By Daniel Macfarlane
Invasive species in the Great Lakes have been a big problem for decades. From the alewife, which first appeared in the Great Lakes in the 1800s, to the zebra mussels in recent decades, the composition of the Great Lakes biomass has been constantly in flux. And the problem is about to get bigger – literally, as Asian carp are knocking on the doorstep.
Granted, “invasive” species is a subjective term. The pernicious sea lamprey, for example, may well have been native to the lower Great Lakes; conversely, exotic species – such as the Pacific salmon, stocked in the Great Lakes to support sports fisheries – aren’t considered “invasive.” Basically, when we don’t like the consequences of new types of flora and fauna, even though most are introduced because of human actions, we call them “invasive”.
Great Lakes newcomers have tended to enter through canals, either moving in the water via locks or hitching a ride in the ballast water of vessels. Asian carp are no exception: during the 1970s they were purposefully introduced into the American South to act as natural vacuums in fish farms. By the 1990s the carp had escaped and have since been inexorably working their way northward up the Mississippi River and its tributaries. The most prominent means, or vector, for the carp to get into the Great Lakes is via the Chicago Sanitary and Ship Canal. Continue reading