As a proxy for broader ecological health in the Northwest, Sightline monitors the populations of five wildlife species. Among the species included in the Cascadia Scorecard, we track the population of Chinook salmon returning in the Columbia River, specifically measured by the number of fish that pass the Bonneville Dam during the spring and summer runs. In 2009, more than 300,000 Chinook passed the dam, 146 miles upstream from the river’s mouth on the Pacific Ocean.

It was a strong showing for the fish: a 29 percent increase over the previous year and the second consecutive year of increasing numbers. Yet annual population fluctuations send murky messages about the health of the fish. Chinook counts in the spring and summer months vary by about 40 percent a year, mostly due to natural population dynamics. Only long-term monitoring can reveal meaningful trends in the population. And last year’s fish count, while good by the standards of the past 25 years, is still a very poor showing in historical terms: less than 11 percent of their estimated abundance in the 19th century.

salmon update

The true story is even bleaker: wild salmon probably return at less than 3 percent of their former numbers. The rest of the returning salmon are hatchery-raised fish, whose numbers are far less meaningful as signals of the region’s ecological health.

Chinook salmon are an important indicator because these fish inhabit the region’s ecosystems to an extent that few creatures other than humans do:  their well-being is dependent on the natural integrity of the forests, deserts, cities, and farms of the Northwest. The largest hydrological system on the West Coast of the Americas, the Columbia River and its tributaries stretch deep in British Columbia, Idaho, Oregon, and Washington. So the health of the river’s signature fish, the spring and summer Chinook, tell us something about how extensively northwesterners have altered the native landscapes of the region.

Restoration of the Columbia Chinook has proceeded haltingly in recent years and many salmon advocates have been disappointed by the Obama administrations efforts to date. In particular, some worry that the federal government is not seriously considering breaching the four dams on the Lower Snake River, which are obstacle to critical upstream habitat. Complicating matters, reducing the Northwest’s greenhouse gas emissions, especially phasing out coal power, may intensify the demand for hydropower production from dams. Yet some recent research suggests that the Puget Sound orcas (which were recently listed as a federal endangered species) rely on Chinook salmon as a dietary staple, underscoring their central place in the Northwest’s ecological web.

Update 10/16/09: I’ve made a few corrections thanks to the sharp eyes of a reader.