In recent years, Steller sea lions have been known to enter the Columbia River estuary and feed on white sturgeon, several salmon species, and rainbow trout, some of which are also listed under the U.S. Endangered Species Act. They are found in the Columbia River nearly year round, with the exception of early summer, going as far upstream as Bonneville Dam. Though not as abundant as the California sea lion, they are still a concern for those agencies charged with managing the fish populations. Since the Steller sea lions are themselves protected under the Marine Mammal Protection Act, managers are compelled to use nonlethal deterrence methods, such as rubber bullets and noisemakers. Deterrence by the public is strictly forbidden.