Dear HLPOA and HLSIO Supporters,
Spring is the time of year we regularly get questions about our Swimmer’s Itch Control Program and what we are doing about all the common merganser sightings on the lake. To efficiently address these questions we have added this new section, “Your Itching Questions for Dr. Blankespoor.”
Your Itching Questions For Dr. Blankespoor:
Q: I’ve noticed a large number of common mergansers in the lake near my cottage this spring. Should I be concerned? Should I report the sightings?
A: Every spring, large numbers of common mergansers migrate north through the state on their way to their summer home, typically in Canada. The Michigan Swimmer’s Itch Partnership (MISIP) lakes throughout the state are reporting a similar large number of fly-throughs. Higgins Lake has always been a popular stop-over lake because our abundant minnow population provides easy food for hungry migrant ducks. We believe the science, data and experience demonstrate that we don’t need to be concerned about these spring fly-throughs so they don’t need to be reported. The late ice out may have compressed the fly-though time window making it seem like there are more common merganser this spring.
Q: Are all these common mergansers going to stay on Higgins Lake this summer?
A: No. Most of these common mergansers will leave the lake after staying only a few days. They will be replaced by new fly-throughs. A few will stay to breed. The males will leave shortly after the hens start incubating their eggs. The hens will stay on the lake to raise their broods. You have probably noticed the lake has been largely common merganser free the past three summers after the fly-throughs leave and all the broods have been captured and relocated.
Q: Won’t these fly-throughs infect our lake with swimmer’s itch?
A: The science, data and our past experience tell us that these common merganser fly-throughs present a very low risk of adding to the swimmer’s itch infection level in Higgins Lake. Necropsies of approximately 50 adult common mergansers lethally taken on Higgins Lake over the past 3 springs have shown about half were not infected with swimmer’s itch parasites and nearly all the rest were only lightly infected. In addition, the very cold spring waters make the snails largely inactive and not receptive to swimmer’s itch infection. In fact, after the Northpoint Fisheries spring harassment program from 2015 to 2017 chased large numbers of common mergansers into the Lyon Township section of Higgins Lake (where they were not allowed to shoot or harass common mergansers) the analysis of snails from both townships showed slightly lower infection levels in Lyon Township snails compared to those from Gerrish Township. And Lyon Township residents reported a similar significant reduction in swimmer’s itch cases as Gerrish Township. So we have strong evidence from Higgins Lake that spring harassment isn’t effective and spring fly-throughs don’t increase the risk of swimmer’s itch.
Q: How many broods are you projecting for Higgins Lake this year?
A: It’s always difficult to predict the number of broods on any lake in any given year. Our best guess is 6 or less in 2018.
Q: Why does your program focus on trap and relocation of common merganser broods?
A: Decades of research has shown that common merganser ducklings are the primary carriers of swimmer’s itch infection on northern Michigan lakes. They spend a flightless summer on the lake and become highly infected. In fact, research has shown their infection levels can be as much as 50 times higher than adults. The trap and relocation method of control targets the primary carriers of swimmer’s itch on Higgins Lake and it has a strong track record for success on other lakes. Brood ducks are relocated to waters that are free of the Stagnicola snails that are needed to cause swimmer’s itch. That’s why several other Michigan lakes are using common merganser trap and relocation as their swimmer’s itch control program of choice.
Q: Broods typically should start appearing on the lake beginning around June 1. If I see a common merganser hen fly into a tree, or a common merganser brood swimming on the lake, where should I report it?