It can't all be about global warming in the case of anchovies because my dad told me Anchovies used to be plentiful on the inside of the strait in the old days. He told me they used to quite plentiful up Indian Arm way back when. He told me they were commercially harvested in the old days, until their numbers dwindled and that was the end of the resident Anchovies. Maybe he was mistaken, but my dads family has lived and fished in this area for over 100 years going back to his father's time. The old timers didn't have computers, but I put pretty good stock in them as a source of information.
Halibut were commercially harvested from Vancouver harbour way back when. The resident population was of course decimated never to return. Sturgeon banks off the mouth of the Fraser obviously was so named, for a reason. Don't think you'll find many Sturgeon there nowadays though. Same with Halibut bank in the Lower Strait. Overfishing just wiped out many of our local stocks.
I'm not denying global warming has many negative impacts on on our local stocks. It's just that global warming generally takes a while to impact a stocks viability. Man is far more devastating to fish stocks in the short term, by simply never knowing when to limit harvesting until it's too late.