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Island Lake gets first cisco stocking

The fatty forage fish is expected to provide a high-calorie food for walleye.

A cisco netted in Hanging Horn Lake near Barnum and stocked in Island Lake near Duluth. It's hoped that the new forage fish will help boost the average size of Island Lake walleyes, which have been consistently smaller than those in other lakes in the region for many years. Contributed / Dan Wilfond, Minnesota DNR

DULUTH — Island Lake has received its first-ever stocking of cisco, a fatty little fish hoped to beef up the size of walleyes in the popular reservoir.

Biologists for the Minnesota Department of Natural Resources netted 250 adult cisco from Hanging Horn Lake near Barnum in early December, just before the fish spawned and just before the lake iced over, and moved them to Island Lake, north of Duluth, where they are expected to provide a high-calorie food for walleye.

It’s the first installment of what should be several cisco stockings, said Dan Wilfond, Duluth-area fisheries specialist for the DNR. The agency intends to stock about 4,000 cisco each year for the next five years.

It’s hoped the cisco will then become self-sustaining, reproducing and filling a niche in Island Lake's food chain.

Hanging Horn Lake was picked as the source because the cisco there were confirmed as disease-free and because it was the closest to Duluth with a sizable cisco population. But the little fish proved maddeningly hard to capture and keep alive, so Wilfond said other donor lakes in Itasca and Cook counties will also be eyed in future years, both to increase supply and add genetic diversity.


“No one should expect that throwing 250 cisco into Island Lake is going to create a big year class of cisco in 2022 and somehow turn the lake around quickly,’’ Wilfond told the News Tribune. “It’s going to be a years-long process … but we're on the board. There are a few of them in the lake now. We've got the process rolling.”

A scoop of cisco, taken from Hanging Horn Lake near Barnum, being released into Island Lake Reservoir north of Duluth in December 2021. Contributed / Dan Wilfond, Minnesota DNR

Island Lake has excellent walleye reproduction almost every year, one of the best lakes in the Northland. But those walleyes then grow extremely slowly, among the slowest of any lake in the Northland. Anglers have complained about the small size of walleyes they catch on Island lake for decades, dubbing the common, 12-inch fish “Island lake Specials.” And DNR surveys found the same thing for the sprawling, 10,800-acre lake: an average size of about 12 inches, down from about 17 inches 40 years ago.

Biologists say an inadequate food supply, too many small walleyes competing for too few minnows, may be part of the problem. So they moved ahead with a two-pronged effort to fix it.

The first change, which began with the 2021 open water fishing season last May, included a new bag limit of 10 walleye daily for Island Lake — up from six fish daily — with anglers encouraged to catch and keep more small fish. All walleyes kept must be under 15 inches. All walleyes 15-20 inches must be immediately released, and anglers can keep one walleye daily over 20 inches.

RELATED: 10-walleye limit for Island Lake is official

It’s the first time ever in Minnesota that the DNR has used a higher bag limit to reduce overall walleye numbers and improve average size. Island Lake now has the highest bag limit for walleye in the state. The increased limit compares to the general limit of six walleyes daily in Minnesota, although many lakes have four-walleye limits and there's a push at the state Legislature to lower the statewide limit to four walleyes daily for lakes that don't have special regulations.


RELATED: On Island Lake, keep the little ones

The cisco stocking forms the other half of the DNR’s Island Lake walleye effort.

“We’ll be monitoring the lake as we continue to stock them , conducting assessments to see whether they take hold or not,’’ Wilfond noted, adding that he’s “cautiously optimistic’’ the DNR efforts will help boost the size of Island Lake walleyes.

In addition to lack of food, Wilfond has said Island Lake walleyes may be impacted by spiny water fleas. In 1990, Island Lake became the first inland lake in Minnesota confirmed with the invasive species, a Eurasian native that likely arrived in the Twin Ports in the ballast of ships. It appears walleye growth has slowed even more since they arrived. It’s possible the spiny water fleas are causing a reduction in some small fish species in the lake that walleye could eat.

Data shows cisco should thrive in Island Lake, especially in the deeper, coolwater zones of the reservoir, but also that cisco eat spiny water fleas and may help reduce spiny water flea numbers in the lake.

It’s unclear if the cisco were so hard to catch because of the unusually warm autumn, that kept water temperatures above the prime spawning level, or some other reasons. Efforts to use traps in shallow waters near where cisco were supposed to be spawning produced zero fish, Wilfond noted. He said it took two weeks of trying before crews finally collected 250 cisco using gill nets that were quickly retrieved to keep the fish alive, far from their 4,000-cisco goal.

Fred Schmitz, a Minnesota DNR fisheries technician, hauls in a net holding cisco from Hanging Horn Lake near Barnum on Nov. 30, 2021. Some 250 cisco from the lake were transplanted into Island Lake Reservoir north of Duluth, the first of several stocking installments that are hoped to provide a new food source for Island Lake's walleyes. Contributed / Dan Wilfond, Minnesota DNR


“Hopefully, we'll have better luck next year and in following years. We’re going to have some other source lakes to fall back on,’’ he said, noting it may be many years until anglers start seeing more big walleyes in Island lake as a result of the effort.

Island Lake is a man-made reservoir created in the early 20th century by damming the Cloquet River. It’s used by Minnesota Power as a water storage reservoir for its hydroelectric dam system on the St. Louis River near Carlton.

The DNR has conducted previous cisco introductions into Lake Elmo in the eastern Twin Cities, into several Cuyuna Range mine pits near Brainerd and into Long Lake near Walker. In each case, the cisco population became self-sustaining.

About cisco

Source: University of Minnesota

Cisco, also called lake herring (especially in Lake Superior) and inland tullibee. The word "cisco" comes from a French name. Cisco are members of the Salmonidae family, which includes trout, salmon, lake whitefish and char.

Where do they live?

Cisco (often called "lake herring") are common in Lake Superior, but they also occur in many inland lakes of the central and northeast regions of Minnesota. The cisco is a cold-water fish that needs well-oxygenated water deep in the lake in summer, so they usually do best in deep, clearwater lakes.

How big are they?

Their size is highly variable depending on the lake. In Cass Lake, for example, adults get as large as 12-14 inches long. In Lake Itasca, they sometimes reach up to 24 inches and 4 pounds. In Ten Mile Lake, they rarely go beyond 3.2 inches. Cisco in Lake Superior average about a foot long, but some have been caught up to 24 inches. The Hanging Horn Lake cisco moved to Island Lake averaged about 6 inches long, with one up to 14 inches.

What do they eat?

They begin eating copepods and small water fleas and later add bigger water fleas, midge and ghost midge larvae. Sometimes they feast on mayflies and caddisflies as the bugs hatch at the water's surface.

What eats them?

Young and smaller cisco fall prey to many kinds of bigger fish, including northern pike, lake trout, burbot, yellow perch, rainbow trout, musky and walleyes. Some people net and eat cisco from some northern inland lakes and they are netted in Lake Superior where the so-called lake herring are considered prime table fare.

How do they reproduce?

They spawn in late fall, usually late November. The spawning sites are commonly in shallow water over bottoms of clean rock, gravel or sand. A single female may lay 3,000-15,000 eggs depending on her size. The embryos develop over the winter and hatch the following spring.

John Myers reports on the outdoors, natural resources and environment for the Duluth News Tribune. He can be reached at jmyers@duluthnews.com .

John Myers reports on the outdoors, natural resources and the environment for the Duluth News Tribune. You can reach him at jmyers@duluthnews.com.
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