Interesting article on cod fishing in Gloucester, Mass. Regulations limiting catch hurt people trying to make a living by fishing, and it's really hard to hold people to limits. It can be done, but in this case doing so provoked a political backlash. In the end it seems that catch shares (ITQ's) are the way things are going to go, but systems don't change lightly.
Since there are externalities in this "commons" situation, using catch shares or taxes are the way to get to the social optimum. It's not easy to figure out what that social optimum is, though, and spreading the pain around so that it doesn't hit anyone disproportionately is virtually impossible. Clearly effective regulations are necessary, but also humane implementation of the regulations is something to strive for. There's already enough pepper spray in the air these days!