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The Carletonian

Arb notes: trapped carp

Rs working on Arb Crew; our job was to walk along the floodplain, picking up any trash washed up from the recent flooding. While passing by the retention pond, a huge fish broke the surface of the water catching our attention. I asked Matt Elbert, Arboretum Manager, what fish that large could be in the pond and he said it was a carp. When the Cannon River flooded it reached much higher water levels, allowing fish to travel from the river to areas previously not connected. After the river receded, many carp end up trapped in ponds and temporary mini ponds left over after the flooding. Later during Arb crew, in one of these shallower pools, I found a carp that was trapped!  It was around one and a half feet long and a hefty 15 pounds. Unfortunately, these carp damage the aquatic ecosystems they are left in. 

With nowhere to go, the carp eat everything: they eat frogs, toads, salamanders, snails, shallowly rooted plants, and plankton. Their messy and aggressive feeding behavior stirs up mud and uproots plants, causing erosion while also increasing water particle content (turbidity/siltation) which affects plankton negatively. This has a ripple effect on insects, fish, water fowl, algae growth and overall biodiversity. In the river especially, they eat a lot of mollusks which ends up affecting native fish, turtles, birds and mammals that eat them too. 

Fortunately, carp are still not completely overrunning the ecosystems of the Arb or Cannon River. The Department of Natural Resources conducts samples of major rivers in Minnesota to keep track of the problem and also looks for potential solutions. Also, after a major flood, carp that find themselves in ponds where they shouldn’t be are frozen out during Minnesota winters. 

If you’re interested, explore along the flood plain and see if you can find any of these invasive carp!

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