By Howard Meyerson
CEDAR SPRINGS — Within minutes of each pulling on a pair of waders, Justin Wegner and Graeme Zaparzynski were focused on a trout — a nice, hidden brookie in the clear, shallow waters of Cedar Creek, a tributary of the Rogue River, a popular West Michigan trout stream.
The Grand Valley State University grad students didn’t have fishing rods or landing nets. They arrived at the streambank loaded with radio-telemetry gear and antennas that would pick up a signal from the tiny transmitter they inserted in the fish’s abdomen in June.
“It’s close, probably under that log,” Zaparzynski noted, pointing the antenna toward the submerged woody debris that lay across the stream. “Its temperature is 13.6 degrees centigrade. It’s running a little cooler today than normal.”
Cooler is good when talking about brook trout. They need cold, fresh water to survive.
The fish being discussed was “No. 7,” one of 10 trout they equipped with transmitters that signal where they are and their internal temperatures. The students are conducting a two-year study to better understand where brook trout go in a stream, why they move and what they eat.
“We want to know whether brook trout are selecting habitat for the structure there or some other factor like groundwater (seeping in) and water temperature,” explained Mark Luttenton, professor of aquatic biology and ecology at GVSU’s Annis Water Resources Institute.
“Do they survive because they find pockets of cold water that allow them to maintain reasonable body temperatures? Several studies show brook trout move to thermal refuges, spots that provide colder water. Our hypothesis is they are finding cold-water seeps, springs near the bottom.”
Cooler is better
U.S. Fish & Wildlife Service scientists report that water temperature is the single most important factor in brook trout survival and growth.
Brook trout growth and reproduction is best when those temperatures are lower than 20 degrees C. Wegner and Zaparzynski have recorded water temperatures from 12 degrees C to 20 degrees C (53.6 to 68-degrees Fahrenheit) so far this summer, using temperature-loggers at 10 stations along a 3-mile stretch of the creek.
No. 7 and others had migrated at least two miles downstream from where they were initially caught and equipped with transmitters in June. They were initially tagged in an open area with little cover. That was before the summer got warm.
They were now in an area offering more shade and presumably, cooler waters.
The tagged fish have been checked three times a week, according to Wegner, who records their whereabouts, the type of habitat where they are found and their internal temperature along with ambient water temperatures there and at random spots nearby.
“We are constantly measuring and taking GPS readings and noting the habitat and flow data,” Wegner said. “If we track a fish to the same spot more than five times, we consider it a home site. If only one time, it is a secondary site. Over the summer, we have established sites where the fish are consistently there.”
Zaparzynski said he is looking at what the trout eat and how they are growing. That information will be correlated with water temperatures in the stream. So far, he finds they are eating well on a diet of slugs, crayfish, beetles and ants, and caddisflies and stoneflies.
Protecting trout environments
The two-year project is being funded by Schrems West Michigan Trout Unlimited, National Trout Unlimited through its Home River Program on the Rogue River and the Cedar Springs Community Building Development Team.
The research might result in a detailed map of the creek and where cold water seeps enter it, according to Luttenton. That, in turn, will provide useful site-characteristic information for groups like TU which does habitat improvement projects on Cedar Creek. And that’s not all.
“All of this has implications for managing groundwater, too,” Luttenton said. “The little (cold water) seeps are critical to protect. Cedar Creek is a groundwater-fed stream. There are spots that are a bit too warm, but there is still enough groundwater to support a cold water fishery. That cold water also pours into the Rogue River (where there are brown trout).”
Wegner and Zaparzynski have spent much of the summer collecting raw data. They say its analysis is still ahead. What they will conclude remains to be seen. The brookies they found were from 6 inches to 12 inches long.
Those are pretty nice fish for a somewhat obscure West Michigan stream. That alone is good reason to protect it.
This column appears in MLive Media Group newspapers and MLive Outdoors.