My limited experience with Blue Fin Tuna supports what you say. These fish are very boat shy. You can't get closer than 100 yards if your engine is running. We sometimes see them while fishing for albacore out of the Golden Gate. We have managed to hook 5 and land 3 over the past 20 years. Getting "spooled" is a heart break. The largest we landed was 115 pounds on basic albacore tackle with a 7 foot Ugly Stick and a 4-0 Penn Senator with 40 pound Ande mono filament. If you manage to get ahead of the crashing fish, shut off the engine, and wait while free lining a live sardine you can get lucky if the school comes towards the boat.
In all due respect, a lot of local fish, doesn't prove much, either way. And sport fisherman take so few, in comparison to commercial interests, that we are not much of an issue. It is the WORLD WIDE take that concerns everyone-and should. With that price tag on their heads, the worry is that, this much money is working against the bio mass, and this concern is backed up by hard facts I'm afraid.