Conservation officials are concerned after a new invasive species known to decimate habitats was found in Lake Superior.
The Wisconsin DNR says a single bloody-red shrimp was found in a net sample taken from Allouez Bay near the Twin Ports of Superior and Duluth last month.
It means the shrimp has now been found in all the Great Lakes, having first been found in Lakes Ontario and Michigan in 2006 and Erie and Huron since then.
"The species, like other invasive species, are known to reproduce and spread, ultimately degrading habitat, out-competing native species and short-circuiting food webs," the DNR told the Wisconsin State Journal.
The bloody-red shrimp
The University of Wisconsin's Sea Grant Institute says the tiny shrimp – which are a quarter to a half-inch long – form swarms in excess of 1,500 individuals per square meter.
"The impact of this species on the Great Lakes is yet unknown, but based on its history of invasion across Europe, significant impacts are possible," it says.
"The bloody red shrimp is an omnivore; its diet includes waterfleas and algae. They may compete with young fish, while providing food for larger fish."
It notes that the shrimp prefer hard or rocky-bottomed habitats and avoids direct sunlight.
When swarming, a reddish blur could be visible near piers, boats or breakwalls.