Stillaguamish habitat

Posted by: Carcassman

Stillaguamish habitat - 06/10/19 02:44 PM

Have a question. I have not worked directly in the Stilly watershed much and have been out of a lot of the day-to-day for a while. But, what specific data do we have that shows the FW environment in the Stilly watershed has degraded since the 70s/80s to where it won't support Chinook? I know that the slides in Deer Creek and Oso have certainly created issues in those specific locations.

Thanks.
Posted by: Salmo g.

Re: Stillaguamish habitat - 06/10/19 07:40 PM

C-man,

I worked as well as fished in the Stilly basin in the mid-70s. The Stilly is a lot like most river basins in the north Cascades, meaning steep with a lot of unstable soils. Or as they say in forestry, especially unstable when disturbed. Only the Stilly is more so. Actually it's not the only one, much of the Nooksack drainage and parts of the Skagit are similar. Finney Creek in the Skagit drainage is on the opposite side of the mountains that form the Deer Creek sub-basin, for example. The difference there I think is that foresters built a logging railroad across from Lake Cavenaugh beginning before 1930, giving the logging of higher elevation steep unstable terrain a bit of a head start over some of the others. Deer Creek and Finney Creek summer steelhead populations sustained into the mid and late 1960s, but were severely depressed by the 1970s, corresponding to a lag time between massive clear cutting and reduced habitat productivity. While Deer Creek's DeForest Creek slide of the 80s, and the Oso slide 5 years ago are well known, there have been numerous large mass wasting slides in Deer Creek, and both the North and South Forks dating back at least to the 1960s following massive clear cutting in those watersheds.

The soils contain a lot of clay and glacial outwash that is highly pulverized. I don't know that these soils contain a higher proportion of the fine sediments that suffocate incubating eggs and sac fry, but it's possible and likely that so much more of it has been eroded that the ability to incubate eggs and fry from September spawning through the heavy winter rainy season to late February and March (peak) emergence just isn't there any more. As bad as the silt load in the Skagit downstream from the Sauk is these days, it's positively clean in contrast to the Stilly. The Skagit Chinook egg to young-of-year smolt survival ranges from 2 to 12%. Recruit per spawner data infers that it's lower in the Stilly. In addition to silt suffocation of eggs and sac fry, the Stilly channel in many places has filled with small gravel, down to pea sized, where spawnable gravel, cobble, rubble, and even boulders used to prevail. I surmise that a lot of the slow velocity shallow areas that formerly provided critical fry colonization habitat for Chinook and other species is now smaller substrate that doesn't provide the cover that fry require. Nor does it produce the diversity of invertebrate species needed as forage for juvenile fish.

A lot of details missing because I haven't kept up with the research, but the upshot is clear when generation after generation of spawning Chinook salmon cannot even replace themselves, let alone provide even a meager harvestable surplus. I think both the Forest Service and DNR have done some specific research on Deer Creek, but I think they tend to skirt the kind of research that implicates forest practices in general, since it's not good for business.

Sg
Posted by: Carcassman

Re: Stillaguamish habitat - 06/10/19 08:39 PM

From the historic photos I have seen of other watersheds, especially the Sky as the railroads followed it, the tree cover was a whole lot less 50-100 years ago, at least along the rail lines. I don't at all dispute that the Stilly is unstable and over-logged, as is (for example) Jordan Creek which I have been in a bunch.

But, R/S is a measure of survival from spawner to spawner. It covers everything from intra-gravel survival through FW rearing through smoltification/migratiion, avian predation, pinniped predation, lack of food in the ocean, and so on.

All of the above affect R/S, all of the above are documented to be occurring and generally increasing in negative impact in the North Pacific so I am curious as how we can be so sure that the FW situation is what is controlling the population.

It seems to me, lacking any data so just going pin my prejudices, that assigning FW habitat as the reason gives a free pass to leaving everything else alone.

Hence, my question. Just what Stilly FW salmonid survival data is there?
Posted by: FishBear

Re: Stillaguamish habitat - 06/11/19 08:54 AM

From what I understand the current condition of Stillaguamsih Chinook is reflective of other PS Chinook stocks, exhibiting many of the same characteristics...

Low Freshwater productivity
Poor marine survival
Adults returning to river not replacing themselves (less than 1 to 1)

Not a recipe for immediate recovery.