While the Cannon River flooding gave us many unique sights (the Great Wall of yellow sandbags, a soggy Froggy Bottom’s, and Carleton’s football-field-turned-toxic-swimming-hole, to name a few), one sight that you may or may not have witnessed was what washed up after the floodwaters began to recede—many of the river’s fish.
Bigmouth Buffalo and the Common Carp were the most prevalent species caught in this unfortunate situation, noted Dr. Ceas, a biology Professor at St. Olaf in a report by Northfield News. These fish have a tendency to move out of the turbulent central flow of a flooding river and swim on the river’s edges. Then, as the floodwaters decrease, some fish get stuck on land, leaving downtown Northfield’s Riverwalk looking like a drained freshwater fish tank once the river returned to a more natural level.
About fifty fish were found on each side of the river in the downtown area, and volunteers moved quickly to get any live Bigmouth Buffalo back into the water. Any live Common Carp, however, were destroyed. Why such discrimination in fish rescue? Bigmouth Buffalo are native to the Cannon and play an important role in the river’s natural ecosystem. Common Carp, on the other hand, are an invasive species introduced to Minnesota in the 1880s as a game fish. The carp’s habit of rooting through bottom sediment while searching for food can seriously alter their environment, releasing phosphorus that increases algae abundance and negatively impacting water quality. Thus, though these two species may look similar (both have large scales and broad bodies—the big distinguishing factor between the two are the carp’s whiskers), one is a rightful resident of Northfield’s waters, and the other is a pesky, unwanted tourist.
The recent flooding has brought these fish, normally hidden below water, (literally) into view, bringing to our attention the river’s other dynamic issues aside from the difficult to ignore, largely destructive flood.
-Rae Wood, ’12, for the Cole Student Naturalists