Why does one need a permit to fish?

Why is overfishing a problem?

Note that this is cod, an ocean fish, and it was once so abundant that people thought that it would never be depleted. Now the fishing industry has collapsed.

See also the Tragedy of the Commons.

And hey, why can’t you just go into a national forest and cut down all the trees? If that forest runs out of trees, you can just go to another one, and after all, new trees grow all the time.

SWEAR TO GOD THIS IS TRUE.
There is a Hunan restaurant by where I live and my friends and I saw the owner go down to a man made lake that is made to be swam in so there are LOTS of chemicals in it, and he took out a fishing poll and caught fish like I had never seen, put them in a cooler he brought with him and left. I would imagine it has something to do with people taking advantage of the fish and no one else would catch them (I believe there is a limit, and rules when you get one)

Depends on what state you’re in. Here’s the website for freshwater commerical fishing in Florida, for example.

You also have to obey catch limits and size restrictions as a commercial fisher.

You’re in luck - it’s the Lord Mayor!

Stuffed, actually: Martha (passenger pigeon) - Wikipedia. But I take your point.