Weiming Li, now FEJ Fry Chair of Environmental Physiology at Michigan State University, labored since he was a Sea Grant-funded doctoral student at the University of Minnesota in the early 1990s to bring a pheromone to the Great Lakes Fishery Commission in a useful form for managing sea lamprey. In December 2015 the U.S. EPA approved 3kPZS for use in the Great Lakes and Canadian approval isn’t far behind.
The smell of success smells like nothing. Well, 3kPZS smells like nothing to you. Yet, mere drops of this species-specific compound will send females whipping miles upstream in a come-hither rush. Emitted by male sea lamprey, the pheromone lures mate-ready females into traps and Li expects it can draw almost-mate-ready lamprey of both sexes to a particular area.
“Love potions” could be pivotal for managing primitive fish. "Lamprey ... I would hardly call them fish…,” says Peter Sorensen, Li’s former advisor and professor at the University of Minnesota, “…they’re some sort of cartilaginous, prehistoric beings. And they’re devils to manage.” The U.S. and Canada have worked for six decades to control a species whose massive olfactory organs rival the size of their brains. Physical barriers, traps and a $20-million-per-year lampricide program have been their tools until now. Experts think pheromonal cues akin to 3kPZS might revolutionize efforts to save Pacific lamprey, and dwindling lamprey populations in Europe.
This is a story about vision and grit. “To make breakthrough advances, you’ve got to have the freedom to make mistakes and you must be given time,” said Sorensen. “I applaud Li’s perseverance and credit the Great Lakes Fishery Commission for affording him the freedom and time to create this useful tool.” If you ask Li, now 25 years in, what he likes best about his work, he is puzzled. “I love it all,” he says. “Discovery is exciting but the questions and methods are, too.”
Sea Grant funded the initial research but the history spans an ocean.The arrival of 3kPZS is preceded by a quest to identify migratory pheromones that bring lamprey into particular streams. In an inspired moment, Sorensen and Li wrote to G.A.D. Haselwood, a biochemist who documented how the bile acids of sea lamprey were peculiar, as if the steroid was constructed backward (1967). Upon receiving the letter, the retired Englishman traveled from his seaside cottage to his old laboratory in London. There, he unearthed a few crystals of the bile salt and mailed them to Minnesota. “We owed everything to him,” said Sorensen. “It was only a couple of crystals but when we exposed sea lamprey to Haselwood’s bile salt we knew instantly how important they were. That’s where this started.”
3kPZS is only the beginning.Fish Pheromones and Related Cues (2015) , co-edited by Sorensen, is ushering the emerging field of managing fish with pheromones along. Meanwhile, related Sea Grant projects have included ruffe,trout and shrimp. The Great Lakes Fishery Commission continues to support sea lamprey work and federal grants are enabling Sorensen’s laboratory to investigate aggregation pheromones to aid in managing invasive carp