By Eric Freedman
Scientists now have evidence that yet another invasive aquatic species — the bloody red shrimp — is established in all five Great Lakes.
Using traps and nets, researchers last summer collected dozens of adult and juvenile specimens, including pregnant females, at Wisconsin Point and the Montreal Pier in Duluth-Superior Harbor, according to a new study.
In 2017, the U.S. Fish & Wildlife Service collected a single specimen from Duluth-Superior Harbor, the study said. In 2025, researchers collected 81 specimens at those two sites but none at a third site, the shore at Barkers Island.
“Lake Superior now becomes the fifth and final Great Lake in which it is considered established,” the study said of the tiny shrimp-like crustaceans. “The delayed establishment in Lake Superior is notable and may reflect barriers such as colder temperatures and geographic isolation.”
This summer, said lead author Donn Branstrator, a biology professor at the University of Minnesota Duluth, the team is collecting specimens biweekly at Montreal Pier and monitoring about a half dozen other locations in the harbor.
The bloody red shrimp (Hemimysis anomala) is “broadly omnivorous and the invasion’s ecological consequences are uncertain, the study cautioned. Based on its history of invasion across Europe, significant ecological impacts are possible,” the study said.
Branstrator said it is “hard to predict with any detail. We don’t yet have firm evidence of adverse consequences in the Great Lakes, but it presents a potential new pathway for nutrients and contaminants to move among species in the nearshore food webs.”
The Minnesota Department of Natural Resources website says, “Since the bloody red shrimp has not established populations in many inland lakes, there is little information about its impacts to smaller lake systems. Therefore, the threat extent to Minnesota waters is currently unknown.”
Research in European reservoirs linked its presence to major reductions in the biomass and diversity of zooplankton — a form of microscopic animal life — the study said.
The invader is native to the Caspian Sea and Black Sea regions and probably arrived in North America in ballast water dumped by transoceanic cargo ships, the study said.
In the Great Lakes, the bloody red shrimp was first reported from samples collected in Muskegon, Michigan, in 2006 in waters connected to Lake Michigan, according to the Great Lakes Aquatic Nonindigenous Species Information System. The same year it was found in Lake Ontario near Oswego, New York.
By 2008, it was also established in lakes Huron and Erie, as well as in the St. Lawrence River and two upstate New York lakes.
The Michigan Department of Natural Resources has no evidence of it becoming established or even detected in inland lakes within the state, department communications specialist Joanne Foreman said.
Foreman said the Michigan department isn’t actively monitoring for bloody red shrimp, “given that the U.S. Fish & Wildlife Service has a Great Lakes Aquatic Invasive Species (AIS) Early Detection Monitoring program that surveys all five lakes for AIS fishes and invertebrates with traditional techniques and more novel techniques such eDNA.”
The study noted that Duluth-Superior Harbor is no stranger to aquatic invasives, and Branstrator said scientists are also watching for other nonnative species that have invaded the other Great Lakes and could reach Lake Superior.
The harbor was the locale of the first documented arrival of the Eurasian ruffe in North America and the first reports of the zebra mussel, quagga mussel, round goby and white perch in Lake Superior, the study said.
As for controlling their spread, the Minnesota DNR says, “There is no known effective population control for bloody red shrimp in natural water bodies at this time.”
Branstrator said scientists are also watching for several other nonnative species that have invaded the other Great Lakes and could reach Lake Superior.
The study by scientists at the University of Minnesota Duluth, University of Wisconsin Superior and Hobart and William Smith College appeared in the Journal of Great Lakes Research.