Invasive shrimp found in Twin Ports harbor
Another foreign, aquatic invasive species has been found in the Twin Ports harbor — this time a small invertebrate called the bloody red shrimp.
A single bloody red shrimp was confirmed this week after analysis of water samples taken last July by the U.S. Fish and Wildlife Service
The critter, which is native to freshwater lakes and rivers of the Caspian region of eastern Europe, was found in Allouez Bay, not far from the Burlington Northern ore docks.
It's the first time bloody red shrimp — hemimysis anomala — have been found in the Lake Superior ecosystem. They were first found in the Great Lakes in 2006 in Lake Michigan at Muskegon, Mich., and have been expanding there as well as in lakes Erie, Ontario and Huron.
"The species, like other invasive species, are known to reproduce and spread, ultimately degrading habitat, outcompeting native species and short-circuiting food webs," the Wisconsin Department of Natural Resources said in announcing the finding.
The tiny creature, not a true shrimp, is up to a half-inch long and often swims in swarms up to 135 per cubic foot of water.
"The good news is that it was just one. The bad news is they found it here," said Doug Jensen, aquatic invasive species expert for Minnesota Sea Grant at the University of Minnesota Duluth.
Jensen notes that it's not yet an official invasion of a new species. Only after multiple, live individuals are confirmed is a species considered established. True invaders also are able to reproduce and expand their range.
"This raises a lot of questions. We really don't even know how it got there. We don't know if it was a ballast introduction or not, or where it came from," Jensen said.
The U.S. Fish and Wildlife Service is expected to resurvey the area and update its sampling techniques this summer to see if others are out there.
That another new creature showed up in the Twin Ports isn't surprising. The Duluth-Superior harbor is the busiest inland port in the nation and receives not just saltwater ships from faraway oceans but by far the most Great Lakes shipping traffic. This has been a hot spot for most major invaders on the Great Lakes, including gobies, ruffe, spiny waterfleas, zebra mussels and quagga mussels — all of which are now major players in the St. Louis River estuary ecosystem.
Jensen said it's unclear what the bloody red shrimp might do to the ecosystem if it becomes established here. Like the other invaders, however, it's more likely to remain in the shallower, darker, more-fertile waters of the harbor and not thrive in the colder, clearer, more-sterile environment of Lake Superior itself.
"They don't like light, so they are often hiding down deeper or in the shade until dark," Jensen noted.
Anyone who sees swarms of reddish critters in the harbor is asked to contact Sea Grant or a local DNR office. The swarms can be seen at night near the surface but will disperse quickly if a light is turned on them. During the day they may be seen in shaded areas, such as under docks.
Boaters are asked to continue their efforts not to move any water from lake to lake or from the harbor to inland waters. The shrimp, like other aquatic invaders, could easily hitchhike in bait buckets or livewells to new waters, Jensen noted.
Other non-native species have been found in the Twin Ports harbor in recent years but none so far have become established, Jensen said, including gizzard shad and white bass, both native to waters south of Lake Superior.
But the bloody red shrimp is the first new foreign aquatic invasive species found in the region in years. In fact, after a century of foreign invasive species that swam or hitchhiked across the oceans in the ballast of salties, the Great Lakes haven't seen a confirmed new aquatic invasive species since 2006. (In late 2016 officials confirmed a new form of zooplankton, Thermocyclops crassus, had been found in Lake Erie. But it's still unclear if it is truly established.)
That appears to show that a U.S. Coast Guard-enforced program requiring ships to flush their ballast at sea is working. That so-called "swish-and-spit'' with saltwater generally kills freshwater species that might survive in Great Lakes ports.
Before the rule, some 185 foreign species invaded the Great Lakes. In the 1990s and early 2000s researchers were finding a new species in the Great Lakes on average every 28 weeks — from gobies and ruffe to quagga mussels, spiny waterfleas and the fish-killing VHS virus.
Since the St. Lawrence Seaway opened in 1959, allowing unfettered access to the Great Lakes by oceangoing ships, more than half of those invading species are believed to have arrived in ships' ballasts. U.S. regulators in 1993 suggested the ballast water exchange program, which became mandatory in 2006 in both U.S. and Canadian waters.
In addition, federal rules are in place requiring saltwater ships entering U.S. ports to have on-board ballast water treatment systems starting in 2021, although efforts are underway in Congress to roll back those regulations.