Effects of incentivized commercial harvest on Common Carp and Bigmouth Buffalo populations

Abstract

Objective: We sought to assess the effects of Common Carp Cyprinus carpio and Bigmouth Buffalo Ictiobus cyprinellus incentivized commercial harvest on seasonal survival from 2017 to 2021 and several additional demographic indices at 5- , 10- , and 20- year timescales.<br/> Methods: We implemented a live–dead capture–mark–recapture study from 2017 to 2021 for Common Carp and Bigmouth Buffalo across seven natural, shallow lakes of northwestern Iowa to estimate annual recapture rates and survival related to estimated exploitation. We then compared Common Carp and Bigmouth Buffalo size distribution, condition, growth rate and maximum length, length at age 3, maximum observed age, and catch per unit effort to long- term harvest at 5- , 10- , and 20- year timescales.<br/> Results: Common Carp and Bigmouth Buffalo summer survival was higher than winter survival that declined with increasing harvest after exploitation reached 15%; Common Carp and Bigmouth Buffalo relative abundance declined and Common Carp size structure increased, whereas Bigmouth Buffalo growth rates decreased, as harvest increased over 5- , 10- , and 20- year timescales.<br/> Conclusions: While commercial harvest may represent additive mortality in short timescales and reduce relative abundance, Common Carp and Bigmouth Buffalo populations showed resiliency in other demographic metrics of growth, age distribution, condition, and recruitment. Incentivized harvest did not achieve goals of reducing Common Carp and Bigmouth Buffalo abundance, and low estimated exploitation (i.e., <10%) led to compensatory mortality in both species. Consequently, higher harvest and supplemental population management is likely necessary to control Common Carp and Bigmouth Buffalo populations.