During our field season, we (NGOS) collect salmon scales while residents are fishing, bits of prey flesh while transients are hunting, bits of shark liver when offshores are hunting. We also collect fecal samples from any ecotype we encounter.
During the May to September field season, Chum, Coho, and Chinook Salmon are very important to our resident killer whales. We are currently in the midst of a major analysis of our collected fish scales, fleshy bits, and fecal samples. We will soon publish a more comprehensive view of these whales' diet. Halibut, Arrowooth Flounder are also consistent prey items, but in much less quantity. Sockeye salmon appear in the diet occasionally, and herring occur in such minute proportions that they may only be secondary prey (consumed actually by the salmon).
We have collected many bits of flesh from predation events, that vast majority from harbor seal and Dall's porpoise. There are some groups that appear to specialize in Steller Sea Lions, and some that appear to have developed the skills to hunt the calves of large whales. In the Aleutian Islands, particularly False Pass, some transients target Grey Whales on their migration north to the Arctic.
In Alaska, when we work with offshore killer whales, we find mostly bits of liver from Sleeper Shark. We also had a day where an offshore killer whale caught a salmon shark, photographed here. In British Columbia, offshores are also known to take Blue shark and dogfish, and a small amount of other fishes. Shark may represent more than 90% of their diet, which explains their worn teeth!