Tiny Shrimp, big concern

Experts fear the bloody red mysid will compete for food with small fish in the Great Lakes.
The Kingston Whig-Standard, Jan. 24, 2007
Jennifer Pritchett

Swarms of fast-multiplying shrimp from Europe and Asia have invaded Lake Ontario and scientists fear the tiny crustaceans will have nasty effects on the Great Lakes' food chain.

The shellfish, called the bloody red mysid, was discovered last spring southwest of Kingston near Oswego, N.Y., according to the Environmental Research Laboratory in Michigan, part of the National Oceanic and Atmospheric Administration.

The invasive species was also found late last year in waters connected to Lake Michigan in Muskegon, Mich.

“The fact that they've been found in Lake Michigan and Lake Ontario means they're probably everywhere in between,” said Steve Pothoven, a fish biologist with the Great Lakes Environmental Research Laboratory in Michigan.

It's the latest of 185 invasive species - a number which continues to grow - to be detected in the Great Lakes.

The red shrimp, too small for human consumption, is a relative of the native Great Lakes opossum shrimp and it's difficult to tell the difference between the two with the naked eye. Only an expert can properly identify them.

The invader is native to Eastern Europe and Western Asia in the Caspian Sea and Black Sea areas - the same region that sent zebra mussels and gobies, other invasive species, to the Great Lakes.

The bloody red shrimp has already invaded waterways in various other parts of Europe.

Based on their invasive behaviour in that part of the world, scientists in Canada and the U.S. fear they could upset the food chain in the Great Lakes, which has already been compromised by invasive species.

Henry Vanderploeg of the Great Lakes Environmental Research Laboratory said the bloody red shrimp is an omnivore that eats a variety of small animals, such as waterfleas, and algae, a similar diet to small fish.

Known by the scientific name Hemimysis anomala, the shrimp typically feeds on zooplankton and phytoplankton, which are also major food sources for small fish.

“We're trying to figure out how it's going to fit into the food web,” said Vanderploeg. “They could become a competitor with (small fish), but on the other hand, they are a potential food source for larger fish. The whole question is whether this shrimp can find hiding places in the Great Lakes so they can't be eaten.”

“It may or may not become abundant.”

To answer this question, scientists throughout the Great Lakes are getting the word out about the bloody red shrimp in order to understand where the species has taken up residence and in what numbers.

“From there, we can determine what the environmental impact will be,” said Pothoven.

He warns the shrimp could have extreme consequences on the Great Lakes.

“Of this type of animal, it's considered to have the highest risk for impact,” he said.

The bloody red shrimp are fast swimmers that hide at the bottom of lakes in shallow, warm water until night when they travel up the water column to feed. They normally live near rocky areas or docks. They avoid sunlight and at night, they can be detected by shining a flashlight into the water.

The species can produce about four generations each year

Pothoven said because there are no other types of shrimp that live near the shore in the Great Lakes, the bloody red may find itself a niche here.

Hugh MacIsaac, one of Canada's foremost experts on invasive species, said the shrimp likely arrived in the Great Lakes through a ship's ballast water, which is how other invasive species have entered the water system in the past.

Ballast water is carried on unladen ships to provide stability. It is taken on board at the port before the voyage begins and tiny stowaways, marine organisms, are taken on board with it.

At the ships' destination, the cargo is loaded and the ballast water, with its surviving stowaway organisms, is pumped out. While both the Canadian and U.S. Coast Guards have regulations surrounding where ballast water can be pumped out, organisms have been known to be transported this way.

“We have to put our emphasis on keeping these species out because once they get in, it's hard to stop the spread,” said MacIsaac, who holds the Department of Fisheries and Oceans research chair for invasive species at the University of Windsor.

In the U.S., scientists are asking the public to report all observations of swarms of the shrimp in new locations at the Great Lakes Environmental Research Laboratory.