Climate impact on salmon populations
We all know habitat can make or break entire races of fish, but it's interesting to read theories and beliefs on effect of weather on overall populations as well...
I'd guess that many west coasters here have heard of the Pacific Decadal Oscillation - PDO - a climate/ocean phenomenon that is correlated with fish run sizes in Alaska and the lower west coast (WA, OR). The PDO seems to flip flop every 20 or 30 years between these areas, and with it, so do fish populations.
It is thought that a flip is happening now. If so, fish runs should rebound in the lower west coast, and fall in Alaska for the next several decades. The "record" chinook runs in the Columbia this past year are often touted as the leading edge of this flip flop.
This is all cool, but superimposing ocean effects on all the other stuff that affects fish (4H's) makes it really difficult to pin down who and what has pushed many runs to the brink of extinction - and beyond. And that's not to say that humans can't affect climate, too, as we are seeing more and more.
I'm at least hoping for good fishing in Oregon over the next several decades!
Interesting correlation in the North Atlantic where research also points to climate change as a factor in the decline of atlantic salmon.
I don't have the reference to hand, so am only going by memory here. But basically it is believed that salmon feed in sea water at a very specific temperature - no doubt the production of plankton at the bottom of the food chain is the key, as the 'Nature' piece mentions. As a result of climate change, the area of the Atlantic that is at this crucial temperature has shrunk to about one-third of its former size. Some have suggested that this is the main reason for the reduction in numbers of salmon returning, which has occurred even where rivers have maintained consistent levels of smolt production.
Yes Johny, there is a "Balance"
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