Midwest Fish & Wildlife Conference 2016

AUTHORS: Nicholas W. Kramer*, Southeast Missouri State University; Quinton E. Phelps, Missouri Department of Conservation; Clay L. Pierce, USGS Iowa Cooperative Fish and Wildlife Research Unit; Michael E. Colvin, Mississippi State University

ABSTRACT: Beginning with the inception of fisheries management in North America, nonnative fish species have been introduced to new waters with the goal of enhancing existing populations. Many of these changes have led to unanticipated, deleterious consequences. This has led to large scale fish removal efforts to combat the negative impacts of invasive fishes such as the common carp, grass carp and silver and bighead Carps. The objective of this study was to determine the amount of harvest required to control these invasive carps in a large Midwestern U.S. river system and its impact on remaining fish groups. We developed a mass balance trophic model of the Middle Mississippi River near Cape Girardeau, MO using Ecopath with Ecosim software (EwE, v. 6.4). In doing so, we developed biomass, production, consumption and diet composition estimates for 35 fish groups using Long Term Research Monitoring Program data for this location. Using the Ecosim component of the software we then modeled increasing amounts of harvest of invasive carps from 5-100% of their initial biomass to determine whether the removal of these nuisance species would either benefit or hinder other species. Common carp and grass carp were more susceptible to increased harvest with populations becoming nonexistent with increased exploitation however, twice as much effort is needed before silver carp and bighead carp showed signs of being overfished. The remaining fish groups exhibited increases in relative biomass with the varying amounts of carp harvest while others, such as the gar spp. or Moronids, showed decreases in relative biomass due to the high composition of invasive carps in their diet. Ultimately, this information can be used by river managers and commercial fisheries coordinators to evaluate management policies promoting the removal of these species from our waters, resulting in enhanced populations of native fish species.