What Are Invasive Species?
You’ve probably heard someone speak about invasive species but what are they, really? And why do they matter? The Wisconsin Department of Natural Resources answers these questions best: “Many non-native or exotic species have been introduced to Wisconsin from other countries or another part of the U.S., either deliberately or by accident. Some of these plants and animals have not been a detriment to the resource; others have become pests and are considered invasive exotics.” Since Mississippi’s invasive species are introduced, some of them affect the river negatively. One of the most common negative effects of introduced species is territory takeover. Introduced species grow and expand at faster rates than native species for many reasons, such as a lack of natural predators. This makes it rather difficult to keep them in control.
5 Invasive Animal Species in the Mississippi?
The Mississippi River is home to many invasive species. Zebra mussels, round gobies, rusty crayfish, Asian carp, and faucet snails are five of the most infamous and detrimental invasive species. They were introduced into the Mississippi River either intentionally or accidentally.
Zebra Mussels
Zebra Mussels are native to Eastern Europe’s Caspian Sea and were first discovered in the waters of Lake St. Clair in 1988. By 1991, they had made their way into the Mississippi River. One fun fact about these animals is that they are the only freshwater mollusk species able to attach to hard surfaces. Mississippi isn’t the only lake invaded by zebra mussels. They are now found in 23 states of the United States. This is primarily because the female zebra mussel can lay up to 1 million eggs per year. They are preyed upon by ducks, crabs, and some fish species. One of the major problems with having zebra mussels is that their ability to attach to hard surfaces causes problems for urban infrastructures, such as underwater electrical utilities and even pipes.
Round Gobies
Native to Central Eurasia, round goby fishes invaded and established themselves in large populations in the Mississippi. They have soft skins and dorsal fins on their small bodies. Round gobies have large eyes that seem to want to pop out. Female round gobies reach maturity within one to two years and can spawn up to six times in a year. They place their eggs in crevices between rocks. Male gobies are extremely territorial and guard their eggs really well. Generally, round gobies are aggressive feeders that hunt and forage easily in total darkness. This invasive species is found in the Mississippi River as well as other Great Lakes. They are also known to have spread into the Ship Canal, Chicago Sanitary, and even the lower parts of the Des Plaines River.
Rusty Crayfish
The rusty crayfish is native to the Ohio River Basin. They are an aggressive and large species of freshwater crayfish. Rusty crayfish have greenish-gray to reddish-brown colors. They get their name from two rusty-red spots on the sides of their back and front claws. When native crayfish in the Mississippi come across predators, they turn around and flee to try to escape. Sometimes, they are caught which keeps their population in check. However, rusty crabs do not flee but fight attackers. Since the fishes that prey on crabs in the Mississippi aren’t used to their prey fighting, they do not attack rusty crabs. This allows their population to grow unchecked. They are also good at avoiding predators and often grow to be too large to be caught or eaten. Rusty crabs also snatch up all the best hiding spots from native fishes. This makes them safe while endangering native Mississippi fishes.
Asian Carp
In the 1970s, Arkansas fish farmers brought bighead carps, silver carps, and grass carps to the U.S from China in Asia. They did this to improve the quality of the water in their fish farms. Carps will feed on algae and can purify waters if used carefully for that purpose. However, in the 1980s, the carps escaped from the farms and made their way to the Mississippi. Carps in the Mississippi feed on large amounts of plankton. They are said to eat their weight in plankton. Eating such large amounts reduces what is left for Mississippi’s natural fishes that feed on plankton. They also feed on other vegetation. This way, they disrupt the balance of the ecosystem.
Faucet Snails
The faucet snail is a European species now found in many Wisconsin lakes including the Mississippi River. It is said that they were introduced by vegetation in packing crates or in ballast water. They have coiled spiral shells and are colored light brown or black. Faucet snails are known to host exotic trematodes or flukes which travel with them to the Mississippi. However, while faucet snails can be majorly harmless, the same cannot be said of the organisms they host. Trematodes are known to cause waterbird mortality as they are intestinal parasites for waterbirds. They are known to have been responsible for the deaths of tens of thousands of ducks. Faucet snails are also known to destroy infrastructure such as pipes as they easily clog them.
How to Help Prevent the Spread of Mississippi’s Invasive Species
If you want to help prevent the spread of invasive species in the Mississippi River, there are things you can do if you swim or fish in the river. First, you can assist natural resource managers to monitor the river and spot these invasive species. If you spot a new infestation of invasive species, you can help by reporting it to the Wisconsin Department of Natural Resources.
