hunting license, fishing license, etc. Anything of that nature.
They can go pick up a day fishing license from Walmart or a sporting Goods store and they will be good to go. I think they're like $2 each. Don't forget to fill out the parking permit at the entrance.
If they are residents, they can get a "hook and line" (cane pole) fishing license for $2.50 and it lasts until June 30.