Midwest Fish & Wildlife Conference 2016

AUTHORS: Michael C. Wolf*, Southeast Missouri State University; Quinton E. Phelps, Missouri Department of Conservation

ABSTRACT: Fish are sometimes transferred to a new region of the world to perform a specific function where they may have the opportunity to become invasive. Grass carp Ctenopharyngodon idella are an invasive fish in the Mississippi River Basin that were brought to control vegetation and later escaped. Potential control of invasive fish relies on knowledge of specific population dynamics. It is commonly assumed that grass carp share characteristics (i.e., fast growth and high mortality) with Asian carp (i.e., bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix) but our findings suggest they are more similar to common carp Cyprinus carpio in terms of growth and mortality. Over 100 grass carp were collected from the Upper Mississippi River between 2014 and 2015. Lengths ranged from 593 mm to 1175 mm and weights from 2.1 kg to 26.8 kg. Preliminary results suggest that total annual mortality is approximately 8.8% with a theoretical maximum age of 33 years. Studies have shown that this invasive fish can consume high quantities of aquatic macrophytes. Aquatic macrophytes are a highly important aspect in some systems connected to the Mississippi River (i.e., impounded portion). The fact that these fish can consume large amounts of vegetation especially at large sizes coupled with their long-lived nature makes management imperative for sustaining current ecosystems. Evaluating the population dynamics of grass carp should provide insight for river management actions.