UNITY (AP) – The polka-dotted, red-bellied brook trout breaking to the surface for food in a laboratory tank at Unity College may look the same to the untrained eye, but Jason Overlock knows just the way to tell them apart.

Overlock, a senior research student from Winslow, claims to have made the discovery that brook trout have individualized dorsal fins – what he calls “fin prints” – that enable observers to differentiate one fish from another.

“I’m getting kind of excited about this,” said Overlock, who believes that the discovery could have applications in medical and environmental research.

One immediate implication, according to A. Jim Chacko, professor of aquaculture at the college, is that testing and research on brook trout will no longer require the cutting or clipping of fins for identification.

“Using our system, you can identify Tom, Dick and Harry among the brook trout. Maybe even Henry and Martha,” he said.

Overlock’s findings emerged as he was working with brook trout in Unity’s wet laboratory, a series of rooms filled with tanks and fish. He suddenly noticed that he could tell the fish apart by the patterns in their dorsal fins.

“I doubted what I was seeing at first,” he said. “I just kept checking and checking.”

After Overlock brought his findings to Chacko, the pair developed a technique to individually photograph the fish and then transfer the patterns on the dorsal fin into black-and-white images.

“The results were astounding,” said Chacko. “No two dorsal fins looked the same. I slapped my forehead with my hand and said, We were missing the most obvious!”‘

Overlock and Chacko expanded the project to include 60 fish, and Overlock began an independent study.

The pair, who are seeking funding to expand the project, plan to monitor some of the fish for long-term changes and would like to develop a computer program similar to the one that the FBI uses for fingerprints.

Although he graduates this month, Overlock hopes to remain involved in the identification project. He has had several environmental job offers, he said, but if he remains in Maine, he will continue the work in his spare time.