Decadal Oscillation,
Salmon and Orcas

Fall, 2003
Finally, some good news...

You’ve probably all heard that we have three newly birthed orcas in our local waters. This, along with four births last season and a dramatic decrease in deaths the last two years is truly good news.

This trend is most certainly not a coincidence. It coincides with a dramatic shift in the wild salmon returns the last two plus years. Three years ago the chinook jack salmon returns to the Columbia River dam fish counting stations were dramatically up from the previous twenty or so years. Jack salmon are fish that return one year ahead of their class.

They are traditionally the best indicator of the numbers to be expected in the parent (next year) class. Indeed, the next year (2001) there was a huge return of chinook to the Columbia. It was even better this year. Concurrently, Puget Sound has realized similarly increased returns of chinook, coho, pinks and chum salmon.

The increased returns are now recognized to be related to a larger weather cycle of twenty plus years, hence the name “decadal oscillation”, that’s been going on forever. This phenomenon causes an upwelling of increased nutrients in the Washington, Oregon, and California coastal waters that results in more feed for salmon, dramatically increasing their survival rate, and therefore improving Orca health in turn.

With abundant salmon to eat, orcas aren’t forced to draw on their PCB laced fat reserves. Living off these toxic fat reserves is widely thought to cause disease, deaths, and low birth rates.

Hopefully global warming won’t in any way cancel the positive effects of this most recent cyclical oscillation that began about four years ago and will probably last another fifteen to twenty years. I think we can look upon these years as a potential grace period where we must work to curb further toxic insults to Puget Sound and improve habitat for salmon, before the ocean cycles back to less favorable conditions.
Dave Anderson