I had a chance the other day to go along on a fish shocking survey run by the Department of Natural Resource. Very illuminating.
You slog upstream in waders and use an electrified probe to temporarily stun the aquatic inhabitants of this nice little river. Some are quite charming.
Others a little less so.
That is a mudpuppy, aka water dog, or more formally Necturus Maculosus. It is an unlovely but benign amphibian that spends its entire life in lakes and small rivers.