Fish by the Light of the Blood Moon: Late-Night Research on Northwoods Lakes

Miriam Burgos collects a scale from a rock bass. The scales can tell researches about age and growth of the fish. Photo: S. Widell

Night was falling quickly over Big Muskellunge Lake. The pink glow of sunset was fading to grey, and a damp wind that cut through my thin raincoat had kicked up over the water.

On our boat, Miriam Burgos pointed low at the horizon.

“Do you see it?” she gasped.

I followed her finger toward the treeline, where the glowing orange edge of the full July Blood Moon was rising from beyond the jagged ridge of cathedral pines across the water.

Just beneath the ascending moon and to its right hung Mars, a bright pinprick of red light in the deepening eastern sky. Mars and the sun were on opposite sides of the earth, and the planet was almost the nearest it would come to both in its orbit. This was the brightest Mars would be for the next 50 years.

“The solar system has aligned for Electrofishing!” Miriam laughed.

Noah Lottig, Trout Lake Station research scientist, guides his electrofishing boat into Big Muskellunge Lake. Photo: S. Widell

Noah Lottig checked his time against the setting sun. He would wait until it was completely dark before he gave Miriam and his other undergraduate researchers the go-ahead to begin collecting fish samples.

Noah is a research scientist at Trout Lake Station who studies long-term ecological trends across lakes in Wisconsin’s Northern Highlands region. On this night, he and fellow researcher Pam Montz were leading a fish survey on Big Muskellunge Lake.

Pam, Noah and their undergraduates had been doing these surveys almost every night for the last month. Sometimes, they don’t finish their sampling until 4:00 a.m. They return to station tired and wet, catch a few hours of sleep and go to work again the next morning.

The July Blood Moon rises over Big Muskellunge Lake as Jake Cavaiani, Michael East and Miriam Burgos prepare to conduct the first round of electrofishing. Photo: S. Widell

For more than 30 summers, Trout Lake researchers like Noah and Pam have been conducting fish surveys like this one on the lakes across Northern Wisconsin. Trout Lake Station is the North Temperate Lakes (NTL) site of the Long Term Ecological Research network (LTER), a nation-wide program funded by the National Science Foundation that monitors the way ecosystems — like the NTL’s eleven Wisconsin lakes — are changing.

“We are doing monitoring, but it also informs questions and research projects when changes are seen,” Pam explained. “It turns out that many ecological processes happen on a longer scale than you might imagine.”

When the National Science Foundation first began to fund LTER in the early 1980s, Pam said it was with the intention of observing the way ecosystems evolve over extended periods of time.

“Lots of biological and ecological changes have cycles that are much longer than people had been studying,” Pam said. “NSF funded this research so we could catch these patterns.”

Those patterns, Noah told me, can be anything from the way fish populations respond to invasive species to how communities shift with a changing climate.

Most of the fish we’d catch on this night were large game fish — deep water species like perch, walleye and rock bass that swim to the shallow shoreline at night to feed.

Miriam weighs a fish. Fish weight helps researchers determine the health and size of the fish population in the lake. Photo: S. Widell

We’d be patrolling the shallows using electrical currents to temporarily stun and catch our sample fish – a method people on station call electrofishing. Unlike some methods of fish sampling, like using gill nets, shocking fish doesn’t injure them. It just temporarily short-circuits their muscles, causing them to float to the surface where they can be scooped out of the water with our nets, weighed and measured and then released back into the lake.

The electrofishing boat is huge — almost 20 feet long — and there is more than enough room for the five of us to walk around comfortably.

Noah stands at the control board, toward the center of the boat, where a mounted GPS screen guides him along the predetermined route – so that he can sample the same sites every year on this lake.

The generator is next to Noah. When he switches the power on, it charges the huge electrodes that dangle off the front of the boat into the water, like giant metal swim noodles. The electrodes release a current through the water that will temporarily stun nearby fish and send them floating up to the surface.

Lights appeared across the lake — red and green for the port and starboard sides of a boat.

“Pam Montz,” Noah said, seeing me look in that direction.

Pam and a few other researchers were waiting across the lake in a wide, flat boat, ready to pull up beside us and transfer the fish we catch during our first round of e-fishing from our on-board live well to theirs.

Michael holds a yellow perch. Fish caught on the shockboat are transported onto a second boat, where more researchers take measurements before releasing the fish. Photo: S. Widell

Pam and her crew measure and weigh the fish, pluck a single scale from each fish and then release them unharmed, back into the lake. That information helps the researchers understand the health and size of the fish populations in the lake, and how those factors change over time.

“Relatively speaking, a big old fat fish is going to have a better body condition than a skinny one,” Noah said. “We put this in our database, and it’s used for a variety of different things.”

One of those things is using the long-term data record to gain insight into the way the abundance of different fish species change from year to year, since the researchers sample the same areas each summer.

Noah checks the time again. By now, darkness has truly descended, and the boat is gliding on the glitter trail of the rising summer moon.

“We can probably start soon,” Noah said.

LTER researchers have been collecting fish on this lake for the last 31 years as part of an effort to monitor the way those populations have changed over time. Photo: S. Widell

At Noah’s call, undergrads Kevin and Jake take their places at the front of the boat, where they will retrieve the stunned fish with long nets. Miriam, standing a little ways behind them, will transfer the fish out of the nets and into a livewell on board.

Kevin and Jake stand on yellow mats that can sense their body weight, a safety feature which causes the charge to shut off as soon as an electrofisher steps off the mat.The shut off function can be lifesaving if someone were to fall in the water while the charge is flowing.

Different currents target different fish species, and Noah can adjust how much charge is flowing through the electrodes depending on what type of fish he wants to catch.

Noah flicks the boat’s powerful headlights on and they beam full and bright into the green water. Leaning over the edge of the boat, I can see straight to the rocky bottom.

“Are you ready?” Noah asks, finger on the generator’s switch.

The generator jumped to life. It was time to start fishing.