When you're dealing with salmon, and previously with the herring fishery, for vessel replacement, you couldn't get a bigger boat to replace the one you had. It didn't have a limit. It only said you couldn't go any bigger.
Those are for fisheries where there is an opening. You would have motivation to get a bigger vessel to take maximum advantage of a two-day opening, a one-day opening, 12 hours, or whatever it might be, for things like salmon or herring.
Where you don't have that and you're dealing with ITQs, it's then up to the vessel owners to figure out what they want to do. For those competitive fisheries, there are size limits in B.C. as well.