The justification to limiting fishing for bottom fish to above 120 feet is that one could release rockfish without causing too much trauma. A hypodermic needle into the swimbladder is an effective way to release the expanded gas in the swimbladder because of the drop in pressure [120 feet = 5 atmospheres of pressure vs. the surface = 1 atmosphere of pressure. The gas which held a rockfish neutrally bouyant at 120 feet expands by a factor 5 to make the fish hyperbouyant when brought to the surface.] However, that would now close off deepwater ling cod and halibut populations, species that lack a swimbladder.
Most of my prior experience has been in observing populations changes via diving and 120 feet is a deep as I have gone on rare occasion. I know that there has been some survey work done with remotely operated vehicles and cameras, but I have not seen the results of those surveys. Yellow-eye, canaries, and boccacio do tend to be deepwater species (and I wonder just how abundant those ever were in Puget Sound even before extensive exploitation). I do not know if other rockfishes that are of concern, like blacks and yellowtail, have extensive deeper water populations. It may well be that the MPAs, placed in the limited, quality shallow-water habitat, are expressly designed to provide refuges for more shallow-dwelling species.
The successful repopulation and growth of some rockfish species, like coppers, does indicate that quality habitats are still there. But neither black rockfish or yellowtail rockfish have made much of a recovery (neither have true cod, another bottom-dweller hammered in the 80's). As Smalma pointed out, not all rockfish are the same. In my experience, while coppers and quillbacks may change depth a bit on the same reef, both blacks and yellowtail appear to move into the Straits in the winter and return to rocky pinnacles, at least in the San Juans. I used to see schools of black rockfish at the same spots year after year until they were fished out. Why their recruitment has been so poor is not clear to me.
The time-scale of recovery is daunting for such long-lived, slow-growing species as rockfish; a several pound rockfish is a decade old, while a several pound pink salmon is two years old. As Smalma points out, successful years for recruitment may happen only a few years in a decade. Why this is so is a great question and I do not know if it is well-understood.
Like any proposal for fisheries management (read people management - the fish would do fine without us), this one deserves scrutiny and critical examination. But scare-tactics, cherry-picking of some scientific studies and ignoring the consensus, and obscuring who the responsible culprits are for the problem (we have met the enemy and it is us), as the knee-jerk opponents of this plan have been doing, is a bad way to set public policy for the good of the public at large. Environments and their resources need to managed for all, not just a special interest group (sport fishers), no matter how dear sport fishing is to our hearts.
Steve