No matter what kind of fishing you do, you must have an Official New York State Fishing license (<--click to get one online) if you are 16 and older. Most sporting goods stores throughout the Adirondacks sell fishing licenses. You will need your driver's license number or some form of identification when purchasing a fishing license.
New York State offers free fishing licenses to active members of the U.S. Armed Forces, resident patients at U.S. Veterans Administration hospitals, members of the Shinnecock or Poospatuck tribes and the Six Nations living on a New York State Reservation.
For more information, check the New York State Department of Environmental Conservation's website or their Fishing Regulations page.