Invasive or not? A Great Lakes puzzle
Around the Great Lakes, millions of dollars are spent to fight invasive species like Asian carp. They cause a lot of damage. But when scientists discover a new animal or plant in the region, it’s not always clear if it’s harmful - or helpful.
That debate has begun over a shrimp.
The bloody red shrimp is roughly the size of a pencil eraser. They came to the Great Lakes around 2006, hitching a ride in the ballast water of cargo ships from the Black Sea.
Since then, they’ve worked their way into all of the Great Lakes except Superior.
Scott McNaught, a biology professor at Central Michigan University, says food sources for the shrimp are mainly animal plankton and algae. But mention the bloody red shrimp as "invasive," and he grimaces.
“'Invasive' is kind of a tricky word. We like to say an organism is invasive if it’s causing some negative impact on the environment," he says. "Or economic impact, or even an aesthetic impact.”
So for the moment, McNaught says, the bloody red shrimp is simply labeled non-native.
Emily Wimmer is a graduate assistant of Scott’s. She’s doing research to see whether the bloody shrimp could have a positive impact on the Great Lakes ecosystem.
“What can we do with them, how can we benefit?" she says. "Can they serve a purpose to something. And here we have a native species, these Lake Trout fry, that are struggling to survive, Can these fry utilize as a food source, can we have a native predator of the Great Lakes come back.”
Wimmer says Michigan is struggling to get Lake Trout to reproduce naturally in the environment -- and some people think a lack of food is the problem.
Maybe, she says, the bloody red shrimp could become a helpful food source.
In a lab used by McNaught and Wimmer, tiny, blue-gray fish dark around a green tub. The lab is chilly, to mimic the cold temperatures of the Great Lakes.
On a table across from the tub are tiny containers for the bloody red shrimp -- marked small, medium, and large.
The shrimp, known as hemimysis, don’t look like much. Translucent with spots of red, and so tiny they're barely visible.
McNaught motions at the tub and points out that the entire school of shrimp would barely make an hors d'oeuvre. These aren’t the kind of shrimp you eat.
Not worth eating for humans, maybe, But Wimmer says the results have been conclusive for young lake trout, known as fry.
“Well, first of all, the lake trout fry are able to eat these hemimysis," she says. "That was the big question that we were looking for.”
So… there’s scientific evidence that the bloody shrimp doesn’t need to be called invasive, right?
Not so fast, says McNaught.
One of his experiments involves invasive quagga mussels. He thinks the mussels and bloody red shrimp together could decimate plankton populations -- which are essential to the local ecosystem.
In the end, a Michigan committee will decide whether to label the bloody red shrimp as invasive.
Even though the shrimp has already made its home in Michigan, it could still be classified as invasive, says Joanne Foreman, who handles communications on invasives for several state agencies.
“We never say, 'It’s already here, it’s too late.' We do look at different stages of invasion," she says.
"And then at each stage we have to determine what is reasonable and what is feasible. What sort of actions might be able to contain and eradicate that species, or if that’s not possible ... how do we manage the effects and try to reduce the spread of that population.”
McNaught and Wimmer say it’s too early to label the bloody red shrimp.
“So what I’m trying to say is that science is not black and white, it’s gray, it’s fuzzy, the screen keeps going on the fritz.”
Until more definitive research comes along then, the bloody red shrimp will continue to swim in that gray area.