A new fish species has been found in the rivers of Idaho and Montana, and it has a disproportionally large head.

The fish is a member of a class called the freshwater sculpin, which dwells at the bottom of cold rivers, Reuters reported.

"The discovery of a new fish is something I never thought would happen in my career because it's very rare in the United States," Michael Young, co-author of the study, told Reuters.

The fish was first discovered when U.S. Forest Service Rocky Mountain Research Station scientists were taking a "genetic inventory" of local fish.

The fish was dubbed "cedar sculpin" after the red cedars that line its home streams. The species has a variation in "spiny structures" located on the head of cedar sculpins. These spines protect the fish from predators. The new species also has a different configuration of pores running down the side of its body, Reuters reported.

"The average person wouldn't be able to tell the difference," said Michael Young, a Forest Service fish biologist. "One of the physical differences is visible only if you dissect the fish. The other involves the placement of pores right before the tail. What tipped us off to this being a new species ... was the genetic work," Young told the Spokesman-Review.

The fish dines on insects and is less than four inches long. The sculpin have a "mottled-brown" color that helps them blend in with murky river floor.

Sculpin are the "preferred" sport fish. Researchers are excited to see a new species emerge, Reuters reported.

"It tells you how much we still don't know about our environment and the interactions of its diverse components," Don Johnson, professor emeritus in fishery biology at Idaho State University told Reuters.