Which explanation BEST gives the reasoning behind hunting and fishing liscenses?

I would say that the best explanation for having a hunting or fishing license is so that if you're caught hunting or fishing by an official you won't be fined for doing it illegally.

The correct answer to this open question is the following.

The reasoning behind hunting and fishing licenses is that the authority wants to keep effective control of the population of animals. The authority has to maintain a stable number of animals in the habitat, that is why it is required to get licenses for hunting and fishing.

The government tries to maintain balance in the ecosystem of the region, and one way to do it is by requiring licenses. So it is illegal to do those activities without the proper license.