Invasive Species An Odd Hero for Native Lakes

by Steven Maier

A native fish may be poised for a comeback in the Great Lakes with the help of an invasive species.

Great Lakes cisco, also known as lake herring, are growing in number. Catch rates are increasing in recreational and commercial fisheries, said Kevin Donner, Little Traverse Bay Bands of Odawa Indians' Great Lakes fisheries program manager. Twenty years ago, it would have been notable to catch a single cisco in a year in Lake Michigan. In the bay, they're now pulled up by the netload.

It's a similar story in Chaumont Bay, Lake Ontario, where researchers have caught thousands of cisco in recent years, said Curt Karboski, a biologist with the Lower Great Lakes Fish and Wildlife Conservation Office in Amherst, New York.

There are different strains of cisco in the region, but Donner describes most of them, "like a whitefish with a shinier, pointed face."

Cisco typically grow about 12 to 15 inches long and at one point supported one of the largest commercial fisheries in the region. They disappeared from much of the basin around the 1950s, Donner said.

Now it looks like the stage has been set for their return–by an unlikely ally.

Invasive quagga mussels have depleted nutrients in the lakes, said Matt Herbert, an aquatic ecologist with the Nature Conservancy. Cisco do well in low-nutrient environments, unlike competing species like the invasive alewife. That gives cisco space to thrive.

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