Fishing is a huge outdoor activity for many Minnesotans. Unfortunately, our native fish are being harmed by some unwelcome invasive species. One such fish is the Silver carp. The Silver carp, Hypophthalmichtyhs molitrix, is a species of fish that is native to eastern Asia and was imported from China to the United States during the early 1970s to help fish aquaculture operations and improve water quality within ponds and sewage lagoons (DNR, 2019). However, generally speaking, whenever we humans decide to “make things better” by messing with Mother Nature, is does not go well (think European Starling and Grass carp). So if these fish are unwanted and harmful, why are they here? To get into that, we’ll define a few things first.
Many times people synonymize “non-native” and “invasive” species to mean the same thing. However, while a non-native species can be invasive, it does not mean that a non-native IS ALWAYS invasive. The National Park Service (NPS) defines a non-native species as any organism (animal, plant, microbe, etc.) that has lived/occurred outside of their normal range or area (NPS, 2019). These regions are of various sizes. For example, a native area of one organism could be an entire country, whereas another organism’s range could be as small as a state within a country for size reference. The NPS then goes onto to define an invasive species. Any non-native species that has caused harm through economic or environmental damage is deemed an invasive species (NPS, 2019). From this, it is a little easier to see how a non-native species does not always mean it is invasive if it has not caused any harm. Some examples of non-native species that are not invasive would be petunias or tomatoes which do not risk the health of any native plants and have been grown and cultivated by humans for many centuries.
Now, our acquaintance the Silver carp, however, is deemed an invasive non-native fish species. Recently, MPR News released a news story stating that the menace was caught in the St. Croix River. This river starts in the northwestern part of Wisconsin and then forms part of the Minnesota/Wisconsin border and emptying into the lower portion of the Mississippi along the lower border of Minnesota/Wisconsin. According to the news story, the carp was caught by a commercial fishing operation. In a statement from the DNR back in April, the first time Silver carp was confirmed to be in Minnesota was in 2017 (DNR, 2019).
Why is this fish considered invasive, and, thus, harmful? Laird and Page (1996) stated that this fish has the potential to cause enormous damage to native species because this fish eats plankton that is required of our native fish and native mussels of the area and thus depletes resources for our native species to thrive. Most recently, a study done by Iron et al. (2007) had demonstrated significant declines in the body conditions of the Gizzard Shad and Bigmouth Buffalo (both native to Minnesota and surrounding areas) that was a result of the invasions of the both the Silver and Bighead carps. This paper came to the conclusion that, because of the decline of the body conditions on these animals, their ability to reproduce and thrive is severely diminished.
What do you do if you come across these unwanted inhabitants? According to the DNR’s website, please report any new sightings of the carp by taking a photo and making arrangements with the DNR to transport the carp to your nearest fisheries office by calling (651) 587-2781 or emailing email@example.com. It is illegal to transport these fish without proper authority, so please be aware! Conservation/ecology are critical components of our scientific community and you can do your part as a citizen scientist by communicating with the DNR.
• Department of Natural Resources (DNR). (15 April, 2019). News release: Commerical fisher captures invasive silver carp in St. Croix River. Retrieved http://news.dnr.state.mn.us/2019/04/15/commercial-fisher-captures-invasive-silver-carp-in-st-croix-river/
• Department of Natural Resources (DNR). (2019). Silver carp (Hypophthalmichthys molitrix). Retrieved from https://www.dnr.state.mn.us/invasives/aquaticanimals/silver-carp/index.html
• Iron, K., Sass, G., McClelland, M., & Stafford, J. (2007). Reduced condition factor of two native fish species coincident with invasion of non-native Asian carps in the Illinois River, U.S.A. Is this evidence for competition and reduced fitness? Journal of Fish Biology, 71, 258-273.
• Laird, C., & Page, L. (1996). Non-native fishes inhabiting the streams and lakes of Illinois. Illinois Natural History Survey Bulletin, 35(1), 1-51.
• MPS News Staff. (15 April, 2019). DNR: Invasive silver carp caught on St. Croix River. Retrieved from https://www.mprnews.org/story/2019/04/15/invasive-silver-carp-caught-stcroix-river-minnesota-wis
• National Park Service. (8 February, 2019). Learn: When a species is invasive and when a species is non-native. Retrieved from https://www.nps.gov/subjects/invasive/learn.htm