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Wednesday, March 29, 2023

Lake of Minnesota Island received its first stocking of cisco

DULUT — The island lake received its first ever stock of cisco, a fatty little fish that hoped to increase the size of pike perch in the popular reservoir.

Biologists from the Minnesota Department of Natural Resources fished 250 adult vendace from Hanging Horn Lake near Barnum in early December, just before the fish spawned and shortly before the lake froze over, and transported them to Island Lake north of Duluth, where they are expected. provide high-calorie feed for pike perch.

This is the first batch of several cisco stockings, said Dan Wilfond, DNR Fisheries Specialist in the Duluth area. The agency intends to stock approximately 4,000 Cisco companies annually over the next five years.

The hope is that the vendace will become self-sufficient, reproducing and filling a niche in the Lake Island food chain.

Fred Schmitz, Fisheries Specialist At The Minnesota Department Of Natural Resources, Hauls A Net Of Omul From Hanging Horn Lake Near Barnum, Minnesota, November 30, 2021.  About 250 Cisco From The Lake Have Been Transplanted Into The Island Lake Reservoir North Of Duluth, The First Of Several Releases Of Stockings That Are Hoped To Become A New Food Source For Island Lake Zander.  (Dan Wilfond / Minnesota Department Of Natural Resources)
Fred Schmitz, Minnesota Department of Natural Resources Fisheries Technician, hauls a net of omul from Hanging Horn Lake near Barnum, Minnesota, November 30, 2021. About 250 cisco from the lake were transferred to the Island Lake reservoir north of Duluth. , the first of several releases of stockings that are hoped to be a new food source for Island Lake walleyes. (Dan Wilfond / Minnesota Department of Natural Resources)

Hanging Horn Lake was chosen as the source because the vendace was confirmed to be disease-free there and because it was the closest vendace to Duluth with a significant population of vendace. But the small fish have proven insanely hard to catch and keep alive, so Wilfond said other donor lakes in Itasca and Cook counties will be looked at in the coming years, both to increase stocks and add genetic diversity.

“No one should expect the addition of 250 ciscos to Island Lake to create a big annual class of ciscos in 2022 and somehow quickly change the lake,” Wilfond told the News Tribune. “It will be a multi-year process… but we are on the board of directors. Now there are few of them in the lake. We are in the process.”

Island Lake has an excellent reproduction of zander almost every year and is one of the best lakes in Northland. But then these pike perches grow very slowly, one of the slowest among all the lakes of the Northern Land. Anglers have been complaining for decades about the small size of the walleye they catch in Island Lake, calling the common 12-inch fish “special island lake fish.” And DNR research found the same for the vast 10,800-acre lake: an average size of about 12 inches, compared to about 17 inches 40 years ago.

Biologists say a lack of food, too many small zander competing for too few minnows, may be part of the problem. So they made a double 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 per day for Island Lake – up from six fish per day – with anglers encouraging to catch and keep more small fish. All zander must be less than 15 inches. All zander between 15″ and 20″ must be released immediately and anglers may keep one zander over 20″ daily.

This is the first time in Minnesota that DNR has used a higher bag limit to reduce the total number of zander and improve the average size. Island Lake now has the highest bag limit for zander in the state. The increased limit compares to Minnesota’s total limit of six perch per day, although many lakes have four perch limits, and the state legislature is pushing to lower the statewide limit to four pike per day for lakes that don’t have special regulations.

The stocking of omul makes up the second half of DNR Island Lake pike perch.

An Omul Scoop Taken From Hanging Horn Lake Near Barnum, Minnesota Is Dumped Into Island Lake Reservoir North Of Duluth In December 2021.  (Dan Wilfond / Minnesota Department Of Natural Resources)
An omul scoop taken from Hanging Horn Lake near Barnum, Minnesota is dumped into Island Lake Reservoir north of Duluth in December 2021. (Dan Wilfond / Minnesota Department of Natural Resources)

“We will be monitoring the lake as we continue stocking them, making assessments to see if they take root or not,” Wilfond noted, adding that he is “cautiously optimistic that DNR efforts will help increase the size of walleye by Lake Island.

In addition to the lack of food, Wilfond said Island Lake walleye could be affected by spiny water fleas. In 1990, Island Lake became the first inland lake in Minnesota to confirm the presence of an invasive species, a native of Eurasia, which likely arrived at the twin ports in ship ballast. It seems that the growth of zander has slowed down even more since its introduction. It is possible that spiny water fleas are causing a decline in the number of some small fish species in the lake, which can be eaten by zander.

The data shows that vendace should thrive in Island Lake, especially in the deeper areas of the cool water reservoir, but also that vendace eats spiny water fleas and may help reduce spiny water fleas in the lake.

It is not clear if the omul were so difficult to catch because of the unusually warm autumn, which kept the water temperature above the initial spawning temperature, or for some other reason. According to Wilfond, attempts to use traps in shallow waters near the supposed spawning grounds for omul have failed. He said it took two weeks of trying before crews finally harvested 250 omul with gillnets, which were quickly removed to keep the fish alive, far short of their goal of 4,000 omul.

“Hopefully we will have better luck next year and beyond. We will have several other original lakes that we can return to,” he said, noting that it could be many years before anglers see more large zander in Island Lake as a result of the effort.

The island lake is an artificial reservoir created in the early 20th century by blocking the Kloké River. It is used by Minnesota Power as a reservoir for a hydroelectric system on the St. Louis River near Carlton.

DNR has made previous introductions of cisco to Lake Elmo in the Eastern Twin Cities, to several quarries in the Cuyuna Mountain Range near Brainerd, and to Long Lake near Walker. In each case, the cisco population became self-sustaining.


Cisco, also called lake herring (especially in Lake Superior) and inland tallibi. The word “cisco” comes from a French name. Cisco belongs to the salmon family, which includes trout, salmon, lake whitefish and char.

Where do they live?

Ciscos are common in Lake Superior, but they are also found in many inland lakes in central and northeastern Minnesota. Whitefish are cold water fish that need well-oxygenated water deep in the lake in summer, so they usually do best in deep lakes with clear water.

How big are they?

Their size varies greatly depending on the lake. In Cass Lake, for example, adults grow to 12-14 inches in length. In Lake Itasca, they sometimes reach 24 inches and 4 pounds. In Ten Mile Lake, they rarely exceed 3.2 inches. Ciscos in Lake Superior average about a foot in length, but some have been caught up to 24 inches. Perch from Hanging Horn Lake that moved to the island lake averaged about 6 inches in length, with one up to 14 inches long.

What are they eating?

They start eating copepods and small daphnia, and later add larger daphnia, midges and ghost midge larvae. Sometimes they feast on mayflies and caddis flies, as the beetles hatch near the surface of the water.

What eats them?

Juveniles and smaller omuls fall prey to many species of larger fish, including northern pike, lake trout, burbot, yellow perch, rainbow trout, musky and walleye. Some people net and eat cisco from some of the northern inland lakes, and they are netted in Lake Superior, where the so-called lake herring is considered a staple on the table.

How do they reproduce?

They spawn in late autumn, usually at the end of November. Spawning grounds are usually found in shallow water above clean bottoms of rocks, gravel or sand. One female can lay between 3,000 and 15,000 eggs depending on her size. Embryos develop during the winter and hatch the following spring.

Source: University of Minnesota.

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