing up about fish and seals as prey:
There are three genetically-distinct "races" or sub-species of orca: resident, transient and offshore orcas. I copied this stuff from Wikipedia and made the most important bits bold.
Resident orcas are the most commonly sighted of the populations, often observed in coastal waters. Female residents characteristically have a rounded dorsal fin tip that terminates in a sharp corner. While nomadic, their range is much smaller, and they are known to visit certain areas consistently.
The resident orcas' diet consists primarily of fish, including salmon and herring, and they frequent areas where preferred fish are abundant. They are continually on the move, sometimes traveling as much as 100 miles in a day, but may be seen in a general area for a month or more. Range for resident orca pods may be as much as 800 miles or as little as 200 miles.
Resident orcas live in complex and cohesive family groups known as pods. Resident pods are generally larger than the transient and offshore pods, having up to 50 or more members. Several pods occasionally join to form what are referred to as superpods, sometimes numbering in excess of 150 animals. They can also be seen swimming with porpoises, other dolphins and sea lions, which are common prey for transient orcas.
Transient orcas generally travel in small groups, usually up to 7 or 8 animals. Unlike residents, transients may not always stay together as a family unit. A female's first son will usually stay with her as an adult, but it is not uncommon for subsequent male offspring to disperse once they reach adulthood.
Transients are often seen cruising along the shorelines hunting for prey, which commonly includes seals, porpoises, and sea lions. Often, to avoid injury, they will disable their prey before killing and eating it. This may involve throwing it in the air, slapping it with their tails, ramming it, or breaching and landing on it. The whole process can be quite lengthy at times, seeming to be like torture for the prey, but is primarily for safety and training for the young orcas.
Female transients are characterized by dorsal fins that are pointier than those of residents. Male transients often have scarred dorsal fins, probably from injuries resulting from hunting and killing prey. Unlike residents, transients often travel and hunt in silence. The range for transient orcas is from southeast Alaska to California. To kill large mammals like whales, transients gather in a super-pod, formed by two or three groups of transients.
Offshore orcas remain offshore, cruising the open oceans and feeding primarily on fish, sharks and turtles. They have been seen traveling in groups of up to 60 animals. Currently there is little known about the habits of this population, but they can be distinguished genetically from the residents and transients. Female offshores are characterized by dorsal fin tips that are continuously rounded.
