Some say it's only a matter of time before the Asian Carp enters the Great Lakes. (Photo courtesy of the USFWS)
More than 160 kinds of foreign creatures are in the Great Lakes right now, and every few months, a new one finds its way into the Lakes. Those invasive species are considered the number one problem by the experts we surveyed. The outsiders crowd out native species and disrupt the natural food chain, and it’s likely more will be coming. Zach Peterson reports scientists are putting a lot of time and effort into figuring out which new foreign creatures might next invade the Great Lakes:
Transcript
There are new problems for the Great Lakes on the horizon. The Great Lakes Radio Consortium’s Lester Graham is our guide in a series that explains that new invasive species are one of the Ten
Threats to the Great Lakes:
More than 160 kinds of foreign creatures are in the Great Lakes right now, and every few months, a new one finds its way into the Lakes. Those invasive species are considered the number one problem by the experts we surveyed. The outsiders crowd out native species and disrupt the natural food chain, and it’s likely more will be coming. Zach Peterson reports scientists are putting a lot of time and effort into figuring out which new foreign creatures might next invade the Great Lakes:
(Sound of boat motor)
Jim Barta is a charter boat captain just above Lake Erie on the Detroit River. He says over the last decade, zebra mussels and other foreign species have altered the habitat of the walleye he fishes for.
Water that once had a brownish hue is now clear. That’s because Zebra mussels have eaten the algae and plankton that used to cloud the water, and that means Barta’s boat is no longer invisible to the fish he aims to hook.
“You could catch the fish a little closer to the boat because they weren’t as spooked by the boat. They weren’t as afraid of what was taking place.”
So Barta had to rethink his tactics. He now casts his lines out further, and he’s changed lures to continue catching walleye.
But there are other problems the zebra mussel is causing. Eating all the plankton means it’s stealing food at the bottom of the food chain. And, that affects how many fish survive and how much the surviving fish are able to grow.
Anthony Ricciardi is trying to help Barta, and other people who rely on a stable Great Lakes ecosystem. He’s an “invasion biologist” at McGill University in Montreal.
Ricciardi looks for evidence that can predict the next non-native species that might make it’s way into the Great Lakes. He says species that have spread throughout waterways in Europe and Asia are prime candidates to become Great Lakes invaders.
“If the organism has shown itself to be invasive elsewhere, it has the ability to adapt to new habitats, to rapidly increase in small numbers, to dominate ecosystems, or to change them in certain ways that change the rules of exsistence for everything else, and thus can cause a disruption.”
Ricciardi says most aquatic invasive species are transported to North America in the ballast tanks of ocean freighters. Freighters use ballast water to help balance their loads. Some of the foreign species hitchhike in the ballast water or in the sediment in the bottom of the ballasts.
Ships coming from overseas release those foreign species unintentionally when they pump out ballast water in Great Lakes ports. Ricciardi says one of the potential invaders that might pose the next big threat to the Great Lakes is the “killer shrimp.” Like the Zebra Mussel, it’s a native of the Black Sea.
“And it’s earned the name killer shrimp because it attacks invertebrates, all kinds of invertebrates, including some that are bigger than it is. And it takes bites out of them and kills them, but doesn’t necessarily eat them. So, it’s not immediately satiated. It actually feeds in a buffet style: it’ll sample invertebrates, and so it can leave a lot of carcasses around it.”
Ballasts on cargo ships aren’t the only way foreign species can get into the Lakes. Right now, scientists are watching as a giant Asian Carp makes its way toward Lake Michigan. It’s a voracious eater and it grows to a hundred pounds or more.
This non-native fish was introduced into the Mississippi River, when flooding allowed the carp to escape from fish farms in the South. A manmade canal near Chicago connects the Mississippi River system to the Great Lakes.
If it gets past an electric barrier in the canal, it could invade. Many scientists believe it’s just a matter of time. Another invasive, the sea lamprey, also got into the Great Lakes through a manmade canal.
But, researchers don’t usually know when or where an invader will show up. David Reid is a researcher for the Great Lakes Environmental Research Laboratory in Ann Arbor. He says they can’t predict the effect an invader will have when it arrives in its new ecosystem.
“That’s the problem. We don’t know when the next zebra mussel’s going to come in. We don’t know when the next sea lamprey type of organism is going to come in. Generally, if you look at the invasion history of the Great Lakes, you’re seeing about one new organism being reported probably about once every eight months.”
Knowing what the next invader might be could help biologists, fisheries experts, and fishermen know what to do to limit its spread. Invasional biologists hope that their work will help develop the most effective measures to limit harm to the Great Lakes.
For the GLRC, I’m Zach Peterson.