Salmon Runs Boom, Go Bust Over Centuries
Salmon runs are notoriously variable: strong one year, and weak the next. New research shows that the same may be true from one century to the next.
Scientists in the past 20 years have recognized that salmon stocks vary not only year to year, but also on decades-long time cycles. One example is the 30-year to 80-year booms and busts in salmon runs in Alaska and on the West Coast driven by the climate pattern known as the Pacific Decadal Oscillation.

Now work led by University of Washington researchers reveals those decadal cycles may overlay even more important, centuries-long conditions, or regimes, that influence fish productivity. Cycles lasting up to 200 years were found while examining 500-year records of salmon abundance in Southwest Alaska. Natural variations in the abundance of spawning salmon are as large those due to human harvest.

"We've been able to reconstruct what salmon runs looked like before the start of commercial fishing. But rather than finding a flat baseline -- .... http://www.sciencedaily.com/releases/2013/01/130114153426.htm

There is a lot we don't know....

That is an interesting study. There was a major effort to extend the sampling to lakes in Kamchatka but the Russians wouldn't allow it. It seems that they were suspicious that core sampling in lakes for fisheries research might be a cover for gold prospecting.

On the linked page an article in the related stories caught my eye.

Migrating Great Lakes Salmon Carry Contaminants Upstream (Dec. 6, 2012)

The core samples were basically looking at marine derived nutrients. Marine derived pollutant concentrations may prove to be a good indicator of run sizes in the future.

The sediment cores from Karluk Lake goes back about 2500 years. The two lows are rather recent, coincident with commercial fishing and about 70CE. From about 1200-1850 the runs were 2-4X current "sustainable" levels. The long term data shows the runs cycling up and down over long-ranging cycles.

Steady, consistent runs are a human invention.

Imagine That?

Yep that explains it all...now. Thanks

I don't have that kind of time damn it!

I am sure that when the science proves runs were great at one time that there were runs in famine and vice-versa. Something to think about because science can't always be right.

....and habitat isn't static....

The building up of the Karluk Lake sockeye was occurring at the same time as the central Sierra was undergoing a 150 year drought.

It was increasing at the same time that much of the Southwest was undegoing a large drought that some think was one of the causes of the destruction of the cliff dwellers.