Since the last Ice Age, fish have colonized all the Northwest's abundant rivers. For millennia, these fish, especially spectacular runs of salmon and steelhead, have fed Northwest ecosystems, and Northwest people. As fish populations have declined very steeply in the past century, National Park status offers some protection, but cannot guard from impacts occurring outside park borders. Fish species within Olympic National Park are now being monitored by snorkeling in eight rivers and electrofishing in five streams. Other Network parks may adopt these protocols in future years.