http://www.digitaljournal.com/news/environment/drop-in-native-fish-in-mississippi-river-due-to-asian-carp/article/561884

Drop in native fish in Mississippi River due to Asian carp

Posted Nov 16, 2019 by Karen Graham
The number of sport fish in the upper Mississippi River has declined significantly over the past 20 years and a new study links the decline to an invasive species called Asian carp.
Electrofishing for the asian carp invasive species
Electrofishing for the asian carp invasive species
U.S. Fish and Wildlife Service
In a study published in the peer-reviewed journal Biological Invasions on November 12, 2019, researchers have established a solid link showing the invasive Asian carp is a threat to native species in the Upper Mississippi River System (UMRS).
For years, scientists have suspected Asian carp have been out-competing native sport fish in the upper Mississippi River. From 1994 to 2013 there have been declines in yellow perch, bluegill, and black and white crappie in three areas, the report said.
Lead author John Chick is a fisheries biologist who directs a University of Illinois field station in Alton, Illinois. In an interview with the Associated Press on Friday, Chick said, “The alarms have been out there for a long time now. This adds further mustard to the argument that we need to be taking these things seriously. The trends that have been established here are not the trends we want to see in other places.”
Map shows locations where Asian carp have been found in U.S. as of 2011.
Map shows locations where Asian carp have been found in U.S. as of 2011.
USGF/NWF
Asian carp introduction behind the invasion
During the late 1960s and early 1970s, four species of carp, including the grass carp, bighead, silver, black carp were brought into the United States as a way to keep excess algae under control on catfish farms and waste-water treatment ponds.
While it may have been a good idea at the time, it turned out to be a disaster in the making when the fish began escaping from the fish farms. As they carp multiplied, they moved north. And the bighead and silver carp have turned out to be the most troublesome.
Not only do they eat algae, but they also eat plankton, tiny animals and plants that virtually all juvenile fish species eat. For filter feeders, like clams, krill, and some fish, it’s a lifelong staple.
There have been a number of solutions tried in controlling or eradicating the invasive fish. The federal and state governments have spent heavily on technologies to eradicate the carp, including electric fish fences, water guns, and scent-based lures.
Asian carp get really big! This particular Bighead carp is about to be studied by USGS scientists.
Asian carp get really big! This particular Bighead carp is about to be studied by USGS scientists.
USGS
Compiling the data
Luckily, the Army Corps of Engineers has been monitoring fish in the Upper Mississippi River for decades, including several years before the arrival of the Asian carp. They use electro-fishing to collect samples.
Analyzing the data, the research team found that the number of sport fish dropped about 30 percent in two carp-infested areas on the Mississippi River and one on the Illinois River between 1994 and 2013.
The study focused on silver carp, notorious for leaping from the water when startled because they’re more abundant in the Upper Mississippi than bighead carp. Sportfishing in those areas infested with the Asian carp also declined - while increasing in three other places by 35 percent farther upstream that the carp hadn't reached.
Silver carp jumping out of the water after being startled.
Silver carp jumping out of the water after being startled.
Tennessee National Wildlife Federation
The researchers also took into consideration factors like flooding, temperatures, and sediment pollution - but ruled these issues out as not playing a significant role in sportfishing trends in the Upper Mississippi region. And, the study noted that the carp problem in the Mississippi River has drawn less attention in the carp battle than the Great Lakes.
However, the river's outdoor recreation economy is valued at about $2.2 billion. So the study not only points to the urgency of protecting native fish species but protecting an industry that is economically viable.
Tammy Newcomb, a fisheries biologist and Asian carp expert with the Michigan Department of Natural Resources says “It’s another piece of science that contributes to the overall sense of urgency” to stop the carps’ advance.