Can We Tame Zebra Mussels With Another Invasive Fish?
Round gobies can eat juvenile mussels, which could restore native fish stocks, but they aren't native to the Great Lakes
Invasive mussels have been a huge problem for the Great Lakes ever since they arrived here in the 1980s. Both zebra and quagga mussels arrived in the ballast water of cargo ships, most likely in Lake Ontario and the Saint Lawrence River.
Now they are established in four out of the five lakes and are invading Lake Superior. A tiny little mussel may not sound like a big deal, but they have profound impacts on the ecosystem. These mussels survive by filtering plankton and nutrients out of the water.
On a small scale that’s fine. In fact, the lake is noticeably clearer than it was before the mussels arrived. But there are now so many mussels in the lake that their filtering has deprived everything else of the critical food and nutrients they need to survive. Whitefish numbers have fallen, and the arrival of the mussels marked something of a death knell for commercial fishing in the Great Lakes.
But as destructive as mussels have been to the Great Lakes, no one has been able to find a solution. With mussel densities exceeding 10,000 invasive mussels per square meter, the solution needs to be cheap, non-toxic, and deployable throughout the whole lake.
That’s why poisoning the mussels won’t work. We have a program to kill invasive lampreys with a poison selectively added to rivers, but the amount of toxin needed to make a dent in the population would also severely hurt or kill everything else in the lake.
Scientists have explored many other options for eradicating mussels. One idea involves copying the success of the New World Screwworm program, which releases sterile males into the wild, reducing the number of viable eggs produced. But this doesn’t work with mussels due to the way they breed. Another idea involves adding a sort of trigger molecule or organism to the water, which would make mussels sterile upon ingestion using an RNA trigger.
Some scientists have suggested using a naturally occurring disease to kill off mussels, but one would have to be genetically edited to attack only quagga and zebra mussels. All of these methods suffer the same problem: It’s expensive to mass produce enough of whatever cure is chosen. Michigan simply doesn’t have the resources for that.
Thankfully, scientists have finally discovered a way to remove the mussels on a large scale. The secret is ironically another invasive species: the round gobies.
Round gobies are native to the same parts of Ukraine and Russia as zebra and quagga mussels and got to the Great Lakes in the same way: ballast water discharged from freighters. Since their arrival in the 1990s, they have reached huge populations numbers. While they are destructive to the ecosystem and have a tendency to outcompete native fish, they are less destructive than the mussels.
Scientists always assumed physically removing the mussels with a trawler that crushes them would never work because the mussels would just come right back. But when they tested this, they found that the gobies, while unable to eat fully grown mussels, eat the larvae as they try to recolonize mussel-free areas. What this means is that the process of scraping mussels off the lake bed can begin.
The process isn’t foolproof, but by targeting important areas, we can start to fight back against the mussels ruining our lakes.
