Carving Ice and Catching Smelt: Winter Sampling on Crystal Lake
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Some of the ice is re-purposed as a mount for the gill net. Page clears the hole so the net can then be slowly unwound into the lake.
Last summer, scientists at the CFL launched an ambitious attempt to eradicate invasive rainbow smelt from Crystal Lake in northern Wisconsin. Last weekend, Zach Lawson and Page Mieritz went up north to sample for smelt as researchers look to see what effect the experiment has had on the population.
According to CFL director, Steve Carpenter, “it’s not zero.” In fact, results point to smelt numbers being down by anywhere from 30% to 90%, but we don’t yet know how much of that is natural winter die off versus a result of the experiment. “We have the data to get an estimate, but this is a very complicated calculation,” Carpenter says. The four smelt Zach and Page found over the weekend add to the mountain of data researchers are sifting through to piece the puzzle together.
(Click on any picture below for slideshow view. Photos by Page Mieritz, Zach Lawson)
Blank canvas: an undisturbed layer of snow covers Crystal Lake.
CFL grad student, Zach Lawson, uses a GPS to make sure he sites the net in the right location.
Cutting through ice first means shoveling snow.
A line of holes are chiseled through the ice to guide the chainsaw as it “connects the dots,” producing a long rectangular hole.
Preparing to start the “incision.”
Zach begins cutting through the ice.
Dodging freezing slush and water, Zach cuts from one chisel mark to the next.
Zach cuts the ice into square blocks that can then be lifted free of the hole.
The ice blocks carved from the surface of the lake sit alongside the final product – a gill net-shaped hole.
Some of the ice is re-purposed as a mount for the gill net. Page clears the hole of slush so the net can then be slowly unwound into the lake.
With the hole cut and the net set, all there is left to do is pull up an ice block and wait.
And wait…the net is set for a four hour sampling during the day and then another chunk of time at night. Smeltmovement patterns vary by the time of day.
The final haul: four rainbow smelt, all taken during the night, seem to indicate lower numbers of the invasive fish in Crystal Lake. But gill netting is only one single data point, scientists at the CFL will combine this data with sonar estimates and other information as they work to get a better picture of what’s going on in Crystal Lake.
