The Seattle Times’ article on Treaty Rights at Risk and the decline of salmon habitat in western Washington sparked a massive online response. By Monday afternoon there were 157 comments posted on the article, mostly negative. Most comments focused on tribal sovereignty, the meaning of the Boldt decision or tribal economics. But some focused on fisheries management, specifically the idea that fishing was the cause of the decline of salmon.

From malby:

How about calling off fishing for a few years? Let the stocks recover?

Cmrussell:

Take the nets out of the river’s for 4 years and watch a miracle happen.

In places where salmon habitat is declining, simply shutting down fisheries doesn’t mean more fish will return in the future. That’s because degraded habitat can support only a limited number of fish. Habitat, not harvest, is the limiting factor for these populations.

A great example of this is the Stillaquamish chinook fishery. Since the early 80s the harvest rate (the overall percentage of chinook caught in all fisheries) has declined.

So, obviously, more fish are making it through the fisheries and onto the spawning ground (solid line below). But, that doesn’t mean more wild fish are leaving the Stillaquamish River. The dotted line shows wild chinook in the river, and it is flat despite cuts in harvest.

The Stillaquamish chapter of the State of our Watersheds Report outlines various habitat issues in the watershed, including the increased winter floods that are hurting wild salmon  productivity:

Based on data from the USGS stream flow gage on the North Fork Stillaguamish near Arlington, a peak flow that would have happened once in 25 years in the 1930s now happens once every 2 years.  Six of the largest floods recorded at the North Fork gauge have come in the last 10 years, with the largest flood on record coming December 2010.

Essentially, one of the reasons for declining wild chinook on the Stillaquamish isn’t fishing, it’s because floods are happening more often. There are other habitat issues, but this is a pretty important one. But, why are floods getting worse?

Again, from the State of our Watersheds Report:

Suspected human factors impacting peak flow hydrology in the North Fork Stillaguamish watershed are:

• The conversion of mature forests to immature forests through industrial forest practices.
• The associated building of forest road networks throughout the upper North Fork watershed to support industrial forestry.
• The filling of wetlands and and slough habitats, and the disconnection of those habitats from the mainstem North Fork river.

All of these factors have reduced natural water storage in the basin, resulting in more water being available more often during peak flows.