The video above is an interesting discussion of an experiment being conducted in the US of creating property rights over ocean fisheries. Fishing is a classic case of the tragedy of the commons. Since nobody owns fish in the sea, there's no incentive for anybody to allow the fish stocks to replenish themselves. It's a free-for-all where the only incentive is to fish the sea into oblivion.

The most effective solution to this is to create property rights over fisheries, so that the owners of those fisheries have incentives not to let them die out. The challenge is in the implementation – I don't know if the method being tried in the US will work, but it's good to see some people trying.