An innocent fish, wrongly accused?

PAUL SMITHS, NY (04/06/2015)(readMedia)-- The yellow perch has had a bad rap as an invasive species in the Adirondacks since the 19th century. But now, researchers at Paul Smith's College are using DNA evidence to show that these fish might have been wrongly accused.

Profs. Curt Stager, Lee Ann Sporn, Melanie Johnson and recent graduate Sean Regalado believe the perch might have arrived in Lower St. Regis Lake more than 2,000 years ago, plenty of time to be considered a native species. They published their findings in the scientific journal PLOS ONE last month.

When the researchers first made their discovery, many, including members of the New York State Department of Environmental Conservation, were skeptical. But the new peer-reviewed journal article adds weight to the researchers' claim and raises new questions about the way we manage the species.

Fishery experts and DEC officials have long considered yellow perch to be nuisance aliens that starve out brook trout and compete with them for spawning sites. So they've been on a mission to eradicate the fish using controversial poisoning methods.

The process, known as reclamation, involves poisoning a lake with rotenone, which kills fish but is considered of little threat to other species, including people. Reclamations are usually conducted in the fall, which allows the rotenone to break down before the lake is restocked with more desirable fish – usually trout – the following spring. The mass killing of fish makes reclamation a controversial practice, but even its opponents have agreed that yellow perch are not native to the Adirondack uplands, a conclusion based on early surveys dating back to the 19th century. That's why the new DNA evidence is so surprising: It means perch and trout coexisted in Adirondack waters long before the brook trout's numbers began to dwindle.

To conduct the study, the Paul Smith's researchers took sediment core samples from the lake floor by drilling through the ice during winter. They used those samples to extract DNA from the sediment and looked for genetic sequences that are unique to yellow perch. They expected the perch DNA to show up in only the upper layers of the cores. When it showed up much deeper, even in sediments more than 2,000 years old, they knew they had made an important discovery.

"We now know that yellow perch are as native to the Adirondack uplands as brook trout," Stager said. "What we want to know next is why they've become so much more numerous than before."

Stager believes that these same methods could be used to verify the native or invasive status of other species such as lampreys or Atlantic salmon in North Country lakes. "You could also use ancient DNA to study the evolution of native fish strains or to see if fish once lived in lakes that were recently sterilized by acid rain," Stager said. "The sky's the limit."

ABOUT PAUL SMITH'S COLLEGE

At Paul Smith's College, it's about the experience. Paul Smith's, which was founded in 1946, is the only bachelor's degree-granting institution of higher education in the Adirondacks. Our programs – in fields including hospitality, culinary arts, forestry, natural resources, entrepreneurship and the sciences – draw on industries and resources available in our own backyard while preparing students for successful careers anywhere. For more information: www.paulsmiths.edu.