AKiller whales in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.
BThere is no indication that the sea otter population at any North Pacific location declined in the 1980s because of substantial numbers of sea otters migrating to other locations.
CAlong the Pacific coast of North America in the 1980s, sea otters were absent from many locations where they had been relatively common in former times.
DFollowing the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters' main food source.
EThe North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.