As I said in a post I made in another thread, the numbers (as I understand them, which could be incorrect) don't suggest that overfishing is the major cause of the problem. Here's what I said:
"As I have not studied these issues in depth, I don't purport to understand them very well. However, there is one statistic which is overwhelmingly the most troubling to me, because it clearly points out what we know, namely that that there are many things beyond catching fish (commercially, for sport or for FSC First Nation purposes) that are destroying Chinook salmon populations. The statistic is this one: total fishery mortalities [from fishing] are 16.9% with remaining 83.1% of run going to spawning grounds. Unless, I am mistaken, this suggests it is not overfishing that is the principal cause, or even any cause at all, for this huge decline in the salmon numbers over the last decade or so.
This means that the salmon are not reproducing and/or dying in the ocean without ever being caught by fisherman at rates that will see their permanent demise unless we find out why and do something about if we can. Habitat loss, ocean warming due to climate change, and pollution generally may be the largest reasons for this and if so, I fear that our beloved Chinook are doomed."
So whether they are dying in the rivers or the oceans, fish harvesting seems to not the main cause for the decline. I also base this on what accepted science seems to say: pollution and global warming are responsible for habitat loss and ocean warming (which is really a form of habitat loss) and less survivability in fresh and saltwater.
Now this is an inference I am drawing based on the fact that 83% of the runs make it to the spawning beds. But this could be wrong because perhaps a much larger number (95%) making it to the spawning beds will reverse the decline or even increase populations. And this prompts one to ask why more aren't getting to the spawning beds. Is it fishing, seal predation, environmental degradation (or even other reasons)? Probably a combination of all three; the big and interesting question is which is the largest cause? I don't know and I'm not sure if fisheries experts and scientists can say this. If too much fishing is the problem, then doing less (maybe a lot less) is the easy solution. But I don't think so, unless taking 17% of the potential spawners is enough to cause the population to continue to spiral downward.