With no killer whales around, otter population were just what they had always been. There was no decline. Scientists are concerned not just for the otter. By feeding on shellfish and sea urchins, otters help to maintain the underwater forests of kelp that provide food and refuge for a host of marine creatures. Scientists worry that the declining otter population means that the kelp beds will suffer.
Researchers are also concerned for the killer whales.
They think that the orca population must be pretty hungry to eat otters. For the whales, it must be like trying to survive on popcorn.