AUTHORS: Kroboth, P. T., M. E. Colvin, C. L. Broaddus U.S. Geological Survey, Columbia Environmental Research Center, Columbia, MO 65201
ABSTRACT: Black Carp Mylopharongodon piceus were imported into the United States in the 1980s for use in aquaculture. Since then, escapes have occurred and reported wild captures have increased. Black Carp are a concern because of potential impacts on native ecosystems and direct predation on native imperiled mollusks. Based on commercial captures, hoop nets set in mainstem riverine habitats of the Mississippi River during spring and summer are a potential capture method. We assessed commercial fisheries Black Carp catches by kernel density analysis to identify an area of increased catch. Within this area we assessed the seasonality and rate of commercial captures, and tested targeted hoop net effort for Black Carp during 2021 and 2022. We compared Black Carp catch and co-occurring species using non-metric multi-dimensional scaling. We fit Black Carp catch and environmental covariates by general linear models: Poisson, negative binomial, zero-inflated Poisson, zero-inflated negative binomial, hurdle Poisson, and hurdle negative binomial, with the top fitted models selected based on ΔAIC < 2. The model set was refitted for predictions and inference on the model confidence set. Hoop net captures were 63% of commercial records (n=759). The confluence of the Missouri and Mississippi rivers had the greatest density of commercial captures with 39% of hoop net captures in this area, primarily during July-September. Captures were characterized by median water temperature 26.7°C, median river stage 5.02 m, and median day of year 231 (DOY; mid-August). Ordination identified similarity in covariates of Smallmouth Buffalo Ictiobus bubalus and Black Carp catch. Most captures occurred in select outside-bend or secondary-channel habitats. The probability of capturing ≥ 1 Black Carp increased with depth, DOY through September, and declined with increasing current velocity. Results indicated catch was maximized in summer and early fall when stage and current velocity are lower allowing net sets in deeper areas.
