LANSING — Three men pull a tired cart full of scientific equipment across the sand of Muskegon’s Pere Marquette Beach. Dressed in layers against the cold of late spring, their camouflage-print thigh-high boots give their gait a rocker character not typical of beachgoers.
“It’s one of the most fun things we have to do in our job,” said Steve Pothoven, a fisheries biologist at the National Oceanic and Atmospheric Administration’s (NOAA) Great Lakes Environmental Research Laboratory in Muskegon. .
Pothoven and fellow researchers Jeff Elliott and Aaron Dunnuck work on Lake Michigan beaches in May and June, studying how well young whitefish mature into adults.
Lake Michigan and Lake Huron whitefish have a recruitment problem.
Since the early 2000s, fewer young whitefish are reaching adulthood. Fewer adults mean fewer fish to catch for commercial fishermen.
“We just don’t know much about these fish and what sustains them early in their lives,” Pothoven said.
They are studying the problem at familiar and popular beaches – places like Pere Marquette and Grand Haven State Park.
They get to work.
Dunnuck hits the water. Walking straight into the lake, he drags 150 feet of weighted seine on the bottom, the water rising to his chest. Turning left, he walks parallel to the shore, the net uncoiling, forming a crescent as he returns to shore. He and Elliot pull in the net, scooping up any fish in its path.
On land, they open the net to assess their catch.
That day is little.
A few small silvery fish – what most people would call “minnows” – lay in the net.
They quickly identify and count all the fish, keeping the whitefish and discarding the rest.
Dunnuck returns to the water with a small net on a pole with a small pot on the end to sweep up the water. He collects zooplankton – food for baby whitefish – to see what they have to eat.
Back at the NOAA lab, Elliott examines zooplankton under a microscope, identifying the tiny animals based on differences in their otherworldly bodies. It will open the stomachs of young whitefish to compare what they eat with what lives in the water.
Understanding the decline in lake whitefish recruitment is important as fisheries managers and regulators approach the deadline to update a 2000 Consent Order regulating recreational and commercial fishing in Lakes Huron and Michigan. .
Prized for its mild flavor, finding whitefish on local restaurant menus is an important part of the “Up North” experience for summer tourists.
Lake whitefish account for 95% of commercially caught fish sales in Michigan, with a dockside value of just over $4 million, Sea Grant, Michigan reported in 2020.
For members of tribal communities, lake whitefish is much more than a source of income. Fish have been an integral part of their diet and culture for thousands of years.
Understanding why young whitefish are struggling in much of the Great Lakes is a major goal of state and tribal fisheries research.
“You have to remember that 99.9 percent of all fish eggs laid die,” said Mark Ebener, a fisheries biologist who worked 37 years for two Great Lakes intertribal organizations. He is the lead author of a 2021 study of declining lake whitefish recruitment published by the Great Lakes Fishery Commission.
Most evidence of low lake whitefish recruitment points to one culprit: invasive mussels.
The premise is that quagga mussels have fundamentally changed the way energy flows through the system, dramatically reducing zooplankton in coastal waters, Ebener said.
Zooplankton are the primary food source for baby whitefish.
The timing of the arrival of mussels and the decline in lake whitefish recruitment is likely more than a coincidence.
“Yeah, definitely, we think that’s one of the main causes of the decline in whitefish recruitment – the lack of zooplankton,” Ebener said.
With so many fish-loving people fighting so hard to defend themselves, a key question for negotiators is how much can be harvested each year if fewer reach adulthood.
It now takes longer for lake whitefish to grow large enough to be fished commercially and old enough to reproduce in the next generation.
“It used to only last two to three years and they were in the fishery, probably reproducing,” NOAA’s Pothoven said.
Due to the mussel’s impact on the base of the food web, it now takes at least five years, and possibly up to seven or more, he said.
“They don’t grow like they used to.”
Pothoven and a team attempt to understand the early life of lake whitefish.
The team is led by Kevin Donner, Great Lakes Fisheries Program Manager for the Odawa Indian Band of Little Traverse Bay in Harbor Springs.
“For us, when we started this in 2013, the whitefish was already in decline, but we didn’t know how much,” Donner said.
Predicting the future is always risky.
A major concern is that by the time they collect information on fish large enough to be caught commercially, six or seven years may have passed without anyone knowing that problems could arise when the fish were babies. No one was watching.
“So if something bad happens, for example today, let’s say no whitefish are born for whatever reason, we’re going to continue our merry way for seven years before someone has enough data to say, ‘Oh my God, something is wrong. .’ Donner said.
It could also go the other way.
If the group’s work pays off, it could calm nerves and better predict how many are available for commercial harvest years in advance.
Since 2013, the survey team has sampled beaches in the spring, primarily in the northern Lower Peninsula.
Lake whitefish spawn in the fall, favoring protective rocky coastal areas. When the eggs hatch in the spring, whitefish larvae survive on a yolk sac, a pouch protruding from their belly filled with fat and other goodies, until they have grown large enough to hunt on their own.
When this happens, they venture into open waters, many of them choosing the seemingly arid environment of popular sandy beaches.
“Most people wouldn’t even know whitefish larvae existed right around their ankles just before they were comfortable swimming in the lake,” Donner said.
There are places in the Great Lakes where baby whitefish are faring much better.
Ebener said, “Lower Green Bay is always good, Saginaw Bay is good, Lake Huron North Channel is good, Lake Superior is always good. The problems are in the open waters of the main basin of Lake Michigan, Lake Huron and Lake Ontario.
In areas where lake whitefish are doing best, mussels do not have the stranglehold they have on the open waters of Lakes Michigan and Huron.
It has always been risky to be a baby whitefish. Improving their chances of survival, even just a little bit, can pay off big, Ebener said.
If 99.995% of fish eggs don’t survive, even a tiny bump in surviving baby fish can be very important to the species, he said.
“It’s a numbers game.”
— Kurt Williams writes for Great Lakes Echo.