@PotomacBobIn the USA there are 50 States and every State hasdifferent governing laws.
As for Michigan the laws are as such that the State of Michigan owns and has controlling interest the water rights to any body of water that can be navigated by a canoe.
What this means is if your property completely surrounds a small lake or pond then that body of water is owned by the State and you must follow State laws.
So if you have a lake or pond on your property then by Michigan law anyone can fish, swim, boat, and enjoy the water as long as there is PUBLIC ACCESS. So in Michigan if you see a sign that says private lake the lake actually isn't private but the property surrounding the lake is owned and the general public does not have access to the water.
Now to answer your fishing question in Michigan the law is 17 and old are required to have a fishing license. Everyone including those 17 and younger must follow State fishing laws as the daily numbers and the fishing seasons.
Michigan highly regulates the fishing seasons as to fish breed and locations so it is recommended that when you get your license that you pick up that years fishing guide because fish that you can legally catch in this river or lake may be illegal to catch else where.
Another thing to be mindful of is your location Michigan touches 4 of the 5 Great lakes those being Lake Michigan, Superior, Huron, and Erie. With Lake Michigan you can either be in Wisconsin, Illinois, Indiana, and Michigan and your Michigan fishing license doesn't cover or allow you the rights to fish in the other States controlled waters but you can usually get away with just a warning. Now the other 3 Lakes Superior (also shares with Wisconsin), Huron, and Erie they are half USA/Michigan waters but the other half is Canadian waters and I have known and read the reports of those caught fishing in Canadian waters and while the Canadian Coast Guard is extremely polite in that they will return you to the nearest American port and soil they have no problem with giving out nice large fines, keeping your gear, and boat though depending on the severity they may return the boat and gear after you pay additional fines and penalties. The moral is know where you are as ignorance is not an excuse.
And one last point even if your property completely surrounds the lake or pond and even if you dug out and made said lake and pond you still are governed by the laws of Michigan so yes if you are 17 and older you must have a fishing license and you must obey they fishing seasons.
If you wish to try and follow the Michigan Fishing Seasons for 2021. the 2022 can and may have changes.
https://www.michigan.gov/dnr/0,4570,7-350-79119_79146_81200---,00.html