We barely have sea surface temperatures that go back 100 years along this coast (and patchy at that). So, with post-glacial changes in sea level and imperfect detailed knowledge of coastal currents, the waters off Vancouver Island could have been quite acceptable for bluefin tuna. [Unless they were importing them from the Chumash off Santa Barbara. ] And if there were much larger numbers of bluefins before the development of industrial fishing, there may have been enough competition for food that bluefins would have spread into more marginal parts of their thermal range to forage.Thanks for your input Bob. Having 20 years of perspective from your part of the coast is very much appreciated.
Hard to say where all this is going. I'm no scientist but it seems clear that ocean (and land) ecosystems are migrating north. Species like dorado, yellowtail, and striped marlin would (I think) correlate directly with warmer SST's. Not sure that is the case with bluefin. I keep going back to that archaeological study of coastal BC tribes harvesting large bluefin. Dozens of specimens ranging from 150 to 650#. Found at multiple sites as far north as Haida G'waii. And this was going on for at least 5,000 years.
To me, that says bluefin aren't "exotics" in the PNW. Instead, I'm hoping the massive resurgence of the fishery in SoCal is a reflection of improvements in fishery management. Either that, or bluefin are simply spending more time in the eastern Pacific. One study came across a while back showed a correlation with prey abundance in the western vs eastern Pacific. Which may or may not be related to GW. In any case, it looks like we could be at the start of a longer term cycle which could make things very interesting out there.