Tuesday, March 3, 2015

Asian carp on the menu for native fish

bighead carp (Hypophthalmichthys nobilis) by U.S. Geological Survey Archive, U.S. Geological Survey, Bugwood.org

Asian carp is a common name for several species of fish introduced from Asia.  The two most concerning of the species are silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis), which were brought to the U.S. in the 1970s for use in aquaculture ponds and water treatment systems.  It is thought that flooding in the 1990s allowed the carp to escape into the Mississippi River system where they are trying to make their way into the Great Lakes.  The primary concern with the introduction of these fish is their voracious appetite for plankton, which is a primary food source for larval fish, native mussels, and some adult fish. Current methods of slowing the spread of Asian carp haven't been entirely successful, as they have been found to move beyond electric barriers meant to exclude them from moving further up the Mississippi River.

However, at the recent Midwest Fish & Wildlife Conference, a presentation by Cory Anderson of Western Illinois University showed that some native fish have begun to prey upon Asian carp.  Not only were the Asian carp being fed upon opportunistically, they were finding that certain species' stomach contents indicated that they were deliberately selecting Asian carp as a food source.  Due to the size of the carp, most of the predation occurred on immatures and small adults.  However, blue catfish is a quite large species and found to have consumed carp as large as 22-40 inches long.  Blue catfish aren't native to the Great Lakes, but there is another large catfish, flathead catfish, which may find room on their plate for Asian carp.

For more on the findings: Asian carp being eaten by native fish, new studies find