A Brief History
On June 26, 1959, the St. Lawrence Seaway opened for traffic. (See our other article today.) The seaway opened the Great Lakes to ocean going freighters enhancing the economy of the region and transportation efficiency for the US and Canada. Unfortunately, it also brought invasive species. Sometimes invasive species are brought to a new land or water on purpose, other times by accident. Often times, the introduction of a non-native species has unwanted consequences for their new home and neighbors, be they plant or animal. Here we list 10 of the most irritating (to us; it is a matter of opinion after all), if not the most harmful invasive species. Which ones would you add?
10. Asian Carp (Bighead and Silver).
Having escaped into the Mississippi River drainage from flooding that overflowed ponds at fish farms and sewage treatment plants where the fish were brought to control planktonic algae, these non-gamefish filter feeders are threatening to invade the Great Lakes next. Perhaps you have seen them on the television jumping out of the water by the hundreds when excited by boat motors, landing in the boats and injuring boaters. Fast growing and capable of reaching over 4 feet long and over 100 pounds, they represent a serious danger to the Great Lakes fishery.
Brought to Australia in 1788 as a source of food, an 1859 release caused the population of rabbits to explode, ruining crops and overrunning the countryside. In the 1901 to 1907 period an enormously long (over 2000 miles) “rabbit proof fence” was built in Western Australia in 3 sections at a cost of over 330,000£. Cracked fact: The longest section, 1139 miles, is the longest continuous fence in the world. Camels were imported to assist maintenance men in maintaining the fence. Finally, in the 1950’s the introduction of the myxomatosis virus killed off enough rabbits to bring the population down to manageable size.
8. Water Hyacinths.
A warm weather water plant from South America, its pretty flowers have caused people to make the blunder of bringing it to other places where it rapidly covers the surface of the water blocking the sunlight from reaching other plants. This has the result of reducing oxygen in the water, hurting wildlife, and eliminating other plants that provide food and shelter to fish and other critters. Water Hyacinth infestation also increases mosquito propagation. Choking waterways in tropical and subtropical locations in Africa and the Southern US and Mexico, it has also become a problem in Australia and Asia. Introduced to the US at the 1884 New Orleans World Fair, it rapidly spread to the point of blocking shipping channels. Cracked fact: In 1910 a bill lost by only 1 vote in Congress to introduce the Hippopotamus to Louisiana to control the Water Hyacinth problem!
A fast growing and fast spreading Asian vine, also known as Japanese Arrowroot, kudzu was introduced to the US in 1876 at the Philadelphia Centennial Exposition and rapidly overran the Southeast portion of the country. Kudzu grows fast enough to overwhelm native plants and shrubs, starving them of light and nutrients. It is considered a noxious weed and has recently been found in Southern Canada.
A member of the cichlid family of fish familiar to aquarium enthusiasts, Tilapia are a commonly raised fish farm species for human consumption. Released intentionally and accidentally throughout the world, these hardy fish take to any waterways that remain somewhat warm (minimum temperature of 45-52 degrees F) through the year, and tolerate fresh, brackish, and coastal salt water environs, often displacing native species. In some locations they have survived cold winters by living near warm water discharges of power plants. Breeding throughout the summer instead of just once a year like many native species, these voracious plant eaters have been introduced to the African Rift Valley lakes (especially Lake Malawi) where they have largely displaced and threaten to make extinct many of the 1000 or so native species of cichlids.
5. Zebra Mussel/Quagga Mussel.
Introduced into the Great Lakes via the ballast water of ocean going freighters that travel the St. Lawrence Seaway, they have also invaded many other waterways in lakes and rivers where they reproduce in such massive numbers that they coat internal engine parts of boats, water intakes, and cover every rock and stick in their path. Native Great Lakes fish were found not to eat them at first, but have apparently adapted to eating them. Unfortunately, the filter feeding mussels accumulate large amounts of toxins from pollution and the fish that eat them end up contaminated with the same toxins.
4. Cane Toad.
These largest of the toads (about 4 pounds) are native to Central and South America, and were brought to Australia in 1935 in the hope of controlling certain beetles that threatened the sugar cane crop. The voracious toads proceeded to reproduce beyond all expectation. Eating almost anything that will fit in their mouth (hobbyists feed them mice and dog food among other things) the cane toads gobbled up native amphibians and everything in sight, except of course cane beetles. Worse yet, they secrete a milky toxin on their skin which often kills dogs, birds of prey, snakes and lizards. Cane toads are so hated in Australia that “sports” such as “Cane toad golf” and “Cane toad crickett” have sprouted up, hitting cane toads instead of balls!
3. Norway Rat.
Also known as the Brown Rat or Common Rat, this native of Northern China has been spread all over the world except Antarctica by hitching rides on ships and vehicles. Possibly the most “successful” mammal on earth, this vermin spreads disease and destroys millions of tons of human and animal food every year. Controlled only partially by use of cats and small dogs, the more people are clustered into an area the more rats you will find.
2. Common Carp.
A longtime Eurasian foodfish, this hardy big brother to the goldfish was brought to North America by enthusiastic European settlers, and to say they successfully made the transition is an understatement. Found in rivers and lakes throughout the US and much of Canada and Mexico, the large minnow family fish can grow to nearly 100 pounds. Not considered a game fish (almost impossible to catch on an artificial lure), they do fight hard if hooked, but are not considered table fare by the vast majority of North Americans. They are bottom feeders that root around the bottom, stirring up mud and eating the eggs of other fish.
Brought to North America by European settlers in the 1600’s, these familiar “flying rats” are found both in the cities and the rural areas. In large city flocks they create mass quantities of pigeon droppings on motor vehicles, outdoor furniture, and just about everything else. At times large flocks can even constitute a hazard to aircraft. Another intensely irritating feature is the habit of dominating backyard bird feeders meant to attract native songbirds.
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For more information, please see…
Forever, Wildlife. Invaders of the Great Lakes: Invasive Species and Their Impact on You. Adventure Publications, 2013.