In the 1970s, two species of foreign carp known as bighead carp and silver carp, collectively known as “Asian carp,” were introduced to isolated ponds in the southern US to help control algae. Due to heavy flooding, the carp were eventually washed out of their ponds and into the Mississippi River drainage. Since then, Asian carp have multiplied readily throughout the Mississippi and its tributaries at the expense of native fish populations. If these fish were released into the Great Lakes basin, their impact would be devastating to the habitat and populations of native fish to the lakes, so much so that it would decimate current species and heavily affect the fishing industry on the Great Lakes.
Currently, there are canals that barges use to get from the Mississippi to the Great Lakes, the largest being in Chicago. The problem with the canals is that if boats can get through, so can fish. It’s an open gateway for Asian carp to waltz into Lake Michigan. Once the carp are in :ale Michigan, the will likely quickly migrate to the other 4 great lakes.
Due to this massive threat to the Great Lakes ecosystem, the US Army Corps of Engineers has set up a series of electrical barriers designed to keep the carp out. Electricity is pumped through stretches of the canal from shore to shore in three places in hopes of deterring any and all fish from moving between the Mississippi and the Great Lakes basin. These fields don’t actually stun fish, but the electrical current is a repellent to them. Studies have shown that the barrier works well on large fish, but there have been a few cases of fish under 2” swimming through. Without filling in the canal and closing off one of the biggest water shipping routes in the US, only so much can be done. Hopefully science can stay one step ahead of the invasive species and keep them at bay.
Prieur, Danielle. “Better Living through Electricity – Keeping Asian Carp out of the Great Lakes.” Medill Reports Chicago, Medill News Service, 8 Mar. 2016, news.medill.northwestern.edu/chicago/better-living-through-electricity-keeping-asian-carp-out-of-the-great-lakes/.
Ready, Richard C., et al. “The Potential Impact of Aquatic Nuisance Species on Recreational Fishing in the Great Lakes and Upper Mississippi and Ohio River Basins.” Journal of Environmental Management, vol. 206, 2018, pp. 304–318., doi:10.1016/j.jenvman.2017.10.025.