Lake Superior’s cisco boom is creating many big fish

Duluth, Minn. — It’s a good time to be a Lake Superior angler.

Last year, Minnesota DNR fisheries biologists found huge numbers of 1-year-old ciscoes, or lake herring, in their survey nets. It turned out to be a historic year-class from 2022 for a forage fish that serves as the base for Lake Superior’s fishy food chain.

Lake trout, Chinook and coho salmon, steelhead, and even walleyes have taken advantage of the herring boom, state officials, charter boat captains, and others say, and are growing bigger and fatter. The fishing during the past two years has been steady and mostly good, even though many trout and salmon have bellies full of the now-abundant prey species.

If those same herring continue to survive and grow during the next two years, the region’s commercial fishing market – and North Shore restaurants – could be set for years to come with the tasty fish coveted for its fillets and eggs, which can be made into caviar.

“The general public doesn’t hear a lot about Lake Superior,” said Cory Goldsworthy, Lake Superior fisheries supervisor for the Minnesota DNR. “Not a whole lot happens. It’s a cold, deep (lake) and isn’t as productive as Lake Michigan. But this is an unprecedented occurrence that we likely will not see again in our lifetimes. It’s incredibly exciting.”

In fact, Goldsworthy said, Lake Superior is in “unprecedented territory” on numerous fronts, thanks to the 2022 cisco recruitment explosion.

“I’ve heard reports of anglers catching bigger Chinooks in Lake Superior right now than in Lake Michigan, which is unprecedented,” he said. “We’ve broken the coho salmon state record three times in the last year, which is unprecedented.”

Goldsworthy also said DNR survey crews this year have been catching 100-plus 2-year-old juvenile ciscoes in their small-mesh lake trout survey gear. “In a ‘normal’ year, we catch zero,” he said.

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Herring history

According to Goldsworthy, Lake Superior herring have a history of being over-fished, particularly throughout much of the 20th century.

As a result, herring stocks plummeted. But more strict commercial fishing regulations (including closed seasons in the fall) spurred their revival starting in the 1970s. 

Herring are a classic boom-or-bust species, and they need perfect conditions to successfully hatch their eggs and proliferate. For one, Goldsworthy said the water needs to be “icy cold.” Second, the water needs to be rich in zooplankton so that young herring can grow and survive.

“Ciscoes can live up to 40 years in Lake Superior,” Goldsworthy said, adding that lake trout are their top predator. “But for eggs to hatch, conditions have to be just right.”

According to Goldsworthy, Lake Superior, which is more than 20 million acres in size (about 32,000 square miles and more than 8 million hectares), had its best herring recruitment year on record in 1984. That’s when researchers from the U.S. Geological Survey – which conducts an annual spring survey – estimated that there were 748 young herring per hectare.

Many herring year-classes are “busts.” The last noteworthy year-class came in 2003, when an estimated 175 young herring per hectare made it to a year old. In 2022, the herring-per-hectare estimate ballooned to 1,019.

“This recent boom is about 20% larger than the record in 1984,” Goldsworthy said.  “We’ve seen a nearly immediate positive impact in terms of growth of non-native steelhead and salmon. This is a once-in-a-career, or once-in-a-lifetime occurrence, so it’s difficult to say what the ultimate outcomes will be, but at this point everything is looking to be a positive.”

Noticeably bigger fish

Capt. Jordan Korzenowski agrees. He’s co-owner of FishNorthMN in Duluth, and he’s been guiding anglers on Lake Superior for eight years, from roughly May to early October each year, and he’s been fishing on the lake for the past 20. He said the influx of ciscoes has not only provided his clients with excellent fishing, the size structure of the fish – from lake trout to coho salmon to walleyes – also has gotten noticeably bigger.

“It’s been lights out,” Korzenowski said of the fishing. “We’ve had some slower times, obviously. But we’re seeing a great number of fish with size. The July bite is typically tough, historically. But the last two years, we’ve caught fish across the board. It’s been really good.”      

While the state record for coho salmon has been broken three times during the past year, Korzenowski said he wouldn’t be surprised to see another salmon species break a state record – a sentiment shared by Goldsworthy and other guides.

“I would not be shocked at all to see a record king (Chinook) salmon caught this August,” Korzenowski said. The state record is 33 pounds, 4 ounces.

Goldsworthy, a self-described Lake Superior data junkie, said after roughly two decades of poor herring survival, he wasn’t sure he’d ever witness a decent year-class, let alone a historic one.

It appeared the lake could no longer support high herring numbers. Invasive species have disrupted parts of the food chain, he said. Lake Superior is freezing less – which, he said, is likely climate related – and storms during the spring and fall are more intense.

“I have to say I was concerned,” Goldsworthy said. “It’s great now to see this amount of food in Lake Superior and have predator fish respond like they have.”

How long will it last?

But sport fish gorging themselves with the 2022 year-class of herring can’t last forever.

“I predict by this winter the majority of age-2 ciscoes will be too large to be eaten by walleyes, steelhead, cohos, Chinooks, and small lake trout,” he said. “There may be enough slow-growing smaller ciscoes to keep this food fest up for one more year, but we’ll see.”

Goldsworthy said he’s hoping that in two years, when lake herring from the 2022 class grow to roughly 14 inches or more, ice anglers near Duluth will have a chance to fish for them. But that all depends on local ice conditions.

“I’d really like to see it, but it’s very rare where we have stable ice conditions on Lake Superior near here. It happens probably once every decade,” Goldsworthy said. “The last time it happened was in 2014 during the Polar vortex.”

Editor’s note: The Minnesota DNR is continuing its predatory-prey research on Lake Superior for at least the next year – and anglers can help. The research is measuring the diet composition of predator fish in Minnesota waters of the lake. For more information on how to submit samples, see https://minnesotasteelheader.com/projects/ppp