It takes a lot of work to stock fish in the Great Lakes, and hatcheries want to know if their efforts are working.
At the Jack Wolf Fish Hatchery in Illinois, a group of volunteers from Salmon Unlimited spend a day or two clipping fins to make sure they can track the success of stocked fish.
The following video from the Illinois Department of Natural Resources gives just a taste of what the volunteers do.
For the past 30 years, 30 to 35 volunteers from Salmon Unlimited have been a time-saver for hatchery staff. It would take them over week to do what the volunteers do in a day.
That's 16 hours, hands stuck in 54 degree water, clipping fins to help track the fish. It's a labor of love so that officials have the information they need to keep track of the health and population of the fish they stock.