Problem:
Overfishing of various fish species.
In the normal action of free markets, if there is an economic profit to be made by producing a product it will be made.
If there is a demand for a certain type of fish, then there will be fishing to supply that demand.
At some point, the number/rate of fish caught commonly exceeds the rate at which those fish reproduce. This leads to a declining supply.
The overall demand for the fish will not change with increased prices, leading to more profit on a per fish basis, leading to more economic incentive to fish.
The scarcer the fish, the more profit there is in catching it. Eventually you get a collapse of a fish species, and occasionally, outright extinction.
What is the "free-market" solution for preventing this that requires no governmental intervention?