The fight against invasive species in the Great Lakes just reached a milestone. The U.S. Environmental Protection Agency and Health Canada Pest Management Regulatory Agency registered a sea lamprey mating pheromone, 3kPZS, as the first ever vertebrate pheromone biopesticide during late 2015 and early 2016. Like an alluring perfume, the mating pheromone is a scent released by male sea lampreys to lure females onto nesting sites. Notably, a critical step in the registration process was research completed by U.S. Geological Survey (USGS) Great Lakes Science Center scientist Dr. Nick Johnson, located at Hammond Bay Biological Station in Millersburg, Michigan. Another key player was Jane Rivera, a biologist at the USGS Upper Midwest Environmental Sciences Center, who spearheaded the registration. Research and development of the mating pheromone was funded by the Great Lakes Fishery Commission, with additional support from the Great Lakes Restoration Initiative, in collaboration with federal government agencies, university, and private industry partners.
Since the 1990s, scientists have been researching the use of pheromones - natural odors used by sea lampreys to communicate - in order to manipulate sea lamprey behaviors. The newly registered mating pheromone has been used as bait in traps that collect and remove adult sea lampreys before they have a chance to spawn. Although the registration uses the term "biopesticide," many biopesticides, such as 3kPZS, occur naturally in the environment and, though extremely potent, are not harmful substances.
Dr. Suzette Kimball, USGS Director, praised the registration of 3kPZS as "a milestone for control of invasive species and protection of natural biodiversity."
Dr. Robert Hecky, chair of the Great Lakes Fishery Commission, explained the significance of the event, stating: "Registration of the sea lamprey mating pheromone opens the door for use of the pheromone in the commission’s sea lamprey control program, which protects Great Lakes fisheries from destruction caused by invasive sea lampreys."
Since invading the Great Lakes in the 1800s and early 1900s, sea lampreys - parasitic, jawless vertebrates that feed on the blood and body fluids of other fish - have caused enormous ecological and economic damage. To combat this menace, the commission coordinates an integrated sea lamprey control program implemented by the U.S. Fish and Wildlife Service and Fisheries and Oceans Canada that combines lampricides, barriers, and traps. The control program is remarkably successful: sea lamprey populations in most areas of the Great Lakes have been reduced by 90% of their historical highs.
"Our research has shown that the sea lamprey mating pheromone holds great promise for the sea lamprey control program," explained Dr. Weiming Li, professor at Michigan State University. Dr. Li collaborated with Dr. Johnson on the research required for registration. "With a large-scale field trial, we demonstrated that pheromone baits can increase trapping efficiencies by up to 53% and baited traps can capture up to two times the sea lampreys that un-baited traps can." While initial trials were completed with pheromone derived from live male sea lampreys, the researchers also discovered the molecular structure of the mating pheromone and contracted with Bridge Organics, a private company in Michigan, to manufacture a synthetic version.
Bridge Organics was a key partner in both the development of the synthesized mating pheromone and the registration process. Like using a blueprint to construct a high-tech building, Bridge Organics used the molecular structure provided by the scientists to construct the exact pheromone molecule from scratch. "Our company is proud to have developed the chemistry to synthesize the mating pheromone and to have coordinated testing of the compound during the registration process," said Dr. Ed Hessler, president of Bridge Organics.
The registration covers both the synthesized male mating pheromone as well as the mixture of synthesized pheromone and solvents used in field applications. The mating pheromone is classified as a biopesticide, a designation that includes any naturally occurring substance that controls pests. Other registered biopesticides include the pheromone disparlure, which is used to detect and control small infestations of gypsy moths.
"Registration of the sea lamprey mating pheromone is the first for a vertebrate biopesticide," explained Ms. Rivera. "The registration also marks the first joint review between the United States and Canada of a vertebrate biopesticide through the North American Free Trade Agreement" - a process that was first suggested by Ms. Rivera. More generally, registration of the sea lamprey mating pheromone provides a path for additional chemical-cue compounds to be registered as means to control other vertebrate species.
With registration of the sea lamprey mating pheromone complete in the United States (December, 2015) and Canada (March, 2016), 3kPZS can now be used to help control invasive sea lampreys throughout the Great Lakes on both sides of the international border. Scientists, including Dr. Johnson, continue to explore other attractant and repellant pheromones that could be similarly used to pull sea lampreys into traps or push them away from prime spawning areas.
"I am grateful to the dedication of our partners, the hard work of my research team, and the many others who provided support for the registration of the sea lamprey mating pheromone," acknowledged Dr. Johnson. "I began research on sea lamprey behavioral responses to 3kPZS as a graduate student at Michigan State University over a decade ago. My research since that time has been a remarkable journey. I look forward to what the future holds for sea lamprey control using 3kPZS and possibly other sea lamprey pheromones."
(USGS-Great Lakes Science Center’s Dr. Nick Johnson holds a mature male sea lamprey. Male sea lampreys release a cocktail of pheromones into the surrounding water, including the recently registered mating pheromone, 3kPZS. Photo Credit: USGS)