Asian Carp in the Mississippi River Basin

Asian carp, collectively bighead (Hypophthalmichthys nobilis) and silver (H. molitrix) carp are invasive fishes that have established feral populations in the Mississippi River Basin.  Previous studies have revealed that these highly planktivorous fishes may negatively influence native planktivores.  Bighead and silver carp were first recorded in the Long Term Resource Monitoring program (LTRM) collections in the La Grange Reach of the Illinois River in 1995 and 1998, respectively.  Leading up to 2008, LTRM pulsed-DC, day electrofishing catch rates for silver carp in the La Grange Reach of the Illinois River increased exponentially.  Since 2009, Asian carp catch rates have decreased, but still make up a substantial proportion in our fish collections.  Rapid growth rates were observed during the early years of the Asian carp invasion, but have appeared to decrease in recent years.  To evaluate growth rates, we removed post cleithrums from a subsample (N=315) of Asian carp collected in 2011 LTRM day electrofishing collections.  Post cleithrums from each individual were sectioned and aged to determine growth information.   Future plans for a large-scale Asian carp removal effort are being discussed and will be directed by an interagency collaboration within Illinois.  Once implemented, this effort will attempt to reduce the density of these invasive fishes in the Illinois River.  We will continue LTRM collections and this age and growth study to test for changes in Asian carp growth rates.  The LTRM dataset has served great importance in tracking Asian carp populations in the La Grange Reach and in other LTRM sample locations and will continue to be in the future.