Through her research, University of Winnipeg professor Dr. Sara Good hopes she can help protect Canada’s fisheries from a devastating invasive species.

Sea lampreys are parasitic aquatic creatures that have decimated freshwater fish populations ever since they made their way into the Upper Great Lakes in the 1920s.

“In North America, native sea lampreys reproduce in freshwater streams on the East Coast, including New Brunswick,” Dr. Good explained. “They go downstream to the Atlantic Ocean and, in the Atlantic Ocean, they prey on sharks, rays, and other large fish. But, since they have co-evolved with them, lampreys don’t typically kill their host.”

When sea lampreys became landlocked in the Great Lakes, they began feeding on lake trout, lake whitefish, walleye, and many other species. Because freshwater lake fish are not adapted to them and are smaller than a sea lamprey’s native prey, the lamprey typically kills the host fish.

“By the 1940s, sea lampreys were exerting a huge negative toll on freshwater fisheries in the Upper Great Lakes,” Dr. Good explained.

This led to the formation of a binational organization, the Great Lakes Fisheries Commission (GLFC), which has established multiple mechanisms to help control the number of sea lampreys in the Great Lakes. For example, physical barriers help prevent the fish from migrating throughout the system and a lampricide treatment is applied every few years, which kills their larvae.

Another method is to catch male sea lampreys before they spawn upstream. These males are then treated with a chemical that makes their sperm non-viable. These sterile males are released into the spawning area, but aren’t able to fertilize a female’s eggs.

“This multi-pronged approach has been largely effective for controlling the population,” Dr. Good said. “But lampreys are phenomenally prolific and still exert a reasonably heavy toll on the freshwater fisheries. There are still tens of thousands getting through the system.”

Dr. Good’s latest research aims to add a new tool to the fight to control this invasive species.

Through her research, Dr. Good hopes to identify which sea lamprey’s genes are responsible for making it male or female in order to manipulate the sex determination system.

“We’re trying to find genes that could be targets to knock out fertility of sea lampreys,” Dr. Good said. “So, rather than bringing them in and just sterilizing males, you could introduce genes that make individuals sterile in populations. That could be another mechanism to reduce the negative impact of sea lampreys in the Upper Great Lakes, but would have to be implemented very carefully.”

With funding through NSERC, Dr. Good also hopes to understand how the process of sex determination and differentiation in lampreys compares to that of other vertebrates.

“Geneticists, in particular, use a lot of models. And different species serve as good models for different things,” Dr. Good explained. “We use models to understand genetic pathways. A mouse is a great model for humans for many things, but not for everything. The worm, C. elegans, for example, turns out to be a great model for the nervous system.”

Dr. Good’s research uses sea lampreys as a model to better understand the hypothalamic–pituitary–gonadal (HPG) axis, which regulates reproductive activity and sexual development.

“Sea lampreys are about 100 million years older than any other living vertebrate, but they are true vertebrates,” Dr. Good said. “They’re also the oldest taxa that have the HPG axis.”

The sex hormones estrogen and testosterone are produced in the gonads following specific signals from the hypothalamus, pituitary, and gonad. The coordinated signalling system of the HPG axis in humans regulates, among other things, the menstrual cycle in females and spermatogenesis in males.

“The HPG axis is not present in non-vertebrates. But lampreys have it,” said Dr. Good. “I’m looking at the oldest vertebrate, so I’m basically working to understand the core components, potentially, of the HPG axis system.”

The main application of Dr. Good’s research is to help control the invasive populations of sea lampreys in the Upper Great Lakes, work she is doing in collaboration with Dr. Margaret Docker (University of Manitoba) and many others working for the GLFC. But, she also hopes that in the future her research could help us better understand what impacts reproduction and fertility.

“Not just for humans,” Dr. Good concluded. “We’re having huge impacts on aquatic species. And many of the chemicals, including endocrine disruptors and forever chemicals that are in our water systems, do impact the fertility of other species.”

This article has been adapted and published with the permission of the University of Winnipeg.