Common Carp Impacts in a Shallow Lake: A Systems Modeling Approach to Restoration and Management

Commercial fisheries are commonly used to manage nuisance fishes in freshwater systems, but often unsuccessfully.   We evaluated strategies for successfully controlling a nuisance common carp (Cyprinus carpio) population by pulsed commercial harvest using a combination of field sampling, population estimation and CPUE indexing, and simulation using an exponential semi-discrete biomass dynamics model (SDBDM).  The range of annual fishing mortalities resulting in successful control were narrow (F=0.244-0.265).  Common carp biomass dynamics were sensitive to unintentional under-harvest due to high rates of surplus production and a biomass doubling time of 2.7 years.  Simulations indicated that biomanipulation never achieved successful control unless supplemental fishing mortality was imposed.  Harvesting a majority of annual production was required to achieve successful control, as indicated by the ecotrophic coefficient (EC).  Readily available biomass data and tools such as SDBDMs and ECs can be used in an adaptive management framework to successfully control common carp and other nuisance fishes by pulsed commercial fishing.