Come on! How veraciuos can a few otters be? Not as veraciuos as the hundreds of hoopers that are out there every season I bet! Not to mention the sealions!!
Dude... BAD. They're ridiculously voracious. They eat 20% of their body weight each day in shellfish!
In the areas with lots of otters, you pretty much don't see any abalone. Sealions don't eat much shellfish at all really so they're a non-issue. As far as hoopers go, well they aren't catching any abalone.
Of course, as you noted, the lobster fishery has fishing pressure (as it should, being a valuable resource.) But I'm not following your logic that because it's fished already, more pressure from otters won't matter. Also, otters also don't obey size and bag limits, unfortunately
The history of otters off California is an interesting one. Fossil records show that Native American hunting of otters directly correlates to dramatic increases in shellfish populations. When the population started rebounding from a major crash in the early 20th c., there was a corresponding crash in the cen-cal ab and urchin fisheries. After seeing that, the state set up a "no otter zone" from Pt. Conception to the border with only San Nic as a safe haven to protect so-cal from the destruction they saw up north. It's no longer enforced, but as we've seen, the otters have not readily colonized in so-cal anyway.
Like I said, cen-cal can keep them!