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Aquatic INvasive Species of Green Lake Aquatic invasive species (AIS) are plants, animals, or pathogens that are introduced by human action to an area where they do not naturally occur. Once they establish breeding populations, they spread rapidly in their new environments. AIS lack natural predators and competitors, which contribute to their population explosions. There are many remediation and prevention efforts currently being implemented on Green Lake. We are helping to prevent the spread of AIS through our Clean Boats, Clean Waters program. Learn more about the following AIS species by clicking on the links below.
Zebra Mussels (Dreissena polymorpha) The Zebra mussel is a small bottom dwelling relative of the clam native to the waters of Europe and Asia. The most likely explanation for their introduction into the Great Lakes region is hitching a ride in the ballast water of ocean going ships. Zebra mussels were first discovered in Wisconsin waters of Lake Michigan in 1990. Since then, they have spread to the Mississippi River and inland waters. Zebra mussels pose ecological and biological effects, as well as health related concerns. Here are just a few ways zebra mussels impact our waters:
Watch the video below to learn about the research and negative impact the zebra mussel is having on the Great Lakes region, including Green Lake and its watershed.
Purple Loosestrife (Lythrum salicaria) Purple loosestrife is a wetland and marsh plant that grows 3’-7’ tall with a purple spike flower at its top. It was first introduced as a garden perennial and a medical herb from Europe. Once in an area, it has the ability to choke out native moist soil plants. One stalk of Purple loosestrife has the potential to produce 100,000 – 300,000 seeds per year, with a seed survival rate of 60 – 70 percent!The Green Lake Sanitary District's purple loosestrife program helps control the growth and spread of this AIS. Each year, volunteers, local high school students and faculty rear leaf feeding beetles, the plant's natural predators. They are released annually into infested areas to specifically target purple loosestrife. These efforts have had great success in significantly decreasing its numbers in previously infected areas. Eurasian Water Milfoil (Myriophyllum spicatum) Eurasian water milfoil is a feathery aquatic plant native to Europe and Asia. It was first introduced to the U.S. around 1900 and found its way into Wisconsin in the 1960s. As of 1993, established populations of Eurasian water milfoil were located in 54 percent of the counties in Wisconsin. The plant relies heavily on fragmentation for reproduction. Parts of the plant are broken off and transported elsewhere, whether it by wind or boaters. These plant fragments are capable of producing rooted plants again. Eurasian water milfoil begins growth in the spring before all other plants, giving it a distinct advantage over native species. The mats grow so thick that other species can’t gather sunlight creating a monotypic stand of Eurasian water milfoil that can disrupt predator-prey interactions in established ecosystems. There are several ways to help control the spread of Eurasian water milfoil.
Curly-leaf Pondweed (Potamogeton crispus) Curly-leaf pondweed is an invasive aquatic perennial. Like many of the other invasive species, curly-leaf pondweed is native to Europe, Asia and Australia. It was introduced to the United States by hobbyists who used the plant for aquariums. Curly-leaf pondweed has very distinct wavy leaves that are lasagna noodle-like. Curly-leaf pondweed can tolerate very low temperatures and low light conditions. Because of these tolerances, it often begins growing while ice is still present on a water body. This gives curly-leaf pondweed a major head start over all other aquatic plants. In mid-July these plants begin to die off, which may result in dissolved oxygen loss and the decaying plants can contribute to algae blooms.Rusty Crayfish (Orconectes rusticus) Rusty crayfish are native to the Ohio River basin and the states of Ohio and Kentucky. These crayfish have most likely spread to other areas from anglers who have used them as bait for fishing. As populations of rusty crayfish increase in various areas, they are harvested for biological supply companies, food, and fishing bait. These activities are most likely aiding in the spread of rusty crayfish as well. Rusty crayfish can cause a variety of ecological problems. They displace many of the native crayfish populations because they are more capable to compete for a limited food source. Maybe the most serious impact rusty crayfish have on a water body is aquatic plant bed destruction. Research suggests that rusty crayfish eat roughly twice the amount of plants that native crayfish do. These crayfish also eat fish eggs, which can dramatically effect fish populations. Green Lake has a small population of rusty crayfish. However, rusty crayfish don’t pose a big problem to Green Lake because of its sustainable fish populations. Species of bass and bluegill feed on rusty crayfish. The abundant populations of both fish in Green Lake should be able to keep the rusty crayfish numbers limited. View rusty crayfish locator map. Spiny Waterflea (Bythotrephes cederstroemi) The spiny waterflea was introduced to the Great Lakes in the 1980s from the ballast water of ocean going ships from Europe. It is relatively small, but tends to gather in masses on fishing line. They consume small zooplankton putting them in direct competition with young fish. Young fish who try to consume the spiny waterflea often get them caught in their throat because of their long spiny tails. Fortunately spiny waterfleas are not present in Green Lake; however, there are other waterbodies in Wisconsin that are affected by spiny waterfleas. Once introduced to new areas, control methods to eliminate these critters are unavailable, so prevention is the key to its introduction. View spiny waterflea map locator. Viral Hemorrhagic Septicemia (VHS) VHS is a deadly fish virus that is also considered an invasive species. VHS was first discovered in European freshwater trout back in the 1930s and continues to plague European trout. It was first discovered in the Great Lakes back in 2005. Lake Winnebago, Lake Michigan and Green Bay are the only water bodies in Wisconsin to have reported cases of VHS. Some of the symptoms that would indicate that a fish has VHS are hemorrhaging, bulging eyes and bloated abdomens. This viral disease is transmitted by the urine and reproductive fluids of fish. Once expelled from an infected individual, the virus can enter the blood stream of a healthy individual via a fish’s gills. Boaters and anglers can prevent the spread of VHS by taking a few simple steps.
Learn more about aquatic invasives or view a complete list of aquatic invasive species in Wisconsin. |
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