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Researching a Great Lakes Migration: The Sucker Spawning Run

No hooves pound a path into the Illinois prairie, no bugling Vs pierce the springtime sky. But sometime between March and May, a massive migration of equal urgency and importance takes place in the Great Lakes: the spawning run of white and longnose suckers.

Shedd research biologist Karen Murchie, Ph.D., studies the spring migration of these two abundant native fish species. She is assisted by a small army of volunteer citizen scientists who collect data at 17 sites in Illinois, Wisconsin and Michigan’s Upper Peninsula on the movement of the fishes from Lakes Michigan and Superior to spawning streams.

The data Murchie is compiling is for a first-ever, long-term study investigating what environmental cues—water temperature, stream flow, or a combination of factors—trigger the migrations of the adults, as well as how the timing of the suckers’ movement might be shifting as the climate warms. The project is a collaborative effort with Pete McIntyre at Cornell University.

A crowd of brown-striped suckers swim along the pebbled bottom of a river in the Great Lakes region.
Karen Murchie, Ph.D., Shedd's Director of Freshwater Research, smiles warmly in front of Shedd's Great Lakes exhibit.

An ecologically important Great Lakes fish you’ve probably never heard of

Suckers, whose common name refers to their feeding behavior—vacuuming up aquatic plants, algae and small invertebrates from the lake floor—are ideal study subjects. They are big—averaging 19 inches—and distinctive looking, with full, fusiform bodies and pectoral and pelvic fins that stick out from their sides like wings. They move in large numbers, making them easy to see from a streambank or bridge. And they occur throughout a long north-south gradient within the Great Lakes, offering Murchie a comprehensive sample. (The yellow dots on the map mark the monitoring sites.)

Suckers are known mainly to locals and have no commercial or sport value. “Some people do pickle them,” Murchie says, “but that’s more of a local delicacy.” But by virtue of their numbers, these fishes play a key role during their brief forays into stream ecosystems.

Shedd researcher Karen Murchie, Ph.D., stands in a cold local stream taking measurements.

“Suckers have an important ecological role to play because they’re making these early-spring mass migrations into the tributaries and contributing nutrients that kick-start the food web,” Murchie says.

In other words, as the fishes feed, they fertilize. Waste products as well as unfertilized eggs benefit every part of the stream food web, beginning with plants and insects, which in turn are food for larger animals coming out of hibernation or returning from their own migrations. Shifts in the timing of the spawning runs could change the dynamics of nutrient inputs, seriously affecting entire stream ecosystems.

“Suckers have an important ecological role to play because they’re making these early-spring mass migrations into the tributaries and contributing nutrients that kick-start the food web.”

Karen Murchie, Ph.D., Shedd research biologist

Logging in

The research season begins well before the first suckers nose their way up gravel-bottom streams, pools and riffles, including three small rippling tributaries along Highland Park’s lakeshore.

On a raw, overcast day in early March, Murchie pulls a minivan into the parking lot at Rosewood Beach, the first of three sites within the Park District of Highland Park that she’ll visit. A stiff wind blows across the lake, and whitecaps crash on a rock breakwater protecting a small creek, sending up a fan of spray. But Murchie is dressed for the weather and her work in chest waders over a parka. A heavy knitted cap is pulled down over her ears as well. Her task this day is to meet with the monitors, distribute equipment and install a data logger at each site.

Karen Murchie, Ph.D., Shedd's Director of Freshwater Research, attaches flow meters to cinderblocks in her van on site near a local stream.
A data logger device used in sucker research is zip tied to the side of a wooden dock.

As she waits for her team in the shelter of the van, she assembles the environmental monitoring stations. Spread across the floor are the black 6-inch, torpedo-shaped instruments, along with 8 x 8 concrete blocks, 4-foot steel bars and 3⅓-foot rulers called staff gauges. She also has lots of heavy-duty zip ties and metallic Sharpies to code the data loggers to their location. She uses the zip ties to attach a logger, business end down, to a concrete block.

Holding up a data logger, Murchie says, “The volunteers collect data on the depth, but this is recording temperature, barometric pressure and water depth every 15 minutes, whereas the citizen scientists will come out once per day and log the depth by reading from the staff gauge as they begin monitoring. They don’t have to take temperature, however; we don’t need them getting in the water.”

She continues, “What we’re looking for with the depth data is getting a surrogate for flow to see whether it’s water level changes or velocity helping to drive the fishes into the tributaries in the first place.”

Restoration reopens spawning streams

Liz Ettelson, of the Natural Areas Program of the Park District of Highland Park, arrives. She is a returning monitor. Standing on a small wooden bridge that crosses the tributary and soon-to-be spawning stream, she says, “This was restored between 2012 and 2014. The channel was ‘daylighted.’ Before, the parking lot extended to this bridge, and there were two culverts.

“‘Daylighting’ literally means removing the culverts and exposing the stream to daylight. So we’ve created the opportunity for fish passage. Fishes were not able to enter the stream from the lake prior to restoration.”

“What we’re looking for with the depth data is getting a surrogate for flow to see whether it’s water level changes or velocity helping to drive the fishes into the tributaries in the first place.”

Karen Murchie, Ph.D., Shedd research biologist

But remove the barrier and they will come: In spring 2015, with the stream restoration complete, Ettelson says the suckers appeared. The project began in 2010 at the ravine in Millard Park (now another sucker monitoring station) with the restoration of 1,000 feet of stream from the lake inland, including creating or improving existing riffles and pools. It was accomplished in large part with funding from the Great Lakes Restoration Initiative (GLRI). Administered by the Environmental Protection Agency and supported by 15 other federal agencies, the GLRI is the largest federal investment in the Great Lakes, and it receives strong bipartisan support.

