When zebra mussels were finally found in Lake Mendota in the fall of 2015, most aquatic ecologists in Wisconsin had the same thought – “What took them so long?” These notorious little bivalves were firmly planted on the radar of resource managers and scientists, since they had already overrun the Great Lakes and had been moving into Wisconsin waters for years. Which begs a couple of questions. What else is out there that keeps lovers of Wisconsin’s waters awake at night? What species might invade next?
We asked new Center for Limnology director, Jake Vander Zanden, who has made a career out of studying invasions, to give us his Top Five:
1. Quagga Mussels
Quagga mussels and zebra mussels seem to go hand in hand, where one is, the other soon follows. Like zebra mussels, quagga mussels were brought to the U.S. from somewhere around the Ukraine and the Caspain Sea in the ballast water of ocean-going ships headed for Great Lake ports. Since the first documented specimen was found in Lake Erie in 1989 and the Mississippi River near St. Louis in 1995.
2. Round Goby
“The roundy goby will do well in Lake Mendota now that we have zebra mussels, which is their favorite food,” says Vander Zanden. And, indeed, this is a prediction also anchored in what we’ve seen play out in the Great Lakes. Shortly after zebra mussels were discovered in Lake Erie, round gobies – which are also natives of the Caspian Sea and likely transported in ballast water when their larvae got sucked up into the holds of ocean-going tankers – turned up in Lake St. Clair. According to Michigan Sea Grant, “Once established, gobies can displace native fish, eat their eggs and young, take over optimal habitat, spawn multiple times per season and survive in poor quality water.” In other words, they can do all the things that gets an exotic species slapped with the “invasive” label.
3. Gizzard Shad
Unlike our first two entries, gizzard shad aren’t entirely foreign to Wisconsin waters. According to the USGS, their native range extends to the southern and western edges of Wisconsin, especially in and around the Mississippi River. But, like most invasive species, this oddly named and oddly shaped fish – got a hand in expanding its range from humans, as waterways constructed in the Great Lakes, like the Ohio Canal and Chicago River Canal, helped them move in to new waters. As did it’s popularity as a bait fish and accidental introductions from inattentive anglers. Gizzard shad have also been stocked as a forage fish for popular sport fishing species where they are good eating for other fish while young but have the slight problem of growing too big as adults for most species to prey on.
4. Common Water Flea (Daphnia lumholtzi)
Readers of this blog will no doubt have positive associations with the word Daphnia, since we write so much about our awesome native grazers of algae, Daphnia pulicaria. But Daphnia lumholtzi, or the invasive common water flea, is a whole different story.
5. Bloody Red Shrimp (Hemimysis anomala)
With a name ready-made for a horror movie, bloody red shrimp sounds like a species to strike fear in the heart of any native species. But, so far, the tale of this recent Great Lakes invader is more of a mystery. It is native to – you’ll never guess – the Caspian Sea and spread across European waterways before being sucked up in the ballast water of an ocean-going vessel and being dumped in the Great Lakes Basin. It was first detected in water samples from Lake Michigan that were collected by NOAA near Muskegon, Michigan. Since then, it’s also been detected in Lake Ontario, making scientists suggest that it’s more widespread than is currently documented.
According to Wisconsin Sea Grant, a swarm of bloody red shrimp “has a unique swarming behavior unlikely to be confused with anything else in the Great Lakes.” During daylight hours, the animal avoids direct sunlight “and may be observed forming reddish swarms in the shadows of piers, boats or breakwalls.” Like most invasive species, it seems to have a gift for growth – it lives for 9 months, can grow to maturity in 45 days and produce four generations of offspring a year, which is a far more rapid and prolific lifestyle than native shrimp in the Great Lakes.
Wouldn’t it be great if we never found out?