FLYFISHERMAN JASON Overlook has been seeing his quarry in a new light since last winter, when the senior in aquaculture studies at Maine’s Unity College was feeding brook trout in a laboratory tank and noticed that each dorsal fin appeared to have a different pattern.

After getting the go-ahead to conduct research, Overlook caught specimen brookies from an iced-over Moosehead Lake and supplemented his collection with hatchery trout. Back in the lab, he photographed and compared the patterns of each dorsal fin. Although further study is needed, preliminary results support his theory that brook trout have individualized “fin prints.”

The finding could make fish researchers’ jobs much easier. “We could develop scanning equipment to record dorsal fins and put them in a database like the FBI scans for fingerprints,” Overlook says. “With that information, we wouldn’t have to clip fins or tag fish.”

But Overlook is finding that it’s hard to leave the lab behind when he’s out fishing for fun. “Every time I catch a trout, I have to get a mental picture of the dorsal fin,” he says. “And now I’m starting to look at the tail fin–does one have 20 spots and another have 15? It can cut seriously into your fishing time.” –RICH LANDERS