St. Croix Creature Feature: Eels migrate between the St. Croix River and Atlantic Ocean

The strange and seldom seen fish grow up in the lower St. Croix, then make an incredible journey back to the Sargasso Sea to breed.




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American eel (Anguilla rostrata) | Photo: Duane Raver/USFWS

Jim Shiely of Prescott, who has been fishing the Lower St. Croix since he was a boy, sent along the photo below of himself holding an American eel he caught in the river years ago. The snakelike fish are not common in the St. Croix, but they are here.

In fact, the Minnesota state record American eel was caught in the St. Croix River near Stillwater in 1997, weighing just under seven pounds.

Jim also pointed me in the direction of some interesting information about the incredible journey eels take from their birthplace, to the St. Croix, and back to the breeding grounds to reproduce once and die.

Jim Shiely, Prescott, WI, approx. seven years old, holding an American eel he caught in the St. Croix River.

“The species has survived multiple ice ages and seems to be equipped to withstand the cycles and fluctuations inherent in ocean dynamics,” the U.S. Fish and Wildlife Service says. “Some scientists consider the highly adaptive American eel to have the broadest diversity of habitats of any fish species in the world.”

American eels are born in the Sargasso Sea, an area of the Atlantic Ocean off the East Coast of the United States. To get to the St. Croix, they travel through the Gulf of Mexico to the Mississippi River, and then 800 miles upstream, and turn off at Prescott.

But only females make the trip. Male eels spend most of their lives at the mouths of rivers in the Gulf.

Location of Sargasso Sea (Wikipedia)

Females live in the St. Croix and the rest of the Mississippi’s tributaries for 10-20 years, then head back for the Sargasso Sea, where they lay millions of eggs, and then die.

They are considered a species of special concern in both Minnesota and Wisconsin, while little is known about much of their life cycle.

The U.S. Fish and Wildlife Service has reviewed the status of the American eel in 2007 and in 2015, finding both times that Endangered Species Act protection for the American eel is not warranted.

Jim also sent this video of someone who caught a 40-inch eel in the St. Croix in 2013:

Everything eels

Here is more information about eels, from a 15-year-old webpage written by Nicole Paulson & Jay T. Hatch in cooperation with the Minnesota Department of Natural Resources’ MinnAqua Aquatic Program.

American eels used to be much more common in Minnesota then they are today. Today American eels are found mostly in the lower Mississippi River and its larger tributaries, such as the St. Croix and Minnesota rivers. Occasionally they are found in Lake Superior.

To reach Minnesota, American eels have to swim all the way up the Mississippi River from the Gulf of Mexico or all the way through the St. Lawrence Seaway and Great Lakes to reach Lake Superior. Only the females make the long swim to Minnesota (see reproduction below).

When not migrating, female American eels live in medium to large streams and lakes with muddy bottoms and quiet waters. They are most active at night. So, during the day they are found hiding in the mud or under objects such as rocks and logs at the bottom of the lake or river.

How Big Do They Get? How Long Do They Live?

American eel females grow larger than the males. They commonly grow up to 90 cm (3 ft.) in length, but they have been recorded as big as 150 cm (5 ft) and 2.3-3.2 kg (5-7 lbs). The male eel generally reaches a length of no more than 50 cm (1.5 ft) and a weight of 1.4-1.8 kg (3-4 lbs). The Minnesota state record for this fish is a whopping 2.98 kg (6 lbs, 9 oz). Its was caught in the St. Croix River in Washington County.

We do not know exactly how long American eels live, but females spend 10-20 years before they become mature and return to the oceans. They die after breeding once.

“Cool Fact”: American eels may live longer than most Minnesota species. One American eel lived in captivity for 88 years.

What Do They Eat?

American eels do most of their feeding at night and are exclusively meat eaters. They feed on almost anything they encounter, including fish, frogs, crayfish, insects, snails, and even earthworms. They even have been known to feed on larval lampreys.

What Eats Them?

The young American eels (called elvers) have many natural predators, including predatory fish like walleye, and fish-eating birds like herons, cormorants and mergansers. There are also records of them being eaten by land animals, such as minks and otters. The adult eels fall prey to anglers in freshwater and to sharks and swordfish after they return to the ocean.

How Do They Reproduce?

Once the female eel has reached maturity (after 10-20 years in the freshwater streams and lakes), she starts back down the main river (Mississippi River or St. Lawrence Seaway) towards the ocean to spawn. By the time she gets to the brackish (a little salty) water to meet up with the male eels, she has stored a lot of fat. The fat is high in oil and is used for the long journey ahead.

Males and females may swim for 2 to 3 months until the reach the spawning area, which is in the Sargasso Sea. They arrive at the spawning area in the late winter or early spring when water temperatures there are about 22°-25° C. The breeding extends into the summer months, and the adult American eels then die after spawning.

The female American eel may lay 10 to 20 million eggs during the spawning period. A newly hatched eel is a transparent, leaf-shaped larva called leptocephalus. These leptocephalus larvae drift in the ocean currents, which take them to the mouths of rivers off the coast of North America.

As the larvae drift, they slowly get bigger, and after one year are about 60 to 65 mm. At this size, they are small and transparent and are called glass eels. When they reach a coastal river, the males hang around in the estuaries, while the females swim far upriver. At this point they are about 65 to 90 mm long, have some coloring to them, and are called elvers.

“Cool Fact”: The American eel is Minnesota’s only Catadromous fish. It lives most of its life in freshwater and migrates to the ocean to spawn.

Conservation and Management

The American eel is not a popular food fish in Minnesota, but its close relative is in Europe. There are even festivals dedicated to eating eel prepared in many different ways. In the eastern U.S. the American eel is harvested commercially and has a modest following of devoted consumers.

Have you ever seen an eel from the St. Croix? Send your photos to and I’ll share them.


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St. Croix Creature Feature: Eels migrate between the St. Croix River and Atlantic Ocean