By Alan Marble - July 19, 2018
Who cares about the Itch? Everyone who loves our beautiful Crystal Lake!
Swimmer’s itch has dominated discussion around the CSA for several years. A natural phenomenon, it is an allergic rash reaction being mistaken for a host species by a nearly invisible parasite (cercaria), which has gone through its life cycle and is searching for yet a new host. One of the links in its life cycle in Crystal Lake is the common merganser, a fish-eating duck that thrives in the lake’s clear, cool water where its brood of ducklings find ample minnows and fry to sustain them.
Enough about the “itch.” What is being done about it? The Crystal Lake & Watershed Association (CLWA) has dedicated hundreds of volunteer hours and thousands of dollars it has raised to research and combat the insidious “itch.” Employing a private sector company, Swimmer’s Itch Solutions, the CLWA has worked with public input to locate, trap and relocate broods of merganser ducklings under a permit from the Michigan Department Of Natural Resources (MI DNR). While the adult hens may very well find their way back to Crystal Lake in the subsequent spring, their ducklings “imprint” on their new location and should return there in following years to breed. Relocation settings are approved by the MI DNR, and are waters near enough to be practicable, but far enough to deter a duckling’s return. These settings lack one or more elements of the complicated lifestyle chain that perpetuates the “itch.” The trap-and-relocate program is in its second year through the CLWA. Click this link to report a common merganser nest or brood on Crystal Lake.
Some simple numbers…
In 2017, 14 broods of mergansers were captured and relocated. A total of 116 ducklings were relocated along with 10 hens. To date in 2018, 16 broods have been captured and relocated, totalling at least 105 ducklings and 7 hens (three broods relocated late this week included an unknown number of birds as of this writing).
Scientific analysis of snail samples (a key element in the life cycle of the parasite that causes swimmer’s itch), in 2016 showed a ratio of infection in the snails of 1/100 sampled. The sample in 2018 showed a significant reduction, in which only 1 of every 350 snails sampled were infected.
The CSA has worked closely with the CLWA by recording statistics on the waterfront that reflect the number of swimmers each day (broken down by morning and afternoon); the incidence of rashes reported (similarly broken down); the wind direction and velocity, and water temperature. Leslie Ritter, CSA Waterfront Director, and her staff have done a remarkable job in documenting these factors on a daily basis for a period of 6 years.
Trying to compare apples to apples, some numbers from two years - 2016 pre-program and 2018 the second year of program.
- 2016: 1,557 persons reported swimming 109 reported cases of rash/itch
- 2018: 3,016 persons reported swimming 25 reported cases of rash/itch (from start of season through July 18)
While this information is perhap a bit anecdotal, taken as a whole it shows that the efforts of the CLWA are working towards reducing the natural phenomenon of swimmer’s itch to an acceptable level. Leslie Ritter told me she was holding her breath when the 4th of July week began, and she was thrilled that the incidence of “itch” remained so low. Parents are letting their kids swim again, and today was a classic reminder of what a unique jewel we are in temporary custody of - Crystal Lake.
The CLWA is hard at work to preserve this resource for generations to come on many levels: the “itch,” the spread of invasive species, working with local units of government to protect sensitive habitats and limit non-point pollution, and so on. If you are not already a member, please join the CLWA to insure the lake’s qualities for generations to come. Come to the CLWA annual meeting this Saturday, July 21st, at the CSA Assembly Building beginning at 9:30 am. You will see many familiar faces, and you will help insure our mutual future.