The most effective policy would be to outlaw the use of nets with very small holes, which catch even young, immature fish. Imposing a minimum mesh size (the distance between the threads of the net mesh) would immediately allow small fish to escape the net and survive to breed. Within 2 -3 years the fishermen would have larger fish, and more of them, to catch. However, until then they will catch very little - which illustrates one of the economic problems with this policy!
