A Gear Evaluation of Push Nets, Benthic Sleds, and Light Traps for Sampling Larval Bigheaded Carp in Backwater Reaches of the Upper Mississippi River

Bigheaded Carp (Bighead and Silver Carp) have become widely established throughout much of the Mississippi River drainage basin since their introduction in the 1970’s. However, abundances of Bigheaded Carp have remained low in Pools 17, 18, and 19 of the Mississippi River, due to the structural characteristics of Lock and Dam 19 limiting expansion upstream. Adult Bigheaded Carp have been closely monitored, however larval fish communities have not. Monitoring their reproduction and early life history requires using unbiased and precise sampling methods. The objectives of our study were to 1.) determine the frequency and magnitude of Bigheaded Carp larval emergence and 2.) evaluate the effectiveness of multiple sampling gears for capturing larval Bigheaded carps and native species in backwater reaches of the Upper Mississippi River. A total of 444 samples were collected in backwaters in pools 17, 18, and 19 of the Upper Mississippi River from May through September 2018 using push nets, benthic sleds, and light traps. Larval fish collected were enumerated, all larval Bigheaded Carp were identified to species and all other fishes identified down to family. A linear mixed-effects model was used to determine effects of gear, habitat, water temperature, and discharge on abundance of larval fish.