The third site, Moraine Park, has not been restored, but suckers have been able to navigate the gradual incline of the long, rocky stream that cuts through a steep ravine to the lake.

Karen Murchie, Ph.D., stands in the water of a local stream installing a research device attached to a cinderblock.
A closeup of a research log document held by a Shedd field researcher.

Murchie pulls on long-sleeve rubber gloves (“They make me look like I’m ready to birth a cow,” she quips), grabs a steel bar and small mallet and picks her way down the steep sand-and-rock embankment to the stream. Standing in knee-deep water, she repeatedly tests the bottom for a rock-free spot, then pounds the rebar about a foot into the streambed. She snugs the stream gauge to the bar with zip ties, then lowers a data logger block over the bar, settling it on the stream bottom. She adjusts the orientation of the staff gauge so it can be read from the bridge, then returns to the parking lot.

She gathers the volunteers and hands out red folders containing data sheets, a pencil and a neck-warming cowl printed with suckers—the latter a little bit of bling, but also an eye-catching conversation starter to talk about the project with curious beach users.Everyone present is a veteran of the first year, but Murchie still goes over the drill: “The whole idea is to figure out when the suckers show up and to document the peak. Ideally, we’re going to monitor for the whole run, but let’s at least be sure we capture the peak.”Each volunteer is responsible for visiting all three Highland Park stations on the same day each week for as long as suckers are present, and they quickly decide who takes what day.Murchie tells the group that they can easily wait until the following week to begin checking the sites for the migrants. “But I would love a heads-up of when you do see the suckers. Just say, ‘Hey, they’re here!’”

Weather, water, fishes

Ray Laudano, a first-time monitor, reports the start of the spawning run on April 26 at Rosewood Beach. A fisherman who never travels without a rod, he heard about the project when Murchie and Ettelson recruited volunteers at his Trout Unlimited chapter. “I’m a chemist by profession,” he says, “but what I really like is biology and the environment. I’ve always been active in outdoors activities and stewardship.”

Shedd researchers install a water height and flow measurement device in a Great Lakes stream.
Two white suckers, well-camouflaged with their brown scales , huddle against the rocky, pebbled floor of a river.

Laudano covers the three Highland Park stations on Thursdays. “The protocol is to observe at each location for 10 minutes between 1100 hours and 1300 hours,” he says, observing Murchie's preference for military time notation. On his data sheet, in addition to the date and time, Laudano fills in several environmental factors: weather (sunny, partly cloudy, overcast, windy, choppy, raining, snowing); water depth, read from the gauge, as well as the lowest number visible on the water gauge; and water clarity (clear or muddy). The last two criteria can influence how well monitors can see the fishes, which swim along the stream bottom.

And, of course, he notes whether suckers are present at each monitoring station and how many he sees in the 10-minute timeframe. The monitoring stations, located in pools or other wider, slower sections of the streams, were selected because these are areas where the fishes will rest during the day, conserving energy for their next move upstream.

After his observations, Laudano enjoys looking for suckers elsewhere in the streams. “The other day they were spawning in the fast-moving, gravel-bottom riffles, even with their backs out of the water. A big female would be surrounded by a bunch of smaller males trying to fertilize her eggs.”

The mating activity is typical of both white and longnose suckers. They do not build nests or exhibit parental care. Instead, the stream’s current spreads the eggs across the bottom where the milt from the males can settle on them. “From my tagging/tracking studies,” Murchie says, “the same fish tend to remain in a creek for a number of days, but we don’t know how many times they spawn while they are in there.” At the end of the mating season, the suckers head downstream to open water again.

“The other day they were spawning in the fast-moving, gravel-bottom riffles, even with their backs out of the water. A big female would be surrounded by a bunch of smaller males trying to fertilize her eggs.”

Ray Laudano, volunteer

Crunching the numbers

When Murchie collates the data from the 17 sites in three states, she has a total of 10,805 longnose and white suckers documented in the daily 10-minute sessions over the course of spawning runs of various lengths.

In Highland Park, volunteers saw 76 at Rosewood over two weeks, beginning April 26; 157 during the nearly four-week run—April 19 to May 13—in the Millard ravine and 27 in seven days, starting May 3, at the Moraine site. The earliest arrivals were farther north, showing up at Oak Creek, a tributary in south Milwaukee, on March 10. The latest migration began May 17 in Pikes Creek in Bayfield, Wisconsin.

“A calendar date doesn’t necessarily mean a lot for a fish,” Murchie says. “It’s more like what was the water temperature or flow that initiated the run. Likely it is a combination of the two factors.

“If we can get a hold of more historical data of sucker spawning runs from sites nearby where we are monitoring, we can start to do more to look at trends in the timing of their migrations. This is a long-term study, and time will tell.”

She adds, “The good news is, citizen science is a good approach to this type of a research question. So far, we have had most of the same volunteers for the same sites both years. They’re going to become the experts and pick up what’s going on in these locations. And they’re going to become advocates for the species and for restoration efforts.”

At the same time that Murchie relies on the citizen scientists, the volunteers thank her for giving them an opportunity to connect with the nature in their own back yards.

“I think people are hungry for opportunities to be engaged and play a role in conservation,” Murchie says. “And that’s pretty awesome.”

—Karen Furnweger, web editor